That’s assuming perfect conversion of energy to body fat. That’s never the case due to losses, and everybody is _vastly_ different:

> In response to 84 days of 1000 kcal/day of overfeeding, 12 pairs of monozygotic twins gained on average 8.1 kg, but the range was from 4.3 to 13.3 kg.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2897177/

Your arithmetic does not support the use of the word vastly. It only diverges by mine on the line above by 25%.

> 4.3 to 13.3 kg

That’s not a vast range? It means some people gain more than they „should“, and some less than half of the caloric intake.

It’s also not „my“ arithmetic btw.

Apologies. Though my statement holds with s/Your/That/.

My original response was to a comment suggesting that overweight and obese people get home and eat 15 chocolate bars. My observation, supported by your additional evidence, is that a small imbalance has a substantial cumulative effect.

The study was with 12 pairs of identical twins. Variation of 25% in IDENTICAL TWINS suggests that variation among genetically different individuals is probably going to be much larger.