Acute exercise improves postprandial cardiovascular risk factors in overweight and obese individuals
Introduction
Cardiovascular disease (CVD) is a major cause of death in Australia and most industrialized countries [1]. Atherosclerosis is the main cause of coronary heart disease. The initiation of atherosclerosis involves the accumulation of lipids deposited by circulating lipoproteins within the arterial wall. Several lipoprotein types are thought to contribute to the initiation of atherosclerosis, including low density lipoprotein (LDL) and postprandial lipoproteins such as chylomicrons and their remnants [2].
Acute exercise may reduce the risk of atherosclerosis by decreasing concentrations of triglyceride (TG) and circulating atherogenic lipoproteins in the blood [3] while also increasing levels of beneficial high density lipoproteins (HDL) [3]. The effect of a single session of aerobic exercise, such as walking and cycling, on lipid metabolism has been investigated in several studies [3], [4], [5], [6]. However, these studies have been restricted to healthy, active, normal-weight participants. In addition, exercise interventions have commonly been of 60–120 min duration at a moderate-intensity ranging from 50% to 75% of VO2max [3], [4], [5], [6]. Postprandial lipaemia has been shown to be greater in the overweight and obese compared to normal-weight individuals after both exercise and no exercise conditions, possibly due to greater fat mass and its negative effect on lipoprotein lipase (LPL) activity [7]. Few studies have investigated the acute effect of exercise in overweight and obese individuals, a group now comprising the majority of the Australian adult population.
In one of the few studies to investigate the effect of resistance exercise on acute postprandial lipaemia [8], participants completed 3 sets of 10 repetitions lasting 88 min compared with the control condition of no exercise and aerobic exercise for the same amount of time. Participants were lean and apparently healthy males and females aged 21–40 years who were recreationally weight trained. Baseline TG levels were lower after resistance exercise compared to control (21%) and aerobic exercise (23%). Furthermore, the area under the curve (AUC) for TG was significantly lower after resistance exercise than after control (14%) and aerobic exercise (18%). Zafeiridis et al. [9] also compared the effect of low- (39 min) and high-volume (79 min) resistance exercise on postprandial lipaemia in healthy young men with normal body weight. Investigators observed a significant decrease in TG AUC for both conditions compared to control. However, the effect of resistance exercise in overweight and obese adults is unknown.
Current Australian physical activity recommendations suggest that adults should undertake 30 min of moderate-intensity physical activity on most days of the week to enhance health [10]. However, it is not known how 30 min of exercise affects postprandial lipaemia in the overweight and obese as previous studies only investigated bouts of at least 60 min in lean, healthy individuals [3], [4], [5], [6], [8]. In addition, reduction in postprandial lipaemia as a result of different modes of exercise has not been examined and there are no definitive recommendations regarding the exercise modality the overweight and obese should undertake for the best health outcomes. We hypothesized that compared to being inactive, a 30-min bout of moderate-intensity exercise would have positive effects on postprandial lipaemia, glucose and insulin levels of a meal consumed the next day, improve endothelial function, increase resting energy expenditure and increase fat oxidation in those who are overweight and obese. There is a need to examine whether the 30 min dose of exercise, as suggested in current physical activity guidelines, have a beneficial effect on metabolic factors in the overweight and obese. This information should provide the evidence to either support the guidelines or will help to advocate whether different and more specific recommendations should be made for this group.
The aim of this study was to investigate whether a single 30-min bout of resistance, aerobic or combined exercise at moderate-intensity would decrease postprandial lipaemia, glucose and insulin levels as well as increase resting energy expenditure and increase fat oxidation following a high fat meal consumed 14 h after the exercise bout, in overweight and obese individuals compared to no exercise. We also compared the between-group effects of the different exercise modalities in the same measurements.
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Participants
Twenty overweight or obese postmenopausal women and two men, between the ages of 50 and 67 years were recruited from the general population. Both men and women were used as the majority of previous studies have not reported a difference between genders [8], [11]. Participants were required to be sedentary or relatively inactive, having undertaken less than 1 h of moderate physical activity each week over the last 3 months. Exclusion criteria included diabetes mellitus, pre-existing heart
Results
Of the 22 participants who started the study, 18 finished and 4 were unable to continue due to unrelated illness or work commitments. There were no significant differences in energy or macronutrient intake three days prior to the postprandial measurement between the different exercise conditions (Table 2).
Discussion
Previous studies have demonstrated the beneficial effects of a single session of aerobic or resistance exercise on postprandial lipaemia [3], [4], [5], [6], [8], [9]. However, these studies were restricted to healthy, active, normal-weight participants. In addition, the duration and intensity of exercise interventions have commonly exceeded current Australian physical activity recommendations for adults. Therefore the aim of this study was to investigate the acute effects of a 30-min bout of
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