We sought to determine whether lipolysis, fatty acid (FA) mobilization, and plasma FA oxidation would remain elevated for hours following isoenergetic exercise bouts of different intensities. Ten men and eight women received a primed-continuous infusion of [1,1,2,3,3-2 H 5 ]glycerol and continuous infusion of [1-13 C]palmitate to measure glycerol and plasma FA kinetics. On Day 1 (D1), participants were studied under one of three different conditions, assigned in random order: (1) before, during and 3 h after 90 min of exercise at 45%V O 2 peak (E45), (2) before, during and 3 h after 60 min of exercise at 65%V O 2 peak (E65), and (3) in a time-matched sedentary control trial (C). For each condition, participants were studied by indirect calorimetry the following morning as well (D2). Rate of appearance (Ra) of glycerol (Ra GL ) increased above C during exercise in men and women (P < 0.05), was higher in E45 than E65 in men (P < 0.05), and was not different between exercise intensities in women. During 3 h of postexercise recovery, Ra GL remained significantly elevated in men (P < 0.05), but not women. FA Ra (Ra FA ) increased during exercise in men and women and was higher in E45 than E65 (P < 0.05), and remained elevated during 3 h of postexercise recovery in both sexes (P < 0.05), but with a greater relative increase in men than women (P < 0.05). Plasma FA oxidation (Rox) increased during exercise with no difference between intensities, and it remained elevated during 3 h of postexercise recovery in both sexes (P < 0.05). Total lipid oxidation (Lox) was elevated in both sexes (P < 0.05), but more in men during 3 h of postexercise recovery on D1 (P < 0.05) and remained elevated on D2 in men (P < 0.05), but not in women. There were no differences between E45 and E65 for postexercise energy substrate turnover or oxidation in men and women as energy expenditure of exercise (EEE) was matched between bouts. We conclude that the impact of exercise upon lipid metabolism persists into recovery, but that women depend more on lipid during exercise whereas, during recovery, lipid metabolism is accentuated to a greater extent in men.

Production of trimethylamine-N-oxide (TMAO), a biomarker of CVD risk, is dependent on intestinal microbiota, but little is known of dietary conditions promoting changes in gut microbial communities. Resistant starches (RS) alter the human microbiota. We sought to determine whether diets varying in RS and carbohydrate (CHO) content affect plasma TMAO levels. We also assessed postprandial glucose and insulin responses and plasma lipid changes to diets high and low in RS. In a cross-over trial, fifty-two men and women consumed a 2-week baseline diet (41 percentage of energy (%E) CHO, 40% fat, 19% protein), followed by 2-week high- and low-RS diets separated by 2-week washouts. RS diets were assigned at random within the context of higher (51–53 %E) v. lower CHO (39–40 %E) intake. Measurements were obtained in the fasting state and, for glucose and insulin, during a meal test matching the composition of the assigned diet. With lower CHO intake, plasma TMAO, carnitine, betaine and γ-butyrobetaine concentrations were higher after the high- v. low-RS diet (P< 0·01 each). These metabolites were not differentially affected by high v. low RS when CHO intake was high. Although the high-RS meal reduced postprandial insulin and glucose responses when CHO intake was low (P<0·01 each), RS did not affect fasting lipids, lipoproteins, glucose or insulin irrespective of dietary CHO content. In conclusion, a lower-CHO diet high in RS was associated with higher plasma TMAO levels. These findings, together with the absence of change in fasting lipids, suggest that short-term high-RS diets do not improve markers of cardiometabolic health.

No abstract

After exercise bouts, women are better able to maintain glucose concentrations at sedentary control levels, thus not requiring the counter-regulation of glucose production that is seen in men and requiring less accentuation of lipid metabolism.

We examined the effect of endurance training on energy substrate partitioning during rest and exercise in postmenopausal women. Ten healthy sedentary (55 ± 1 yr) subjects completed 12 weeks of endurance exercise training on a cycle ergometer [5 days/wk, 1 h/day, 65% peak oxygen consumption (VO2 peak)]. Whole-body energy substrate oxidation was determined by indirect calorimetry during 90 minutes of rest and 60 minutes of cycle ergometer exercise. Subjects were studied at 65% VO2peak before training and after training at the same absolute exercise intensity (same absolute workload as 65% of pretraining VO2peak) and same relative exercise intensity (65% of post-training VO2peak). After training, VO2peak increased by 16.3 ± 3.9% and resting heart rate decreased by 4 bpm (p < 0.05). During exercise at same absolute intensity, mean arterial pressure decreased by 8 mmHg (p < 0.05), heart rate decreased by 19 bpm (p < 0.05), energy derived from carbohydrate decreased 9.6%, and the energy derived from lipid increased by 9.2% (p < 0.05). Lactate concentration was lower at the same absolute and relative exercise intensities (p < 0.05). Changes in substrate partitioning during exercise were accomplished without changes in dietary composition, body weight, or body composition. We conclude that endurance training in healthy postmenopausal women that remain in energy balance, results in many of the classic cardio-pulmonary training effects, decreases the reliance on carbohydrate and increases lipid oxidation during a given submaximal exercise task without a reduction in body weight.