OK, here's my explanation for why the Developed World is suffering a crisis of obesity, diabetes, depression, malnutrition and the ubiquitous 'tired all the time' syndrome that all doctors see every day and have no idea what to do about.
If it's true, then any Third World society that adopts our lifestyle will suffer.
Those descended from wheat growing, potato growing, or rice growing ancestors will suffer from the problems that we're suffering from.
Those that are descended from hunter-gatherers who never went through a farming phase, or from those who farmed crops which are low in fast carbohydrate will suffer horrific problems. Epidemic Diabetes, Widespread Uncontrollable Obesity, Widespread Suicidal Depression.
The staples of our modern diet are wheat, rice and potatoes.
Almost all our foods are based on them. What did you have to eat today? A sandwich? A pizza? Pasta? A curry? Rice with that or chips?
Wheat and rice are just types of grass. Grasses distorted out of all recognition from their ancestors by generations of selective breeding so they've got huge seeds. Potatoes are just some freaky stuff from the other side of the world. No ancestral human ever ate one.
We were never really meant to eat grass! Wheat and rice are absorbed far too fast into our blood, causing "sugar shock".
The sugar shock, although dangerous, is actually pleasant. A feeling of fast relief from hunger. We become addicted to it in the same way that smokers become addicted to cigarettes.
By releasing insulin we can deal with the sugar shock, but the recently absorbed carbohydrates are quickly stored as body fat, blood sugar levels overshoot on the way down, and we soon feel tired and hungry again.
We get into a cycle of over-eating, with periods of satiation interspersed with periods of lassitude.
The mood swings and tiredness make our lives burdensome, and can lead to full scale depression.
Anyone trying to resist this cycle feels as though they are constantly trying to give up smoking. Anyone just going with the flow get steadily more and more obese.
If you do large amounts of exercise, you can hold your weight steady, but even this doesn't really work, because if you actually manage to put yourself into a state where you're using more calories than you're consuming, you get hungry and eat more to make up. And every time you take a week off....
So anyone eating wheat or rice or any other high carbohydrate, high GI food is on a sort of ratchet.
If you act as you like, you will get steadily fatter and fatter.
If you exercise heavily, you will stop the increase in weight, but not reverse it.
If you starve yourself deliberately, you can actually reduce your weight, but you will do it mainly by reducing muscle mass, which just makes the fat gain problem worse once you stop starving yourself.
Unfortunately, "high carbohydrate, high GI food" describes the normal diet of Europeans and Americans, and indeed is the diet generally considered to be healthy in the West.
High carbohydrate, high GI food is the diet recommended by governments and most organisations promoting weight loss.
The constant sugar shocks cause our insulin system to fail. After many years of them, we develop type II diabetes. This combination of overweight and diabetes, together with a few fat-related conditions that are probably to do with crap like margarine and the trans-fats that are ubiquitous in processed food, are known as the 'metabolic syndrome'.
Luckily for us, we've had some time to adapt. The invention of agriculture was maybe 10 000 years ago. The new foods must have killed in vast numbers at the same time as they caused the population explosion that led to civilization.
We are the descendants of those that survived. We are better able to tolerate this stuff than the wild hunter-gatherer humans we descended from and have largely exterminated.
But we're still ironing out a few wrinkles.