• The body weight of adopted children shows no correlation with the body weight of their adoptive parents, who feed them and teach them how to eat. Their weight does have an 80 percent correlation with their genetic parents, whom they have never met.
• Identical twins, with the same genes, show a much higher similarity of body weights than do fraternal twins, who have different genes.
• Certain groups of people, such as the Pima Indian tribe in Arizona, have a very high incidence of severe obesity. They also have significantly higher rates of diabetes and heart disease than other ethnic groups.
• We probably have a number of genes directly related to weight. Just as some genes determine eye color or height, others affect our appetite, our ability to feel full or satisfied, our metabolism, our fat-storing ability, and even our natural activity levels.
  

We probably have a number of genes directly related to weight. Just as some genes determine eye color or height, others affect our appetite, our ability to feel full or satisfied, our metabolism, our fat-storing ability, and even our natural activity levels.