Am I Going To Get (Type II) Diabetes From Ultrarunning?

We have a long-running joke around my household, “Oh, Corrine is just a handful of chocolate chips away from diabetes…” and although it’s not entirely true, I will acknowledge that I have a terrible sweet tooth and eat more sugar than I probably should. The ongoing joke planted a seed that turned to lingering fear, which ultimately prompted me to get blood work done. Sure enough, my fasting blood glucose was higher than I expected; 96 mg/dL (milligrams of glucose per deciliter of blood) to be precise. This is below what is considered ‘prediabetes’ (100 to 125mg/dL), but still it made me stop and think, Holy s^*t, am I going to get diabetes?! 

Since then, I’ve started out on a knowledge quest of my own. Asking questions like, how important is my genetic history? How about my diet and lifestyle? How much gummy candy is too much gummy candy (read: so much fear!)? And how do all these things factors interact when it comes to influencing my blood glucose and insulin response on a day-to-day and long-term basis?

To get us started, there are two main types of diabetes; Type I and Type II. For our purposes, we’ll focus primarily on Type II diabetes. Type I diabetes is an autoimmune response that causes the body to stop producing the hormone insulin, and is most frequently diagnosed during childhood. People that have Type I diabetes have to take insulin (administered via an injection) in order to manage their blood glucose and if left untreated it can lead to serious health consequences including death. Type II diabetes is characterized by your body becoming less responsive to insulin, also referred to as insulin resistance. When this happens, you cannot properly use the glucose present in your blood for energy and your blood-glucose levels rise. This is important because your body not only uses insulin to access glucose in your blood to use it for energy but it also plays a key role in storing excess glucose as glycogen and fat to be used for energy later. In the early stages of Type II diabetes, or prediabetes, your pancreas is trying to get your cells to respond by producing more and more insulin, but over time gets worn down and stops functioning properly. When this happens, and your body can no longer keep up, your blood glucose (used interchangeably with blood sugar) rises as your body can no longer use insulin to keep your blood glucose within a normal range, 70 to 99mg/dL.

Lucky for us, a bunch of endurance junkies, for much of the past six or seven decades, exercise has largely been seen by both the scientific and medical communities as an effective means of lowering your risk of developing Type II diabetes. In fact, exercise is often prescribed as treatment and management for the disease (1). This is because short and long-term effects of exercise lead to weight loss/weight management, an increase in muscle mass, management of blood glucose by increasing its use via muscle contractions, and improved insulin sensitivity (7). One study showing the importance of not just weight management but lean muscle mass for fighting Type II diabetes risk found that for every 10% increase in skeletal muscle mass, an 11% reduction in insulin resistance and a 12% reduction in the prevalence of prediabetes was seen in their volunteers (8). In the graph below, you can see how glucose levels change during exercise, lowering insulin production and making more glucose available to your working muscles. In this sense, exercise over time is believed to make you more sensitive to insulin, or rather your body can utilize insulin more effectively.   However, in recent years, there has been a growing concern that our increased reliance on processed foods–that are generally higher in added sugar and simple carbohydrates–and our increasingly sedentary lifestyle might be leading us toward a Type II diabetes epidemic of sorts. Alarmingly, in the Centers for Disease Control and Prevention’s 2017 diabetes report, they suggested one in 10 Americans has diabetes, and that 90 to 95% of those cases are Type II diabetes (2).

Diabetes and ultrarunning graph 1

J. Wilmore, D. Costill, & L. Kennedy. (2007) Physiology of Sport and Exercise, 4th Edition

Because risk factors include being overweight, physical inactivity, poor dietary choices, and smoking, it seems odd that endurance sports could possibly be a contributing factor for Type II diabetes risk. In a study conducted by Marty Hoffman and Eswar Krishnan looking at medical issues amongst a wide range of 1,212 ultramarathon runners, only 0.7% reported having diabetes (3), far below the rates in the average population. So where does this fear come from?

Most of the arguments supporting this fear come from the link between high carbohydrate intake and chronically elevated blood sugar. See, when you eat carbohydrates, your digestive system breaks them down into sugar which can enter the blood, a la blood glucose. If you are chronically eating large quantities of carbohydrates, your body has to constantly work to manage that ever-shifting blood-glucose level while your muscles are not utilizing glucose for fuel. This is especially true of foods that have been classified as having a high glycemic index and glycemic load. The scale ranks carbohydrates from 0 to 100 based on how fast and by how much they cause your blood-glucose levels to rise after eating. Foods that rank high on this list are often processed like white rice, white flour products, refined breakfast cereals, sugar-sweetened beverages, my beloved gummy candies, and more. The fear is that as endurance athletes we may have a tendency to eat more of these products both on and off the trail, from our gels and love of coke to our pasta dinners and our “you ran today extra piece of pie.” That being said, this is a perceived fear and there are many of us on both sides. I’ve seen you with your pre-race sweet potatoes and I’ve seen myself shoveling candy directly into my face.

Like many things in life, timing is incredibly important. First, you should know that your blood glucose will naturally rise during and after exercise so that your muscles can get the blood sugar they need for energy. Blood-glucose levels will ebb and flow naturally but avoiding major sustained spikes and crashes in blood-glucose level is key. During exercise, blood glucose comes from a number of sources, including from the glycogen stored in your liver and muscles from carbohydrates you’ve ingested between your workouts and from the food/fluid you are taking in right before or during exercise. Our bodies are super smart and want to use the most readily available energy source. That being said, there is an ideal time and place for these easily digestible, quick-energy foods, and unfortunately it’s not all the time. The current recommendation from the World Health Organization is to limit your added sugar intake to roughly 5% or less of your daily caloric intake. So with an average caloric intake of 2,500 calories a day, that would limit me to no more than 31.25 grams of sugar per day or a little more than one serving of Swedish Fish. Not all, but many of us are probably toeing that line. As active people, we do have the ability to fudge that number a little bit, but likely need to tame what we are reaching for when it comes to food eaten away from our exercise. It’s important to note that although endurance athletes have a slightly higher recommendation for carbohydrate intake than the general population, the recommendation for sugar is the same.

