The average teenager gains about 40 pounds through their teenage years naturally. So if I'm eating and gaining weight and lifting I'm good gaining muscle. However if I'm not able to lift for a couple days (say I was allready fully recoverd from the last workout), and I gain weight from eating a lot like normal will some of this weight still be muscle? Obviously some will be fat from the lack of lifting, but should some still be muscle put on naturally from my age? I would also get back to training ASAP.

The reason I ask this is because for the last week I wasn't able to hit the weight room on vacation (still did some light bodyweight exercises) but nothing compared to normal. My weight went from 149 to 151. Not sure if its all fat or some muscle too.