Exercise performed in a postprandial state does not increase 24-h fat oxidation of male and female subjects. Conversely, it has been shown in male subjects that exercise performed in a postabsorptive state increases 24-h fat oxidation compared with that in sedentary control and that with exercise trials performed after breakfast, lunch, or dinner. There is a paucity of study evaluating the effect of exercise performed in a postabsorptive state in female subjects.Nine young female subjects participated in indirect calorimetry measurement over 24-h using a room-size metabolic chamber in which subjects remained sedentary or performed 60 min exercise before breakfast at 50% of [Formula: see text]. Exercise was accompanied by an increase in energy intake to ensure that subjects were in a similar state of energy balance over 24 h for the two trials.Compared with the sedentary condition, exercise performed before breakfast increased 24-h fat oxidation (519 ± 37 vs. 400 ± 41 kcal/day). Time courses of relative energy balance differed between trials with transient negative energy balance observed before breakfast. The lowest values of relative energy balance observed during the 24-h calorimetry, i.e., transient energy deficit, were greater in exercise trials than in sedentary trials. The transient deficit in carbohydrate balance was also observed before breakfast, and magnitude of the deficit was greater in exercise trial compared to that of sedentary trial.Under energy-balanced conditions, exercise performed in a post-absorptive state increases 24-h fat oxidation in female subjects. The effect of exercise performed before breakfast can be attributed to nutritional state: a transient deficit in energy and carbohydrate at the end of exercise.

BACKGROUND:As part of the growing lifestyle diversity in modern society, there is wide variation in the time of day individuals choose to exercise. Recent surveys in the US and Japan have reported that on weekdays, more people exercise in the evening, with fewer individuals exercising in the morning or afternoon. Exercise performed in the post-prandial state has little effect on accumulated fat oxidation over 24 h (24-h fat oxidation) when energy intake is matched to energy expenditure (energy-balanced condition). The present study explored the possibility that exercise increases 24-h fat oxidation only when performed in a post-absorptive state, i.e. before breakfast.METHODS:Indirect calorimetry using a metabolic chamber was performed in 10 young, non-obese men over 24 h. Subjects remained sedentary (control) or performed 60-min exercise before breakfast (morning), after lunch (afternoon), or after dinner (evening) at 50% of VO2max. All trials were designed to be energy balanced over 24 h. Time course of energy and substrate balance relative to the start of calorimetry were estimated from the differences between input (meal consumption) and output (oxidation).FINDINGS:Fat oxidation over 24 h was increased only when exercise was performed before breakfast (control, 456 ± 61; morning, 717 ± 64; afternoon, 446 ± 57; and evening, 432 ± 44 kcal/day). Fat oxidation over 24 h was negatively correlated with the magnitude of the transient deficit in energy and carbohydrate.INTERPRETATION:Under energy-balanced conditions, 24-h fat oxidation was increased by exercise only when performed before breakfast. Transient carbohydrate deficits, i.e., glycogen depletion, observed after morning exercise may have contributed to increased 24-h fat oxidation.

OBJECTIVE: Whole body fat oxidation increases during exercise. However 24-h fat oxidation on a day with exercise often remains similar to that of sedentary day, when energy intake is increased to achieve energy-balanced condition (Exercise Sport Sciences Reviews. 37: 93, 2009). However, literature also suggests the possibility that nutritional state when exercise is performed affects 24-h fat oxidation. Exercise has little effect on 24-h fat oxidation when performed after breakfast, but that performed before breakfast increases fat oxidation during (Metabolism. 62: 793, 2013). The present study aimed to examine a possibility that time of the day when exercise is performed makes differences in 24-h fat oxidation. As a potential mechanism of exercise affecting 24-h fat oxidation, its relation to exercise-induced transient energy deficit was examined. METHODS: Young subjects underwent sessions of indirect calorimetry using a whole room metabolic chamber, in which subjects (male or female) performed session (bout of 60 or 100 min or two sessions of 50 min) exercise with a given intensity (50 or 65% of VO2 max) at predetermined time (before breakfast, after breakfast, after lunch, or two sessions of exercise before breakfast and after lunch). Experimental meals were designed to achieve individual energy balance. RESULTS: 24 h energy expenditure was not affected by exercise, but 24-h fat oxidation was increased when exercise was performed before breakfast compared with exercise after breakfast, lunch and supper, or non-exercise control trial. Time course of apparent energy/carbohydrate balance revealed that it was significantly decreased immediately after exercise performed in a postabsorptive state, i.e. before breakfast. The magnitude of transient energy deficit was negatively correlated with 24-h fat oxidation. Similarly, the transient carbohydrate deficit after exercise was negatively correlated with 24-h fat oxidation. CONCLUSION: In addition to energy balance over 24-h, time of the day and/or nutritional state when exercise is performed affects 24-h fat oxidation. Transient energy/carbohydrate deficit is implied as a factor affecting 24-h fat oxidation even when 24-h energy intake and expenditure was matched.