A lot of concern was raised recently by a particular study that came out in 2016 that followed 10 athletic individuals for a week using a continuous glucose monitor (4). In this particular study, the individuals were classified as “subelite,” but there is no great standardized rationale for classifying individuals into groups in much of the literature. These volunteers in particular exercised on average six hours a week, had “average” to “excellent” VO2max values for their age and gender based on the general population, and had resting heart rates of less than 60 beats per minute. In general, they likely represent an average active population. What they found was that four of the 10 athletes spent more than 70% of the testing period with blood-glucose levels above 108 mg/dL. This result startled people, including researchers, because it was not what had been hypothesized at all. What was overlooked, however, was that the four athletes with the prediabetic blood-glucose levels had more differences than similarities. Two of the four athletes were the most active of the entire cohort during the testing week, while the other two were among the least active. One of the four under-consumed the recommended percentage of carbohydrates in their daily diet and still had high blood glucose, while another volunteer greatly overconsumed sugar by more than three times the recommended daily amount and still had completely normal fasted blood-glucose levels. Basically, there was a whole lot of variability with no definitive cause.

Having spent years on track to become the physiologist I had admired and looked up to, those same physiologists instilled in me the understanding that the correct answer in sports science is often, “it depends.” You see, what many overlook is the variability of individuals. Exercise physiology operates in shades of grey where there is rarely one right or wrong answer. Something might not work for everyone, and context is key. This is becoming better appreciated as our understanding of genetics develops. So, will consuming a balanced diet, a diet low in carbohydrates and high in fat, or one that utilizes periodized carbohydrates tip the scales for you? The correct answer is again, it depends. Like many diseases, the risk of developing Type II diabetes may largely depend on your genetics, which can predispose you for developing the disease. Additional factors to take into account are your training intensity and volume as well as what you chose to fuel your body with. A study highlighting this was conducted in Israel in 2015 monitoring 800 participants using continuous glucose monitors. They monitored the individual post-meal glycemic response and found that it varied greatly between individuals (8). Below you can see that a sample of the participants had different responses to the same foods, and that stresses the point that individuality should not be overlooked when drawing conclusions.

Diabetes and ultrarunning graph 2

Zeevi, D. et al (2015), Personalized Nutrition by Prediction of Glycemic Responses

So what can you do?

  • Avoid under fueling. We’ve all heard the adage, “calories in should equal calories out,” and there’s truth to that. Chronically starving your body of the calories it needs around intense exercise creates extra stress on our systems. Work stress, life stress, lack of sleep, and the stress that comes with the midterm I haven’t studied for all elevate your cortisol levels. Cortisol is a stress hormone that allows your body to function quickly and efficiently when threatened by increasing blood glucose into your bloodstream. This gives your brain the glucose it needs to act quickly and also increases the bioavailability of other substances to repair tissue from injury/inflammation/training stress. However, cortisol levels are supposed to drop off and return to baseline levels as your body resumes normal activity. Chronically high levels of cortisol disrupt the body’s normal functions, keeping your blood glucose high when your body does not need it.
  • Eat enough fiber. This is especially true when it comes to soluble fiber (think oatmeal, sweet potatoes, citrus, and black or kidney beans) as it alters the rate of carbohydrate absorption. Slowing your body’s carbohydrate absorption slows your post-meal blood-glucose response and limits spikes in your blood glucose, which can help to regulate your insulin production (5).
  • Match your carbohydrate intake to your training load. More and more scientific evidence is coming to the table in support of periodized carbohydrate intake. This means when workouts involve high-intensity or high volume, you should shoot for higher carbohydrate availability leading up to and during that day. Whereas, when your workouts are lower intensity, carbohydrate availability is less important, and you can reduce your carbohydrate intake. From a performance standpoint, you need both the adequate fuel stores for your race and metabolic flexibility so you can efficiently utilize multiple pathways when it comes to meeting your energy demands (6). Essentially, your body is never using only one energy pathway, which depends on a number of individual factors including intensity and your ability to utilize carbohydrates and fats at those different intensities. As you run longer and longer, it is especially advantageous to be able to utilize fat efficiently as well as carbohydrates. And if you are prone to gastro-intestinal distress, being able to take in slightly fewer grams of carbohydrates per hour can make the difference between that buckle or a DNF. By periodizing your carbohydrate intake, you can maximize your ability to utilize fat more efficiently as fuel while not compromising your ability to train at high intensities.
  • Work with a sports dietitian to figure out what your individual dietary needs are. How you choose to fuel your body is as important as all the miles you run. As sports dietitian Dina Griffin would say, “we cannot outrun our crappy diets.”

So, am I going to get Type II diabetes? In all likelihood, no. Personally, thanks to a combination of good genetics, managing my stress, bringing my cortisol levels down, and matching my carbohydrate intake to my activity level, my fasted glucose levels are well within the normal range and will hopefully stay that way for years to come. And for you, my iRunFar audience, are you going to get diabetes? Truthfully, I don’t know. That’s between you, your genetics, and timing that extra piece of pie for your hard training day.

Call for Comments (from Meghan)

  • Have you ever used a continuous glucose monitor to track your blood-glucose level over an extended period of time? If so, what did you find?
  • Have you worked with a sports dietician to learn about your body’s specific needs and tailor your diet to them? What did you learn from that expert?
  • Are you an ultrarunner with Type I or Type II diabetes? Would you care to share what you have learned about your body’s specific needs in the sport?


