Most people believe that those who carry extra weight choose to do so, but this is simply untrue. There is overwhelming evidence that weight excess is largely determined by our genes and then triggered by our environment.
Twin studies demonstrate a very strong correlation (0.74) of weight between identical twins. Even if those twins were adopted and reared in different families, their weight correlation with each other was still 0.70, even though they had never met each other!
Adoption studies also show that children reared apart tend to match their biological parents rather than their adoptive parents, showing us how important genes are in determining weight.
There is no one gene that causes obesity but there are approximately 100 genes contribute to weight gain. For any one individual, the contribution of genetics to their weight is somewhere between 40-70%.
How do genetics affect my weight?
Genetics will affect our hunger and appetite hormones, our tendency to fidget and “waste energy” and our set point of weight.
People who carry extra weight will have higher levels of the hunger hormone — ghrelin, and reduced sense of fullness even after a large meal.