Date Published: July 10, 2017
Publisher: Public Library of Science
Author(s): Kaito Iwayama, Ryosuke Kawabuchi, Yoshiharu Nabekura, Reiko Kurihara, Insung Park, Masashi Kobayashi, Hitomi Ogata, Momoko Kayaba, Naomi Omi, Makoto Satoh, Kumpei Tokuyama, Andrew Philp.
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 V˙O2max. 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.
Fat oxidation increases during exercise, and its determinants are well-characterized; exercise intensity [1,2], exercise duration , training status [4,5], nutritional state [6,7], and gender are the factors affecting fat oxidation during exercise. Fat oxidation during exercise is expected to be increased by prolonged exercise at moderate intensity performed in a post-absorptive state and to be greater in trained individuals and females.
Physical characteristics of subjects were 23.9 ± 1.3 year of age, 161.4 ± 1.6 cm of height, 57.8 ± 1.6 kg of body weight and 26.9 ± 1.2% of body fat. Their maximal oxygen uptake (V˙O2max) was 43.6 ± 1.7 ml/kg/min. Habituation of weekly exercise was 2.6 ± 1.0 (h/wk). Work load, relative intensity of the exercise and average heart rate during 60-min exercise session were shown in Table 1. As intended, relative intensity of the exercise was close to 50% of V˙O2max.
The main finding of the present study was that exercise performed after overnight fasting increases 24-h fat oxidation in female subjects. Previous studies evaluating in an energy-balanced condition demonstrated that exercise performed in a postprandial state does not increase 24-h fat oxidation in male and female subjects [11,12,15,16]. Conversely, exercise performed before breakfast increased 24-h fat oxidation more than exercise performed after breakfast, lunch, or dinner, or in a sedentary control trial in male subjects [16–18]. Taken together, it is suggested that exercise performed in a postabsorptive state but not that performed in a postprandial state increases 24-h fat oxidation in male and female subjects.