Diet and overweight. Epidemiological studies on intake, environment and genetics

Aim and methods This thesis aimed to study the role of a wide range of dietary factors on the development of overweight from a population perspective. First, we estimated the energy gap, i.e. the excess daily energy intake over the daily energy expenditure, responsible for excess weight gain during 4-years in 2190 2-year old Dutch children from the PIAMA birth cohort. Second, we performed three association studies of determinants in the field of nutrient metabolism, maternal diet and individual dietary intake with overweight and its important consequence type 2 diabetes. We investigated the association between: 1) 327 variants in 239 genes involved in fatty acid and glucose metabolism and overweight phenotypes in 3575 Dutch adults from the Doetinchem cohort study who were examined 3 times in 11 years; 2) maternal fish consumption during pregnancy and the child’s body mass index (BMI) reported 11 times between birth and 14 years of age (n= 3684; PIAMA birth cohort); 3) energy density of diets (the amount of available kilocalories per unit weight of foods) and the risk of type 2 diabetes in more than 12,000 incident type 2 diabetes cases embedded in a large European study (EPIC-InterAct). Third, we assessed changes in the Dutch school food environment based on data from two nation-wide surveys conducted in 2006/2007 and 2010/2011 among secondary schools (n=187). Results A daily energy gap of 75 kcal was responsible for the excess weight gain in 90% of the children who were overweight at the age of 5-7 years. We detected strong associations between adult BMI and/or waist circumference and five genetic variants located across the NR1H4, SIRT1, SMARCA2, SCAP and IL6 genes. So far, only for SIRT1, there is growing evidence for a role in the regulation of body weight. We found no clear evidence for an association between maternal fish consumption during pregnancy and BMI in children or an association betweenconsumption of high energy dense diets and risk of type 2 diabetes among adults. We observed favorable changes in the food supply, attitudes and beliefs regarding overweight and policies on health and nutrition at secondary schools between 2006/2007 and 2010/2011. For example, the presence of water coolers increased from 12% to 33%. However, less favorable changes were also observed. For example, more schools had vending places of unhealthy foods in their vicinity after four years (73% vs 85%). Conclusion A small energy gap of 75 kcal in children implies that restoring energy balance on the population level does not necessarily require large behavioral changes, like consuming 1 glass of soft drink per day less. This suggests that prevention of overweight should be feasible. The finding that the food environment at secondary schools has become less obesogenic at several aspects is of great public health importance. Supportive evidence shows that such improvements can result in a more favorable dietary intake and BMI among children. Creating a supportive food environment can facilitate individuals to adhere to a healthy diet and may suppress the effect of an individual’s genetic susceptibility to overweight.