The 23-year-old swapped West Brom for the Potters in the winter window after a difficult spell that saw him ostracised at The Hawthorns by Baggies boss Tony Pulis.
The spell on the sidelines saw him sent to France for a conditioning programme having been deemed unfit but the striker feels refreshed in his new surroundings and is reaping the benefits as he looks to get back amongst the goals.
"I've lost about six kilograms, six or seven," he said. "It's been very easy for me to shift that weight. The way my body is, when I'm playing, I trim down. When I'm not playing, I put on weight. I've got to blame my family for the genes they gave me.
"It's just that I put on weight easily if I don't move. If I don't do exercise, my weight just goes up. That's what happened at West Brom."
With only three top-flight games left this season, Berahino will not have many more opportunities to play before the summer, yet he has assuaged fears he could soon be out of shape again by vowing to embark on a lengthy pre-season programme.
"It's difficult when you're not involved," Potters manager Mark Hughes added of Berahino.
"We know the circumstances at West Brom. He's benefited from Premier League training day in, day out. He's in a better place physically and mentally.
"Clearly, he's playing games and enjoying it. There's more to come from him. It will take time. He's looking forward to next year - he's telling me he's going to have a week off and that's it, he's going to work all summer - that shows the attitude.
"It doesn't surprise me. We've been really pleased with him. He's trying to get back to what we know he's capable of. He's not there now and it's frustrating for him. It plays on his mind - he wants to get off the mark. It'd be nice to get him on scoresheet before the end of the season - that would be perfect."