Helping my SO diet/eat healthy.

I don't know if you could call it a diet but I've completely switched what he eats to fruits and vegetables. No more fast food or fatty fried foods. I have an app where I log is foods and watch his calorie intake. I'm just having trouble getting him to do some forms of exercise. He is highly asthmatic and I told him if we start out slow and build up his body should get used to it. I've suggesting taking walks at night so the heat doesn't get to him. But he works on cars and stands on his feet 10 hours of the day so he doesn't want to do anything that would involve him being on his feet. How do you expect to lose weight if you're not going to work for it?! I don't know what to do