Judith,
You indicated that you think your husband is being denied a wage increase and/or promotion because of his weight. You haven't, however, provided any information to support your belief. You have indicated only that your husband's employer hired a 21 year old to be the manager rather than promote your husband. There could be many legal reasons why your husband hasn't been promoted or why the 21 year old was hired. And, since you don't work there, you may be totally unaware of them. It's also possible that in selecting the 21 year old to be manager, your husband's employer overlooked a number of other employees, including slender ones.
Someone earlier suggested your husband's next step. He needs to discuss his situation with his employer and find out the employer's explanation for his situation. Your husband needs to calmly state his concern about his pay and promotional opportunities, get the employer's reasons, and find out what he needs to do to increase the likelihood of a pay increase and a promotion.
None of the federal anti-discrimination statutes require an individual to prove that s/he suffered discrimination to file an administrative claim. However, there needs to be a reasonable suspicion of discrimination based on factual information. That appears to be missing from the situation you describe.
You will find useful, helpful and correct information here, some of which is provided by sensitive people. My advice is to focus on that information and ignore the rest. You don't want to be an enabler.