Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Effects of energy balance on postprandial triacylglycerol metabolism Maria Maraki and Labros S. Sidossis Introduction Elevated levels of plasma triacylglycerols (TAG) are associated with increased risk for atherosclerosis inde- pendently of other known cardiovascular risk factors [1]; therefore, interventions that decrease or prevent an increase in plasma TAG concentrations may be valuable in reducing the risk of coronary heart disease (CHD). Considering that free-living humans spent most of their time in the postprandial state, along with recent evidence of the independence of postprandial TAG as a CHD risk factor [2], suggests that interventions should focus on the improvement of postprandial TAG metabolism. The effects of negative energy balance on postprandial TAG metabolism have not been elucidated. Most of the data come from studies investigating the effects of an increase in energy expenditure (exercise) and/or of reduction in energy intake (diet), either in the short-term (acute effects), or in the long-term (accompanying with weight loss). One of the main assumptions underlying the hypotheses of hypotriacylglycerolemic effect of energy deficit is that the body may intensify the clearance of TAG from the circulation when energy is available (i.e., during the postprandial period) in order to replenish the energy stores used during energy deficit. Effects of acute negative energy balance on postprandial triacylglycerol metabolism Accumulated evidence suggests that a single bout of aerobic exercise reduces postprandial TAG concentrations (pTAG) the next day (Tables 1 and 2). However, in most of these studies, the extra energy expenditure due to exercise relative to rest period (net exercise energy expenditure) has not been compensated with increase in energy intake; therefore patients in these studies were in energy deficit due to increased energy expenditure. Moreover, regular physical activity does not influence pTAG when the effects of last exercise bout, and hence of exercise-induced Department of Internal Medicine, Sealy Center on Aging, Institute for Translational Sciences and Shriners Burns Institute, University of Texas Medical Branch at Galveston, Texas, USA and Laboratory of Nutrition & Clinical Dietetics, Department of Nutrition and Dietetics, Harokopio University, Athens, Greece Correspondence to Labros S. Sidossis, PhD, Laboratory of Nutrition & Clinical Dietetics, Department of Nutrition and Dietetics, Harokopio University, 70 El. Venizelou Ave., Athens 176-71, Greece Tel: +30 210 954 9154; fax: +30 210 954 9141; e-mail: lsidossis@hua.gr Current Opinion in Clinical Nutrition and Metabolic Care 2010, 13:608–617 Purpose of review To present the effect of negative energy balance on postprandial triacylglycerol concentrations (pTAG), an independent risk factor for the development of cardiovascular disease. Recent findings Aerobic exercise reduces pTAG; however, recent findings confirm that this effect is only evident with an accompanying energy deficit. Moreover, a recent study showed that acute diet-induced energy deficit also reduces pTAG. The extent of energy deficit required to significantly attenuate pTAG depends on the type of given meal, the type of deficit (aerobic/resistance exercise, diet, or combination of diet and exercise), and patients’ health status. Apart from the acute effects, prolonged energy deficit leading to moderate weight loss attenuates pTAG, when it is combined with other known hypotriacylglycerolemic agents, such as carbohydrate restriction. Summary For healthy population, it seems that it is up to patient’s preference and ability which type of energy deficit will follow to attenuate pTAG; an energy deficit of approximately 30 kJ/kg of body mass is required; for resistance exercise a smaller deficit is probably sufficient. More studies are needed to investigate dose–response/plateau effects, the effects of energy deficit–energy surplus every other day, and the threshold of energy deficit-weight loss in diabetics and other high-risk populations. Finally, investigation of the underlying mechanisms may be clinicall helpful in individualizing the appropriate intervention. Keywords diet, energy deficit, exercise, postprandial lipemia, weight loss Curr Opin Clin Nutr Metab Care 13:608–617 ß 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins 1363-1950 1363-1950 ß 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI:10.1097/MCO.0b013e32833f1aae