For me it is both but mostly I'd say it is malabsorption. I can feel well and eat like crazy but my body just never seems to take it in, keep it there, and turn it into weight. That has been a battle all my life. I have tried and tried many times to gain weight over the years, but just as things start to look up, I start shrinking again for no reason. There are some times when I have really bad stomach issues and just dont want to look at food let alone eat it, but I have tried to force myself to eat anyways. For the most part even when I don't feel well, like now, I still eat as much as I can... even when it means take a few bites then waite and come back 15-20 mins later for a few more bites.