Ways to SLOW the metabolism: do they exist? For my entire adult life (I'm 34 now), I've had a fast metabolism. 

I've had my thyroid function tested 2 - 4 times in the past decade, and it always comes back normal. Usually it leans slightly toward the "fast" end of normal, but definitely NOT in the range of hyperthyroidism (overactive thyroid). 

I've also had bloodwork to see if I have malabsorption of certain nutrients, which could explain my difficulty in gaining weight and might indicate an intestinal or metabolic disorder. Those tests came back normal also.

So basically I have a fast metabolism and need to live with it. However, now that I got a new job that's more active, and now that I'm on Wellbutrin for my ADHD & anxiety, I'm actually losing weight -- and I don't want to! :( Being underweight has its own set of health risks; it's not just overweight that's bad!

There's a million ways to boost the metabolism, but I've never heard of anything to SLOW it. I'd prefer natural remedies if possible. Any tips??

Summarized question: What treatments help combat weight loss as a side effect of Wellbutrin?