Post-Exercise Carbohydrate-Energy Replacement Attenuates Insulin Sensitivity and Glucose Tolerance the Following Morning in Healthy Adults

Abstract

The carbohydrate deficit induced by exercise is thought to play a key role in increased post-exercise insulin action. However, the effects of replacing carbohydrate utilized during exercise on postprandial glycaemia and insulin sensitivity are yet to be determined. This study therefore isolated the extent to which the insulin-sensitizing effects of exercise are dependent on the carbohydrate deficit induced by exercise, relative to other exercise-mediated mechanisms. Fourteen healthy adults performed a 90-min run at 70% trueV˙O2max starting at 1600–1700 h before ingesting either a non-caloric artificially-sweetened placebo solution (CHO-DEFICIT) or a 15% carbohydrate solution (CHO-REPLACE; 221.4 ± 59.3 g maltodextrin) to precisely replace the measured quantity of carbohydrate oxidized during exercise. The alternate treatment was then applied one week later in a randomized, placebo-controlled, and double-blinded crossover design. A standardized low-carbohydrate evening meal was consumed in both trials before overnight recovery ahead of a two-hour oral glucose tolerance test (OGTT) the following morning to assess glycemic and insulinemic responses to feeding. Compared to the CHO-DEFICIT condition, CHO-REPLACE increased the incremental area under the plasma glucose curve by a mean difference of 68 mmol·L−1 (95% CI: 4 to 132 mmol·L−1; p = 0.040) and decreased the Matsuda insulin sensitivity index by a mean difference of −2 au (95% CI: −1 to −3 au; p = 0.001). This is the first study to demonstrate that post-exercise feeding to replaceme the carbohydrate expended during exercise can attenuate glucose tolerance and insulin sensitivity the following morning. The mechanism through which exercise improves insulin sensitivity is therefore (at least in part) dependent on carbohydrate availability and so the day-to-day metabolic health benefits of exercise might be best attained by maintaining a carbohydrate deficit overnight.

Dietary sugars, exercise and hepatic carbohydrate metabolism

“…Furthermore, during non-exercise conditions, the increase in postprandial liver glycogen concentrations seen with a 7 d high-glycaemic index diet occurs in tandem with increases in liver fat content ( 101 ) . The proposed relationship between liver glycogen and lipid metabolism supports the idea that regular exercise can obliterate the negative effects of fructose overfeeding in healthy men ( 8 , 69 ) , since exercise results in rapid glycogen turnover, and there is clear evidence that the carbohydrate deficit from exercise is a key factor in exercise-induced increases in whole-body glucose control ( 102 ) .…”

Immediate post-breakfast physical activity improves interstitial postprandial glycemia: a comparison of different activity-meal timings

“…In healthy individuals, ingestion of carbohydrate prior to exercise has in some studies blunted improvements in fitness or performance adaptations [21,35,40] but, in the context of glucose control, the optimal activity-meal timing is unclear. The earliest work examined 1 h of cycling in 10 men with diabetes [33,34].…”

Sources of Inter-individual Variability in the Therapeutic Response of Blood Glucose Control to Exercise in Type 2 Diabetes: Going Beyond Exercise Dose

“…That said, Chacko’s points are specific to the acute response to exercise. In healthy individuals, ingestion of carbohydrate prior to exercise has been shown to blunt adaptations to training ( Van Proeyen et al, 2010 ) as well as acute bouts of exercise ( Gonzalez et al, 2013 ; Taylor et al, 2018 ). Thus optimal benefit may be conferred from fasted exercise.…”