Q: Mike, I recently went on vacation for 2 weeks and very quickly gave up the good fight and ate well out of the diet I have been eating (you described my diet as 'excellent' in a past question). During my vacation, I went to the gym 3 times and although I continued eating my veggies, oatmeal, and lean chicken, I also indulged in pastries, chocolate, ice cream, pizza, lasagna, schnitzel, and things such as this. After weighing myself upon returning to my gym, I gained approximately 8 pounds (I hit 193) and, a week later, took off 3 of those pounds. I expect to lose a significant bit more by next Friday. I have returned to my regular diet and workout schedule. My question (which may be unanswerable) is how much of my 8 lbs. is likely fat that has been added to my body and how much is just food sitting inside my system? My clothes still fit. I had a great vacation, BTW but am glad to be eating right again and going back to the gym.

A: While as you said there's no way to know exactly, I would guess that at least 3-4 pounds was just water gain which is also evidenced by how fast you were able to lose it back. In order to gain 4 pounds in 2 weeks, you'd need to overeat by about 1000 calories every single day which is quite a bit. I would be surprised if you overate that much and even supposing you did, not all of these 4 new pounds would be fat, especially since you continued to work out. So in the end I'd guess you gained around 2-3 pounds of fat, maybe 1 pound of muscle and the rest just water weight.

Sounds like you had a great vacation and now doing exactly the right thing by just getting back to your regular routine.