https://pubmed.ncbi.nlm.nih.gov/15534426/
“In humans, the coefficient of variation in the components of total daily energy expenditure is around 5-8% for resting metabolic rate.”
That is nothing. That means the most extreme examples of this would be 200-300kcal. It’s often just used as an excuse for a bad diet. And people believing in this myth is hindering them in making informed decisions.
In my personal experience people judge it to be more like 25-100%. But I stand by 200kcal being nothing. It’s not a make it or break it kind of difference. 200kcal more doesn’t make someone obese or even fat. If you over eat by 200kcal a day it will take a long time to get fat and you will have years to intervene with a slight change that will fix it. And that would only be in the most extreme case. For most people we are talking about much less than 200kcal. If you have actually only a differnce of let’s say 50kcal from the median and cite that as a reason for being over or underweight it’s just wrong. But I have seen people use it as a reason so many times.