When did your metabolism slow down?

Just wondering when or if your metabolism slowed down? I’m trying to gain weight and have managed to put on over 40 lbs although there is still work to do but it is hard as my metabolism seems so high – I eat every 2-3 hours.

Metabolism depends on your age, size and how active you are.   Feed your body properly and your metabolism will be running at full speed.  As you gain weight, your energy needs increase. If you're a 6'3", young man you need a lot of energy.  (See this link...http://www.bcm.edu/cnrc/bodycomp/bmiz2.html ) In another post you seem to be doing a lot of exercise..... that'll mean you need even more energy so you should look at cutting that back for a while. 

If gaining is still difficult, add an extra 500 cals to whatever it is you're currently eating and if that doesn't work, add another 500... and so on.  To be honest, I don't think your metabolism is at fault.  You're just not eating enough.

Mine slowed down in my early 20s.  When I was a kid and teenager, I could eat whatever I wanted - and I ate ATROCIOUSLY: pizzas, hamburgers, french fries, non-diet sodas, dessert with every meal, etc.  and still I stayed stick thin with no exercise.  Then once I entered my 20s, suddenly I started packing on the pounds, even after I started eating more healthy and adding regular exercise.  It sucks when you get used to eating everything in sight and remaining thin, and then you suddenly have to change your diet to carrot sticks just to maintain your weight (OK slight exaggeration there :))