Obesity is a medical issue and frequent cause of premature death faced by a large proportion of persons with mental illness. The medications that we must take often have an effect on metabolism, directly causing weight gain and sometimes diabetes. The medications often make it more difficult to get physical exercise because of the sedation (which is common among numerous classes of these drugs.) Many psychiatric drugs also increase appetite.
It is harder for someone with a mental illness to cut back on food intake, because going hungry, even if for a relatively short time, sometimes has a destabilizing effect. Lack of food affects which parts of the brain are used and this can sometimes create a "fight or flight" reaction. This is a ticket to psychosis for people who have that tendency.
In the mental health treatment system, in which people are given medication, psychotherapy and milieu therapy on an outpatient basis, fattening foods are served. Some mental health treatment venues do not make an effort to cut back on the fat and sugar intake in the meals that are offered. It is not always practical for someone with mental illness receiving treatment at these places to supply their own healthier food, as many do not have access to food preparation facilities, or might lack the income to pay for their own food.
Many people eat poorly merely as a bad habit, without having a good reason. It might never occur to someone with mental illness that they ought to watch their calorie intake and possibly eat foods that are more nutritious.
Healthier eating habits seem to normally come with middle-age for persons who do not have mental illness. Persons with mental illness do not always have the same learning curve and in some respects, we may continue to behave as though in our twenties.
I became overweight for many of the above reasons, a