Behavioral and physiological regulation of body fatness : A cross-sectional study in elderly men

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إنجليزي. OBJECTIVE: To identify the characteristics of physical activity that are the most correlated to total and truncal fatness and to physiological parameters involved in fat oxidation in elderly men. DESIGN: Cross-sectional study. SUBJECTS: A total of 25 healthy elderly men selected with a wide range of physical activity behavior (65.9 +/- 3.4 years).Measurements:Total and truncal fat masses (by dual-energy X-ray absorptiometry), time spent and energy expended (EE(day)) at specific activity intensities (<40, 40-60, >60% VO2max) during 1 week in free living conditions (using heart rate recording and individual calibrated equations), sport-exercising volume (V(sport), using Baecke questionnaire), maximal oxygen uptake (VO2max), muscle fat oxidative capacity (OX(FA), using muscle biopsy), lipid oxidation and respiratory exchange ratio during exercise at 50% VO2max (using indirect calorimetry). RESULTS: V(sport) was the main determinant of total and truncal fatness, VO2max and OX(FA) (r = -0.69, P < 0.0001; r = -0.80, P < 0.0001; r = 0.70, P < 0.0001; r = 0.66, P<0.001, respectively). Among physical activity parameters measured over a week, total EE(day) was the main determinant of total fat mass. Furthermore, EE(day) at % VO2max > 60 was closely correlated to truncal fat mass, VO2max and OX(FA) (r = -0.58, P > 0.01; r = 0.55, P < 0.01; r = 0.49, P < 0.05, respectively). Finally, VO2max and OX(FA) were positively correlated to absolute fat oxidation and to the contribution of fat to energy production during moderate exercise. CONCLUSION: Sport-exercising volume is the main factor regulating total and truncal fat masses and physiological parameters involved in fat oxidation. With regard to the characteristics of physical activity, overall energy expended during the alert period plays a major role in the regulation of total body fatness. In addition, vigorous exercises may be beneficial for the regulation of abdominal fat depot partly through the stimulation of muscle fat oxidation during the effort.