Unrefined, natural carbohydrates (vegetables, fruits, whole grains, potatoes) burn like softwoods in your fireplace. In addition to being rich sources of vitamins, phytochemicals, and minerals, these foods provide a steady burning fire that will last many hours.
According to the diet recommended by Nutrition and Your Health: Dietary Guidelines for Americans (fifth edition, 2000), more than 60 percent of our foods should be in the form of complex carbohydrates. Lots of salads, fresh or lightly cooked vegetables, and raw fruits are primary in this approach. Whole-grain cereals and breads, brown rice and other whole grains, beans, nuts, and seeds - these foods will adequately supply necessary fiber as well as fuel reserves.
While these dietary guidelines may not be the ideal for everyone, as you'll see a little ahead, in general they offer a sane starting point, an alternative to the highly saturated fats and the sugars that are so rapidly damaging health and leading to obesity.