In the 1980s, the big "discovery" was the importance of fiber in the diet. There were dozens of reports explaining how high-fiber diets could prevent heart disease, ease common digestive problems, and help dozens of other health problems. I'd like to add another key health benefit of fiber: weight loss. If you want to lose weight or maintain a proper weight, a diet rich in the highest fiber foods can help.
There are two kinds of fiber in food—soluble and insoluble. In a nutshell, insoluble fiber doesn’t dissolve in water and is considered "roughage." It swells and softens the stool, and it also scrubs and stimulates the intestines as it passes through. It helps protect against constipation, cancer, and the formation of pockets and inflammation in the colon.
On the other hand, soluble fiber dissolves in water and forms sticky gums and gels. They tend to absorb certain compounds like toxins, bile acids, cholesterol, et cetera. They also slow the digestion of food, which improves insulin regulation and helps prevent diabetes.
The overall highest fiber foods include fruits and vegetables (with the skins left on when possible), beans, and whole grains. Stay away from such refined foods as white flour, cream of wheat, oat flour, cornstarch, and white rice—all of which are low in fiber.
From a dietary standpoint, high-fiber foods are very versatile. Some, like beans, can be the main course, while others, such as fruit, popcorn, and raw vegetables, make excellent snacks. High-fiber foods generally are very low in fat and are made up mostly of high-quality proteins and complex carbohydrates. The fiber itself has no calories, yet provides bulk and a sense of fullness. Fiber isn’t the cure for obesity, but a high-fiber diet with proper nutrition can definitely help you lose weight.
A high-fiber diet decreases what is called "transit time" in the gastrointestinal tract—the time it takes for food to move through your body. A shorter transit time results in less formation and absorption of toxic material into your system. Be aware, though, that higher-fiber diets require an increase in fluid intake. As you start to add more high-fiber foods, be sure you’re drinking plenty of water.
Estimates are that most adults consume between 10 and 15 grams of fiber a day but should be taking in at least 25 to 30 grams. Eating 30 grams a day has been shown to reduce the weight gain that seems to gradually accumulate as one gets older.