Could it be a sign that your husband is cheating if he suddenly decides to start an exercise program?

I would say that only a suspicious mind would make that jump in logic. There are many reasons to work out, getting healthy is the biggest one. He needs to stay healthy to have more time to spend with you.

Answer

No. My husband has Atrial Fibrillation and I have a few pounds to shed as well, so I asked him if he would like to joing the gym with me (take men/women) and he jumped at the chance. It's something we can join together and if one or the other of us gets too lazy we can kick each other's butts. LOL Why not ask your husband if you could join the gym with him (if they allows women.)

no i don't think so