- The Search for a Better Fiber
- Using the Most Viscous Fibers
Soluble fiber includes pectin, gum, and mucilage. Soluble fiber tends to form a gel when added to water. Soluble fiber is found in oat bran, barley, vegetables (carrots), and fruits (apples and oranges). Insoluble fiber is made from cellulose that is used primarily as structural material in plants. Insoluble fiber functions to increase the bulk of stools.
A study examined the use of fiber in a weight-loss program: 53 moderately overweight females (BMI >27.5 kg/m2) on reduced energy intake (1200 kcal/day) were treated for 24 weeks with a fiber supplement on a random, double-blind, placebo-controlled basis. The fiber was administered as an initial dose of 6 grams and a maintenance dose of 4 grams. After treatment, mean weight loss in the fiber group was 8.0 kg (17.6 pounds) versus 5.8 kg (12.76 pounds) in the placebo group (Birketvedt et al. 2000).
A review of published studies on the effects of dietary fiber on hunger, satiety, energy intake, and body composition in healthy individuals found that under conditions of fixed energy intake, the majority of reports indicate that an increase in either soluble or insoluble fiber intake increases post-meal satiety (sensation of fullness) and decreases subsequent hunger. When energy intake is not restricted, mean values from published studies indicate that consumption of an additional 14 grams per day of fiber for more than 2 days is associated with a 10% decrease in energy intake and body weight loss of 1.9 kg over 3.8 months. The observed changes in energy intake and body weight occur both when the fiber is from naturally high-fiber foods and when it is from a fiber supplement. The authors concluded that increasing dietary fiber intake to at least the minimum recommended by the American Heart Association (25-30 grams per day) may help to decrease the currently high national prevalence of obesity (Howarth et al. 2001).
The best time to take fiber is with the highest-fat meal of the day. The objective is to have the fiber absorb some of the dietary fat to prevent it from absorbing into the bloodstream where it helps contribute to body fat accumulation. Do not take fiber at the same time you take beneficial fatty acids such as CLA, EPA/DHA, and GLA. The fiber can absorb these critically important fatty acids before they can reach your cells. Some people experience unpleasant gastrointestinal side effects when taking high doses of fiber. It is best to begin with a very low dose, increasing the dose slowly. Fiber supplements consisting of guar gum, pectins, and psyllium seed husks are available in capsule form and in powder that can be mixed in liquid and consumed immediately before eating a fatty meal.The Search for a Better Fiber
Scientific studies consistently document the ability of water-soluble fibers to inhibit carbohydrate absorption, reduce cholesterol and low-density lipoprotein (LDL), and induce some weight loss (Marlett 2002, Jenkins 2002). When taken before meals, these fiber sources bind to water in the stomach and small intestine to form a gelatinous, viscous mass that slows the absorption of sugars and inhibits the re-absorption of intestinal cholesterol excreted from the liver. The net effect is a reduction in the number of absorbed calories and an induction of a feeling of satiety.
The problem until now is that the large quantity of fiber required to produce a meaningful effect has resulted in poor compliance, primarily because of upper and lower gastrointestinal-related discomfort.
In the early 1990s, scientists at the University of Toronto began to investigate a novel class of viscous fibers in order to identify a low-dose blend that would reduce blood glucose, insulin, cholesterol, and LDL levels. Initial studies confirmed the beneficial effects of these soluble fibers. Compared to placebo, those consuming highly viscous fibers before meals showed improvement in glycemic control, blood lipid levels, and blood pressure (Vuksan et al. 1999, 2000) The problem, however, remained—these beneficial effects could be produced only by ingesting large amounts of this fiber.
To overcome this problem, the scientists tested hundreds of different fiber blends with the objective of achieving significant benefits from only a few grams of soluble fiber per meal.
One of the initial findings that motivated the University of Toronto scientists to pursue this research occurred during a study that measured the glycemic-index response to different forms of fiber (or no fiber). In this study, three grams of various fibers were administered prior to a 20-gram glucose challenge. As expected, the glycemic index of the control group receiving no fiber was 100. Those receiving three grams of psyllium and xanthan showed only negligible glycemic index reductions (3% and 6%, respectively). By contrast, test subjects receiving three grams of a novel fiber blend showed a remarkable 39% reduction in their glycemic index. This finding demonstrated that consuming just three grams of this highly viscous fiber before a meal could significantly reduce the number of insulin-spiking carbohydrate calories absorbed (Kim et al. 1996).Using the Most Viscous Fibers
Glucomannan possesses the greatest viscosity (gelling property) of all known soluble fibers (Kim et al. 1996; Gonzales et al. 2004).
Four to five grams of glucomannan blended into fluid or mixed with food can slow carbohydrate absorption into the bloodstream and dampen the ensuing insulin spike by up to 50% (Kim et al. 2002). Controlled clinical studies document that glucomannan can promote satiety and induce modest weight loss (Walsh et al. 1984; Vitamin A et al. 1992; Cairella et al. 1995; Liviera et al. 1992). It has been shown to significantly lower LDL and total cholesterol, improve diabetic control, and correct constipation (Bell 2001; Ceriello 2004; Lebovitz 2001; Marlett et al. 2002; Jenkins et al. 2002; Vuksan et al. 2000; Vuksan et al. 1999; Kim et al. 1996; Gonzalez et al. 2004; Walsh et al. 1984; Vitamin A et al. 1992; Cairella et al. 1995; Livieri et al. 1992).
