Effects of exercise before or after meal ingestion on fat balance and postprandial metabolism in overweight men

Abstract

It is unclear how timing of exercise relative to meal ingestion influences substrate balance and metabolic responses. The present study aimed to compare the effects of exercise performed before or after breakfast on fat balance and postprandial metabolism. A total of ten sedentary overweight men (aged 28·1 (SEM 10·7) years, BMI 29·0 (SEM 2·8) kg/m 2 ) underwent three trials in random order involving: (1) performing no exercise (CON), or walking for 60 min at 50 % maximal O 2 uptake either (2) before (Ex-Meal) or (3) after (Meal-Ex) consuming a standardised breakfast meal. In each trial an ad libitum lunch was provided 3·5 h after breakfast. Substrate utilisation was assessed by indirect calorimetry and blood was taken at regular intervals over an 8·5 h observation period. At the end of the observation period, fat balances in the Ex-Meal (21043 (SEM 270) kJ) and Meal-Ex (2697 (SEM 201) kJ) trials were both significantly lower than CON (204 (SEM 165) kJ) and fat balance in the Ex-Meal trial was significantly lower than in the Meal-Ex trial (all P , 0·0001). Compared with the CON trial, the 8·5 h postprandial TAG response was only significantly lowered in the Ex-Meal trial (217 %, P ¼ 0·025) and not in the Meal-Ex trial (211 %, P ¼ 0·20). Both the Ex-Meal and Meal-Ex trials showed significantly lowered insulin responses relative to the CON trial (by 19 and 24 %, respectively, P , 0·01 for both). There were no differences in lunch energy intake between trials. The present findings suggest that there may be an advantage for body fat regulation and lipid metabolism in exercising before compared with after breakfast. However, further study is needed to determine whether the present findings extend over the long term under free-living conditions. Key words: Exercise: Postprandial metabolism: Fat balance: Appetite: Energy balance: Ad libitum energy intake Loss of body fat requires the imposition of a negative fat balance, which is achieved when fat oxidation exceeds fat intake (1) . Exercise provides a potent means of increasing fat oxidation, both during the exercise itself and in the hours afterwards (2) , and thus can potentially contribute to the formation of a negative fat balance. However, as exercise can also influence food intake (3) and the metabolism of ingested food (4,5) , it is necessary to also consider the interactions between exercise and food intake to fully evaluate the overall effects of exercise on fat balance. It is well-known that consuming a meal prior to exercise reduces fat, and increases carbohydrate oxidation during the exercise period (6,7) , whereas a post-exercise meal can attenuate the shift from carbohydrate to fat oxidation that normally follows exercise (8) . Thus, the timing of exercise relative to meal ingestion influences the pattern, and potentially the extent, of the exerciseinduced increase in fat oxidation. Studies comparing the effects of exercise before or after a single meal have reported greater total fat oxidation over observation periods of 2 -8 h when exercise was u...

The Effect of Timing of Exercise and Eating on Postprandial Response in Adults: A Systematic Review

“…Seventeen studies met the inclusion criteria for this systematic review (Table 1). These studies included adults with T2D [17,18,20,21,[23][24][25][26][27][28][29], as well as healthy [30][31][32][33] individuals and those with overweight/obesity and no reported comorbidities [19,34]. In terms of the interventions, included studies examined the effect of exercise performed relative to a meal on PP metabolic response.…”

“…A considerable number of studies have examined the association between timing of exercise relative to a single meal or over a single day with health [17][18][19][20][21]. Joint consideration of the timing of these two behaviors is critical in the context of their potential synergistic relationship with long-term health.…”

Is breakfast the most important meal of the day?

“…70 While in the future it might become possible to justify a rationale for defining meals 71 based on a certain mixture of nutrients, a logical starting point to define the essential conditions 72 of breakfast per se would be based on the quantity and timing of energy consumed. We propose 73 that a quantity of 50 kcal represents an appropriate arbitrary threshold to exclude common 74 ingestive behaviours that would neither be recognised as a 'meal' by the majority of people nor 75 meaningfully shift our physiology towards the fed-state, a marker of which could be a detectable 76 perturbation in exogenous and/or endogenous substrate utilisation (thus one standard tea/coffee 77 would be unlikely to meet this criterion).…”

“…This has also been observed over a full 24-h 434 period with room calorimetry and fixed energy intake (75) . Given the importance of endogenous 435 carbohydrate stores for exercise tolerance (76)(77)(78) , the preservation of whole-body carbohydrate 436 balance in the presence of a negative fat balance (32,74) could be an attractive metabolic milieu for 437 the regular exerciser.…”

Effect of Circadian Rhythm on Metabolic Processes and the Regulation of Energy Balance

“…Exercise before or after a meal has different effects on fatty acid oxidation and appetite metabolism [61][62][63]. However, it is still unclear when (pre-meal/post-meal exercise) is the most effective time to lose weight.…”