Low-Fat and High-Fiber Diets

Some studies suggest that replacing foods high in fats with low-fat complex carbohydrates (fruits, vegetables, and whole grains) may be more effective than calorie counting, particularly in maintaining weight loss. This dietary approach requires counting only grams of fat with goal of achieving 30% or fewer calories from fat. (One gram of fat contains nine calories while one gram of carbohydrates or protein has only four calories, and dietary fat converts more readily to fat in the body than carbohydrates or proteins.) Simply switching to low-fat or skimmed diary products may be sufficient for some people.

There are possible drawbacks to this approach, however:

  • Some people who reduce their fat intake may not consume enough of the basic nutrients, including vitamins A and E, folic acid, calcium, iron, and zinc. People on low-fat diets should consume a wide variety of foods and take a multivitamin if appropriate.  
  • Many people over-increase their intake of carbohydrates, believing that they are not adding calories. No one should use a low-fat diet as an excuse for over-consuming carbohydrates, particularly starchy foods and sugar. A high calorie diet from any source will add pounds.  
  • Replacing fatty foods, such as cakes, cookies, and chips, with their commercial “low-fat” counterparts does not constitute a low-fat diet. These foods generally contain more sugar and hence calories, not to mention other ingredients which have virtually no nutritional value. In fact, a 2002 study suggested that increasing sugar may overtime reduce levels of HDL cholesterol, the so-called good cholesterol.  
  • Very low-fat diets may increase the risk for stroke from hemorrhage in the brain.  
  • Very low fat diets may reduce calcium absorption, which may be particularly harmful in women at risk for osteoporosis.

Some fat in a diet is essential. It should be derived from plant oils and fish, however, and not from saturated fat from animal products or trans-fatty acids from hydrogenated (hardened) oils.

Fat Substitutes. Fat substitutes added to commercial foods or used in baking deliver some of the desirable qualities of fat, but do not add as many calories. It should be noted, however, that one study suggested that people who consume foods that contain fat substitutes do not learn to dislike fatty foods, while people who learn to cook using foods naturally lacking or low in fat eventually lose their taste for high fat diets. They include the following:

  • Plant substances known as sterols have long been known to reduce cholesterol by impairing its absorption in the intestinal tract. Sterols are now being isolated as sterol derivatives or as stanols (which are saturated sterols) to produce margarines (Benecol, Take Control). Benecol is derived from pine bark and Take Control from soybeans. Studies on such margarines are reporting that either two servings a day as part of a low-fat diet can lower LDL and total cholesterol. It should be noted, however, that these margarines may be hydrogenated and include some trans-fatty acids. Of further concern is the possibility that stanol may block absorption of important fat-soluble nutrients, including vitamins A, E, and D and carotenoids (compounds, such best carotene, that convert to vitamin A). One study suggested that it had no effect on the vitamins but did impair absorption of beta carotene. In people already on a low-fat diet, the addition of these margarines may not produce much additional benefit.  
  • Olestra (Olean) passes through the body without leaving behind any calories from fat. (It should be noted, however, that foods containing olestra still have calories from carbohydrates and proteins.) A 2000 study reported healthful changes in cholesterol levels in people who had been eating olestra for a year. Early reports of cramps and diarrhea after eating food containing olestra have not proven to be significant. Of greater concern is the fact that even small amounts of olestra deplete the body of certain vitamins and nutrients that are important for protection against serious diseases, including cancer. The FDA requires that the missing vitamins be added back to olestra products, but not other nutrients.  
  • Under investigation are fat substitutes derived from beta-glucan, the soluble fiber found in oats and barley (eg, Nu-Trim). They may have health benefits beyond reducing calories and replacing hydrogenated or saturated fats.

Complex Carbohydrates. In all cases, complex carbohydrates found in whole grains and vegetables are preferred over those found in starch-heavy foods, such as pastas, white-flour products, and potatoes.

Fiber. Fiber is an important component of many complex carbohydrates. It is almost always found only in plants, particularly vegetables, fruits, whole grains, nuts, and legumes (beans and peas). (One exception is chitosan, a dietary fiber made from shellfish skeletons.) Fiber cannot be digested but passes through the intestines, drawing water with it and is eliminated as part of feces content. The following are specific advantages from high-fiber diets (up to 55 grams a day):

  • Studies suggest that diets rich in fiber from whole grains reduce the risk for type 2 diabetes. Sources include dark breads, brown rice, and bran.  
  • Insoluble fiber (found in wheat bran, whole grains, seeds, nuts, and fruit and vegetable peels) may help achieve weight loss.  
  • Soluble fiber (found in dried beans, oat bran, barley, apples, citrus fruits, and potatoes), has important benefits for the heart, particularly for achieving healthy cholesterol levels and possibly benefiting blood pressure as well. Simply adding breakfast cereal to a diet appears to reduce cholesterol levels. People who increase their levels of soluble fiber should also increase water and fluid intake.

Sugar and Sugar Substitutes. A number of artificial sweeteners are available, including saccharin, aspartame (Nutra-Sweet), acesulfame K (Sweet One), and sucralose (Splenda). Sucralose usually leaves no bitter aftertaste as others do, and unlike most other artificial sweeteners, it works well in baking. Although contrary to previous concerns, there appear to be no health hazards involved with artificial sugar, but using these substances may give false comfort to some dieters who then increase their fat intake. Studies indicate that consuming some sugar is not a significant contributor to weight gain as long as the total caloric intake is under control.

Provided by ArmMed Media
Revision date: July 3, 2011
Last revised: by Sebastian Scheller, MD, ScD