Boss Man wrote:It depends on the circumstances. If you replaced some fat with the same muscle weight, because the muscle was helping to burn some of the fat, then theoretically your body composition could change without weight changing.
I agree though that at a lean weight it would be more unlikely, but if the person was somewhat overweight, then it would be more likely.
You hear of people complaining that the scale appears not to be moving, but when they say they are getting a thinner waist and heavier lifts, it makes sense. More strength, replacing less fat, equalling the same weight, but different body composition.
Though I agree if the person was for example 12% fat, then gaining muscle would be likely to add weight, either from the muscle or from some additional fat too.
I agree. You can reduce your waist size and not lose any weight by weight lifting. But the original poster said "...I am very lean and thin...". From that remark I would suggest that he increase his caloric intake significantly along with his protein intake.
There are members here who are far more knowledgable about nutrition than I am, but I was always told to take in one gram of protein daily for each pound of body weight you wish to achieve.
So the O.P. is 5' 7" and weights 48 kg (106 pounds). I would say that at that height he could easily carry 165 pounds. So I think he needs to increase both his caloric intake eating calorie-dense foods and also increase his protein intake.
And if my weight calculation is correct, then I think both his self-image and his health would improve by gaining some weight.