My daughter knows she is overweight but my worry is the size of her legs they are really big. the cause please if you can thx?

Genetics: Everyone gains weight differently. Some people put on abdominal weight, others weight in their legs. Genetics plays a role but diet and exercise are important to either keep weight off or loose the weight already gained. Work with primary doctor to develop a weight loss plan and exercise regimen that fits your daughters goals and values.