    1. Borghouts, L., & Keizer, H. (2000). Exercise and Insulin Sensitivity: A Review. International Journal of Sports Medicine, 21(1), 1-12.
    2. National Diabetes Statistics Report, 2017. (n.d.). Retrieved November 13, 2017, from
    3. Hoffman, M. D., & Krishnan, E. (2014). Health and Exercise-Related Medical Issues among 1,212 Ultramarathon Runners: Baseline Findings from the Ultrarunners Longitudinal TRAcking (ULTRA) Study. PLoS ONE, 9(1). doi:10.1371/journal.pone.0083867
    4. Thomas, F., Pretty, C. G., Desaive, T., & Chase, J. G. (2016). Blood Glucose Levels of Subelite Athletes During 6 Days of Free Living. Journal of Diabetes Science and Technology, 10(6), 1335-1343. doi:10.1177/1932296816648344
    5. Ullrich, I. H., & Albrink, M. J. (1985). The effect of dietary fiber and other factors on insulin response: role in obesity. Journal of Pathology Toxicology and Oncology,5(6), 137-55.
    6. Burke, L. M. (2015). Re-Examining High-Fat Diets for Sports Performance: Did We Call the ‘Nail in the Coffin’ Too Soon? Sports Medicine, 45(S1), 33-49. doi:10.1007/s40279-015-0393-9
    7. Lebrun, C. (2011). Exercise and Type 2 Diabetes: American College of Sports Medicine and the American Diabetes Association: Joint Position Statement. Yearbook of Sports Medicine, 2011, 162-163. doi:10.1016/j.yspm.2011.03.038
    8. Zeevi, D. et al (2015). Personalized Nutrition by Prediction of Glycemic Responses. Cell,163(5), 1079-1094. doi:10.1016/j.cell.2015.11.001
    9. Srikanthan, P., & Karlamangla, A. (2011). Relative Muscle Mass is Inversely Associated with Insulin Resistance and Prediabetes. Findings from the Third National Health and Nutrition Examination Survey. Journal of Clinical Endocrinology & Metabolism. 96(9) 2898-2903. Doi:10.1210/jc.2011-0435
Corrine Malcolm and her donut

The author enjoying a pastry. Photo courtesy of Corrine Malcolm.

There are 47 comments

  1. Andy

    Great article. I am an ultrarunner with lifelong (since age 3, now 50+ years) Type I diabetes. The joys of managing insulin and calorie requirements over 50 or 100 miles is, perhaps, a topic for another article. Let’s just say there are advantages and disadvantages of “teaching” your body to run (literally) with blood sugar levels in the 40s!!

    Of more relevance to the article and the audience, two thoughts: (1) Although being “pre-diabetic” is not good, we should also be mindful of the pertinent outcome measure, namely, health. I doubt there are many data on this, but I would guess that ultrarunners with BGs hovering at 100-110 are far less likely to develop micro-vessel, general cardiac illness, and other maladies associated with diabetes than sedentary folks with the identical BGs. So fitness is a huge protective or mitigating factor; (2) re diet, taking in healthy fats and proteins also (I think) prolongs the absorption and availability of glucose; I would opt for these during races over fiber for obvious reasons!

    Again, kudos to Corrine and iRF for posting good, science-based stuff to chew on!

    1. Jeff

      And I would add that, as a father of two T1 diabetics, blood glucose levels that average in the range of 110 — although higher than normal — look downright fantastic. It all depends on your perspective. I would agree that with a healthy lifestyle, there are probably very few long-term adverse effects.

  2. Dale

    I am a type 2 diabetic and became an runner after developing diabetes and this lead to completing 2 ultramarathons with hopefully many more to come. I do take some medication but mostly control my diabetes with diet and exercise. I am hoping when the Freestyle Libre blood sugar meter becomes available I will be able to get one to continuously monitor my blood sugar. I am especially interested in what my blood sugar does during my long runs and ultramarathons.

    1. KenZ

      Congrats on the ultras! Understood you’re an experiment of one, but would you say diet or exercise plays a greater role? Or are they too coupled to make that call? Just that I’ve heard of people treating type 2 with purely diet, but never purely exercise without a commensurate diet change.

      1. Betsy

        KenZ, I know you were asking Dale… (CONGRATS DALE!) But I really want to weigh in because you’ve asked such a good question. I started the journey and it was 100% diet. (400 pounds, 50(ish) units of lantus/metformin, NO ACTIVITY. Walking into the grocery store put me in a full sweat.) I mean – I was too fat to really move so I didn’t have a choice. :) I know of NO ONE that’s kept it at bay with 100% diet. It eventually seems to creep back in — mostly because of the whole insulin/hormone/muscle bio-mechanics/chemistry thing. PLUS most of the folks I know who had T2/pre and worked with their diet eventually felt good enough to walk, hike, SUP, yoga — something — so activity has crept in. So they’re doing diet/exercise. But as soon as I started walking, then running things were pretty damn even at 50/50. Some days were more one than the other. (Eat too much banana or run too hard and I would have to drink water, go for a walk or eat some strategic/healthy carbs….) But if I can keep carbs in a reasonable window 24/7 (My magic number is 90 +/- grams per day NET) and get moving AND keep my muscles strong — that’s the balance that seems to work. I LOVE talking about this. I know there are other T2/pre folks out there in our ultra world. Wish I could find them.

        1. KenZ

          Hi Betsy- thanks for the response. So to get to your last point: finding other ultra people who were/are T2/pre, I’ve got a funny story. A couple of years ago I ran Spartathlon (a 153 mile ultra in Greece). The morning after finishing, I’m hanging out with three other finishers after breakfast. The female finisher asks me why I started running, and I said to lose weight (I lost 35 lbs, but wasn’t pre or T2). She looks at me and says “I lost 80 lbs,” the guy to my right (and the top american finisher) says “I lost over 100 lbs.” The guy to my left looks sheepish and says “I’ve never been overweight.” Anyway, both the woman who lost 80 and the guy who lost over 100 hold current American records of various types, and we got into a very interesting discussion as to if that actually gave them some sort of advantage, and if that advantage was physical, mental, or both. Physical: could it be that losing that much weight resulted in some superior ability to burn fat as fuel? Mental: could it be that the obsessive-compulsive nature that led to their being overweight was now applied to sport? Anyway, I find the entire thing very fascinating. There are so many great stories to be told in this crazy sport. We all battle our various demons; running is the best way I find to shut mine up!

