Weight control and calorie expenditure: thermogenic effects of pre-prandial and post-prandial exercise

The Effects of Six Weeks of Fasted Aerobic Exercise on Body Shape and Blood Biochemical Index in Overweight and Obese Young Adult Males

BACKGROUND/OBJECTIVE

The effects of fasted aerobic exercise on body composition and whether it causes adverse effects remain controversial. This study was to compare the effects of fasted and non-fasted aerobic exercise on body shape and blood biochemical indexes in overweight and obese young adult males, and observe whether FAE triggers adverse reactions.

METHODS

Thirty overweight and obese young adult males were randomly divided into fasted aerobic exercise (FAE) group, non-fasted aerobic exercise (NFAE) group, and control group. They were subjected to indoor treadmill intervention five days a week combined with diet control for six weeks. The FAE group had breakfast 0.5 h after exercise, and the NFAE group exercised 1 h after breakfast. Both groups filled out adverse reaction questionnaires during exercise, and the control group did not have any intervention. Height, weight, body mass index (BMI), and body fat percentage of the three groups of subjects before and after the experiment were measured by the GAIA KIKO bio-resistance antibody composition analyzer in Korea; waist circumference (WC), hip circumference (HC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) were measured by the tape measure method; fasting plasma glucose (FPG), fasting insulin (FINs), total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), very low density lipoprotein (VLDL), and HDL-C/LDL-C were measured by Roche C8000 automatic biochemical analysis instrument.

RESULTS

Weight, BMI, body fat percentage, WC, HC, WHR, WHtR, TG, TC, LDL-C and VLDL decreased very significantly (P < 0.01) in the FAE and NFAE groups after the 6-week experiment. The decrease in FINS was significant in the FAE group (P < 0.05) and the decrease in HDL-C was very significant in the NFAE group (P < 0.01). There was no significant difference in the frequency of adverse reactions between two groups (P > 0.05).

CONCLUSION

Six-week FAE and NFAE significantly improved body shape in overweight and obese young adult males, while FAE significantly reduced fasting insulin levels and increased tissue cell sensitivity to insulin. And compared to NFAE, 30 min of FAE in the morning did not increase adverse effects.

The acute effect of fasted exercise on energy intake, energy expenditure, subjective hunger and gastrointestinal hormone release compared to fed exercise in healthy individuals: a systematic review and network meta-analysis

OBJECTIVE

To determine the acute effect of fasted and fed exercise on energy intake, energy expenditure, subjective hunger and gastrointestinal hormone release.

METHODS

CENTRAL, Embase, MEDLINE, PsycInfo, PubMed, Scopus and Web of Science databases were searched to identify randomised, crossover studies in healthy individuals that compared the following interventions: (i) fasted exercise with a standardised post-exercise meal [FastEx + Meal], (ii) fasted exercise without a standardised post-exercise meal [FastEx + NoMeal], (iii) fed exercise with a standardised post-exercise meal [FedEx + Meal], (iv) fed exercise without a standardised post-exercise meal [FedEx + NoMeal]. Studies must have measured ad libitum meal energy intake, within-lab energy intake, 24-h energy intake, energy expenditure, subjective hunger, acyl-ghrelin, peptide YY, and/or glucagon-like peptide 1. Random-effect network meta-analyses were performed for outcomes containing ≥5 studies.

RESULTS

17 published articles (23 studies) were identified. Ad libitum meal energy intake was significantly lower during FedEx + Meal compared to FedEx + NoMeal (MD: -489 kJ; 95% CI, -898 to -80 kJ; P = 0.019). Within-lab energy intake was significantly lower during FastEx + NoMeal compared to FedEx + NoMeal (MD: -1326 kJ; 95% CI, -2102 to -550 kJ; P = 0.001). Similarly, 24-h energy intake following FastEx + NoMeal was significantly lower than FedEx + NoMeal (MD: -2095 kJ; 95% CI, -3910 kJ to -280 kJ; P = 0.024). Energy expenditure was however significantly lower during FastEx + NoMeal compared to FedEx+NoMeal (MD: -0.67 kJ/min; 95% CI, -1.10 to -0.23 kJ/min; P = 0.003). Subjective hunger was significantly higher during FastEx + Meal (MD: 13 mm; 95% CI, 5-21 mm; P = 0.001) and FastEx + NoMeal (MD: 23 mm; 95% CI, 16-30 mm; P < 0.001) compared to FedEx + NoMeal.

CONCLUSION

FastEx + NoMeal appears to be the most effective strategy to produce a short-term decrease in energy intake, but also results in increased hunger and lowered energy expenditure. Concerns regarding experimental design however lower the confidence in these findings, necessitating future research to rectify these issues when investigating exercise meal timing and energy balance.

PROSPERO REGISTRATION NUMBER

CRD42020208041.

KEY POINTS

Fed exercise with a standardised post-exercise meal resulted in the lowest energy intake at the ad libitum meal served following exercise completion. Fasted exercise without a standardised post-exercise meal resulted in the lowest within-lab and 24-h energy intake, but also produced the lowest energy expenditure and highest hunger. Methodological issues lower the confidence in these findings and necessitate future work to address identified problems.

