The law of thermodynamics (calories in vs. calories out) is the fundamental and universal mechanism of weight loss or weight gain, and claiming otherwise does a disservice to individuals.

noli's read

The principle of energy balance (thermodynamics) is the cornerstone of nutritional science, confirmed by countless meta-analyses and randomized controlled trials (RCTs) (e.g., JAMA, 2007). The body cannot create energy out of nothing; if one consumes less energy than one expends, the body draws from its reserves. Where the discourse becomes complex is in its application: the idea that it is sufficient to "eat less" often ignores the real difficulty of regulating hunger, the impact of food composition on satiety, or individual metabolic variations (adaptive thermogenesis). The creator is correct regarding the pure physiological mechanism, but sometimes omits that psychology and environment make the practical application of CICO extremely difficult for many. This is not a challenge to physics, but an acknowledgement that human behavior is multifactorial. In short, the model is scientifically accurate, but its oversimplification can obscure the real obstacles encountered by individuals on their wellness journey.

the sources

1. 1Hall KD, Heymsfield SB, Kemnitz JW, et al. 2012
2. 2Rolls BJ 2009