by Sheri Colberg, Ph.D., FACSM
A study published in Diabetologia in October 2016 (1) discussed whether exercise training is more important than other lifestyle changes in preventing type 2 diabetes (and possibly reversing prediabetes). Honestly, I was very heartened by its findings.
Although the Diabetes Prevention Program (DPP) was able to establish that lifestyle changes (that included a lower calorie and lower fat diet, exercise and weight loss) as the primary means to prevent type 2 diabetes in at-risk adults, the researchers on this study wanted to find out how much of that preventative effect is actually attributable to physical activity alone. They also studied whether the type of activity undertaken (moderate vs. vigorous) is better for blood glucose homeostasis in 237 adults, ages 45 to 75, who were sedentary and non-smokers, but had prediabetes (diagnosed with elevated fasting glucose levels).
Participants were assigned randomly into one of four exercise groups for six months: (1) a low amount of exercise at a moderate intensity (the equivalent of walking ∼8.6 miles per week); (2) a high amount at the same moderate intensity (like walking 13.8 miles per week); (3) a high amount of exercise at a vigorous intensity (the caloric equivalent to group 2, but with vigorous-intensity exercise; and (4) dietary changes plus a low amount of moderate exercise like group 1, but with diet and weight loss (7%) to mimic the first 6 months of the DPP.
The conclusions based on their results when they measured the participants’ ability to handle a glucose load after six months (an oral glucose tolerance test) were these: a high amount of moderate-intensity exercise alone was very effective at improving oral glucose tolerance despite a relatively modest 4.4 lb (2 kg) loss of body fat. In other words, walking ∼13.8 miles at a moderate intensity per week was found to be nearly as effective as a more intensive, DPP-like approach of moderating diet, exercising, and losing weight when it comes to preventing type 2 diabetes in adults who already have prediabetes.
One thing of note was that dietary changes and weight loss may contribute more to changes in fasting glucose than exercise does. In these participants, only the full DPP lifestyle change group experienced a significant reduction in their fasting blood glucose levels. This finding was expected, though, as impaired fasting glucose is generally indicative of hepatic insulin resistance, whereas impaired glucose tolerance reflects peripheral (muscle) insulin resistance.
So, why do these results matter? Many people at risk for developing type 2 diabetes are sedentary and either unwilling or unable to participate in high-intensity exercise training, even though high-intensity interval training is the latest fitness fad. Luckily for them, all these adults may really need to do is walk enough at a moderate pace to prevent type 2 diabetes, and doing that is much more sustainable over a lifetime than vigorous training. It’s a lot easier to keep up walking regularly than worry about making a lot of other lifestyle changes at the same time.
A meta-analysis in the same journal issue reinforced this idea (2). That analysis also found that adults who are the least active to start out with benefit the most in terms of diabetes prevention from doing any level of physical activity is reassuring. Of course, doing more is better, but in a nonlinear manner. While it appears to lower risk to do more activity, the meta-analysis suggests that people are not required to get insane amounts of weekly activity just to lower their diabetes risk enough to matter. In that case, increasing physical activity opportunities with the built environment may work to lower diabetes risk at the population level.
Again, while vigorous intensity is superior for improvements in cardiorespiratory fitness, for the majority of adults, it’s a good thing that moderate-intensity exercise may be better than the same caloric equivalent of vigorous-intensity exercise for maintaining cardiometabolic health and preventing the development of diabetes in at-risk individuals (1) and that the most sedentary individuals have the most to gain by simply becoming more active, even if it’s just doing moderate walking (2). Vigorous training is certainly not for everyone, but at least it appears that you may be able to keep diabetes at bay by walking the equivalent of 30 to 60 minutes at a moderate pace most days of the week. So, stop reading this article and go take a walk!
(1) Slentz, C.A., Bateman, L.A., Willis, L.H. et al. Effects of exercise training alone vs a combined exercise and nutritional lifestyle intervention on glucose homeostasis in prediabetic individuals: a randomised controlled trial. Diabetologia 2016; 59: 2088. doi:10.1007/s00125-016-4051-z
(2) Smith AD, Crippa A, Woodcock J, Brage S: Physical activity and incident type 2 diabetes mellitus: a systematic review and dose-response meta-analysis of prospective cohort studies. Diabetologia 2016; Oct 17 [epub ahead of print]
In addition to my educational web site, Diabetes Motion (www.diabetesmotion.com), I also recently founded an academy for fitness and other professionals seeking continuing education enabling them to effectively work with people with diabetes and exercise: Diabetes Motion Academy, accessible at www.dmacademy.com. Please visit those sites and my personal one (www.shericolberg.com) for more useful information about being active with diabetes.