          1. Betsy Hartley

            OH to have been a fly on that wall! I once had someone tell me ‘you have very strong legs’. I wanted to say — yeah running has done that. But the truth is that I carried 400 pounds around for 10 years. My legs are HELLA strong. :) And battling T2 was GREAT prep for ultras. :) Thank you for replying and sharing this story. Spartathlon is on my bucket list. :)

      2. Dale


        I think they are dependent on each other. I have lost 100 lbs since I was diagnosed n June of 2013 and I think that has the biggest impact. I have tried to control it with just diet and exercise but I can’t get my A1C low enough with out metformin. I eat a mostly based plant diet of vegetables that are low in carbs. I try to get at least 30 to 45 minutes of cardio everyday. Being diagnosed with diabetes probably saved my life by getting me to take a serious look and change my lifestyle. My wife was prediabetic but with the change in diet she is no longer prediabetic and she doesn’t exercise at all and she is also overweight. So for her the change in diet is the most important thing in controlling her blood sugar. I have started traing for a 100 mile ultra this summer and my wife thinks I am crazy. I hope this answers your questions.


  3. Brett

    The title says “Am I going to get (type 2) diabetes from ultrarunning?”. The answer should be a definitive no. You may get diabetes in spite of running. But if you do, you are highly likely to have gotten it anyway due to your lifestyle choices.

    Lets look again at the study: 1,212 ultramarathon runners, only 0.7% reported having diabetes. This is 8 people out of 1,212. As an earlier poster reports, did they have diabetes before they started running? How many of those 8 people are obese? You can be an ultrarunner and still be way overweight. I myself probably could stand to lose 10-15 pounds. If I ever get type 2 diabetes, it won’t be because I run. It will be because of my eating habits, despite my running.

    Which begs the question, how many of those 1,212 ultrarunners would have had type 2 diabetes if not for running? We’ll probably never know the answer to that question.

    But no, ultrarunning does not give you type 2 diabetes.

  4. Mike H

    Thanks, Corinne, for the article. I think this is a sound overview and some good advice on periodization for diet.
    As for specifics to endurance athletes, I think there are some missing and open questions not addressed here (perhaps that’s where your career might take you). For example: “That being said, there is an ideal time and place for these easily digestible, quick-energy foods, and unfortunately it’s not all the time. The current recommendation from the World Health Organization is to limit your added sugar intake to roughly 5% or less of your daily caloric intake.” I thought there would be a natural discussion of nutrient timing regarding glucose uptake right after exercise, and the WHO recommendation bit doesn’t address needs (and conventional approach) for racing or intense or The Srikanthan results are interesting, I think the cited reference is mistyped in your text (8 instead of 9), but it’s critical to note that the findings were on a cross-section and were in regard to skeletal muscle mass *index* (or ratio or percentage) differences (yes, a percent increase of a percentage), rather than raw increase in muscle mass. Testing the latter hypothesis would require an intervention/longitudinal change of individual increases in muscle mass. This is important because we need to know, as endurance athletes, if increasing muscle mass (via weight/resistance training, etc.) is useful or not.

    I think there is interesting work yet to be done and understood in the aging endurance athlete with regard to muscle insulin sensitivity, adipose tissue, and hormonal changes (e.g. menopause/andropause), and I think we need to understand individual longitudinal changes. It is a ripe area for research and discussion, thanks for bringing it up!

  5. Paula Shackles

    I am insulin resistant and prediabetic and started running ten years ago at age 32, before that I was a gym rat for about ten years, so 20 years of exercise. I have trouble fueling runs and having energy. For the last few years just massive fatigue. Both my parents and many other relatives including grandparents and great grandparents were diabetic. I hope to get better and get back to longer races. I would like advice on fueling for runs, if any diabetics out there read this. At the moment considering maybe some green tea with a pinch of sea salt in it? Maybe a little dash of tailwind?

    Eating mostly low carbohydrate, although I do eat fruit, half a nanner, half an apple with peanut butter or something as my pre-run fuel. Would really love to hear what other people are successfully doing.

    1. Corrine Malcolm

      Hi Paula, I would definitely encourage you to reach out to other runners that struggle with insulin resistance and/or a sports dietitian. A few folks have commented above you, and I have several friends who would be happy to help as well, we can hopefully help to connect you guys behind the scenes if that interests you.

        1. Betsy

          Paula! I was trying to get help from other T2’s and those with insulin resistance and finally found solid, useful help with a sports dietician. Other runners are figuring out what works for them and it was endless trial and error and ‘character building’ moments. Wish I would have sought out a sports dietician 2 years ago. Corrine’s right — get connected to someone who knows sports AND DM!

  6. Brian

    It seems to me there is still some debate as to weather high carbohydrate or high fat intake is the cause of type II diabetes or if it is some combination of the 2. Even the overview of the research addressed in this article seems indicate there is not a clear understanding in this regard. Some sources say sugar is the culprit but then I have seen others that suggest it is high fat intake that is the culprit, and this even further confused when many of the things people think of as being loaded with sugar are also loaded with fat (such as the pastry the author is enjoying in the picture). Perhaps it is less about sugar vs fat and more about sugar and fat together in high amounts that leads our bodies down a bad path?

  7. SageCanaday

    I don’t think as many people should be considered about white rice as being bad (many in the world would
    not consider that a highly processed or ‘bad food’). Heck most of the world that regularly consumes rice does not have issues with type II diabetes (and i know many that consume it nearly daily in copious amounts).
    Good points with getting more fiber as well. Of course what we know with glycemic indexes of foods is that they rapidly change with the intake of fiber.

    Final excellent point that Brian brought up: People often don’t realize how much fat they are eating. A donut or ice cream
    isn’t just a “high carb, high refined sugar” treat…it is usually also a very “high fat treat.” and of course high fat diets/food items have been shown to induce insulin resistance and cause these types of health problems. So it is a like a double whammy with eating a donut (I love donuts by the way!)…you are getting very high fat and very high sugar. And your insulin receptors are getting hit really hard.

    1. Corrine Malcolm

      Hi Sage, maybe I should have included processed pasta instead, but similar to potatoes, white processed flour products, they all trend high on the GI index which does cause problems with blood glucose spiking. This is definitely something to be aware of. You are correct, we also eat copious amounts of fat in a lot of that processed food as well, especially if are trending towards baked goods (I know how much butter goes into an excellent croissant), and you’re right it truly isn’t just “too much sugar, too much carb” it’s really just too much junk. A lot of the most recent literature focuses on the sugar/carb side of things, which has gotten increased attention from the LCHF community. Maybe the best summary is simply, experiment and eat good fuel.

