Using my rights,
You have to look at lean body mass, and you have to look at overall body weight. In your case you probably haven't got much fatter and maybe a bit stronger. from 140 to 155 you said. I'll assume that at 140 you were in fairly good shape for a 17 year old and maybe you were 10% body fat 14 pounds, 126 pound lean weight. Now at 155 lets say half the gain is fat and half muscle, then your lean body is now 134 pounds and your body fat is now 22 pounds.
If you were to keep to 25% of your lean weight, you would carry no more than 33 pounds of gear, but if you were to subtract your 22 pounds of body fat from the 33 pounds, then you would have 11 pounds left for gear, or 7% of your body weight.
This is to say that there is no percentage of body weight rule that makes sense, unless it framed in terms of your condition.
BUT - if you loose 15 pounds of body fat that you have gotten used to carrying around, you can add 15 pounds to your pack. People have very different amounts of muscle and in different places. You may have a whole 20 pounds of leg muscles carrying 180 pounds up a hill.
Now when I weighed 145 and I was about 5% body fat, I carried a 45 pound pack and it was about the limit. Now at 175 and 60 years old I prefer to stay under 25 pounds if I have to do any climbing, or 14% of my body weight and I am less thn 10% body fat again.