In our conversation toward the end you asked a question and I didn't give a complete answer. Many people do not have to resort to extreme diets to avoid diabetes and other problems of dietary excess. They don't have to go on diets to lose weight. Why some and not others? There's an overarching issue, and aspects of that issue. Basically it comes down to quality of calories, and how many calories are consumed vs burned. It's not a mystery, but in the modern world we are mystified, and as a result many of us develop health problems that are dietary in origin. These health problems can take many forms, collectively they are known as "metabolic syndrome". Here's the Mayo Clinic page for metabolic syndrome https://www.mayoclinic.org/diseases-conditions/metabolic-syndrome/symptoms-causes/syc-20351916
Ironically allopathic medicine isn't very good at treating this condition. I base that on the fact the vast majority of people with the condition end up in doctors offices and are given medications that are not really helpful. The only real fix is dietary, and doctors are not in the business of teaching lifestyle change. For people in that situation lifestyle change is typically difficult, we unconsciously associate survival with early dietary patterns. We really need a psychotherapy focused on lifestyle change, but current psychotherapy doesn't do that. Meanwhile current conventional treatment is not effective for the most part.
That is the reason movements like paleo and whole food plant based spring up, grass roots solutions that can be very effective. These provide cultural support for new dietary patterns, which helps with the unconscious survival association problem. Without some kind of support along these lines, most find losing weight nearly impossible, the yo-yo diet problem. "Diets don't work" for a variety of reasons, one of them is we tend to think of them as a fix as opposed to a permanent change of lifestyle. Permanence requires underlying cultural support.
Vegan and paleo are pretty vague terms, hostess twinkies, basically just a metabolic poison, are "vegan". The better term is whole food. As a plant based person I frequently send people who would be receptive to the plant based approach to The Physicians Committee for Responsible Medicine in DC for information and perspective. https://www.pcrm.org/ They have been effective in holding the FDA's feet to the fire in various ways, one is the influence they've had on the Dietary Guidelines Committee who update recommendations every 5 years. The Physicians Committee has been effective in countering the influence on the recommendations process from industrial groups with big DC lobby organizations.
Most people are not receptive to the plant based approach, although that is changing rapidly at this point, and for them paleo will be the "accessible" solution.
To summarize, some people do not have to think very much about eating more healthfully because they were raised that way, and are more resistant to the processed food industry's tidal wave of toxic "food like" substances deliberately engineered to be addictive. In addition to manufactured addictive "foods" are other factors: the fast food restaurant industry, our overall inability to stem the tide of toxins disguised as food, and conventional medicine's inability to address the problem. The combination of these factors has produced a developed world health disaster that is particularly pernicious in the US.
Consider one statistic alone: Covid related mortality in the US from the beginning of this epidemic, about 9 months now, is currently at 250.000. In any nine month rolling period US heart disease mortality runs at 600,000. But heart disease is reversed with a whole foods plant based diet, and rather quickly at that.
Part of government resistance to supporting this is "former patients" who reverse metabolic (diet caused) health conditions will no longer "need" the variety pack of medications the pharmaceutical industry produces for metabolic conditions. In fact continuing these medications after conditions are cleared becomes dangerous to health. The combined revenue from these medications is probably where most of the profit is produced by the pharma industry (fact checking that angle of inquiry is not all that easy). Revenues lost by a whole cloth adaptation of whole food diets, especially a more plant based diet, would have sizeable negative impact on GDP, producing an economic problem at a point in time when developed world economies are laden with debt and already very fragile.
So we have a large scale health and economic conundrum on our hands, with no quick and easy solution. Meanwhile individuals can reverse all these metabolic syndrome conditions if they are lucky enough to bump into the right information, and motivated enough to make those changes.
