AMA #22: Losing fat and gaining fat: the lessons of fat flux

You can absolutely be in ketosis and gain weight. You can absolutely be [a] 'fat burning machine' and still accumulate fat.

How do you lose fat? So, broadly speaking, there would be two approaches to this. One would be to reduce the total number of fat cells. Another way would be to shrink the fat cells.

Mass cannot be created from nothing, and mass cannot disintegrate into nothing. So, if a fat cell gets larger, there is a net accumulation of fat in that cell relative to how much goes out of it. And the converse is true.