Does weight issues is related to mental health conditions and with disabilities in individuals?

Definitely weight can be one element of mental health and disabilities, but this is a very narrow question. Certainly eating disorders are often mental health conditions, which often relate to an unhealthy conception of weight as the most important "thing." Of course, real health depends on a lot more than weight, weight is only one measure, and not even an especially telling one. Many people are overweight and still generally healthy. It's unusual to be underweight and healthy, but that happens too. Many people find that their mental health improves when they start eating better. That's not directly related to weight, but rather both weight and mental health are affected by eating well and getting exercise!