Attività
Physical Activity, Obesity and Health
Why we become obese: a conflict between genes and modern lifestyle
Klaas R. Westerterp,
Director Department of Human Biology, Maastricht University, The Netherlands
The current obesity epidemic is a consequence of changes in eating pattern and physical activity in combination with a genetic susceptibility for weight gain. Research is focused on the interplay between genetic background and environmental factors that lead to a positive energy balance. Options are the comparison of individuals with a low and high genetic susceptibility and interventions in subjects with an identical genetic make-up. Overfeeding identical twins resulted in at least threefold more variance in response between pairs than within pairs for gains in body weight and fat mass. About 40% of the variance in resting metabolic rate, thermic effect of food, and energy cost of low-to-moderate intensity exercise is explained by inherited characteristics. However, segregation of the genes involved in the susceptibility to obesity is not easy because of the attenuation or exacerbation by non-genetic factors. The susceptibility to obesity is not necessarily manifested in body weight and fat mass. Many obesity prone subjects are restrained eaters, which also seems to have partly a genetic background. They maintain a reduced body weight by consciously restricting food intake. On the other hand obesity can be the result of external factors, i.e. overeating in response to traumatic environmental circumstances. Here, the focus is on the genetic determinants of energy expenditure: metabolic rate, spontaneous physical activity and substrate oxidation. Activity induced thermogenesis is the most variable component of daily energy expenditure and therefore an important determinant of energy balance. A recent study in our group provided indirect evidence for a genetic basis of daily physical activity in humans. In a current project, the inference of genetic influences from the phenotype is studied in monozygotic and di-zygotic twins.
