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Affecting Weight Loss
What is the purpose of fiber supplementation?
The Life Extension Foundation claims that fiber supplements are used to help induce fat loss (http://www.lef.org/newshop/items/item00261.html). Joseph Carlson, RD, PhD, (a research associate and registered dietitian at the Stanford Center for Research in Disease Prevention), agrees with the theory of fiber enabling weight loss or maintaining weight (http://www.imdiversity.com/villages/african/Article_Detail.asp?Article_ID=2455). The Greenbush Natural Products website asserts that the herb psyllium, found in fiber supplements, is very simple, yet effective in controlling weight. However, they do not support their claim with any evidence whatsoever (http://www.greenbush.net/psylliumseed.html). In general, according to Greg Annussek in the Gale Encyclopedia of Alternative Medicine (resource used for the Supplements and Diets website), a high fiber diet promotes weight loss; therefore, the use of fiber supplements creates the same effect (http://www.supplements-and-diets.com/html/weight_loss.html).
How does fiber work?
According to the Herbal Marketplace website, fiber supposedly removes the fat from food eaten (http://user.aol.com/genery/wtloss.htm). The Life Extension Foundation website says that it does this by absorbing a partial amount of dietary fat that usually goes into the bloodstream. It furthermore prevents serum glucose from changing into body fat and reduces carbohydrate cravings. The physical affects of this, besides weight loss, according to L.E.F., are that fiber produces a full feeling, usually causing people to eat approximately 10% less food so long as it is taken a certain amount of time before a meal (http://www.lef.org/newshop/items/item00261.html). More specifically, BodyandFitness.com claims that soluble fiber supplements, if taken with enough water, bind with water inside the stomach and become a gummy-like substance. This substance is what makes a person feel full (http://www.bodyandfitness.com/Information/Weightloss/fiber.htm). According to the InteliHealth website, fiber feels filling as a food, secondly, because it takes longer to chew. The site claims that fiber foods also help with weight loss because they are generally low in calories and if fiber is taken in supplement form, it most certainly has fewer calories, with a similar effect on the stomach (http://www.intelihealth.com/IH/ihtIH/WSIHW000/325/7095/34043.html?d=dmtContent) - expanding the stomach, causing a full feeling and diminishing hunger pangs (http://www.bodyandfitness.com/Information/Weightloss/overweight.htm). Also, Konsyl Pharmaceuticals states that filling up with low-calorie fiber foods allows less room for highly caloric, fatty foods (http://www.konsyl.com/index.htm). Another explanation of why fiber causes weight loss is that it strengthens and tones people’s digestive tracts (http://www.ivillage.com/diet/experts/askdiet/articles/0,5050,221775_72787,00.html). In relation to this, fiber has been found to help with correct bowel elimination, which is the process used to excrete toxins and excess fats (http://family.go.com/yourtime/fitness/feature/dony0100altmd_weightls/dony0100altmd_weightls2.html).
What claims are made about the effectiveness fiber supplementation?
William D. Nelson, N.D., a naturopathic doctor at the Docere Naturopathic Centre in Colorado Springs, suggests that people get their fiber from food rather than supplements because food has nutrients that a supplement does not. Also, a problem with taking in an extreme amount of fiber is that it can block the absorption of iron, calcium and other minerals. Jennifer Brett, N.D., a naturopathic doctor at the Wilton Naturopathic Center in Stratford, Connecticut suggests consuming fiber through psyllium seed powder over taking fiber as a capsule or tablet, which are less beneficial. She states that one reason is because it requires more supplements to achieve the same amount of fiber present in a comparatively smaller amount of psyllium seed powder. Another reason is that people tend to continue use of the powder more than they do of pills because of the great number of other pills they take (http://www.bodyandfitness.com/Information/Weightloss/fiber.htm). In comparing different fiber supplements, one doctor stated that, for weight loss, psyllium and glucomannan are the most effective because of their abundance of soluble fiber. However, the person preferred glucomannan over psyllium because it contains more fiber per pill (http://www.bodyandfitness.com/Information/Weightloss/overweight.htm). This information is helpful to know because Konsyl pharmaceutical researchers have found that if Americans doubled their intake of fiber, they could reduce the amount of calories consumed daily by 100. This has the possibility of taking off ten pounds of weight per year (http://www.konsyl.com/index.htm). Therefore, taking the supplement with the most amount of fiber gives a better chance of fulfilling a person’s fiber needs.
What evidence if any is offered in support of the claim of weight loss as a result of fiber intake?
