I'm used to be a quite a thin person when I was in high school, but I've been getting heavy inier for years.

I played tennis atin the past, and now my hobbies are oil painting and espresso, so I'm having fewergetting less exercise.

I'm used to be a quite a thin person when I was in high school, but I've been getting heavy in forier during the past few years.

I played tennis atin the past, and now my hobbies are oil painting and drinking espresso, so I'm having fewerless exercise.

I'm not that interested in my body shape ifas long as I am in a healthy range.

I'm used to be a quite thin person when I was in high school, but I've been getting heavy inier for years.

I played tennis at the past, but now my hobbies are oil painting and espresso, so I'm having fewer exercise less.

I'm not that interested inconcerned about my body shape ifas long as I am in a healthy range.

I'm used to be a quite thin person when I was in high school, but I've gradually been getting heavy inier for years.

The "gradually" here helps express the idea that you started gaining weight as the years went by.

I once played tennis atin the past, nowbut lately, my hobbies arehave been oil painting and making espresso, so I'm having fewer (coffee), so I've been getting less exercise.

I used "...I've been getting less exercise." here, but a shorter way would be "...I've been exercising less."

I'm not that interested in my body shape if I am in the healthy range.