Back when I was a teenager I used to smoke crack a lot and I was very lean despite the amount of food I was eating. I smoked a lot of crack so my appetite wasn't too suppressed due to my heavy tolerance. Because of this I used to eat many calories while being high on crack, sometimes up to 4 thousand. Because of this I was perceived as having a fast metabolism. People usually believe that naturally lean people have fast metabolisms so they are able to eat as much food as they want. I also believed this, but now i know, they were SMOKING CRACK.
I'm naturally skinny and I think part of the reason is that I don't find food as rewarding as other people. It probably has something to do with dopamine circuitry.
Also, it appears that a history of dieting is a big risk factor for being overweight. Maybe naturally lean people never got suckered into being on diets when they were teenagers and therefore never messed up their metabolism.
Yes, I have been naturally skinny all my life. In fact at one point the more I ate the more I seemed to lose weight! It turns out I had celiac disease. Remember skinny does not always equal healthy.
For me, it's probably genetic. I'm slightly over 6 feet tall and have been between 175 and 180 since high school, which was some number of years ago. My body maintains a tight homeostasis in that range, regardless of my eating habits. If I pig out and not exercise I will add body fat (apparently at the expense of lean mass), but without gain in overall weight.
I wonder about Paleohacks sometimes - as soon as I come up with a question, somebody out there is already asking it.
I cannot answer your question. I cannot even offer any plausible explanation, but I can describe my trail of thought.
All my life I was somewhat chubby and was unable to lose weight no matter how hard I tried.
The only two times I actually lost weight were the periods of time when I was quite happy.
Well, just recently I was diagnosed with hyperinsulenimea. However, it only manifested itself when my gut was completely screwed up.
I know a family where both the mother and daughter eat a $hitload of cookes, cakes and other things on a daily basis, tons of carbs, including pasta - yet they both are incredibly slim and beautiful! No anorexia or bulimia of any sorts.
The way my body reacts to carbs - it takes me 10 plums a day, I mean just ten! to gain weight.
However, while being pregnant with me my mom was under a lot of stress and I was quite a heavy baby (around 9 lb) when I was born. I suspect gestational diabetes that went un-diagnosed and untreated.
So, here are some of my guesses, and they are mere guesses:
1. Your metabolism is closely tied to your gut flora.
2. Your metabolism is affected by your emotional state and stress response.
3. Your metabolism is set in the womb and it is affected by the amount of stress the pregnant woman experiences as well as the stress the child is exposed to. Epigenetics are a huge factor in all this.
leaner people eat less and/or move more than less lean people. Having lots of lean muscle mass can help if your metabolism is slower than you would like.
I think it has to do more with bone structure & frame size. I know some pretty lean people who don't look it at first glance because either their hips are too wide or their face is fat. I have huge thighs but I consider myself lean.