[He knows that Ed would never leave him behind, and he knows that his body would eventually put on weight, but that isn't the issue here. This place is so dangerous and everyone needs to pull their weight or else the whole group could be in danger.

He can't be that burden on them, just like he couldn't be that burden during the fight with Father.]

Brother...

[He reaches out a skeletally thin hand to take Ed's, still feeling a thrill of skin on skin even if his mood remains sober.]

You know it won't be that easy here, food is scarce at the best of times and moving through the snow will get a lot more dangerous if you're slowed by me.