Protein and fat calories are digested and stored for other important uses, like making new muscle cells and accumulating concentrated energy for potential future use. But the fuel that gets us going in the morning and keeps us going all day long comes from our carbohydrate foods.

Choose the Carbs Our Bodies Know Best

The carbs that work best for us are the ones most familiar to the human digestive system, dating all the way back to Paleolithic times: unrefined, minimally processed high-fiber whole grains, fruits and vegetables.

Stone-ground 100 percent whole grain breads, old fashioned rolled oats, brown rice, pasta and noodles made from durum wheat, yams and sweet potatoes, steamed or raw vegetables, berries, citrus fruits, apples, pears, stone fruits and grapes are some common examples of these “familiar” carbohydrate foods.

These carbohydrates are low glycemic index (GI) foods that offer the body many of the daily nutrients it needs (calories, protein, fiber, vitamins, minerals, phytonutrients) while providing slowly released glucose into the bloodstream.

Food editor’s note:Don't neglect getting regular exercise, which allows the body to tolerate more carbohydorates.

Making the switch to low GI carbohydrates? Here are some suggestions:

Read product labels.Seek out products that are made with whole grains and whole grain flours rather than enriched wheat flour, which has had the bran and much of the fiber and nutrients removed. You can also keep an eye out for unwanted ingredients such as trans fats and chemical additives and fillers.

Look for breads and rolls whose first ingredient listed is whole wheat or whole rye flour, rather than enriched wheat flour. Whole wheat pita bread and 100 percent whole wheat English muffins are widely available.

Look for whole grain crackers like Ry Krisp, Ry Vita, and Wasa. Avoid crackers such as Saltines, Ritz, Melba Toast, Wheat Thins and others made from enriched wheat flour.

Choose old fashioned or rolled oatsinstead of quick, one-minute or instant oats.

Choose minimally processed high-fiber cerealslike Kellogg’s Complete Oat or Wheat Bran Flakes, All Bran With Extra Fiber, Kashi and Fiber One.

There are a few fruits that naturally contain a fair amount of glucose: bananas, pineapple, watermelon, raisins and cantaloupe. These fruits are best eaten in small quantities, as part of a fruit salad, for example. Another good rule of thumb is to eat the whole fruit rather than drink the juice. For example, eat an orange rather than drink a glass of orange juice.

Replace white potatoes with sweet potatoes or yams. And remember that potatoes, corn, peas and winter squash are considered starches even though they are vegetables.

Avoid puffed, airy, refined starchy snackslike rice cakes, popped corn or pretzels. Better choices are dry-roasted nuts, cooked sugar-free puddings, reduced-fat or no-sugar-added ice cream, fruit smoothies made with fresh or frozen fruit, skim milk or light yogurt, whole grain or bran muffins and low-fat oatmeal cookieS.