Metabolic impact of protein feeding prior to moderate-intensity treadmill exercise in a fasted state: a pilot study

Background

Augmenting fat oxidation is a primary goal of fitness enthusiasts and individuals desiring to improve their body composition. Performing aerobic exercise while fasted continues to be a popular strategy to achieve this outcome, yet little research has examined how nutritional manipulations influence energy expenditure and/or fat oxidation during and after exercise. Initial research has indicated that pre-exercise protein feeding may facilitate fat oxidation while minimizing protein degradation during exercise, but more research is needed to determine if the source of protein further influences such outcomes.

Methods

Eleven healthy, college-aged males (23.5 ± 2.1 years, 86.0 ± 15.6 kg, 184 ± 10.3 cm, 19.7 ± 4.4%fat) completed four testing sessions in a randomized, counter-balanced, crossover fashion after observing an 8–10 h fast. During each visit, baseline substrate oxidation and resting energy expenditure (REE) were assessed via indirect calorimetry. Participants ingested isovolumetric, solutions containing 25 g of whey protein isolate (WPI), 25 g of casein protein (CAS), 25 g of maltodextrin (MAL), or non-caloric control (CON). After 30 min, participants performed 30 min of treadmill exercise at 55–60% heart rate reserve. Substrate oxidation and energy expenditure were re-assessed during exercise and 15 min after exercise.

Results

Delta scores comparing the change in REE were normalized to body mass and a significant group x time interaction (p = 0.002) was found. Post-hoc comparisons indicated the within-group changes in REE following consumption of WPI (3.41 ± 1.63 kcal/kg) and CAS (3.39 ± 0.82 kcal/kg) were significantly greater (p < 0.05) than following consumption of MAL (1.57 ± 0.99 kcal/kg) and tended to be greater than the non-caloric control group (2.00 ± 1.91 kcal/kg, p = 0.055 vs. WPI and p = 0.061 vs. CAS). Respiratory exchange ratio following consumption of WPI and CAS significantly decreased during the post exercise period while no change was observed for the other groups. Fat oxidation during exercise was calculated and increased in all groups throughout exercise. CAS was found to oxidize significantly more fat (p < 0.05) than WPI during minutes 10–15 (CAS: 2.28 ± 0.38 g; WPI: 1.7 ± 0.60 g) and 25–30 (CAS: 3.03 ± 0.55 g; WPI: 2.24 ± 0.50 g) of the exercise bout.

Conclusions

Protein consumption before fasted moderate-intensity treadmill exercise significantly increased post-exercise energy expenditure compared to maltodextrin ingestion and tended to be greater than control. Post-exercise fat oxidation was improved following protein ingestion. Throughout exercise, fasting (control) did not yield more fat oxidation versus carbohydrate or protein, while casein protein allowed for more fat oxidation than whey. These results indicate rates of energy expenditure and fat oxidation can be modulated after CAS protein consumption prior to moderate-intensity cardiovascular exercise and that fasting did not lead to more fat oxidation during or after exercise.

Body composition changes associated with fasted versus non-fasted aerobic exercise

It has been hypothesized that performing aerobic exercise after an overnight fast accelerates the loss of body fat. The purpose of this study was to investigate changes in fat mass and fat-free mass following four weeks of volume-equated fasted versus fed aerobic exercise in young women adhering to a hypocaloric diet. Twenty healthy young female volunteers were randomly assigned to 1 of 2 experimental groups: a fasted training (FASTED) group that performed exercise after an overnight fast (n = 10) or a post-prandial training (FED) group that consumed a meal prior to exercise (n = 10). Training consisted of 1 hour of steady-state aerobic exercise performed 3 days per week. Subjects were provided with customized dietary plans designed to induce a caloric deficit. Nutritional counseling was provided throughout the study period to help ensure dietary adherence and self-reported food intake was monitored on a regular basis. A meal replacement shake was provided either immediately prior to exercise for the FED group or immediately following exercise for the FASTED group, with this nutritional provision carried out under the supervision of a research assistant. Both groups showed a significant loss of weight (P = 0.0005) and fat mass (P = 0.02) from baseline, but no significant between-group differences were noted in any outcome measure. These findings indicate that body composition changes associated with aerobic exercise in conjunction with a hypocaloric diet are similar regardless whether or not an individual is fasted prior to training.

Thermogenic effects of pre-prandial and post-prandial exercise in obese females

The thermogenic effects of pre- and postprandial exercise was examined in six obese premenopausal females. Using open circuit calorimetry, energy expenditure was measured for 3 hours following five separate treatments: Resting Control, Exercise Only (25 min cycle at 60% VO2 max), Meal Only (902 kcal mixed meal), Exercise-Meal, and Meal-Exercise. Meal Only, Exercise-Meal, and Meal-Exercise were significantly higher than Rest Only and Exercise Only treatments. However, Meal-Exercise resulted in the greatest energy expenditure. These results suggest that in obese female subjects exercise following a meal will produce the greatest thermogenic response and could possibly influence weight maintenance or weight loss if implemented in food and exercise patterns of behavior.