Almost all nutrition science is junk science. Most studies are observational, rely on self reporting, lack a biological rationale beyond fitting into the fantasy universe of nutrtion science, or have issues regarding data mining, and those are only the most glaring deficiencies.
But recently I came across a very well done study:
"Effects of a low-carbohydrate diet on insulin-resistant dyslipoproteinemia—a randomized controlled feeding trial"
The study has the following characteristics:
There is a sound physiological rationale underlying the research
It is randomized (but not blinded or double blinded which would not be possible)
The intervention is precisely defined and controlled and allows for evaluation of dose/effect (the subjects received free food)
There was a proper run-in (all subjects were fed a hypocaloric diet leading to weight loss prior to the study period)
End points are well defined
There is more, but the listed characteristics are what distinguishes this study from nutrition junk science.
Here is an editorial explaining the physiologic model used for generating the research questions:
The carbohydrate-insulin model: a physiological perspective on the obesity pandemic"According to a commonly held view, the obesity pandemic is caused by overconsumption of modern, highly palatable, energy-dense processed foods, exacerbated by a sedentary lifestyle. However, obesity rates remain at historic highs, despite a persistent focus on eating less and moving more, as guided by the energy balance model (EBM). This public health failure may arise from a fundamental limitation of the EBM itself. Conceptualizing obesity as a disorder of energy balance restates a principle of physics without considering the biological mechanisms that promote weight gain."https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8634575/The study itself:
Effects of a low-carbohydrate diet on insulin-resistant dyslipoproteinemia—a randomized controlled feeding trial https://academic.oup.com/ajcn/article/115/1/154/6369072And a video discussing the study in lay terms (mostly) from Mayo Clinic:
https://www.youtube.com/watch?v=PWi3GKH0R-w