I think the reason it helps people is because fat and protein can keep you feeling fuller longer than carbs. A calorie is a calorie, though, and when you're normal weight you have to cut really low to lose weight, exercise really hard, and/or settle for very slow weight loss. If you don't have problems controlling your hunger, it's probably best to eat normally. There was a study awhile back where they put people on exact calorie-controlled diets and the keto ones actually lost weight slower. I've never been more than 5 lbs overweight (which yes was gross), so I don't know about tightening up loose skin, though.