When it comes to diet, it’s now clear that one size doesn’t fit all. Different people have different metabolic types, so meat that is life-saving to some and sheer poison to others.

We also have very different levels of the fat hormones leptin and ghrelin, which regulate appetite and fat levels, and appear to play an essential role in regaining lost pounds after a severe weight-loss regime.
Even the state of your microbiome, and the particular bugs that inhabit it, can play a big part in whether or not you can easily reverse illness or lose weight.
Then there are individual reactions and intolerances, even to healthy foods.
Several years ago, two scientists at the Weizmann Institute of Science in Israel carried out a unique study of 800 people, attempting to identify which foods caused blood sugar spikes after meals. They’d hoped to determine the foods and dietary factors responsible for the worldwide epidemics of obesity and diabetes.
The problem was, they found no single uniform response to any food, even sugar.
Virtually everyone in the study had highly individual reactions to plates of food put in front of them. One prediabetic woman cut out all offending foods, but still couldn’t control her blood sugar until she discovered that the true culprits causing her own spikes were tomatoes.
Certainly more and more forward-thinking doctors and naturopaths are turning to the paleo diet to heal chronic conditions.
Less is more
But if I had to choose a single diet that is essentially good for almost everyone it would be the not-eating diet—at least for a spell.
New evidence shows that the ultimate one-size-fits-all diet for restoring full health is either a short-term fast on water or liquids or intermittent fasting—controlling not simply what you eat, but when you eat.
Giving your body a short break from food affords it a chance to do a major clear-out, breaking down old and possibly defective cells and consuming them.
Monitored water or juice fasts have been shown to reduce aging and to prevent or heal cancer, dementia, arthritis, high blood pressure, and other conditions that lead to heart disease. It even helps to target chemotherapy more successfully, suggesting that the standard medical advice to cancer patients, to consume lots sugar-laden food to keep their weight up, is completely counterproductive.
But water- or juice-only fasts need to be monitored and short term. And they aren’t a successful means of losing weight. Usually, any weight loss is short term, and the body, which goes into starvation mode, slows down its metabolic processes.
Timed intervals
The latest tweak on fasting is intermittent fasting. Researchers are discovering that leaving a larger span of time between your last meal of the day and the first one the following day also has an extraordinary number of health benefits, including weight loss, without the difficulty of depriving yourself of food.
Pushing breakfast to noontime, cutting out dinner or eating your meals during an eight-hour window has been shown to decrease not only blood glucose levels but also evidence of inflammation in the body.
In many animal and human studies, periodic fasting has shown exciting evidence of protection against a vast array of degenerative diseases and even brain seizures. And perhaps most exciting of all, it appears to help cells regenerate themselves, including in the brain.
Diets where you focus on restricting both the amount and types of foods during certain periods are showing extraordinary benefits, not only for weight loss, aging and a host of diseases, but even bone renewal.
Of course, there are certain people who should never fast. Pregnant women, type 1 diabetics, those with liver disease and others come to mind. You need to work with a qualified professional, and you need to know how to prepare your body for a fast and then how to start re-introducing food.
My late friend nutritional pioneer Annemarie Colbin once told me of a woman who, convinced that a fast would cure her long-standing health problems, embarked on her own strict liquid-only fast, trudging through the freezing New York weather without sustenance for months, only to find that she was more ill than she had been before she began
But given the longevity research showing that many people living in the Blue Zones, those areas like Okinawa in Japan and Sardinia in Italy with the longest-living people on earth, eat 10–40 percent fewer calories than the Western average, we might all do well to adopt the Okinawan blessing at dinner time as our New Year’s resolution: Hara hachi bu. 
“May you eat until you are eight-tenths full.”