There are so many variables to account for, it would be hard to glean anything from one random study. I think a really good one would be to get all your volunteers from the same height and weight, ones they have been at for at least a year. So a bunch of 5’9" guys that weigh 160.
Then go to a different group, guys that are 5’9" and 185…And on and on. From that kind of study you might get some good info. But you have to account for anyone that has gained or lost a bunch of weight in the past 6 months or so. If some guy went from 180 to 160 3 months before the study, pretty much guarantee he is going to gain more weight than the others.
I guess this was a sedentary study too? Adding exercise would just add a bunch more variables to the noise that is already there…Good stuff though, I love these sorts of things, and eventually they get include in some meta study where some of the noise gets cancelled by numbers…
What else should they have accounted for in order to answer this specific research question? It was a remarkably thorough study. I mean, they even measured calories in their shit. They controlled intake at exactly 1,000kcal abundance, monitored activity and expenditure and also measured every conceivable way that substrates can be handled in a mammalian organism. The reason I shared this paper is because it was the first to provide the preeminent answer to the question “why is there so much variability in weight gain from individual to individual”. So when your family is all together over the holidays and some of them are complaining about weight gain, while others are entirely unafflicted, this study provided the answer to that frustrating and puzzling question. They clearly demonstrated that NEAT accounted for this variability at r = -0.77; body size, sex, resting metabolic rate, lean mass, etc…none of it was related. This is still the current state of knowledge. Are there situations where you can upset this relation? Probably, but that’s out of the scope of this particular question.
The bold is the variable here. How do they KNOW they were fed an extra 1000kcal? How do they know, to the kcal, how many calories any one person expends on a day to day basis? The answer is they cannot know that.
You can’t cheat physics here. Thermodynamics works. Now, could some people have been fed the extra and “used” it by twitching more? By shaking their legs uncontrollably? By feeling the need to get up and walk around more? Certainly. Adding extra food to your diet gives you more energy to do stuff, or some people bleed off excess energy by fidgeting. We triathletes purposely overfeed ourselves in order to expend that energy training. And it’s certainly possible for some of it to be accounted for by an increase in basal metabolic rate.
However, it is IMPOSSIBLE to control for that 1000kcal exactly.
I think all of that would be more clear to you if you read the paper. In fact, you’re describing their exact finding in your second to last paragraph.