      1. SageCanaday

        I was talking about rice specifically…a staple food for millions of people in the world (who incidentally don’t have very many problems with type II diabetes, obesity and heart disease).

        No doubt highly processed packaged food is not ideal for health (and you can include refined sugar in that). Carbs are certainly not created equal though.

        Again though, there is scientific data showing that high fat messes with insulin receptors. Agree a lot of these health/diet problems are for sure from “too much junk.” It’s too many calories period (Standard American diet) usually (which is already over 30% fat) and not enough fiber/fresh fruits/veggies.

        1. SageCanaday

          Typo above: I mean to say “billions of people” eat rice as a staple food (not just “millions”). Again, GI index changes with fiber combinations. A plain steak will spike insulin by itself as well (if you want to just get into GI spikes).

          1. Wolfgang

            Hi Sage,
            I wonder which scientific data you’re referring to ?
            ( no affront please, am just curious )
            High fat definitely does not mess with insulin receptors. Fat is the only macronutrient which doesn’t prompt an insulin response since it’s absorbed via the lymphatic system. On the other hand, eating high fat together with carbs is a bulletproof way for disaster, the carbs are used for energy production ( carbs = sugar in the bloodstream = toxic, hence our body tries to burn them up, whatever carbs are left turns into fat via de novo lipogenesis respectively into plaque via glycation )
            Eating carbs always leads to an insulin surge –> raised insulin means you can’t burn fat (neither stored one nor the one you’re eating together with the carbs) and it will be stored in your fat cells, too.
            The German translation for Diabetes II is “Zuckerkrankheit”.
            Zucker = sugar; Krankheit = illness
            Which explains it nicely, in case you got already full blown Diabetes II or are pre-diabetic, cut out the damn carbs. ALL carbs by the way, even fruits. ( fructose is processed solely by the liver )
            I highly recommend to read Dr. Jason Fung’s blog
            The information is all there.
            Me, I’m not a doctor but health coach and will gladly answer questions ( as far as I know the answer ) should anybody love to get in touch with my – or
            ( as long as you don’t mind my poor English skills of course :-) )
            Best wishes

            1. SageCanaday

              Martin Cox already pretty much hit the nail on the head with his comments (see below) in response to what you said….and I agree what he wrote whole heartedly (pun intended).

              I also will agree that there is a “double whammy” effect of eating a food (usually a highly processed type of dessert) that is very high in Fat AND high in refined sugar. Obviously not healthy for the human body.

              I’ll link to a study here:

              While the “high fat” diets appear to make one more at risk for developing Type II diabetes, the major concern (and this will probably take another 10-15 years with populations just now going LCHF) is what it will do to heart health. Considering what the standard American diet has been for the past few decades (over 30% of calories from fat and often much higher), and the rates of heart disease we are seeing,….well, it could be a disaster for our health care system….at least in the US.

              Finally, like what Martin alluded too, i think people tend to oversimplify when talking about macros only. Most Americans also do not eat enough fiber (fruits and veggies and legumes). They eat too many calories period and gain weight. Fat (gasp) makes people fat (And so does too much sugar…especially refined sugar). Most people eat too much of both.

              A whole foods, plant based diet (usually around 80% whole grain carbs, 10% fat, 10% protein) is the only diet that has been shown to lower the rates of type II diabetes, heart disease, cancer, stroke and obesity. No other diet can say that!

              Finally, any diet that says “eating fruit is bad” is a pretty crappy diet in my book.

          2. Wolfgang

            Hi Sage,

            Thanks for commenting below.
            ( for whatever reason I can not put a reply to your yesterdays post so take this one )

            I really appreciate, value and respect your comment. Which proves that different things work for different people. You vegan approach ( of course in combination with talent, a lot of training and a bunch of other things ) developed you into one of the best MUT runners in the world. On the other hand, my high fat, low carb approach developed the best person I can be.
            I don’t doubt both of us are perfectly healthy (otherwise we couldn’t do the things we do), so who’s right, who’s wrong ?
            From a professional standpoint as a health coach I strongly believe in the things I “preach” and see tremendous success with the people that are willing to follow.
            ( it is always hard to change believes and habits )
            Is it the only way ?
            Well, you don’t have to look any further than to Sage or Martin I suppose :-)
            Guess there are always (at least) 2 sides to look at things: You mention over 30% of calories in the SAD are coming from fat. Fine, what about the other 70% ? Given 10-15% come from protein, wouldn’t it be appropriate to question whether 55 – 60% carbohydrates are the main culprit ? Or is the ratio not important at all as long as we are eating the right, healthy fats & carbs ?

            Out of interest, is there a study which can prove what you mentioned about the
            “whole foods, plant based diet (usually around 80% whole grain carbs, 10% fat, 10% protein) is the only diet that has been shown to lower the rates of type II diabetes, heart disease, cancer, stroke and obesity. No other diet can say that!”
            I couldn’t find one, not a single one. And honestly, I doubt there exists one. Which isn’t meant to blame this kind of eating, it is just a problem to find ( and fund ) studies that really got enough participants, enough time (with the problem participants need to stick to a diet they’re not used to and might not like) to show clear results that compare for example a vegan diet with a carnivore with a ketogenic with a mediterane with a ……..
            ( which was somehow the problem with the study you mentioned, only 9 people from age 22 – 46, no clue what they usually eat, whether they’re smokers, active, …… Main reason why I consider this study to be ### that they get strong medication ( HR-Eli Lilly ) injected during those 6 hours. Insulin causes insulin resistance, not the lipid ( they didn’t mention which sort of lipid, another flaw. could well be poison like sunflower or even worse margarine ! )
            Anyway, all the best to you Sage,
            good luck with training and racing !

            1. SageCanaday

              There are lots and lots of studies over the past decades showing the benefits of a low fat (i.e. under 15% of calories), high carb (plant based), whole grains/legumes diet.
              And that includes stuff like fruit and rice too!

              Here’s one on the reversal of heart disease:

              Are there any studies that demonstrate that a high fat (animal fat based) diet promote long-term health and longevity – or and/or reverse heart disease?

