Alcoholic and drug addicts can't get disability based on their addiction alone. They must have another qualifying disability. The law was changed quite a few years ago.
As for obesity:
http://www.disabilitysecrets.com/conditions-page-2-45.html
Obesity used to be listed as an impairment in the Listing of Impairments, but the SSA removed it in 1999. The logic was that many obese individuals are able to lead productive lives and hold gainful employment. Today, you can still be awarded disability benefits for obesity, but the SSA will consider obesity under the impairment listings only if 1) its limitations are equivalent to ("equal") those in an impairment listing or 2) it causes or contributes other listed impairments.
As an example of equaling an impairment listing, if the obesity causes an individual to be unable to walk effectively, the individual's condition could "equal" the impairment listing for major dysfunction of a weight bearing joint, an impairment-level listing.
I suggest you turn these people in!