The bible clearly states that gluttony is a sin and that the body is a temple of the holy spirit and should be honored.
It would seem then that people who are overweight are clearly in sin (barring medical conditions)
So why is it acceptable to be a fat pastor in sin, but not a gay pastor in sin?
Let's examine the two sins you mentioned.
One, I do agree with you that gluttony as a sin is overlooked or ignored. Our society usually does not remove someone from their position because they are overweight. Could it be a medical condition? How obese does one have to be? It may not be gluttony.
Gluttony is considered a sin because it means one cannot control their appetites. We are
warned about excess wine and meat which leads to sluggishness and poverty. Jesus taught laziness, sluggishness, and not doing due diligence in investment matters leads to poverty. Gluttony means some kind of problem with self control or lack of and it could affect other areas of your life. Thus, while we do not want to body shame someone for being overweight, it is something to discuss with someone close to you and that you care about.
Homosexuality is a different type of sin. I learned that it is similar to Adam's sin in going against that which God has made a command against. There is a strangeness to this sin which I only learned about last year -- God's punishment for the sin is more of the sin. IOW, homosexuality leads to more homosexuality. It means despite gays getting married now, they will have a hard time being faithful. It also means more disease and early deaths --
Facts and Statistics About Homosexuals. I don't think most of us in society get this information as it is hidden from us.
Thus, I don't think the level of the sin is not the same. Maybe you think different. No self control over gluttony or other fleshly wants may lead to poverty, death, or ill health, but it's something that a person can control more readily by going on a diet and watching over their self-control. It may need a treatment program or counseling with a psychiatrist if the lack of self-control is more severe. Just like someone who cannot control their temper. That's a more serious condition I think and requires psychiatric evaluation and counseling. If a pastor cannot control their temper, then I think it would lead to dismissal.
As for a gay pastor, then it is more of an outward contradiction. If your local or regional church forbids gay clergy, then they have religious grounds to remove them. It also should mean no gay marriages based on what God forbade. It's more difficult to see someone is a glutton or lacks self control and that is something that the church could handle privately with the pastor if it crops up before word gets out.