Calories in &#x2F; Calories out is still perfectly valid.  It&#x27;s just that the same portion of the same food might be considered a different number of &quot;calories in&quot; for different people.<p>The &quot;big-boned&quot; or &quot;genetically fat&quot; arguments still reek of BS, but it&#x27;s worth humoring the idea that we aren&#x27;t 100% efficient machines that absorb the exact number of calories on the Nutrition Facts box, or burn the exact number of calories displayed on the Treadmill screen...<p>There&#x27;s a intelligent middle-ground between equally ridiculous ideas that we are &quot;Healthy at Every Size&quot; and that we are perfectly tuned biological machines.