They come from a life of uncontrolled use of various street drugs. When on regular doses of methadone, patients describe having no euphoria from the drug. Some say it gives them energy, others that it allows them to relax. In the majority of cases, it permits previously unstable heroin addicts to lead normal lives in virtually every respect. It is certainly not 'free'.
All patients eventually lose weight on street heroin.
Hence it is understandable that a number gain weight when on methadone treatment. With the average age of methadone patients now in the mid-thirties, some are bound to get 'middle age spread'. Some eat unbalanced diets and get insufficient exercise. All of these factors are well within the province of the GP to address. There are no restrictions on employment in patients on regular methadone.