[netmonk]

Well your comment is typical to the bias “all calories are equals”

First, all calories are not equals, therefore you can be starving and pushed to store energy, in an abundant calories intake.

What matters here is bio availability or nutrient in the calories intake. If for instance your protein intake is too low, and available vitamins is poor, whatever the amount of “energy” ingested this will trigger starvation mode and energy saving. Have you ever read scientific littérature about how hybernation is dietetary induced in hibernating mammals? As shift of diet to high sugar, high seed oil (from grain) greatly available during summer (weight increase period for hibernating mammals) by lowering metabolism rate, promoting fat storage and torpor.

In early 19th, average calories intake of French and Switzerland was around 4000 to 4500 kcal a day, without obesity crisis while in the same time in American states adopting seed oils emerging products while the daily calories intake was half those amount, overweight appeared and started to spread.

So no, calories in calories out, and all calories are equal, are not true and therefore cannot be used at any prémisses of rational development.