Differences in fat balance underlying obesity.
Energy balance occurs under free-living conditions when macronutrient balance is achieved (i.e., the intake of each macronutrient corresponds to its use). Among the components of macronutrient balance, fat balance is the one which is at greater risk of large deviations because of a reduced potential of fat to decrease food intake acutely and to promote its oxidation. This may represent a problem for individuals predisposed to obesity who are characterized by an increased taste preference for fat and a reduced capacity to oxidize fat when their body weight is normal. When these individuals are exposed to a lifestyle favouring a positive fat balance, a greater demand is imposed on sympathetic nervous system activity which is stimulated by hyperinsulinaemia. Accordingly, muscle sympathetic nerve activity (MSNA) is greater in obese hyperinsulinaemic individuals in the basal state, whereas they display a blunted response in MSNA to the acute administration of insulin. In this context, where the ability to further stimulate sympathetic activity is low, fat gain and its related increased lipid mobilization and oxidation remain the ultimate means to restore fat balance.
Tremblay
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Physical Activity Sciences Laboratory, PEPS, Laval University Ste-Foy, Quebec, Canada.
D001823:Body Composition / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D006801:Humans; D050356:Lipid Metabolism; D009765:Obesity / Q000378:metabolism / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000502:physiology