.
>
> Hmm. Are there any adverse side effects of being *under* weight?
> Providing you're getting all the required nutrients and a reasonable
> amount of calories?

may be more sensitive to hypoglycemia that is in itself very damaging.( no
reserves to buffer ), it could  mean also muscular weakness but some very
underweight peoples in third world countries are able to carry tons on their
back in a day like when unloading a ship for ex .

i can see also maybe of a possibility of hormonal unbalances ( by lack of
fats reserves ?)

jean-claude