&gt; Does this actually happen, I don&#x27;t know, but I believe from personal experience and reading forums that there is a phenomenon of hitting a weight plateau that is not explained by the simplistic calories in, calories out theory.<p>It doesn&#x27;t. People are bad at self-reporting their intake. Reading forums isn&#x27;t a good source of information.<p>Even if there was some kind of ultra-efficiency mode, it&#x27;s worth noting that it doesn&#x27;t mean calories in&#x2F;calories out is wrong. It doesn&#x27;t disprove the law of conservation of energy, I don&#x27;t see why you think these two concept are opposed to one another.<p>The reality is that there is no special starvation mode or metabolic damage that makes people ultra-efficient food processing machines. The research doesn&#x27;t support it and a bunch of forum posts of people self-reporting their intake (badly) or outright falsifying information (but everything on the internet is true!) isn&#x27;t backing up your case.