Similar rates of fat oxidation during graded submaximal exercise in women of different body composition

• Published in: PloS one Vol. 15; no. 11; p. e0242551
• Main Authors: Kerhervé, Hugo A, Harvey, Leonie M, Eagles, Alexander N, McLellan, Chris, Lovell, Dale
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 18.11.2020; Public Library of Science (PLoS)
• Subjects: Adipose Tissue - metabolism; Adult; Biology and Life Sciences; Blood; Body composition; Body Composition - physiology; Body fat; Body Mass Index; Body weight; Carbohydrates; Care and treatment; Energy expenditure; Energy Metabolism - physiology; Exercise - physiology; Exercise intensity; Exercise Test - methods; Exercise Therapy - methods; Fat metabolism; Female; Fitness equipment; Fitness training programs; Health aspects; Heart rate; Humans; Laboratories; Lactic acid; Life Sciences; Medicine and Health Sciences; Metabolism; Obesity; Obesity - metabolism; Overweight; Overweight - metabolism; Oxidation; Oxidation-Reduction; Oxygen; Oxygen - metabolism; Oxygen consumption; Oxygen Consumption - physiology; Oxygen uptake; Physical Exertion - physiology; Physical fitness; Physical Sciences; Physiological aspects; Spirometry; Sport science; Substrates; Weight control; Women's fitness; Womens health; Workloads; Australia; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0242551

Moderate intensity exercise ranging 40-60% of maximum oxygen uptake is advised to promote energy expenditure and fat oxidation in overweight and obese people. Although fat oxidation has been shown to be highly variable among individual, there is still a relative uncertainty regarding exercise prescription for women specifically. This article aimed to determine whether indicators of body composition can be used to narrow the exercise intensity range for exercise prescription in women. A total of 35 healthy women (age 30.8±9.5 yr) classified according to their BMI in normal weight (NOR; ≤24.9 kg·m2), overweight (OVW; 25-29.9 kg·m2) and obese groups (OBE; ≥30 kg·m2) completed a submaximal graded test (intensities eliciting ~30%, 40%, 50% and 60% of maximum oxygen uptake). Blood lactate, perceived exertion and absolute and relative substrate oxidation for fat (OXFAT) and carbohydrates (OXCHO) were measured at each stage. Perceived exertion and blood lactate increased as a function of exercise but did not differ across groups. There were no significant changes in absolute and relative OXFAT across groups, or as a function of exercise intensity. Peak OXFAT occurred at the 40%, 50% and 40% stages for NOR, OVW and OBE groups, respectively, with no significant differences across groups. We measured no differences, but considerable inter-individual variation, in fat oxidation in women of different body composition. This result is in agreement with previous research based on exercise performed at constant rate and in independent participant groups. Our findings do not support the fat oxidation hypothesis, and further emphasise the perspective that exercise prescription should be individualised and likely be based on considerations other than substrate oxidation.