Becoming overweight as a child is more likely to be the result of your genes than your lifestyle, claims a study. University College London researchers examined more than 5,000 pairs of identical and non-identical twins. Their American Journal of Clinical Nutrition study found that differences in body mass index and waist size were 77% governed by genes. An anti-obesity group said regardless of genes, a balanced diet and exercise were vital to good health. It is wrong to place all the blame for a child's excessive weight gain on the parents - it is more likely to be due to the child's genetic susceptibility Professor Jane WardleUniversity College London Children who are overweight are likely to be overweight or obese in adulthood, raising the risk of certain cancers, heart disease, stroke and diabetes later in life.