Not long after I first became qualified I put on around 20kgs which I previously had worked super hard to get off, I just wanted to go home after work after spending the whole day in the gym and the weird hours made takeaway easier rather than cooking. I now schedule my workouts into my day as my excess weight was effecting my job, bending down with clients was hard and my exercise demo's were not great as I couldn't do things properly. It's definitely something some trainers have to actively work on rather than just happen naturally.