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Fiber.

Posted Oct 23 2008 9:34pm

By Cynthia Buffington, Ph.D.

"Obesity is a progressive disease of which there is presently NO cure.  Surgery is the most effective treatment for obesity but, even with surgery, there is the risk for some weight regain.  There are, however, certain steps that can be taken to help reduce your risk for weight regain. 

As discussed previously, one of the most important steps in the prevention of weight regain is regular exercise that burns fat for energy.  These include activities that are moderate in intensity such as walking, swimming, cycling, dancing, gardening, and more.  Another step important in reducing the risk for weight gain is the avoidance or limitation of foods that promote fat accumulation, i.e. foods high in fat or sugar.  The next several articles and issues of the Silhouette will address another critical step in weight maintenance, the inclusion of sufficient amounts of ‘anti-obesity foods’ to your diet.

What are anti-obesity foods? These are foods that help to reduce appetite or that cause changes that lower your body’s capacity to store fat.   Such foods are those high in quality protein, omega 3 fatty acids, and calcium or other anti-obesity ingredients found in dairy.  Foods high in fiber also have anti-obesity actions.  High fiber-containing foods include fruits, vegetables, nut, seeds, legumes (beans) and whole grains. 

A number of population studies conducted at various places all over the world have found that individuals whose diets are high in fiber are less likely to be overweight or obese than those whose diets are low in fiber.   The results of long-term studies have, likewise, found an association between weight gain over time and fiber intake. Furthermore, several clinical studies have found that dietary supplements are helpful in assisting with weight loss and weight loss maintenance. 

How does fiber induce weight loss or help to prevent weight gain (regain)? First, high fiber foods are generally low in calories, and diets high in fiber are often low in fat and total calories.  Secondly, fiber, due to its physical nature, alters gastrointestinal (GI) activities in such a manner as to reduce hunger, promote satiety, and decrease the absorption of high calorie nutrients, such as sugar and fat.   Finally, fiber stimulates the production of certain gut factors that have anti-obesity actions.

How does fiber affect GI activities in a beneficial way?  Foods high in fiber must be chewed well, reducing the rate that food can be consumed.  The bulk of fiber and its ability to absorb large amounts of water cause further distention of the stomach.  Such distention signals the brain that the stomach is full, causing feelings of satiety (fullness) and a reduction in meal size and total calorie intake.  The bulking of fiber in the stomach is also believed to be responsible for fiber-induced reduction of in-between meal snacking and subsequent meal size.  This is because high fiber retards digestion and prolongs the time food stays in the stomach and, consequently, the length of time you feel full.

In the gut, fiber impedes the absorption of certain nutrients, such as sugar. A decrease in absorption of sugar by dietary fiber not only reduces the amount of calories that are absorbed but also, and, perhaps, more importantly, decreases insulin production.  Insulin increases fat accumulation by driving fat into fat storage depots, inhibiting the breakdown of fat, and increasing the de novo synthesis of fat from sugar.  Lower insulin levels would, therefore, reduce the storage of fat and weight gain or regain.

High dietary fiber also reduces the absorption of fat, lowering blood lipid levels and reducing the availability of fat for storage in adipose tissue depots.  High fiber foods also cause gut bacteria to convert fat to a form that can be more readily oxidized (utilized) by the obese individual.  An increased capacity for fat utilization, coupled with a lower uptake of fat available for storage, would substantially reduce the risk for weight gain or regain.

Another advantage of fiber is that a diet high in such is believed to increase production of certain gut factors that have anti-obesity actions, i.e. glucagon-like peptide (GLP)-1 and gut factor peptide YY.  These gut factors protect against obesity by reducing appetite and gut motility, regulating blood sugar and insulin levels, and increasing fat breakdown and/or its metabolism.

For all of the reasons described above, fiber can help to reduce body weight or prevent weight regain.  The dietary intake of fiber in this country, however, is among the lowest in the world.  The average daily intake of dietary fiber in the United States is estimated to be around 15 grams.  This amount is about half the daily intake recommended by the American Heart and Dietetic associations, i.e. 25 to 30 grams per day, and is 4 to 5 times less than the daily fiber intake of individuals living in developing countries where obesity is rare.

Question is, how much fiber do YOU consume each day?  30 grams? 15 grams? 10 grams?  less?!   This month, record your daily fiber intake.  Try to slowly over time, increase your fiber intake to the recommended levels of 25 to 30 grams per day.   Remember, as you increase your intake of fiber, it is important to also be sure you are increasing your intake of water. A fiber supplement is likely to be necessary to accomplish this feat, particularly if you are recently out from surgery or have had a gastric restrictive procedure. 

In conclusion, there is considerable reason to believe that diets low in fiber have contributed to the high prevalence of obesity in this country and throughout the industrialized world.   Fiber-rich diets, including fruits, vegetables, whole grains, legumes and nuts, and dietary supplements would be beneficial in the prevention of weight regain post-diet or surgery."

            

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