> This is only true in the first up to 6 months of a calorie-restriction diet. Then, body adjusts its metabolism (lower body temperature, making you feel more lethargic to keep you from exercising, etc) and your weight begins to slowly climb back up, sans any further calorie restriction. At this point, it's easy for a dieter to blame himself of lacking willpower: "it worked, and it stopped working now, I must've been not strict enough!".

> The same thing happens if you force someone to overeat even if they're not hungry. They will gain weight -- for up to 6 months. Then, the body increases its base metabolic rate and adjusts to the new food intake level.

This is pseudoscientific garbage. There is some amount of adaptation that the body experiences in response to a caloric deficit or surplus. It varies by person but is generally not a major effect. A few hundred calories is typical and is largely attributable to changes in NEAT.

This is also not an unbounded effect. It won’t prevent continued weight loss if the starting deficit is greater than the adaptation nor will it prevent continued weight gain if the surplus exceeds the adaptation. The many obese people in the world are proof that the “natural set point” does not place a cap on weight gain.

There is also definitely nothing magic that happens at the 6 month mark and the absurdity of this should be enough to make it clear that this is garbage.