Website claims stating that fiber blocks the absorption of fat and fills the stomach, decreasing appetite and weight, are evidenced by citations of several journals: “International Journal of Obesity,” “British Journal of Nutrition,” and “Medical Aspects of Dietary Fiber” (http://www.ostlerdds.com/fiber.html). Another website supports that fiber foods, instead of supplements, are more beneficial by quoting a research associate and registered dietitian at the Stanford Center for Research in Disease Prevention, Joseph Carlson, RD,Ph.D. (http://www.imdiversity.com/villages/african/Article_Detail.asp?Article_ID=2455). In addition, the preference of glucomannan and psyllium over other fiber supplements and glucomannan over psyllium, is maintained by citing a naturopathic doctor at the Wilton Naturopathic Center in Stratford, Connecticut, Jennifer Brett, N.D. (http://www.bodyandfitness.com/Information/Weightloss/overweight.htm). However, many of the other sources that praised the benefits of fiber, especially those of advertisers, gave no evidence to support their statements. Customers are expected to trust the advertisers and refrain from questioning any of the statements. Also, none of the sources quoted actual scientific research studies.
Who is presenting the information about fiber, and why?
Some of the sources of this information include businesses attempting to sell products such as SlenderLean (http://www.lifeplusvitamins.com/slenderl.htm), Konsyl Pharmaceutical products (http://www.konsyl.com/cgi-bin/content/pageview.pl?command=display&page=4400.htm), Herbalife (http://www.katsherbs.com/herbalife/Fiber.htm) and Chitosan Fat Blocker (http://www.bodyandfitness.com/Information/Weightloss/fiber.htm). Although they are trying to convince the public of their products’ effectiveness, most of the information they provide holds up with other websites that apparently do not have the intention of selling any products, but exist simply to provide information to the public (http://www.angelhealingcenter.com/weightloss.html, http://www.ostlerdds.com/fiber.html).
Recommended Fiber intake:
The American Dietetic Association recommends for adults an average of twenty to thirty-five grams per day of dietary fiber. For children, the recommended intake is their age plus five grams per day (Marlett et al., 2002). However, the population of the United States is not complying to this desired amount and intake of fiber continues to decline. While the amount of fiber in the average American diet has declined, obesity in America has escalated (Hamilton and Anderson, 1992). In conjunction, it is also true that developing countries, which are consuming high amounts of dietary fiber, have lower prevalence of obesity (Kimm, 1995).
Effectiveness of Fiber on Satiety: delays fat absorption/bulking effect Energy consumed in relation to fiber:
A main argument concerning the effectiveness of fiber on aiding the reduction of weight is that fiber promotes a full feeling if taken before the act of eating. The satiated feeling results from its quality of slowly passing through the stomach (Witkowska and Borawska, 1999). Dietary fiber has the ability to increase the feeling of satiety through its prolonged fat absorption (Burton-Freeman, 2000). In two studies by the Department of Human Biology at Maastricht University in the Netherlands, the effects of a water-soluble fiber supplement on satiety were examined. The studies lasted one week and observed obese women who had lost weight. In one study, the intake of energy and feelings of hunger were evaluated while allowing the women to freely control their energy intake. In the second study, the women’s intake was fixed, either at 4 MJ per day, or 6 MJ per day. In the first study, the women ate much less after fiber supplementation. However, their level of hunger and satiety did not change. In study two, the group with lower energy intake (4 MJ) reported less feelings of hunger after fiber supplementation. In the group with energy intake at 6 MJ, the women felt no changes in satiety and hunger like in study one. These results indicate that fiber supplementation aids in reducing hunger, making it easier to follow a low energy intake diet (Pasman et al., 1997).
These results, in support of the theory that fiber inhibits hunger, were also found in another study. One hundred thirty-five members of a weight loss club were randomly given bran or ispaghula granulate (a form of soluble fiber) for two weeks before food. The members who ate the fiber substances before meals reported signs of reduced hunger during the second and third week as well as at meals. The control group, which ingested no fiber compounds, however, reported no change in hunger (Hylander and Rossner, 1983).
In another study by The Jean Mayer U.S.D.A. Human Nutrition Research Center on Aging at Tufts University, oats, as a soluble fiber, were used to estimate fiber’s ability to facilitate compliance to a low energy diet. The subjects on the six-week diet containing high amounts of fiber reported no significant change in hunger in comparison to the group which consumed the low soluble fiber diet. Therefore, dietary fiber, in this instance, does not help people to manage a low energy diet (Saltzman et al., 2001).
Fiber relating to weight loss:
In many cases, fiber seems not to influence weight as proposed by other studies. In example, the aforementioned case found no significant effect of the fiber-containing oats on weight loss (Saltzman et al., 2001). In that instance, neither increased satiety nor weight loss were obtained through the use of fiber. However, satiety and weight loss do not go hand in hand. In the study of the 135 members of the weight loss club who were given bran, ispaghula, or were placed in the control group, feelings of hunger were reduced by the intake of fiber before meals. Nevertheless, the fiber made no difference in weight loss in comparison to the control group (Hylander and Rossner, 1983).
