It seems that some people are more genetically predisposed to
gaining weight than others. But does anyone know how it's expressed?
What physiological difference makes some people gain weight very easily
while others can't seem to gain it at all?
It doesn't seem just a matter of appetite, or is it? If not, then where do the calories
go? Is it a matter of absorption, or the so-called "nutrient partitioning", or differences
in "metabolism"? (whatever they mean by that)
For example. what advice would you give to someone who actually
wants to *gain* weight?

TIA