Research has shown that a single session of exercise can improve insulin sensitivity and reduce blood sugar levels over 24 hours (24hr glycemia) in adults living with obesity who are at risk for type 2 diabetes. However, the extent to which post-exercise nutrition influences these beneficial effects remains unclear.
Now Jenna Gillen, an associate professor in the Faculty of Kinesiology and Physical Education at the University of Toronto, and her doctoral student Alexa Govette are examining whether the macronutrient composition of a post-exercise snack – specifically, snacks with high versus low carbohydrate content – can moderate blood sugar levels over 24 hours and next-day insulin resistance.
“Our findings suggest that consuming a low versus high-carbohydrate post-exercise snack better supports exercise-induced improvements in insulin resistance in women living with obesity who may be at risk for type 2 diabetes,” says Gillen, who specializes in exercise physiology.
Gillen and Govette recruited twenty women living with obesity, who completed two metabolic trials while they were in the mid-follicular phase of two consecutive menstrual cycles. For both metabolic trials, the participants were provided with prepared diets to consume during the 24 hours before and after exercise so that the only difference in diet between trials was the post-exercise snack.
Following a 12-hour overnight fast, the study participants performed high-intensity interval exercise consisting of 10 one-minute cycling intervals at 90 per cent maximal heart rate, interspersed with one-minute recovery breaks. Immediately following exercise, half of the participants consumed a single serving of low-carbohydrate Greek yogurt and half consumed a high-carbohydrate pudding of matching energy value.
Blood samples were taken after the post-exercise snack and the next morning when the study participants returned to the lab to measure glucose, insulin and the homeostatic model assessment of insulin resistance (HOMA-IR). Continuous glucose monitoring measured blood sugar levels over 24 hours following exercise.
The researchers were not surprised to discover that during the three-hour period following the post-exercise snack, average levels of glucose and insulin concentrations were lower after consuming the low-carbohydrate Greek yogurt versus the high-carbohydrate pudding.
“We were most interested in learning whether the post-exercise snack influenced blood sugar after this initial three-hour period,” says Gillen. “Interestingly, while the average 24-hour glucose was the same among all the study participants, next-day fasting insulin resistance (measured by HOMA-IR) was lower in those who consumed low-carbohydrate Greek yogurt versus high-carbohydrate pudding.”
In addition to glycemic control and insulin resistance, the researchers also measured the effects of post-exercise Greek yogurt on other metabolic and musculoskeletal health outcomes, including post-exercise fat oxidation and blood markers of bone turnover.
While this analysis is ongoing, Govette is preparing to present existing data from the research at the 2025 Diabetes Canada and Canadian Society of Endocrinology and Metabolism (CSEM) Professional Conference held in Toronto at the end of November.
This research project was funded by the Dairy Farmers of Canada.
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