In another case, designed by the Department of Human Biology at Maastricht University to see if the use of fiber supplements would help maintain a person’s previously lost weight, the results were very similar. The longitudinal study (study in which one group is observed over a long period of time) included thirty-one obese females. For fourteen months, after being energy-restricted for two months, twenty of the women were given twenty grams of water soluble fiber daily and the other eleven, the control group, received no fiber supplement. The group of twenty women was categorized into two groups: Group A which was at least 80% compliant and Group B, which was 50-80% compliant. Group A showed the same weight gain as the control group after the energy restricted period. Group B was different in that some in it had occurrences of relapse. After the fourteen months, Group B was back to where it had started before the energy restriction. However, Group A and the control group had generally slightly lower body weights. Overall, no meaningful effect was found from the fiber supplements. The entire study may have been influenced by the changing of eating behavior characteristics which could explain the different ways weight was sustained. In this manner, no real conclusion can be made from this study, since other variables come into play (Pasman et al., 1997).
In contrast to these two studies, others support the widely held belief that fiber aids in weight loss. In one meta-analysis by the Jean Mayer U.S.D.A. Human Nutrition Research Center on Aging at Tufts University, it showed that studies found that an added 14 grams of fiber per day on people who were allowed to eat as they pleased resulted in body weight loss of 1.9 kg over 3.8 months (Howarth et al., 2001).
Another study finds the same result of weight loss after fiber intake. In an eight month’s ad libitum (eating as they pleased) low-fat as well as high fiber diet, the 24 subjects body weight decreased after only eleven weeks. However, the 24 subjects in the control group showed no signs of change. The study therefore showed that fiber along with a low fat diet reduces body weight (Raben et al., 1997).
The Jean Mayer U.S.D.A. Human Nutrition Research Center on Aging at Tufts University found the same result. From studies of at least 6 months in length, the effect of high amounts of fiber in a low-fat diet resulted in weight loss three times that of people who only had low-fat diets. In this case, fiber had a drastic effect on the alteration of weight (Yao and Roberts, 2001).
Person’s Weight in Relation to the Effects of Fiber:
In the earlier meta-analysis, research showed that larger, obese or overweight people benefited were influenced more by the addition of fiber to their diet than were skinnier people. Overall energy intake of overweight people was reduced to 82% in comparison to only 94% in thin people. Overweight people lost 2.4 kg in contrast to thinner people’s 0.8 kg (Howarth et al., 2001). In the eight month study of low-fat, high fiber diet effects on weight, it was also noted that the initial weight and amount of fat of each subject correlated to the changes that later occurred in each (Raben et al., 1997).
To look at fiber in relation to weight retrospectively, the Department of Clinical Nutrition at the University Hospital in London, Ontario, Canada examined the amount of fiber consumed by people of different weight. People of normal weight (20.0 < or = BMI < or = 27.0) consumed 18.8 +/- 9.3 grams, while the moderately obese (27.1<or = BMI < or = 39.9) consumed 13.3 +/- 5.8 grams; and finally, the severely obese (BMI > or = 40.0) consumed 13.7 +/- 5.7 grams. The lean group consumed a significantly higher amount of fiber than the moderately or severely obese. In addition, factors such as sex, age, education level and income were taken into account. After that, the total amount of fiber in grams and in g/1000 kcalories was found to be inversely related to BMI using regression analysis (technique used to find a relationship between variables) (Alfieri et al., 1995).
Does it matter if fiber comes in supplement or food form?
Some studies show that fiber, no matter what form, produces the same effect of reducing energy intake and weight (Howarth et al., 2001). However, other studies, such as the longitudinal study of thirty-one obese females by the Department of Human Biology at Maastricht University, fiber supplementation produced no effect on weight loss (Pasman et al., 1997). This effect may or may not be because the fiber was given in supplement form. Nevertheless, fiber in food form has not been completely proven as a method of weight loss. Therefore, the use fiber supplements and fiber foods overall result in indecision as to their effects.
Overall, research seems to not be able to come to a definite answer as to the truth about the effects of fiber on weight. The variety of results in this matter suggests that outside factors influence fiber’s effect on a person’s weight. It is possible that for some people, fiber can induce the desired effects of satiety and reduced weight. At the same time, this is not true for everyone. In the studies in which initial weight was examined before intake of fiber, the major find was that a person’s weight influences the degree of weight loss and hunger after fiber usage.
As to the amount of desirable fiber intake, the consensus seems to be that between twenty and thirty-five grams of fiber per day would benefit people. The fact that the population of America has been consuming less than this amount, and continues to get further from the amount, while also growing in cases of obesity, indicates that the American Dietetic Association is correct in suggesting this quantity. In conclusion, some people may find a benefit in fiber supplementation. However, the benefits are not guaranteed.
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