Maximal fat oxidation at the different exercise intensity in obese and normal weight men in the morning and evening

Abstract

Mohebbi H, Azizi M. Maximal fat oxidation at the different exercise intensity in obese and normal weight men in the morning and evening. J. Hum. Sport Exerc. Vol. 6, No. 1, pp. 49-58, 2011. Introduction: Circadian rhythms regulate some metabolic and hormonal variables that affect fat oxidation rates. Thus, the purpose of this study was to investigate Maximal fat oxidation (MFO) at a different exercise intensity in obese and normal weight men in the morning and evening. Methods: MFO was measured in 12 normal weight (BMI 20-25 kg/m 2 ; VO 2 max 45.7±3.44 ml/min/kg) and 10 obese (BMI >30 kg/m 2 ; VO 2 max 37.2±3.6 ml/min/kg) men during incremental running exercise test with 3 min stages on the treadmill by indirect calorimetry method. Student's t-test and one-way ANOVA with repeated measures were used to analysis variables. Results: We found that fat oxidation rates and energy expenditure in both groups in the evening were higher than morning; there were no significant differences in MFO between obese and normal groups. Furthermore, the fat oxidation rate in low intensity exercise (<60% VO 2 max) was similar in obese and normal weight groups, but in high exercise intensities, in normal weight men were significantly higher than obese men. Conclusion: Our results suggest that independent of exercise intensity and body fat mass, exercising in the evening is more effective on fat oxidation and decrease body fat mass; therefore, it is better for weight loss purposes in obese and normal weight men.

Effect of time-of-day specific obese training on body composition and physical capacity

“…The combined strength and aerobic endurance training we proposed permits fat oxidation during exercise and post exercise as we explained before. So, when we have training in the evening, fat oxidation periods coincides with best periods to fat oxidation which are: evening [17] and night [21]. This concomitance should give more efficiency to the evening training facing morning training [22].…”

“…Knowing one hand that greatest benefits of physical qualities training are achieved when it coincides at the acrophase of the correspondent qualities [22] and secondly that maximal fat oxidation in exercise is in the evening [17], we believe that training in the evening for the obese may be more effective than training in the morning. To our knowledge no study has been devoted to the effect of the time-of-day training on physical capacity, body weight and body composition in obese.…”

“…In a recent study, H. Mohebbi et al [17] revealed that time of day affects significantly the maximal fat oxidation (Fat max) in obese and normal-weight subjects. They found that the measured Fat max in the evening is higher than in the morning in obese and in normal-weight subjects.…”

“…This metabolic action includes reducing insulin resistance by improving the use of energy substrates by the muscle [16]. Otherwise, some of the metabolic and hormonal variables that affect fat oxidation are regulated by circadian rhythms [17]. A. Chwalibog et al [18] indicated that during the day, carbohydrates are the major oxidative fuel, while during the night, changes in the energy status are accommodated by increasing fat oxidation.…”

“…The specific training associated to lower caloric diet has increased physical capacity (17,7% for EG and 15,6% for MG), decreased body weight (7,3% for EG and 6% for MG) fat percentage (19,5% for EG and 11,3% for MG) and waist circumference (10,2% for EG and 8,2% for MG) …”