is single the new diet?

Recently two of my friends who were never out of shape, but were never in real great shape, have both gotten super jacked and super in shape. I was joking with one of them and asking if they were on steroids, and his exact response was
" Not on steroids, we are both recently single"

That made me realize that it is not being single for a long time that makes you get in shape, it is that initial break up and becoming single that pushes you and motivates you to get back into the gym. It makes sense since I know a lot of people that once they are happy in their relationship they slowly stop working out, stop caring about a diet etc, and they are just happy with their life and they do not feel the need to work out.

I view it differently, I always want to stay in shape( or at least try) not only for me but for who ever I am dating. If I run and work out when I am single and when I start dating someone, they probably like that about me. I do not want to get fat and lazy, I want to stay in shape etc so the person I am with is still attracted to me etc.

I do get that a lot of couples work out together or run together or diet, but for the most part, people that are single, esp. recently single tend to workout the hardest and diet the most etc.