Is Fasting Before Exercise Effective to Reduce the Risk of Diabetes?

Kathryn Adel February 10, 2020 Diabetes, Eat Well, Health, sports

A recently published study suggests that training on an empty stomach improves insulin sensitivity and can therefore help reduce the risk of type 2 diabetes. But is that really the case? Let’s dive into this subject!

A recent study looked at the link between the timing of breakfast and the metabolic benefits linked to exercise. To do this, thirty sedentary and overweight or obese men were divided into three groups. The control group continued to be sedentary. The other two groups were supervised during 30 to 50 minutes of moderate-intensity morning exercise (on a treadmill) three times a week, for six weeks, without eating breakfast. Subjects in the second group ingested a carbohydrate-rich vanilla flavored drink (1.3 g of carbohydrates per kg of body weight) two hours before each exercise session and a vanilla-flavored placebo drink containing no carbohydrates after their exercise. The subjects in the third group did the opposite, that is, they did their exercise on an empty stomach by consuming the carbohydrate-free placebo drink before their workout and the carbohydrate-rich drink after their workout.

As expected, the sedentary control group did not improve either their fitness or their insulin sensitivity during these six weeks. The subjects who did their training on an empty stomach (the third group) used more fat as a source of energy during their exercise as compared to the subjects who consumed carbohydrates before their training (the second group), which is normal since, when carbohydrates are not available, the body must tap into its fat stores to produce energy. On the other hand, there was no difference in terms of weight loss and fat loss between subjects who fasted before their exercise and those who consumed carbohydrates before their workout. This suggests that fasting prior to exercise does not allow one to lose more fat when compared to eating before a workout if the total amount of calories consumed per day remains the same. What is more interesting is that the subjects who fasted before exercise saw their insulin sensitivity improve more as compared to those who consumed carbohydrates before their workout, which is to say that their cells did not need to secrete as much insulin to lower their blood sugar. Therefore, fasting before exercise could be beneficial in helping to improve blood sugar control.

Photo: “Person Holding Black Tube”, PhotoMIX Ltd., ©

However, it is not mandatory to train on an empty stomach. According to a review of twelve clinical studies including 135 participants with type 2 diabetes, exercising after a meal is effective in improving blood sugar control. The greatest benefits appear to be seen after performing moderate-intensity aerobic physical activity (i.e. cardiovascular activity) lasting 45 minutes or more, or similarly after performing strength training exercises.

It is well established that any physical activity, regardless of the duration, intensity, or time of day during which it is practiced, is beneficial for health and contributes to improving blood sugar control and preventing long-term complications of type 2 diabetes. Some people may even normalize their blood sugar levels and be able to lower their medication or even stop taking it altogether. Physical activity is an integral part of diabetes treatment just like a balanced diet and medication. The most important aspect is to exercise regularly. Thus, you should choose the time of day that works best for you according to your schedule so that you can exercise regularly, regardless of whether it is before or after a meal. Ideally, it is recommended that you do at least 150 minutes of cardiovascular exercise and two strength exercise sessions per week. However, if that is not possible for you, know that even just ten minutes of exercise a day can still be beneficial!

In people with type 2 diabetes, supervised exercise programs are particularly effective in improving blood sugar control, reducing the need for medication, and enabling sustained weight loss. Do not hesitate to reach out to a kinesiologist who can help you. Combining physical activity and a balanced diet is certainly a winning choice. SOSCuisine offers meal plans that can help you improve your blood sugar control.

References

• Edinburgh et coll. (2020) Lipid metabolism links nutrient-exercise timing to insulin sensitivity in men classified as overweight or obese. J Clin Endocrinol Metab;105(3).
• Boniol et coll. (2017) Physical activity and change in fasting glucose and HbA1c: a quantitative meta-analysis of randomized trials. Acta Diabetol; 54(11):983-991.
• Berror et coll (2018) The Effects of Postprandial Exercise on Glucose Control in Individuals with Type 2 Diabetes: A Systematic Review. Sports Med;48(6):1479-1491.
• Arsa et coll. (2015) Effects of prior exercise on glycemic responses following carbohydrate ingestion in individuals with type 2 diabetes. J Clin Transl Res;1(1):22-30.
• Gilbertson et coll. (2018) Glucose Tolerance is Linked to Postprandial Fuel Use Independent of Exercise Dose. Med Sci Sports Exerc; 50(10):2058-66.
• Association canadienne du diabète (2013). Activité physique et diabète. Comité d’experts des Lignes directrices de pratique clinique de l’Association canadienne du diabète. Can J Diabetes; 37:S403-S408.

Author

Kathryn Adel

Kathryn holds a Bachelor Degree in Nutrition as well as a Bachelor and a Master Degree in Kinesiology, all from Laval University. She is a Registered Dietitian and active member of the Ordre professionnel des Diététistes Nutritionnistes du Québec (ODNQ) and of the American Academy of Nutrition and Dietetics. She holds the Monash University's certification for the FODMAP diet and IBS, and has considerable clinical experience in that area. She is also an accomplished athlete, having ran track and cross-country at a national level. Kathryn specializes in sports nutrition, weight loss, diabetes, as well as heart and gastrointestinal health.