I have no real knowledge of the science behind metabolism.
I know for a fact that when I was in high-school I could never gain any kind of weight....yet I took in nearly 5 thousand calories/day.
Back 6-years ago I was involved in cross-country, in under 3-hours my body would absorb 4 school meals plus 2 cartons of milk.
At this time, I was 5 foot 9 and 140-45 with less than 7 percent fat.
No matter what I did would gain weight.
Now for my regimen change, I started in January of this year.
I cut out any form of junk-food for an entire month, while enduring a extreme series of self-made workouts.
If anything I have gained a slight-knowledge into metabolism by now. During the 1st 45-days I started cutting fat fairly rapidly along with toning. I do not know how I accomplished the feat of toning and cutting fat while maintaining an overall weight range of 173-75 during that 1st period.
After this 45-day period, I started to drop fairly rapidly.
It may seem like a fair amount of time now, but from jan to now I've dropped to 158-pounds 17-pounds.
I now am 5 foot 11....158 with around 10% fat.
For me the metabolism is key.
Throughout life there are bumps along the way some may be painful...others not...who gives a damn in the end you'll still die