HbA1c and Liver Fat After 16 Weeks of Fasted versus Fed Exercise Training in Adults With Type 2 Diabetes.

Purpose: Exercise-nutrient timing is of interest for people with type 2 diabetes (T2D) as a potential method to optimize glycemic control. However, the optimal nutritional environment for exercise is not well understood over the long term. The Fasted Exercise for Type 2 Diabetes (FED) Trial compared 16 wk of fasted versus postprandial morning exercise on glycated hemoglobin (HbA1c) and liver proton density fat fraction (PDFF).

Methods: Twenty adults with T2D were recruited and randomized to complete exercise after an overnight fast versus after their morning meal. Participants walked three mornings per week, progressing to 180 min·wk -1 over 16 wk.

Results: Groups were balanced with five males and five females each. Sixteen participants completed the trial (8 in each group, 50% female). Age, HbA1c, and PDFF were 59.8 ± 9.0 yr, 7.2 ± 0.7%, and 9.3 ± 4.1%, respectively. On average, both groups completed 98% of their walking sessions but there was no change in HbA1c (-0.2%, P = 0.588). However, one participant from each group had changes in their glucose-lowering medication during the trial, and when excluded, the fasted training group had greater improvements in HbA1c compared with the postprandial group (-0.3% vs 0.0%, P = 0.033). There was no difference in changes in liver PDFF between groups (-1.6% vs 0.3%, P = 0.221) but visceral fat and intramuscular fat decreased to a greater extent after fasted exercise.

Conclusions: Although our study had a small sample size, it suggests that exercise after an overnight fast can have high adherence and represents an option for people with T2D to improve longer-term indicators of glycemia and ectopic fat depots.