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Behaviour, Appetite and Obesity
The global obesity epidemic and the growing burden of associated co-morbidities have galvanised the scientific community in its efforts to identify the aetiological triggers that determine individual susceptibility to weight gain and attendant metabolic dysregulation(1,2). Genetic, behavioural and environmental factors have been implicated as contributing to the obese-susceptible phenotype(3,4). What is not clear is the extent to which dietary intake, and in particular, dietary macronutrient intake and substrate oxidation, may be causally associated with obesity, per se and metabolic dysregulation in the obese(5,6). For example, in some studies, the development of obesity has been shown to be associated with a high-fat diet(7,8)as it leads to increased energy intake and has been found to be less satiating than did the other macronutrients(9,10). However, a positive fat balance and subsequent weight gain may not only be linked to intake, but also associated with a reduced rate of fat oxidation(11-14).
Blundell et al.(15)have previously characterised a specific dietary phenotype that consumes a high-energy, high-fat diet (44 % energy from fat) but remains weight stable and non-obese. In comparison with lean habitual low-fat consumers (32 % energy from fat), these individuals are characterised by having higher RMR, significantly lower RER(15)and higher fasting plasma leptin concentrations(16). These characteristics may serve to protect such individuals from weight gain. Furthermore, they found that these two groups displayed different appetite control characteristics(17). When challenged with high-fat meals, the lean high-fat (LHF) consumers ate a constant weight of food, whereas the lean low-fat (LLF) consumers ate a constant amount of energy. Taken together, these findings suggest that these groups make up distinct, specific, dietary metabolic phenotypes.
Blundell et al.(18)have also compared LHF consumers with obese high-fat (OHF) consumers (>43 % of energy) to identify the characteristics that may make some individuals more susceptible to weight gain. They found that, in comparison with...