Medicine & Science in Sports & Exercise:
Covidien Respiratory & Monitoring Solutions, Boulder, CO
Nonfasting triglyceride concentrations are now recognized as a risk factor for both cardiovascular diseases and all-cause mortality (7). Even a single session of aerobic exercise can favorably improve several aspects of postprandial metabolism in study cohorts ranging from young and healthy adults to those with overt disease. Indeed, it has long been established that moderate-intensity aerobic exercise performed 1-18 h before a meal results in reductions in triglyceride concentrations in the postprandial state (6,8). With such a wealth of evidence already in place, it seems well justified to conclude that previous aerobic exercise is an effective intervention for improving triglyceride metabolism in the hours after meal consumption. Case closed-or is it? Recent evidence has suggested that aerobic exercise may not have an effect on postprandial lipid metabolism in the absence of an exercise-induced caloric deficit (2,4). Therefore, the true effect of exercise needs to be considered in the context of nutritional considerations, such as compensatory caloric consumption, which are frequently overlooked by many investigators (1). Furthermore, this opens a debate as to whether or not the aforementioned results from carefully controlled laboratory experiments accurately reflect the effect of exercise on postprandial lipemia in free-living conditions.
In this issue of Medicine & Science in Sports & Exercise, Farah et al. (3) provide insight into this very question by assessing the influence of exercise on postprandial lipemia after ad libitum feeding in overweight men. Several methodological aspects of this study were intended to mimic a real-life setting. First, the single session of aerobic exercise was performed at an intensity of 50% of maximal aerobic power until 33.5 kJ·kg−1 of body mass was expended. Thus, the protocol was consistent with current public health recommendations for the cohort being studied (5). Second, in contrast to previous study designs, the authors took the unique approach of providing ad libitum buffet meals, where participants were allowed to self-select the type and quantity of food. Despite unrestricted access to food, participants did not significantly increase caloric consumption the day after the exercise session. In fact, the caloric deficit that resulted from this exercise and ad libitum feeding protocol was similar to that produced as a result of more regimented laboratory protocols. Interestingly, the authors also reported that previous aerobic exercise attenuated the postprandial triglyceride response to a degree comparable to that documented with other protocols. This highlights the importance of exercise-induced negative energy balance as a key variable in mediating the effect of aerobic exercise on postprandial lipemia. Further creative research, such as that conducted by Farah et al., is warranted to clarify this issue. From a public health perspective, these are the most compelling results to date because they strongly indicate that the ability of aerobic exercise to attenuate postprandial lipemia does in fact extend beyond the laboratory and into everyday life.
Michael Mestek, PhD
Covidien Respiratory & Monitoring Solutions
1. Braun B, Brooks GA. Critical importance of controlling energy status to understand the effects of "exercise" on metabolism. Exerc Sport Sci Rev
2. Burton FL, Malkova D, Caslake MJ, Gill JM. Energy replacement attenuates the effects of prior moderate exercise on postprandial metabolism in overweight/obese men. Int J Obes (Lond)
3. Farah NM, Malkova D, Gill JM. Effects of exercise on postprandial responses to ad libitum feeding in overweight men. Med Sci Sports Exerc
4. Harrison M, O'Gorman DJ, McCaffrey N, et al. Influence of acute exercise with and without carbohydrate replacement on postprandial lipid metabolism. J Appl Physiol
5. Haskell WL, Lee IM, Pate RR, et al. Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc
6. MacEneaney OJ, Harrison M, O'Gorman DJ, Pankratieva EV, O'Connor PL, Moyna NM. Effect of prior exercise on postprandial lipemia and markers of inflammation and endothelial activation in normal weight and overweight adolescent boys. Eur J Appl Physiol
7. Nordestgaard BG, Benn M, Schnohr P, Tybjaerg-Hansen A. Nonfasting triglycerides and risk of myocardial infarction, ischemic heart disease, and death in men and women. JAMA
8. Plaisance EP, Grandjean PW, Mahurin AJ. Independent and combined effects of aerobic exercise and pharmacological strategies on serum triglyceride concentrations: a qualitative review. Phys Sportsmed