> The basic metabolic rate varies between individuals. One study of 150 adults representative of the population in Scotland reported basal metabolic rates from as low as 1027 kcal per day (4301 kJ/day) to as high as 2499 kcal/day (10455 kJ/day); with a mean BMR of 1500 kcal/day (6279 kJ/day). Statistically, the researchers calculated that 62.3% of this variation was explained by differences in fat free mass. Other factors explaining the variation included fat mass (6.7%), age (1.7%), and experimental error including within-subject difference (2%). The rest of the variation (26.7%) was unexplained. This remaining difference was not explained by sex nor by differing tissue size of highly energetic organs such as the brain.
So this study [1] claims ~25% difference in BMR that is NOT explained by sex, weight, height, lean body mass etc. That can mean some people can eat an extra burger a day compared to others without gaining more weight.
It's also important to note that BMR is not the only biological component here. Both CI and CO are biologically determined, they are not under 100% rational control. There are clear differences in people in terms of appetite/hunger reaction, and in terms of desire for physical activity, that we don't have a known explanation for (psychology? endocrinology? metabolic causes? gut biome? other?). This is, in fact, the biggest biologically determined component of obesity that is usually entirely ignored and blamed entirely on the individual's self-control.
[0] https://en.wikipedia.org/wiki/Basal_metabolic_rate#Causes_of...