&gt; regardless of how much they eat and how little they exercise, never put on weight?<p>If I had to choose between thermodynamics and medicine being wrong, and people not being able to accurately estimate how &quot;much&quot; they eat and how &quot;little&quot; they exercise, I&#x27;d bet all my money on the latter.<p>The simple reality is, people have <i>vastly</i> different appetites. I eat fast and am always hungry. I have two coworkers, one eats quite a bit less than me (often struggles to finish a standard portion), the other eats mich more but quite slowly.<p>3 different people, 3 vastly different eating habits. The reason people gain different amounts of weight most likely isn&#x27;t in the differences between our bodies, but the differences between our minds.