Purpose: Previous exercise reduces the lipemic response to meals of fixed size. It is not known whether this triglyceride (TG) attenuation also occurs in response to ad libitum feeding because exercise might induce a compensatory increase in energy intake. It is also unclear whether the effects of a single exercise session on lipemia would be augmented by repeated exercise sessions on consecutive days.
Design: Ten sedentary overweight/obese men (aged 35 ± 6 yr) each participated in three 4-d trials in random order: CON (no exercise on days 1-3), EX-1 (exercise session on day 3), and EX-3 (exercise sessions on days 1-3). Each exercise session expended 33.5 kJ·kg−¹ body mass. Subjects consumed an isocaloric diet (provided by experimenters) and avoided alcohol on days 1-3 of all trials. On day 4 of each trial, participants underwent a 7-h metabolic assessment, during which an ad libitum buffet breakfast and lunch was provided, and postprandial plasma and expired air responses were assessed.
Results: Day 4 ad libitum energy intake was higher than CON in EX-3 (9216 ± 669 vs 7859 ± 492 kJ, P < 0.05) but not EX-1 (8335 ± 683 kJ). Postprandial TG responses were 27% and 25% lower in EX-1 and EX-3, respectively, than in CON (both P < 0.05), and postprandial insulin responses were 26% (P = 0.06) and 31% (P < 0.05) lower in EX-1 and EX-3, respectively, than in CON. Compared with CON, postprandial fat oxidation was 20% higher in EX-1 and 27% higher in EX-3 (both P < 0.05).
Conclusions: Previous exercise attenuates the lipemic response to ad libitum meals, suggesting that exercise's TG-lowering effect will extend into "real-world" settings where food intake is not carefully controlled. This response is not augmented by exercising on repeated days.