The reason glucomannan has fallen by the wayside is that in the 1980s, programs promoting quick weight loss advertised glucomannan as a supplement that could make obese people thin. The FTC stepped in and aggressively attacked those who were making exaggerated fat-loss claims for glucomannan. The subsequent negative reports by the news media caused glucomannan to be viewed by the public as a worthless dietary supplement.THE GLYCEMIC INDEX
- Studies Confirm Effectiveness
- Novel Fiber Limits Sugar Absorption
The glycemic index is a way of calculating the rate by which blood glucose levels rise in response to different food types, with pure glucose producing a reading of 100. The glycemic index measures how fast a particular food triggers a spike in blood glucose. Higher-glycemic foods prompt an elevated insulin release because the pancreas is stimulated to metabolize the sudden surge of glucose into the blood.
The published scientific studies on glucomannan, however, are quite impressive. Although it does not make fat people thin, a double-blind trial showed that compared to placebo, obese subjects taking one gram of glucomannan before each meal lost 5.5 pounds after only eight weeks (Walsh et al. 1984). The subjects were instructed not to change their eating or exercise patterns. Total cholesterol and LDL also were reduced (by 21.7 and 15.0 mg/dL, respectively) in the glucomannan-supplemented group. No adverse reactions to glucomannan were reported.
Several other published studies confirm that glucomannan modestly reduces weight compared to placebo or diet alone (Vita et al. 1992; Cairella et al. 1995; Livieri et al. 1992). Total cholesterol and LDL, along with after-meal insulin and glucose blood levels, are significantly reduced when glucomannan is taken before meals (Vita et al. 1992; Cairella et al. 1995; Livieri et al. 1992).
With this knowledge of glucomannan as a foundation, University of Toronto scientists led by Vladimir Vuksan, PhD, combined glucomannan with two other viscous fibers (xanthan and alginate) in an exact ratio to increase the viscosity of the original glucomannan material by 2.5-5 times (Vuksan). A mulberry concentrate (20:1) was added to enhance the glycemic-control and lipid-lowering effects (Andallu et al. 2001).
The primary benefit of this proprietary fiber blend lies in its superior viscosity. This means that it is better able to expand in the gastrointestinal tract to inhibit sugar absorption and bind cholesterol. This enables much smaller quantities to be taken than of other viscous dietary fibers to achieve comparable health benefits. The fiber blend's trade name is PGX™, which stands for "polyglycoplex."Studies Confirm Effectiveness
At last June's 64th Annual Meeting of the American Diabetes Association, held in Orlando, FL, the results of two studies using the PGX™ fiber blend were presented by researchers from the Risk Factor Modification Centre at St. Michael's Hospital and the University of Toronto (Vuksan et al. 2004). The first study reported on test subjects who took three grams of the fiber blend, followed by a huge 50-gram acute glucose challenge. Compared to the control group, those taking the fiber blend had a 65% reduction in postprandial glucose elevation.
The second study was performed over a three-week period to better reflect real-life experiences. Study subjects took three grams of the fiber blend three times a day before meals. After three weeks, there was a 23% reduction in postprandial glucose, a 40% reduction in after-meal insulin release, and a 55.9% improvement in whole-body insulin sensitivity scores. In addition, this proprietary fiber blend reduced body fat by 2.8% from baseline by the end of the three-week study period.
As a result of these findings, a large, longer-term clinical study has been initiated to further evaluate this unique fiber blend's effects on weight loss.Novel Fiber Limits Sugar AbsorptionUsing Fiber to Aid Weight Loss
Critics have attacked the use of fiber supplements because they are not a cure for obesity. While this is true, clinical findings reveal that ordinary fiber supplements can reduce the number of calories consumed by 30 to 180 calories per day (Vuksan et al. 2004). While modest, this reduction in calorie absorption would, over the course of a year, result in a weight loss of 3-18 pounds (Murray 2003).
The PGX™ high-viscosity fiber blend may provide better results than ordinary fibers used in previous studies. Clinical studies have repeatedly shown that after-meal blood sugar levels decrease as soluble fiber viscosity increases (Jenkins et al. 2002; Jenkins et al. 2000). This relationship has also been shown with improved weight control and diminished appetite (Walsh et al. 1984; Vita et al. 1992; Cairella et al. 1995; Livieri et al. 1992). We are anxiously awaiting the results of the ongoing weight-loss study of PGX™.
In the meantime, however, the dramatic effects shown by the PGX™ fiber blend in reducing insulin, glucose, LDL, and total cholesterol make it a common-sense supplement to take before meals. Any reduction of calorie absorption should benefit overall health. Taking steps to reduce excess insulin secretion may help protect against a wide range of degenerative processes.Fiber: Limits to Weight Loss
With all the books that have been written about the obesity-inducing effects of excess insulin, one would think that weight loss would automatically occur in response to a lowered intake of high-glycemic foods combined with a high intake of soluble fibers.
The problem is that age-associated weight gain is a multifactorial process that can be only partially addressed with existing approaches. This protocol on obesity describes why it is difficult for people to lose significant amounts of body fat. There is help on the way, but the total solution in a pill is not yet here.
In the meantime, Life Extension recommends that people seeking to lose weight consume a high fiber diet, particularly PGX™ highly viscous fiber blend 1000-3000 mg 5-10 minutes before each meal with 8-16 ounces of water.Continued
. . .