Metabolic Flexibility during Exercise in Children with Obesity and Matched Controls Academic Article uri icon

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abstract

  • BACKGROUND: Impaired metabolic flexibility (MetFlex) could contribute to ectopic fat accumulation and pathological conditions, such as type 2 diabetes. MetFlex refers to the ability to adapt substrate oxidation to availability. To the best of our knowledge, no studies have examined MetFlex under exercise conditions in children with obesity (OB) compared with a control group (CON) without obesity. Therefore, the primary objective was to compare MetFlex during exercise in children with OB compared with CON matched for chronological age, sex and biological maturation. A better understanding of MetFlex could help elucidate its role in the pathogenesis of childhood obesity and insulin resistance. METHODS: Children with obesity and without obesity, ages 8-17 y attended 2 visits, which included anthropometric measurements, blood work (OB group only), a maximal aerobic fitness (V[Combining Dot Above]O2max) test, and MetFlex test with a C-enriched carbohydrate (1.75g per kg of body mass, up to 75 g) ingested before 60 min of exercise at 45% V[Combining Dot Above]O2max. Breath measurements were collected to calculate exogenous CHO (CHOexo) oxidative efficiency as a measure of MetFlex. RESULTS: CHOexo oxidative efficiency (CHOexo oxidized/CHO ingested*100) during exercise was significantly lower in OB (17.3±4.0%) compared to CON (22.6±4.7%, p<0.001). CHOexo contributed less to total energy expenditure during exercise in OB compared to CON (p<0.001), while the contribution of endogenous CHO (p=0.19) and total fat was not significantly different (p=0.91). CONCLUSION: The ability to oxidize oral CHO, an indicator of MetFlex, was 23.5% lower in children with obesity compared to controls, independent of age, sex and pubertal effects. Thus, obesity at a young age could be associated with reduced MetFlex and future co-morbidities.

publication date

  • June 8, 2020