title: Effect of protein-supplemented fasting on the fuel-hormone response to prolonged exercise in obese subjects.
abstract: This study aimed at investigating the influence of protein-supplemented fasting (PSF) on the tolerance and the fuel-hormone response to endurance exercise in the severely obese subject. For this purpose, eight obese men (27 +/- 2 yr, 182 +/- 7 per cent of ideal body weight) exercised on a horizontal treadmill (4 km/h) during 3 h before and after 13 d of PSF (Alburone, 70 g protein/day). Because of the 8.9 +/- 0.7 kg weight loss and the corresponding lower energy cost, exercise oxygen consumption decreased from 1.6 +/- 0.1 (before PSF) to 1.4 +/- 0.1 l/min (after PSF). In contrast, mean exercise heart rate was identical (119 +/- 5/min) in both conditions, resulting in a lower oxygen pulse after PSF. The mean respiratory quotient measured during exercise was lower after PSF (0.72 +/- 0.01 vs 0.75 +/- 0.01 2 P less than 0.05), thus demonstrating a higher fat utilization. This was supported by a higher exercise-induced plasma free fatty acid (FFA) mobilization after PSF (delta plasma FFA: + 675 +/- 101 vs + 376 +/- 121 mumol/l, 2 P less than 0.05). This metabolic adaptation mainly results from two mechanisms: a significantly lower plasma IRI at rest and during exercise after PSF (5.7 +/- 0.8 vs 11.4 +/- 1.4 microunits/ml, 2 P less than 0.001); and a lower basal blood glucose (4.2 +/- 0.2 vs 4.6 +/- 0.1 mmol/l) and an earlier decrease of glucose (30th vs 90th min) during exercise after PSF, suggesting a relative depletion of the carbohydrates stores. The lipolytic hormones (glucagon, epinephrine, norepinephrine, cortisol, growth hormone) did not significantly increase during exercise after PSF when compared to exercise before PSF; thus, their role in the enhanced FFA mobilization appears less important. Only two of our eight subjects were unable to achieve the third hour of exercise after PSF; however, no major clinical events or electrocardiographical disturbances were observed in any of the eight subjects. In conclusion, moderate exercise can be tolerated at least for 2 h during PSF when appropriate fluid, mineral and vitamin therapy is given. Under these conditions it induces a preferential utilization of fat-derived substrates and selectively augments fat mobilization which favors weight loss. For these reasons, moderate exercise can be recommended under strict medical supervision as part of all weight reduction therapy.
mesh_terms: D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D004044:Dietary Proteins / Q000008:administration & dosage*; D004734:Energy Metabolism; D005215:Fasting; D005230:Fatty Acids, Nonesterified / Q000097:blood; D006339:Heart Rate; D006728:Hormones / Q000097:blood*; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D010101:Oxygen Consumption; D005082:Physical Exertion; D011863:Radioimmunoassay; D012119:Respiration
chemical_list: D001786:Blood Glucose; D004044:Dietary Proteins; D005230:Fatty Acids, Nonesterified; D006728:Hormones; D007328:Insulin