|We can't say with certainty what IS an optimal diet, but we can say that this is probably not it.|
The actual study is cited below.
The gist of it is, the few remaining hunter gather cultures we can study tend to be healthier (albeit there live are much rougher in most every way than ours) and while their diets are not identical to each other, they all share one thing: they all eat real food. And while on average they do get more exercise than we do, actual energy expenditures are not much different than ours.
When it happens that former members of these groups move to the city, take on modern jobs and start eating like us, they get fat and sick like us.
So, eat real food and move around on a regular basis. There may not be anything more optimal than that.
Pontzer, H., et al. “Hunter-Gatherers as Models in Public Health: Hunter-Gatherer Health and Lifestyle.” Obesity Reviews, vol. 19, Dec. 2018, pp. 24–35. Crossref, doi:10.1111/obr.12785.