Exercise before breakfast increases 24-h fat oxidation in female subjects

Abstract

BackgroundExercise 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.MethodNine 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 . 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.FindingsCompared 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.InterpretationUnder 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.

Time-of-Day-Dependent Physiological Responses to Meal and Exercise

“…As one of its mechanism, it is suggested that it is easy to shift the fuel source from carbohydrate to fat because prior to breakfast, because it is the longer fasting condition within a day, resulting in depletion of energy derived from a carbohydrate source like glycogen (132). Similar responses are observed in women (133). Thus, acute response of fat oxidation to exercise is greater in the evening while the longer effects of exercise on fat oxidation are observed before breakfast.…”

Effect of pre-exercise carbohydrate availability on fat oxidation and energy expenditure after a high-intensity exercise

“…As higher fat oxidation post-exercise has an important role in exercise-induced fat loss ( 3 ), this mode of training might be an interesting approach to overcome the sedentary lifestyle associated with the lack of free time in modern life ( 4 ). Furthermore, any manipulation able to improve post-exercise fat oxidation would be an interesting approach to enhance exercise-induced health benefits ( 5 ).…”

“…Endogenous CHO availability is commonly manipulated as follows: 1) by an 8–12 h fasting period before training, reducing liver but not muscle glycogen ( 7 ); 2) by reducing CHO diet content for a few days, reducing mainly liver glycogen ( 8 ); 3) by performing a pre-exercise before the main exercise to reduce pre-exercise liver and muscle glycogen ( 9 ); 4) or by a combination of two or more of those approaches ( 6 , 9 ). Regardless of the different ways to manipulate CHO stores, some evidence suggests that fat oxidation over the 24-h post-exercise period is increased when exercise is performed with a certain level of CHO depletion ( 5 , 7 ).…”

Relationship of Consistency in Timing of Exercise Performance and Exercise Levels Among Successful Weight Loss Maintainers

“…This categorical timing scheme was modeled off of prior studies . However, as noted, we further differentiated early‐ and late‐morning exercisers because of potential biological and behavioral benefits of early‐morning PA.…”

“…Exercising shortly after waking and before other obligations have a chance to interfere with PA plans may also facilitate greater PA levels. Additionally, preliminary research indicated that there may be physiological benefits of early‐morning exercise for weight control . Further examination of the relationship between PA timing and PA levels, including differentiating the potential importance of early‐ versus late‐morning exercise, is warranted.…”