The golden rule of reducing fat: strength training+aerobic exercise+dieting. First, 40 minutes of strength training will consume a lot of sugar in the body first, and then aerobic exercise will burn a lot of fat in the body, and the effect is more obvious. Practice three points and eat seven points, not only eating meat, but also high-energy substances such as chocolate and carbonated drinks will make your exercise in vain, so eat low-fat and low-energy food.

40 kg is too thin. You'd better lose weight to 50 Jin first. With proper training and diet, 3 months is ok.