              Getting a little off topic here, but it might also be worth mentioning that when you eat a lot of animal products (higher fat like you seem to be promoting) you are also usually getting a very, very big hit of protein. Too much protein is going to cause a lot of kidney strain over time.

              Best of luck to you too and thanks for the discussion,

      2. Martin Cox

        Interesting stuff, but you seem to have overlooked one glaring physiological fact, and the question “Am I going to get Type 2 Diabetes from ultra-running” would seem to be moot… The biology of Type 2 Diabetes is pretty complex, but most research now suggests that the typical high in animal protein and fat ‘Western diet’ is to blame, and the avoidance of carbs would only make things worse… It’s a very common misconception that too much sugar is the cause Type 2 Diabetes… Muscle cells actually become resistant to the effects of insulin thanks to FAT (not sugar) – fats (known as intramyocellular lipids) build up inside muscle cells, preventing insulin from letting glucose enter the cell… End result – insulin resistance – no matter how much insulin you produce, your fat-compromised muscle cells can’t effectively used it… In short, it’s a high fat diet that can impair the body’s ability to handle sugar…

        1. Wolfgang

          Hi Martin,
          Is that you, the great mountain runner Martin Cox from the UK ? What a pleasure, we met a couple of times running the good old WMRA Mountain Grand Prix back in the day (but of course I was never anywhere close to you)
          What are you up to recently running-wise ?

          Anyway, it’s indeed fat which is causing insulin resistance but not dietary fat but the fat which is produced in the liver via de novo lipogenesis after eating too many carbs. Dietary fat – given it’s from the healthy sort aka olive oil, coconut oil, butter, lard, etc. and not the crapy stuff coming from sunflower, soja, safflower,….. – does never lead to insulin resistance. That’s impossible since it does not provoke insulin at all.
          It’s all the fat from carbs which is leading to insulin resistance.
          You can find a much better explanation than I can give under

          1. Martin Cox

            Hi Wolfgang, Yep, that’s me, not so sure about the ‘great’ though… I’m still racing a lot in the mountains and on the roads, but I’m 48 so I’m not as fast as in the old days! I hope you’re still running well yourself…

            I don’t want to get into a debate about this subject because you have a business which profits from to selling the LCHF/ketogenic/paleo diet to consumers and it’s therefore highly unlikely I’d be able to change your mind on the subject even if I were I to spend hours citing volume upon volume of good evidence based peer reviewed science… But if you are interested in learning just how wrong the likes of Volek & Phinney, Fung, and Mark Sisson might have got things, I’d suggest you start by reading T. Colin Campbell… I do find it interesting though that Tim Noakes, the modern-day Messiah of LCHF – who has said that “carbs are the devil” – hasn’t succeeded in curing his own diabetes with his miracle diet…

            When it comes to athletes, they need both carbs and fats, although I find talking about food in terms of macro nutrients somewhat pointless… I take a holistic view when it comes to an athlete’s nutritional needs and consider what might be called a whole-food plant-based diet optimal… Interestingly, the whole-food plant-based diet has proved to be a highly successful treatment for Type 2 diabetes in the States…

            All the best, Martin.

            1. Wolfgang

              Hi Martin,
              What a pleasure to meet again !
              Last time was……..guess in 2006 when you won the 3 Zinnen Marathon ?
              Time goes by so quickly……
              But you’re too modest, for the people who don’t know Martin, he’s a two time winner of the WMRA Grand Prix (=Mountain Running World Cup), 4th place taker at the Mountain Running World Championships (Innsbruck 2002, freaking steep in the pouring rain !) and winner of numerous races all over the European Alps.
              Thanks for asking, I am still running on a (nearly) daily basis but not much racing any more since I’m working hard to build my Health & Running Coach business while still working full time to support my family.

              The saying goes you should never discuss politics & religion in the public – and maybe we should add diet, too :-)
              Probably neither I can change your opinion nor you mine. But I guess that is perfectly fine since our very own approaches on nutrition seem to work for us pretty well. On the other hand it’s very similar, both of us believe in a whole-food (organic whenever possible/affordable) diet, even if yours more plant-based while I prefer animal food.

              You’re definitely right what you’re saying about athletes and carbs. Carbs are not evil per se, only the overconsumption is. I see them as a tool – a valuable tool when used in the correct manner. ( I guess “..see them as a tool” was first termed by Zach Bitter. He’s blog is worth a reading, just recently he posted a 4-part series “Periodizing nutrition”)
              But building the whole nutritional approach around simple sugars and carbs is receipt for disaster. And no, not even hard training ultrarunners should fall in this trap. You only need to look around at races how many overfat runners take part.
              ( “overfat” fast termed by Dr. Maffetone back in the Seventies. Being overfat does not necessarily mean overweight. A simple measurement of the waist size says it all, more than 50% of ones height indicates too much abdominal fat, hence overfat. Me personally I like to see people 10 – 15% lower than those 50% )

              Sorry, this is a pretty long reply. Since I got lunch break I got the time :-)
              Yes, a couple of years ago I read Dr. Campbells “The China Study”. I can’t recall it too well, guess the main outcome was the Chinese rice eaters are the healthier the less processed grains they eat ? One thing which is pretty important comes to my mind, we always talk about WHAT to eat but never WHEN. Back when I (and you) was a kid we ate 3 times a day: Breakfast, Lunch & Dinner.
              Today people eat all the time, they eat 5, 6 times per day, right from when they raise ’til bedtime. No wonder we see obesity explode, no matter which food you eat. The funny thing about it, people started to put on weight when someone came around proclaiming “You’re too fat and you’re eating 3 times a day. I tell you what, you should better eat 6 times a day and you will lose weight !” Doesn’t that sound pretty stupid ? So people, no more bagels, muffins, energy bars or sports drinks in between !

              Last thing before I let you go, from what I heard Dr. Noakes is off from insulin and other medication following a strict ketogenic diet and intermittent fasting. I’m not sure about that but believe I heard him say in a Podcast his doing fine but his pancreas’ beta cells are irreversible damaged after all those years on a high carb diet he believed to be healthy. Here’s a quote of him: “If you’ve got Lore of Running, tear out the section on nutrition”

              All the best to you too, Martin.
              Let me know in case you’re planning to run in Austria next year, would be a pleasure !

