Healthy eating

I'm concerned about my partner he has got into a very unhealthy life style and put on a lot weight since has been with me. I've tried taking to him about it but he just says' he knows he need to change' but does nothing. I'm a typically heathy  and exercise I try get him to do it with me but just says he's tired and Go's and watches t.v or X-box. I love him to bits but he just worries me that he's not doing the best for his body. Any advice to get him to choose the healthy lifestyle?