Whole body fat oxidation increases during exercise. However, 24-h fat oxidation on a day with exercise often remains similar to that of sedentary day, when energy intake is increased to achieve an energy-balanced condition. The present study aimed to examine a possibility that time of the day when exercise is performed makes differences in 24-h fat oxidation. As a potential mechanism of exercise affecting 24-h fat oxidation, its relation to exercise-induced transient energy deficit was examined. Nine young male endurance athletes underwent three trials of indirect calorimetry using a metabolic chamber, in which they performed a session of 100 min of exercise before breakfast (AM), after lunch (PM), or two sessions of 50 min of exercise before breakfast and after lunch (AM/PM) at 65% of maximal oxygen uptake. Experimental meals were designed to achieve individual energy balance. Twenty-four-hour energy expenditure was similar among the trials, but 24-h fat oxidation was 1,142 ± 97, 809 ± 88, and 608 ± 46 kcal/24 h in descending order of its magnitude for AM, AM/PM, and PM, respectively (P < 0.05). Twenty-four-hour carbohydrate oxidation was 2,558 ± 110, 2,374 ± 114, and 2,062 ± 96 kcal/24 h for PM, AM/PM, and AM, respectively. In spite of energy-balanced condition over 24 h, exercise induced a transient energy deficit, the magnitude of which was negatively correlated with 24-h fat oxidation (r = -0.72, P < 0.01). Similarly, transient carbohydrate deficit after exercise was negatively correlated with 24-h fat oxidation (r = -0.40, P < 0.05). The time of the day when exercise is performed affects 24-h fat oxidation, and the transient energy/carbohydrate deficit after exercise is implied as a factor affecting 24-h fat oxidation.

BackgroundThere is no official recommendations for physical activity level or steps for preventing and improving child obesity in Japan.MethodsThree hundred and two Japanese children aged 9-12 years were recruited wore 3-D speed sensors. Subjects were divided into two groups using the criteria for child obesity in Japan. Body composition was measured on bioelectrical impedance analysis. Physical fitness test was done to evaluate physical strength. Twenty-four hour total steps, energy expenditure, and metabolic equivalents (MET) from Monday to Sunday were consecutively measured. The cut-offs for steps and physical activity level for preventing child obesity were evaluated on receiver operating characteristic curves. Daily life-related risk factors for child obesity were assessed on logistic regression analysis.ResultsIn both sexes, body volume; bodyweight, body mass index, fat mass, and percentage body fat in the obese group was significantly higher than in the normal group, but age and height were not different (P < 0.001). Aerobic power, running speed, and explosive strength in the obese group were inferior to those in the normal group (P < 0.001). More than 40min of 4MET exercise, defined as moderate-vigorous exercise, and 11000 steps per day are essential to prevent child obesity. Additionally, >2h TV viewing per day is a significant risk factor for child obesity (OR, 3.43; 95%CI: 1.27-9.31).ConclusionCut-offs for physical activity and potential risk factors for child obesity have been identified. Recommendations for changes to daily lifestyle for school-aged Japanese children are given.