SPECIAL COMMUNICATIONS: Response
We appreciate the letter from Drs. Miyashita and Stensel regarding our recent paper demonstrating that low-intensity aerobic exercise reduces postprandial lipemia (PPL) as effectively as moderate-intensity aerobic exercise in men with metabolic syndrome (MetS). We also reported that accumulating aerobic exercise over two sessions did not attenuate PPL (2). In opposition to this latter finding, recent work by Miyashita provides evidence that accumulating 30min of moderate-intensity aerobic exercise reduces PPL in obese men (3). Despite differences in subject population and test meal composition, we agree that these results assist in the interpretation of our data. We speculated that the total energy expenditure (TEE) of our accumulated exercise protocol may have been insufficient to reduce PPL. However, the TEE in Miyashita's study (∼200 kcal) was substantially lower than ours (∼500 kcal). Thus, Miyashita has uniquely demonstrated that accumulating a TEE consistent with physical activity recommendations (1) is indeed sufficient to reduce PPL in response to a single test meal in a clinically relevant population.
In addition to differences in TEE, our subjects performed two isocaloric sessions of aerobic exercise separated by ∼4h. In contrast, Miyashita had subjects perform ten 3-min bouts of aerobic exercise each separated by 30 min of rest. Therefore, his results indirectly support our postulate that aerobic exercise may need to be accumulated over more than two sessions to reduce PPL in obese men with MetS. Drs. Miyshita and Stensel hypothesize that this may be due to frequent increases in muscle blood flow resulting in increased triglycerides exposure to skeletal muscle lipoprotein lipase. As the mechanisms underlying aerobic exercise-induced ameliorations in PPL are not fully understood, we encourage Drs. Myashita and Stensel to substantiate this with further research.
Although we advocate additional research on accumulated aerobic exercise and PPL, we do so with an important qualification. We agree that Miyashita has clearly shown that accumulating exercise in sessions less than 10 min in duration effectively reduces PPL. Yet, it is our contention that the efficacy of aerobic exercise as a therapeutic option for reducing PPL in at-risk populations (e.g., MetS) should be evaluated using practical exercise protocols. Although we have no direct evidence to support this, we speculate that it is unlikely that individuals would consistently engage in 10 sessions of aerobic exercise per day, despite the short duration. Accordingly, we suggest directing future work towards testing combinations of aerobic exercise frequency and duration that are likely to promote exercise adherence. We believe this will provide the most useful information for health care providers to effectively prescribe aerobic exercise to reduce PPL.
In closing, we thank Drs. Miyshita and Stensel for highlighting these important issues concerning aerobic exercise and PPL. We strongly endorse further research in this area to ensure that the most suitable strategies are recommended to effectively address this emerging cardiovascular disease risk factor.
Michael L. Mestek, PhD
James Kyle Taylor, PhD
Sang-Ouk Wee, MS
Peter W. Grandjean, PhD
Department of Kinesiology
Eric P. Plaisance, PhD
Department of Anatomy, Physiology, Pharmacology
Lance A. Ratcliff, PhD
Department of Nutrition and Food Science
1. 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
2. Mestek ML, Plaisance EP, Ratcliff LA, et al. Aerobic exercise and postprandial lipemia in men with the metabolic syndrome. Med Sci Sports Exerc
3. Miyashita M. Effects of continuous versus accumulated activity patterns on postprandial triacylglycerol concentrations in obese men. Int J Obes