          2. Martin Cox

            Wolfgang, I don’t mind talking about nutrition, it’s a big part of my job… if you want examples of how a whole food plant based diet has been proved beyond all reasonable doubt lower the rates of type II diabetes (and other autoimmune diseases), heart disease, cancer, stroke and obesity then i would suggest you start by reading what Garth Davis has to say on the subject… my own diet is probably about 80% carbs and includes ZERO animal products – this is mainly for ecological and ethical reasons, although the health benefits of a vegan diet undeniable as well… It’s impossible to argue that eating animals is anything other than a really evil thing to do… Do you know why most survivors of the Holocaust are vegan? It’s because they know what it’s like to be treated like an animal…

            1. Wolfgang

              Hi Martin,
              Ethical reasons are a damn good reason for not eating animals, I totally understand that. Even if I wouldn‘t go so far to compare somebody eating animal products with SS/The Hitler regime.
              Once again, good luck with your training, take care!

          3. Brian

            Wolfgang, I just want to point out something here. First off I have read Jason Fung’s Fasting 101 have done some IF as well as extended fasting and have read many of Jason Fung’s blog. What I would like to point out is that in several instances you have said ‘dietary fat does not provoke and insulin at all’. This is one of those cases where Jason Fung contradicts himself quit a bit, because he will say these same things, then later admit that it does just not as much as carbs. The bit that you are you either omitting or overlooking and that Jason Fung downplays to say things like ‘fat doesn’t provoke an insulin response’ is that insulin levels can naturally rise and fall even with no calories being taken in at all. The very thought of eating can cause insulin to rise, so to eating even just straight fat with nothing else will do the same. Jason Fung even discusses this in Fasting 101 when he addresses that insulin levels start low in the morning and rise throughout the day. And this is exactly why he recommends fasting and not just eating nothing but fat throughout the day, because if the goal is to lower insulin then not eating anything is the only way to ensure insulin stays low. Yes, eating fat with no carbs will keep it lower but it does not eliminate it. It is misleading to suggest anything else.

  8. Johnny P

    The title of this article should be “Am I going to get diabetes from eating tons of sugar that I think is justified because I’m active?”. No one will ever get diabetes from ultra running.

    It would be interesting to see a similar study done with athletes from a non-westernized country. Like the Kenyan runners who get most of their calories consuming very simple, processed carbs, but without the rest of the western diet. It would be interesting to see where their blood glucose levels are.

    White rice is getting lumped in with sugary drinks and gummy candy?

  9. Brian

    To add to the comments about the title of the article – it would be nice if you changed the title to specify Type 2 Diabetes right in the title of the article. I found the article via my phone and everything in the headlines just refers to Diabetes (without regard to Type 1 or Type 2).

    As a parent of a 9 year old with Type 1, I am somewhat shocked by the level of misunderstanding (dare I say ignorance) about the differences between Type 1 and Type 2. In my opinion, any article or headline that doesn’t differentiate between the two diseases contributes to the level of misunderstanding that exists.

    And I agree with the other comments, the suggestion that you may get Type 2 Diabetes from ultra-running is ludicrous.

    1. Corrine Malcolm

      Brian thanks so much for your thoughtful comment. We have edited the title, and the second paragraph delineates Type I and Type II diabetes. We definitely included that paragraph from the beginning for that very reason, that there is so much misunderstanding about Type I and Type II diabetes. The title plays off my own personal story, not that running is going to give me Type II diabetes but rather that I personally justify some of my really bad eating habits because I so much. I hope that helps.

  10. Doug K

    a good friend got type II at age 55, he doesn’t run but now walks and bikes daily. His diabetes is completely under control now without drugs, only exercise and diet modifications.
    as a side benefit, he stopped laughing at me for all the running/biking/swimming I do.. ha.

  11. Betsy


    Thank you. Thank you for pulling this together and inviting stories and commentary.

    I have some thoughts from ‘the trenches’. I was 400 pounds. Type 2. Diagnosed with an a1c of 11 and fastings in the 600. Lantus (72 u), metformin (2000 mg), Byetta (20mcg) for over 10 years. Running saved my life. In the early days of adjusting my diet (I didn’t do surgery, I used diet and exercise) I knew I was making a lifetime decision to trade food for meds. And I had to learn which foods were like sugar for my system Experiment of ONE — as you pointed out and I will continue to yell for from the ROOFTOPS! Everyone is so, so different. Where I can not eat pineapple or bananas or rice or a snickers bar — I do OK with dates and apples. I just have to really pay attention.

    I am NO LONGER t2 (it was 4 years this Sept.) No meds, no doc care. :) I lost 220 pounds. I’ve finished my first 100 miler and have attempted 2 others and DNF’ed 75+. But in those early days of being on insulin, running and going longer distances fueling was a NIGHTMARE for me. Do I eat sugar? Calculate a bolus? Go without and hope if I do bonk that some trail angel gets me to my car? Am I low and need fuel or is this a diabetic low that won’t stop until it levels me to the ground? I’m not kidding. I did not have a cgm — but I carried my meter and would test pre-run/post-run and if running and I felt wonky — I’d test to see if I was high/low. I started carrying a hydration pack for 3 mile runs and endured some ridicule — but I was carrying a meter and insulin and sugar…. And for bonus fun — stick your finger to draw blood while you’re running and suddenly you, your pack and possibly the surrounding area look like a crime scene from the oxygenated blood. :) I had close friends who knew I was trying to reverse the disease and that every run was going to be a crap shoot. and they supported me 100%. And learned to know the sings of grumpy runner/bad run VS DIABETIC EMERGENCY. I honestly don’t know how I got through itall and wish I would have taken better notes and written about it more. And then sliding off of insulin and using JUST food for fueling was another level of intrigue and fear and mystery. Remains a prominent issue these days to be honest. I am still classified insulin resistant because of my history, not because of current #’s. (Aic is 4.9, fasting are very typically 82-86) I have recently started work with a sports dietician to help me figure out how to change my way of eating to support my running better and how to fuel as a has-been-diabetic who very literally is probably just a few steps ahead of it at this point…

    I thought this article was thought provoking for those who don’t start their version of healthy in the kitchen…. Running is a tool. And the food we choose to sustain life and fuel those endeavors is a pretty important pedestal in the foundation. I hope some other T2’s write in. I would love to find others who have found running and battled T2.

