Eat food. No too much. Mostly plants.
Human digestive tracts are made for high-quality (bio-available energy/mass) nutrition-dense foods, unlike ruminants, or large apes like the gorilla.
And most people get plants confused with seeds. No other animal eats seeds in the quantities we do, especially as Omega-6 rich seed-oils.
Pollan has become a touchstone for many, but imho he's fairly wrong.
very good video, learned a lot
It's also perfectly healthy to eat predominantly meat, organs, and dairy if the animals are properly pastured. So the "mostly plants" claim makes little sense without a lot of qualification.
Why not?
Maybe you can achieve similar effect with some other precise diet but eating mostly plants is the easiest way to improving your health and lower you calories intake.
"Dietary and lifestyle determinants of mortality among German vegetarians" found that "A longer duration of vegetarianism (> or = 20 years) was associated with a lower risk, pointing to a real protective effect of this lifestyle"
"Vegetables, fruit, and cancer prevention: a review" states that "the evidence for a protective effect of greater vegetable and fruit consumption is consistent for cancers of the stomach, esophagus, lung, oral cavity and pharynx, endometrium, pancreas, and colon. The types of vegetables or fruit that most often appear to be protective against cancer are raw vegetables, followed by allium vegetables, carrots, green vegetables, cruciferous vegetables, and tomatoes"
"Nutrients and food groups and large bowel cancer in Europe" found that "most vegetables, including pulses, were inversely associated with cancer of the colon and rectum."