Low-carb enthusiasts, passionate Reddit threads, and that one guy at the gym all say that athletes are at risk for diabetes. Is it true?
In a small-scale, 2016 study, researchers monitored the blood glucose levels (blood sugar) of 10 “subelite athletes” with a training schedule consisting of about 6 hours/week.
These athletes wore the monitor for 6 consecutive days. Based on VO2MAX and resting heart rate, they appear to be representative of an active population.
The head researcher is an endurance athlete herself, and according to an interview with Outside Magazine, she conducted this study to see if athletes could become “bonk-proof” by monitoring blood glucose levels during events.
She anticipated that with careful timing, she could dial her calorie intake into an optimal range.
She expected she would find that endurance athletes would have, on average, lower blood glucose levels than sedentary people. She found the exact opposite.
During her study, 4/10 athletes spent “more than 70% of the total monitoring time above 6.0 mmol/L even with the 2-hour period after meals is excluded. Fasting BG was also in the ADA defined prediabetes range for 3/10 athletes.” (Thomas, et al.)
The 6.0 mmol/L figure is important because the World Health Organization (WHO) defines normal glycemia as fasting glucose less than 6.1 mmol/L and recommends that glucose be <7.8 mmol/L 2 hours after a 75 g oral glucose tolerance test (OGTT) test.
The researcher concluded that for athletes, high blood glucose levels appear to be of greater concern—not less.
It was then inferred that this study suggests that athletes are more susceptible to diabetes than the average population.
And there is no shortage of case studies to support this claim, including endurance swimmer and cyclist, Peter Attia and runner Tim Noakes, as well as a host of Reddit threads.
Are athletes at high-risk for type 2 diabetes?
Clearly, it is physically possible for athletes to become prediabetetic, experience insulin resistance, and suffer from diabetes.
The observation that athletes can develop diabetes may be surprising.
But, the question at hand is whether athletes are more susceptible than other populations. The answer? Absolutely not!
And instead of citing my one friend Jan who read a blog post by a stock trader who cut sugar out of his diet last month and just feels oh-so-good now, I’ll show you some research.
Despite what’s trending on Quora, the vast majority of scientific literature does not suggest athletes are at greater risk for diabetes.
The bulk of scientists and health professionals claim that obesity, inactivity, and genetics are the three key risk factors for developing Type 2 diabetes.
Being an elite athlete who eats carbohydrates isn’t on their list.
Actually, research shows that exercise is critical for diabetes management. (Shugart, et al.)
A 2014 study of 1,212 ultramarathon runners found that only a mere 0.7% reported having diabetes, compared to 9.4% of Americans with the disease. (CDC)
To say that diabetes is less frequent in endurance athletes is an astounding understatement.
The study also found that compared with self-reported data from the general population, the prevalence of virtually all chronic diseases and mental health disorders appeared lower in the ultramarathon runners. (Hoffman)
But you likely don’t need to read Hoffman’s report to see this trend for yourself.
- Consider how many sedentary people you know with diabetes.
- Then, jot down how many people you know who exercise regularly (at least 3 times a week) with diabetes.
- After that, right down how many competitive athletes you know with diabetes.
While it is certainly possible for athletes to develop Type 2 diabetes, there is no compelling research to suggest they are more susceptible to diabetes than other populations.
Certainly, the fact remains that athletes have a very low risk of the disease.
Problems with the study
So, what do we make of the study that fueled this discussion? A lot of assumptions were made that led to the conclusion that athletes are at high-risk for diabetes.
Assumption #1: High blood glucose levels indicate you’re on track for diabetes.
Perhaps these athletes showed a higher average BGL throughout the day simply because they ate more calories or consumed calories more frequently.
It could even be possible that healthy BGL for athletes differs from sedentary populations, or that a high BGL doesn’t necessarily indicate insulin resistance in athletes.
Assumption #2: Blood glucose level averages are an accurate way to measure health.
Researchers reported that even without taking into account the two-hour period after eating, 4/10 athletes still had higher-than-normal BGL. What wasn’t made clear was what constituted as a “meal.”
For example, snacks eaten throughout the day or performance drinks during exercise will, of course, elevate BGL. For an athlete consuming upward of 4,000 cal/day, it may be difficult to avoid skewing results simply due to continuous calorie intake.
And by the way, exercise will slightly elevate BGL in nondiabetic people for up to an hour after exercise.
Therefore, an athlete’s average BGL may not be the best method to diagnose prediabetes in an active population.
Assumption #3: Blood glucose levels from a small sample (with considerable variation in lifestyle) offers enough information to draw a conclusion.