    1. Andy

      Huge congrats to you in your successes in running and managing T2!! As a T1, I can certainly related to the challenges of running with meters, testing on the trail, managing epic BG bonks, etc — have lived this way for 50+ yrs and have now survived 35 or so ultras over the past 8 seasons. Managing calories, hydration, etc. over 50 or 100 miles is hard enough, but add in DM and it’s another level altogether! Would be happy to connect back-channel to compare notes and strategies.

      1. Betsy

        PLEASE! I have a good friend running ultra’s who is T1 and struggling. Frustrated and swinging highs/lows. And I’m no help except that I can help manage an emergency. Which is not a whole lot of fun for either of us. I would love to make a connection and get some support as I figure out how to do this thing and not create a welcoming environment for T2… or Facebook. :)

  12. David

    Thanks for the article. With the high tax digestive, endocrine, and urinary system take on race days (especially hot and high altitude races), its good to think about how to manage the stress on the hidden aspects of the body.
    Keep up the good thoughts

  13. DJ

    Of course these endless debates regarding ‘food’ is, once again, a typical ‘first world’ issue….

    I spent 2 years living in a village in Indonesia. People lived to a good (and quality of life) old age, mostly eating (as Sage points out) a diet of rice, fruit and vegetables – occasionally some fish and (on high days and holidays) some meat. They had zero problems with that western thing called diabetes. They also spent most days doing quite hard physical labour and they slept for 10 – 12 hours per day.

    The rich living in cities ( Jakarta etc) , drinking coke, eating less fruit and veg and consuming a typical western diet due to a misplaced idea of ‘status’ have a shorter life expectancy and only hang in there due to thier ability to afford high standard health care.

    You can’t talk about diet without looking at the massive majority of the worlds population that have (largely) plant based eating habits plus consuming (often huge!) amounts of white rice, corn or potatoes – minus any health problems!

    It’s worth noting that the USA is not at the heart of every topic – with all (or any) of the answers…after all life expectancy is dropping in your country. Pretty damn frightening!

  14. Kathy

    Timely article. I have wonderful lab results in every regard. My doc raves about them. But as an endurance athlete, I take a closer look at many of the values (e.g., iron, vit d, etc). The only one that brings a frown to my face is the glucose. They hover in high nighties and have for decades. These are fasting levels. I did a glucose fasting test once (ugh, that was awful) and no problems noted. So, this article was very helpful. By the way, I eat very little sugar, very little processed food and carbs, and eat a high amount of fiber. When exercising I stay away from the gels, etc and only use them during races or perhaps a few high volume/ intensity (5hour + bike or 3 hour +run) workouts per year. I have had genetic testing done and no diabetes type stuff there or on a personal level.Thus, I am another data point in this whole mix. This article (and comments) have been very helpful.

  15. Gordo

    Good article, and good recommendations … but … the “tired pancreas” theory of insulin resistance/T2DM has largely been retired. The latest thinking is that an excess of calories is to blame. When fat is stored in the liver and pancreas, it disturbs their function. Note that this theory explains why you see skinny people with T2 and obese people without – they have different thresholds for partitioning fat to body stores vs organ stores. It also explains why you can become diabetic on either a high-fat or a low-fat diet. There’s even a plausible link with processed foods – which are calorie dense, low in fiber, engineered to be binge-worthy, and are low in nutrients. Any of those can lead to over consumption. Taken together, it’s almost a perfect storm for over eating. Eating more than your body can handle at any given time leads to fat storage. If you lost the genetic lottery, it goes into your pancreas and liver. Those folks need to learn to pace their eating appropriately.

  16. John Andersen

    Great article! Follow up question, and this is so Ultra-endurance specific that i wonder if there is even evidence-based information about it:
    So let’s say my diet and exercise is great, i am far from prone to type II DM. What are the effects of us eating so much sugar DURING our races and training? On my two long runs per week, i am often guzzling down sugary drinks (Tailwind/rocktane, etc) as well as candy bars, etc to keep me fueled appropriately DURING the run. Our bodies do process sugar differently WHILE we are exercising, but often when I’m eating a snickers bar on a morning run or downing my 10th bottle of Tailwind during a 100 miler, i often think “what is the consequence of this?” (And let’s please stay away from comments about being more fat adapted;) – I’m talking about when we are running hard and needing quick carbs for performance:) Thx in advance for thoughts!

  17. Octavia Henderson

    Hi Corrine,

    Thank you for the insightful article. In school (exercise science) I was always taught that type 2 only stemmed from poor eating choices and lack of activity. While I completely understand that one can never out exercise poor eating choices, getting a deeper understanding of the physiological of type 2 diabetes concerning genetics and/or an adaptive response of endurance athletes would be amazing.

    I’m an avid runner and marathoner and have been eating lower carb (i.e. roughly 25% of my daily caloric intake is carbs) for over 8 years. I was recently shocked during an annual physical when my labs (fasting) came back showing my A1C at 5.8%. I expressed concern about this to my health care professional, but who only had the usual generic response of eat healthy and exercise more. I’m not asking for medical of course, but I was wondering if you came across any research specifically concerning endurance athletes and type 2? I’ve run (no pun intended) across information concerning type 1, but not 2.

    Thanks so much for your article.

  18. Louan Minzner

    Thank you for this insightful and illuminating blog. I am an endurance athlete, 55 years old, training for a marathon in October, and pre-diabetic. Several months ago I came across information about a subset of diabetes called lean diabetes, which affects 10-15% of type II diabetics. My bmi is under 21. My dad developed diabetes in his 50s and he was also lean and active (though not as active as me). Next week I am starting a BG monitoring system for two weeks so I am excited to see what kinds of trends I can spot. I am really hoping that bananas spike my BS but chocolate cake doesn’t (that might just be wishful thinking). I avoid the sugary sports drinks and gels, opting for smoothies with whole fruit and beets before runs. I do have a sweet tooth but have been trying to sub in low sugar/stevia substitutes.

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