As I mentioned above, more than half your daily calories should come from the two lower levels of the pyramid, which are principally sources of carbohydrates. By following this recommendation, you will automatically correct the typically excess intake of fats and animal protein so detrimental to the health of the cardiovascular system, liver, and kidneys. Because carbohydrate foods tend to be less calorie dense, people following this type of diet often weigh closer to the desirable than those eating the typical American diet. These carbohydrate foods are a better source of calories to fuel your muscles and brain, and should comprise the bulk of your daily intake of food.

Carbohydrates come in two forms: the first is digestible, consisting mainly of complex starches and simpler sugars; the second is indigestible fiber Many dietary guidelines recommend eating less sugar; one good reason is that for some people simple carbohydrates can make blood fats rise, perhaps even raising cholesterol levels. Some experts suggest that overconsumption of sugars also brings on diabetes. Don’t forget that alcohol of all kinds contains concentrated amounts of sugar.

Complex carbohydrates come from whole grains, fruits, and vegetables, especially the starchy vegetables such as potatoes, corn, and winter squash, and legumes such as peas, beans, and lentils. All of these foods are naturally high in vitamins, minerals, and fiber. Increasing carbohydrates in the diet is generally a good idea because they are less efficiently converted to storage fat, are more filling (which enhances the feeling of fullness), and lower in calories per volume than comparable processed and refined foods. I recommend getting 60% to 65% of total daily calories from carbohydrate foods; whenever possible, use whole grain bakery products such as breads, muffins, and so on made with reduced amounts of total and saturated fats. These products are higher in vitamins, minerals, and fiber, other nutrients that may help to postpone the onset of cardiovascular disease, arthritis, diabetes, and other chronic diseases.

The easiest way to tell which carbohydrates are simple or complex is to refer to their glycemic index, which is a measure of the carbohydrate’s ability to raise your blood sugar in a given period of time: the higher the index, the faster the blood sugar rises. High-index sugars and starches cause a quick spike in blood sugar often followed by a quick decline. The roller-coaster ups and downs may leave you looking for more sugar too soon, and in some sensitive people, may even raise saturated fat and insulin levels more than is healthy. Lower index sugars and starches sustain your energy and suppress your appetite over a longer period of time, usually without triggering fat and insulin overproduction.

Not surprisingly, simple sugars like glucose, honey, and maltose have the highest indices, followed by alcohol and refined breakfast cereals such as corn flakes or "puffed" grains. Both baked russet and instant potatoes are higher index foods. Refined (white) and wholemeal flours, as are found in most bread and bakery products, are all indexed at 100 by definition. Most people are surprised to learn that there is no difference between wholemeal and white breads; I presume it is because today’s whole wheat bread flour is as finely ground as white wheat flour. Wheat kernels themselves, as used in cracked wheat bread, for instance, have a much lower index. Other whole grains, all fruits, all legumes, all pastas, and all other starchy vegetables are moderately to extremely low on the glycemic scale. Some are lower because the fiber, which has not been stripped away by milling or processing, slows down their absorption, while others are lower due to the nature of the carbohydrate itself slowing the digestion. I believe the latter reason explains the interesting fact that honey has one of the highest indices and fructose, a common fruit sugar, is among the lowest of all foods. Fructose can be used as a sweetener that does not produce rapid rises in blood sugar. Another oddity is that both boiled and sweet potatoes are lower index foods, while baked russets are higher. I recommend using high-index carbohydrates sparingly, using the coarsest textured bread and bakery products, and using other whole grains, fruits, pastas, and starchy vegetables liberally.

Glycemic Index of Some Common Foods

In order to set a base number, researchers fed subjects 50 grams of white bread and measured their blood glucose level. This was assigned the number 100. Other foods are rated in comparison to this standard.