An “ecological” approach to the obesity pandemic

The increasing prevalence of obesity in many countries means that it should now be considered a pandemic.1 One estimate from Australia suggests that over the past decade the average adult has been adding 1 gram a day to body weight.2 This has occurred in the face of increasing knowledge, awareness, and education about obesity, nutrition, and exercise. It has been suggested that a paradigm shift is necessary if future progress is to be made.3 Traditionally, weight gain was thought of as caused by eating too much or exercising too little, or both (changes in weight=energy intake-energy expenditure). This led to the search for small deficiencies in energy metabolism such as a reduced thermic effect of food to explain obesity.4 Treatment was dominated by calorie counting, and public health messages extolled people to balance their intake and output. This paradigm has changed with the increasing understanding of the dynamic relations between energy stores, appetite mechanisms, and energy metabolism and of the wider recognition of nutrient partitioning.5 6 From studies which have shown that fat balance is equivalent to energy balance,7 the fat balance equation was developed (rate of change of fat stores=rate of fat intake-rate of fat oxidation).5 This equation is more dynamic than the original static equation and reflects energy balance under normal conditions of free access to foods. Because fat intake and oxidation are not closely balanced,8 this approach does not need metabolic abnormalities or genetic mutations to explain weight gain. Indeed, the differences in body fat between people living in the same environment could be better described as normal physiological variation. This paradigm is more helpful in explaining changes in body fat within an individual over time, but it does not account for the wider influences within and around individuals …