The assumption that Western population have an increased risk of obesity because of reduced total energy expenditure (TEE) and physical activity levels (PAL) is not supported by real world data. Researches from the University of Chigaco1 have performed a meta-analysis on research investigating TEE and PAL from countries with a low or middle human development index (HDI) compared to those with a high HDI to assess the effects of energy expenditure on body size. The results showed that the mean body mass index was lower in countries with a low or middle HDI compared to those countries with a high HDI, as might be expected. This was the case for both men and women. However, there was no association between the HDI status of the country and the TEE or the PAL. There was an inverse association between age and TEE for both sexes and a positive association between weight and TEE.
These results support a growing body of evidence that suggests that the epidemic of obesity in Western nations is not caused by reductions in the amount of physical activity or energy expenditure in these populations. This is supported further by a growing body of evidence that shows that exercise programmes do not cause long-term weight loss in over-weight and obese individuals. Instead, evidence suggests that weight gain is caused my metabolic abnormalities as a result of low quality diets. These metabolic changes include insulin resistance, changes in gene expression, systemic inflammation and high levels of oxidative stress. Increasing the quality of the diet appears to reverse these metabolic abnormalities, with the result that normal homeostatic control mechanisms begin to function correctly. This then lead to modulation of satiety and energy balance which returns weight to normal.
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