&gt; &quot;No dude, you are ignoring the fact that these people did not have ample fat stores.&quot;<p>I don&#x27;t think I am ignoring it. You seem to be asserting that their issues with calorie restriction were lack of body fat. There is no evidence for that I am aware of. A simple rejoinder based on anyone&#x27;s experience, do fat people get hungry? If they do, why? They have all that energy available. But I don&#x27;t need to rely on arguments like that, since in the vast corpus of research on this at this point, it&#x27;s pretty well established that calorie restriction <i>by itself</i> (even with exercise) does not work long-term. The failure rate is astronomical and it is in part due to what plain old calorie restriction as we&#x27;ve been told to do it does to metabolic energy and also due to the psychology of hunger. Also, and this is very important, <i>a full fast does not have these effects according to the evidence.</i> People can totally abstain from food for very long periods of time (depending on body fat), with very little hunger. It is smaller scale calorie reductions, without breaks (like the breaks intermittent fasting provides) and without much dietary fat since fat is highly satiating, that cause these reactions to calorie restriction.<p>&gt; &quot;This is basically unrelated to your statements about insulin though, so don&#x27;t conflate the two.&quot;<p>Again, I&#x27;m not. I was responding to the request for a source on the idea of energy output reduction in response to lower calories. I&#x27;m not claiming there is a link between energy output reduction and insulin.<p>Fat people <i>can</i> get energy from fat stores, just not in the way we are typically told. If it was impossible to get energy from fat no one would ever lose weight, which is trivially and obviously not true.