The thing with food science is that not every human is the same and people react differently to different things. Some people may thrive on a high fat diet, other might tolerate or even need more carbs, it really depends and isn't black and white. Thats why it's important to look at the sample size of studies among other factors.
Is there some evidence that humans really react that differently all else being equal?
Literally anything that can affect our bodies might be a confounding factor: sleep; water intake; type, frequency, duration, and difficulty of exercise; sunlight exposure; climate (average temperature, humidity, temperature swings, atmospheric salinity); elevation; latitude, etc...
