title: Fat oxidation, hormonal and plasma metabolite kinetics during a submaximal incremental test in lean and obese adults.
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 (VO2peak) in O than in L and from 65 to 85% VO2peak in L than in O (p ≤ 0.05). FORs were similar in O and in L from 35 to 60% VO2peak. 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.
authors: Institute of Sport Sciences University of Lausanne (ISSUL), University of Lausanne, Lausanne, Switzerland ; Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
authors: Stefano
authors: S
authors: Lanzi
authors: Pulmonary rehabilitation department, San Giuseppe Hospital, Istituto Auxologico Italiano Piancavallo, Verbania, Italy.
authors: Franco
authors: F
authors: Codecasa
authors: Pulmonary rehabilitation department, San Giuseppe Hospital, Istituto Auxologico Italiano Piancavallo, Verbania, Italy.
authors: Mauro
authors: M
authors: Cornacchia
authors: Molecolar biology laboratory, San Giuseppe Hospital, Istituto Auxologico Italiano Piancavallo, Verbania, Italy.
authors: Sabrina
authors: S
authors: Maestrini
authors: Pulmonary rehabilitation department, San Giuseppe Hospital, Istituto Auxologico Italiano Piancavallo, Verbania, Italy.
authors: Alberto
authors: A
authors: Salvadori
authors: Medicine rehabilitation department, San Giuseppe Hospital, Istituto Auxologico Italiano Piancavallo, Verbania, Italy.
authors: Amelia
authors: A
authors: Brunani
authors: Institute of Sport Sciences University of Lausanne (ISSUL), University of Lausanne, Lausanne, Switzerland ; Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
authors: Davide
authors: D
authors: Malatesta
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D000886:Anthropometry; D001823:Body Composition; D015992:Body Mass Index; D001835:Body Weight; D002153:Calorimetry, Indirect; D003720:Densitometry; D004952:Esters / Q000737:chemistry; D005080:Exercise Test; D005227:Fatty Acids / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D007700:Kinetics; D008055:Lipids / Q000737:chemistry; D008297:Male; D009765:Obesity / Q000097:blood* / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry
chemical_list: D004952:Esters; D005227:Fatty Acids; D007328:Insulin; D008055:Lipids; D010100:Oxygen