2 Fitness is more effective for shaping. Fitness will reduce fat, but at the same time it will strengthen muscles, and generally the weight will not change much in a short time.

If you want to lose weight (or gain weight), I'm afraid fitness alone is not enough. More importantly, it is combined with diet. For example, to lose weight, you need to eat less high-calorie foods, eat more fruits, etc., and exercise more to increase energy consumption. You can eat more food such as steak to gain weight.