At only 10 participants, the sample size was very small, and yet, there was an incredible amount of variation between subjects.
Out of the four athletes who were in the prediabetic range, two were the most active out of the cohort. The other two were among the least active.
One participant ate over 4,000 cal/day, while another consumed only 1,800 cal/day.
One athlete consumed 3x the recommended amount of sugar and yet had a BGL in the normal range, while another consumed less than the recommended daily carbohydrate intake and was in the prediabetic range.
There were too many variables and too few participants to infer that athletes are at high risk of diabetes.
So what does this all mean?
While outliers exist, the majority of the scientific community agrees that athletes are, in broad strokes, less likely to form diabetes.
Body composition and exercise are still two out of the three determining factors of diabetes and prediabetes.
But what these studies do show is that even elite athletes are not immune to diabetes. After all, genetics is the third determining factor, and you don’t really have much of a say in that department.
This study shows that athletes are not immune to diabetes. It does not suggest athletes are unusually susceptible to diabetes.
But just because something is possible doesn’t make it probable. As an athlete, you are still the least likely demographic to acquire insulin resistance. Despite how many carbohydrates you consume.
And of course, for every account of a single competitive athlete with insulin sensitivity, there are tenfold (hundredfold? Maybe thousandfold?) case studies of competitive athletes who consume insulin-spiking carbohydrate during and after exercise and do not have, and will never have, type 2 diabetes, prediabetes, or any form of insulin resistance.
Just because something is possible doesn’t mean it’s inevitable. It doesn’t even mean it’s likely.
Should this research influence how I consume carbohydrates?
No, the study of 10 sub-elite athletes shouldn’t impact your diet.
But your relationship to the three determining factors of Type 2 diabetes just might.
Three key factors of diabetes:
- Inactivity
- Body composition
- Genetics
If you don’t exercise, then YES, you absolutely should worry about Type 2 diabetes.
If you exercise regularly but still carry an unhealthy amount of fat, then yes, you should be concerned about Type 2 diabetes.
And if you have a family history of diabetes and are otherwise healthy, you should consider monitoring your carbohydrate intake.
Should athletes avoid sugar and carbohydrates?
Of course not! If you have no family history of diabetes, if you carry a healthy amount of fat, and if you exercise regularly, you have no reason to avoid carbohydrates.
If you are a passionate endurance athlete, you need carbohydrates.
While there is disagreement over the optimal diet for endurance sports, most experts agree that simple sugars and carbohydrates are critical for top performance.
Carbohydrates don’t cause weight gain, excess body fat, or adverse blood lipid profiles. On the contrary, carbohydrates are the preferred source of fuel during high intensity, anaerobic exercises.
However, if you’re concerned about diabetes or you want to increase your performance, you may want to be mindful when you’re consuming carbohydrates. How your body uses fuel depends on the timing of carbohydrate intake.
And lastly, don’t buy into the idea that every time you so much as lift a weight you need a recovery drink.
You don’t need a handful of gummy bears to walk to the mailbox. But if you have some anyway, try to time your sugar rush with your training.
Matt Mosman (MS, CISSN, CSCS) is a research scientist, endurance athlete, and the founder and Chief Endurance Officer at EndurElite. Matt holds his B.S. in Exercise Science from Creighton University and his M.S. in Exercise Physiology from the University of California. Matt and his family reside in Spearfish South Dakota, where they enjoy running, mountain biking, camping, and all the outdoor adventures Spearfish has to offer.
References:
- Adams OP. The impact of brief high-intensity exercise on blood glucose levels. Diabetes Metab Syndr Obes. 2013;6:113–122. doi:10.2147/DMSO.S29222
- New CDC report: More than 100 million Americans have diabetes or prediabetes. July 18, 2017
- Hoffman MD, Krishnan E. Health and exercise-related medical issues among 1,212 ultramarathon runners: baseline findings from the Ultrarunners Longitudinal TRAcking (ULTRA) Study. PLoS One. 2014;9(1):e83867. Published 2014 Jan 8. doi:10.1371/journal.pone.0083867
- Shugart C, Jackson J, Fields KB. Diabetes in sports. Sports Health. 2010;2(1):29–38. doi:10.1177/1941738109347974
- Thomas F, Pretty CG, Desaive T, Chase JG. Blood Glucose Levels of Subelite Athletes During 6 Days of Free Living. J Diabetes Sci Technol. 2016;10(6):1335–1343. Published 2016 Nov 1. doi:10.1177/1932296816648344
- World Health Organization. Definition and Diagnosis of Diabetes Mellitus and Intermediate Hyperglycemia. Geneva, Switzerland: World Health Organization; 2006. [Google Scholar]
