Evidence is accumulating that contradicts the widely held belief that obesity and weight gain are caused by laziness and greed. Metabolic syndrome is now associated with abdominal adiposity, diabetes and cardiovascular disease and research suggests that it is caused by an underlying metabolic disorder with an underlying genetic component. The cause of obesity is unknown, but still believe its cause is a positive energy balance, caused by too little energy expenditure and too great an energy. Despite this, research has repeatedly shown that calorie restriction and exercise regimens do not cause long term weight loss in a subset of obese individuals. In contrast, research that has used dietary guidance, advice and attempted to substitute unhealthy foods for healthy alternatives, has demonstrated that food choice is more important in weight loss that calorie restriction and exercise (here).
Evidence suggests that inherited traits are responsible for obesity, when combined with specific environmental conditions such as particular types of food. Research1 published in the American Journal of Clinical Nutrition in 2003 studied one hundred and one 8y old prepubertal girls with two lean parents, one obese parent, or two obese parents. Measurements of weight, height and body composition were taken 1 and 2 years after baseline, and their energy expenditure, muscle metabolism and levels of fitness was also assessed. Over the two year study period, girls with two obese parents had a 4.7kg increase in fat mass and a 4.1% increase in body fat. However, those girls with two lean parents only had a 2.3kg increase in fat mass and a 2.0% increase in body fat. Interestingly those with one obese parent had an increase in fat mass that was between the other two groups (3.5 kg).
These step-wise results suggest that weight gain in these girls had a strong genetic component. The same group of girls were studied in another paper published by the same group2 and they concluded that there was a significant heritable component to body mass index and percentage body fat between the girls and their parents at baseline. The percentage of girls who became obese after two ears was 7%, 34% and 44% in the two lean parents, one obese parent and two obese parent groups, respectively. The study also showed that fat mass and percentage body fat were negatively associated with energy expenditure at rest and while sleeping, but not with activity energy expenditure. A low muscle oxidative capacity and low physical fitness predicted high rates of fat gain. Interestingly, high total energy expenditure was associated with high rates of fat gain, perhaps because of larger body sizes.
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