[show abstract][hide abstract] ABSTRACT: This study aimed to compare fat oxidation, hormonal and plasma metabolite kinetics during exercise in lean (L) and obese (O) men. Sixteen L and 16 O men [Body Mass Index (BMI): 22.9±0.3 and 39.0±1.4 kg(.)m(-2)] performed a submaximal incremental test (Incr) on a cycle-ergometer. Fat oxidation rates (FORs) were determined using indirect calorimetry. A sinusoidal model, including 3 independent variables (dilatation, symmetry, translation), was used to describe fat oxidation kinetics and determine the intensity (Fat max ) eliciting maximal fat oxidation. Blood samples were drawn for the hormonal and plasma metabolite determination at each step of Incr. FORs (mg(.)FFM(-1.)min(-1)) were significantly higher from 20 to 30% of peak oxygen uptake ([Formula: see text]) in O than in L and from 65 to 85% [Formula: see text] in L than in O (p≤0.05). FORs were similar in O and in L from 35 to 60% [Formula: see text]. Fat max was 17% significantly lower in O than in L (p<0.01). Fat oxidation kinetics were characterized by similar translation, significantly lower dilatation and left-shift symmetry in O compared with L (p<0.05). During whole exercise, a blunted lipolysis was found in O [lower glycerol/fat mass (FM) in O than in L (p≤0.001)], likely associated with higher insulin concentrations in O than in L (p<0.01). Non-esterified fatty acids (NEFA) were significantly higher in O compared with L (p<0.05). Despite the blunted lipolysis, O presented higher NEFA availability, likely due to larger amounts of FM. Therefore, a lower Fat max , a left-shifted and less dilated curve and a lower reliance on fat oxidation at high exercise intensities suggest that the difference in the fat oxidation kinetics is likely linked to impaired muscular capacity to oxidize NEFA in O. These results may have important implications for the appropriate exercise intensity prescription in training programs designed to optimize fat oxidation in O.
PLoS ONE 01/2014; 9(2):e88707. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: PURPOSE: It is demonstrated that aerobic exercise plays an important role in weight loss programs for obesity by increasing 24 h metabolic rate. While aerobic exercise can result in health and fitness benefits in obese subjects, also independently of weight loss, not completely clear are the effects of bouts of hard exercise on metabolic outcomes. The aim of this study was to test the hypothesis that short-term aerobic activity with anaerobic bouts might result in a greater improvement in the management of obesity than aerobic activity alone. METHODS: We studied 16 obese subjects (eight men) during a progressive cycloergometric test up to exhaustion, before and after 4 weeks of two different training schedules (6 days/week). Insulin and glycaemia, non-esterified fatty acids (NEFA) and lactic acid were sampled. Group A (eight subjects, four men) performed an aerobic cycle workout; Group B (eight subjects, four men) performed a 25 min aerobic workout followed by 5 min of anaerobic workout. All the subjects maintained their individual eating habits. RESULTS: The post-training test showed a decrease in AUCs NEFA in Group A (p < 0.05) and an increase in Group B (p < 0.05), together with an increase in lactic acid in Group A and a decrease in Group B (p < 0.01). β-cell function (HOMA2-B) revealed a reduction only in Group A (p < 0.05). Group B achieved a greatest reduction in body fat mass than Group A (p < 0.05). CONCLUSIONS: Aerobic plus anaerobic training seem to produce a greater response in lipid metabolism and not significant modifications in glucose indexes; then, in training prescription for obesity, we might suggest at starting weight loss program aerobic with short bouts of anaerobic training to reduce fat mass and subsequently a prolonged aerobic training alone to ameliorate the metabolic profile.
European Journal of Nutrition 04/2013; · 3.13 Impact Factor
[show abstract][hide abstract] ABSTRACT: Growth hormone (GH) secretion is normally sensitive to physical exercise. Intensity and duration of exercise, fitness and age can all influence the GH response to exercise. In obesity, GH secretion is decreased both in basal conditions and in response to exercise.
To analyse the dynamics of GH response to a progressive cycloergometric test, conducted up to exhaustion, in adult normal subjects and obese patients, after a reconditioning program at different workloads.
We studied eight lean subjects (four men, mean age 34.3 years, range 26-47 years, mean body mass index (BMI) 22.1 kg/m(2)). GH was sampled at baseline and during the last 30 s of each power output increase. Anaerobic threshold (AT) was detected by the V-slope method. The same test was carried out in 16 obese subjects (seven men, mean age 39.1 years, range 20-59 years, mean BMI 35.8 kg/m(2)) and repeated after a 4-week reconditioning program consisting of aerobic workout (Group A, eight subjects, three men, mean age 40.5 years, range 22-59 years, mean BMI 33.6 kg/m(2)), and aerobic plus anaerobic work (group B, eight subjects, four men, mean age 37.6 years, range 20-56 years, mean BMI 38.0 kg/m(2)) for 6 days/week, with no dietary restrictions.
Mean exercise peak occurred at higher intensity in controls (140 vs 110 W, P < 0.05), and AT exceeded at higher work outputs than in obese subjects (102 vs 74 W, P < 0.05). In controls, GH response to exercise was prompt and further sustained after AT; in obese subjects, GH increased slowly and insignificantly before AT, thereafter it increased to lower levels than in controls (P < 0.001). Following the reconditioning period, both Group A and Group B of obese subjects failed to improve exercise performance as well as GH response to exercise before AT; beyond AT, a greater GH response to exercise occurred in Group B than Group A (7.59 ± 0.32 μg/l at peak of exercise) with significantly different Delta AUCs (Area Under the Curves) following AT: 30.5 ± 12 μg.min/l in Group A vs 124.2 ± 38 μg.min/l in Group B, P < 0.05.
Our results confirm the blunted GH response to exercise in obese adults when compared to lean counterparts. With obesity, aerobic training poorly increases the GH response beyond AT, while supplemental anaerobic workload appears to increase GH response beyond AT. These observations may have implications for the prescription of physical exercise, which is one of the recommendations in the management of obesity.