As much as I'm not exactly a gym guy myself, if I happen to see one in a gym I wouldn't put too much thought about it but wish him the best and good luck in transforming himself. It might trigger anxiety at first but that's what gyms were built in the first place right? To help people stay in good shape? Don't give a damn what other people think as those who make fun of him earlier would eventually compliment him right after he starts showing progress.
Though for me personally, if you want to lose weight as well as being healthy, you don't necessarily have to hit the gym. There are other types of versatile, cheaper workouts. You can first start with simple one like jogging a few kilometers each day, rope skipping and eventually push ups, pull ups, sit ups, squads and any other. By the time you start hitting the gym, you might have lost several pounds already…
That is, if you keep it up consistently