The previous exercise turned the body into muscle. Once you stop exercising, your muscles will be covered with fat. Usually such obesity is the most difficult to reduce!
Losing weight is a cliche. Just do sit-ups every night. Don't set your goals so far, start with thirty every day.
Stick to it for a while, and it will be very effective in two or three months. If you feel relaxed, increase it to 50 (in fact, you can achieve the expected goal without increasing the amount, as long as you can persist)
Still that sentence?
Persistence is victory!
Come on!