With an Ivy League PhD in physics, I’m a big fan of science.
I have not observed a scientific approach to diet effective in promoting health.
In my albeit limited observation, I observe no correlation between knowing a lot about food, digestion, etc and fitness or healthiness. In particular, American culture appears to approach diet most scientifically, yet has probably the least healthy population. Meanwhile, many illiterate cultures appear to have healthy diets (implying thousands of years of trial and error, admittedly a form of science, works).
My observations are anecdotal, not data, so feel free to dismiss them as such. I just suggest all scientific results so far, compared to what we’d need to meaningfully predict healthiness in a diet, negligibly less anecdotal.
The body is incredibly complex and diet involves multiple internal systems — digestive, motivational, cardio-vascular, etc — interacting with huge varieties of foods — themselves sets of incredibly complex systems. Looking at parts of these systems doesn’t seem effective in helping people get healthy, at least not at the level science is at today.
Generations from now science may be able to grasp this complexity and predict healthy diets at the individual level. For now, I appreciate people researching it, but I found all of their predictions for what makes healthy food based on so many untested assumptions and other logical jumps as to be worthless for anything but displaying the pre-conceived notions of the experimenters.