The US Department of Agriculture has made recommendations for a healthful diet. They have presented their suggestions in the form of the pyramid, with the foods that should be eaten in the largest quantities on the bottom, and those that should be largely avoided at the narrow top.

The base of the food pyramid is grains: bread, cereal, rice and pasta. The USDA recommends 6 to 11 servings of these per day. The next tier contains vegetables, recommended at 3 to 5 servings, and fruit, at 2 to 4 servings. Above those are dairy products, suggested at 2 to 3 servings, and meat, poultry, fish, dry beans, eggs and nuts, at 2 to 3 servings. At the top are fats, oils and sweets, with the admonition to use sparingly¹¹.

Following the recommendations of the food pyramid will yield a diet of between 2,000 and 2,500 calories per day, with these calories distributed as 30% fat, 30% protein and 40% carbohydrate.

For an adult man, a calorie restricted diet would have a 40% reduction in total calories, to about 1,500 per day. These calories would come in the form of mostly fruits and vegetables, with fewer of them from meats or starches. A calorie-restricted diet does not require a reduction in the proportion of fat intake below 30% of the total, but because total calories are less, total fat is less. Meals would be small, portions would be small, and condiments would be few.

A calorie-restricted diet will produce weight loss, to the point that most adherents appear ill. Followers of calorie restricted diets are generally cold and always hungry. Because they lose so much body fat, they lose the protective cushions that protect their bones. Sitting can be painful due to pressure on bones. Walking can hurt, due to the loss of the pads on the bottoms of feet. The digestive system can be constantly upset¹².

Few adults have the ability to sustain such a diet for any length of time, much less for their entire lives. Nevertheless, there are some who do it. Whether they live longer and healthier remains to be seen and will need to be confirmed by scientific studies that include large numbers of people.