| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Health and Medical Research Center (G.R.K.)
Center for Epidemiology and Biostatistics, University of Texas Health Science, Center at San Antonio (J.E.M.)
San Antonio, Texas, Department of Physiology, Georgetown University, Washington, DC (H.G.P.)
Address reprint requests to: Gilbert Kaats, PhD, FACN, Health and Medical Research Center, 4940 Broadway, Suite 201, San Antonio, TX 78209. E-mail: gil{at}hmrcenter.net
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSCONCLUSIONACKNOWLEDGMENTSREFERENCES |
|---|
Design: In a randomized, double-blinded, placebo-controlled dietary intervention protocol, subjects were assigned to a treatment group (TRT), a placebo group (PLA) and a control group (CTL).
Subjects: A total of 150 overweight adults enrolled; 134 (89.3%) completed the study; 111 (82.8%) were women who were similarly distributed in the three groups.
Intervention: The TRT group took six 500 mg chitosan capsules per day and both TRT and PLA groups wore pedometers during their waking hours and recorded daily step totals. The CTL group followed weight loss programs of their choice, and took the same baseline and ending tests.
Measures of Outcome: Outcome measures were Dual Energy X-ray Absorptiometry tests, fasting blood chemistries, and self-reported daily activity levels and caloric intakes.
Results: Compared to CTL, the TRT group lost more weight (–2.8 lbs vs. +0.8 lbs, p < 0.001) and fat mass (–2.6 lbs vs. +0.1 lbs, p = 0.006). Compared to PLA, the TRT group lost more weight (–2.8 lbs. vs. –0.6 lbs, p = 0.03), % fat (–0.8% vs. +0.4%, p = 0.003), fat mass (–2.6 lbs vs. +0.6 lbs, p = 0.001) and had a greater body composition improvement index (BCI) (+2.4 lbs vs. –1.9 lbs, p = 0.002).
Conclusions: These data provide evidence for the efficacy of a chitosan compound to facilitate the depletion of excess body fat under free-living conditions with minimal loss of fat-free or lean body mass.
Key words: chitosan, weight loss, fat loss, body composition, adipose tissue
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSCONCLUSIONACKNOWLEDGMENTSREFERENCES |
|---|
Recently, chitosan has been proposed as a safe and efficacious dietary supplement that can contribute to weight loss by reducing the amount of absorbed dietary fat and thereby improve calorie balancing [8,9]. In the past, pulverized powders from the exoskeleton of crustaceans were used in environmental spills of oil to "soak up fats" [8]. The powder was spread over the surface of water, where it would immediately absorb toxic substances such as greases, oils, and/or dangerous heavy metals. Based upon this potential for binding fat and other lipids such as bile acids that could influence fat absorption, it was postulated that oral intake of chitosan would bind ingested fats and prevent their absorption. The present study was designed to determine effects of chitosan on body composition under conditions that closely approximate those conditions under which the supplement is most likely to be used.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSCONCLUSIONACKNOWLEDGMENTSREFERENCES |
|---|
Protocol
After completing baseline testing using a random numbers chart, study participants were assigned to one of three study groups: (a) a treatment group (TRT) that consumed a chitosan preparation and followed a self-monitored behavior modification program; (b) a group that consumed a placebo supplement (PLA) and followed the same behavior modification program; and (c) a minimum intervention control group (CTL) that completed the same beginning and ending tests as the other groups but followed any program of their own choosing. Subjects in the TRT and PLA groups received a complete report of their test results at the beginning the study, while those in the CTL group received both their beginning and ending reports at the conclusion of the study.
Testing
Body Composition.
At the beginning and end of a 60-day treatment period, all subjects completed a Dual Energy X-ray Absorptiometry (DEXA) test for body composition and bone density and a 43-chemistry blood test. DEXA provides a three-compartment model of body composition: fat, fat free mass (FFM), and bone mineral density (BMD).
In contrast to scale weight readings that reflect the amount, not the kind of weight changes, DEXA measurements provide for assessment of the kind of weight that is lost or gained—fat, FFM and BMD. Reductions in fat mass and additions of FFM are typically considered positive treatment outcomes, while increases in fat mass and decreases in FFM are considered negative treatment outcomes. Therefore, as an index of efficacy, we added a body composition improvement index (BCI) [10] to the study end points that is the net result of adding the losses of fat and the gains of FFM, and subtracting the gains of fat and the losses of FFM. Thus, the greater the BCI, the more safe and efficacious the intervention.
Blood Chemistries.
In order to provide an additional measure of safety, subjects had fasting venous blood samples drawn at any one of four laboratory stations. Blood samples were collected in EDTA (1 mg per mL) and were centrifuged within 4 hours; the plasma was separated, and then shipped at 4°C to a central laboratory. Analyses were made by routine clinical procedures.
Tracking Forms.
Participants in the TRT and PLA groups completed weekly tracking forms. They recorded positive and negative side effects, actual amounts of the supplement taken, estimates of daily caloric intake and daily activity levels as measured by a pedometer [10]. The pedometer used in this study (Digiwalker, Yamax USA, San Antonio, TX) has been used in numerous other studies because of its reported accuracy, precision and durability [11].
Behavior Modification Plan (BMP)
The lifestyle change plan provided to subjects in the TRT and PLA groups contained a workbook outlining general procedures for estimating caloric intake, a hand-held calculator containing nutritional information on 5,000 common foods, and a log book for calculating and recording estimated daily calorie balances and dietary fat consumption [12]. To monitor physical activity levels throughout their waking hours, subjects were asked to wear the pedometer and to record the number of steps taken during each day as well as the step-equivalents for other activities in which they participated.
Dietary Supplements
Subjects in the TRT group were asked to consume six capsules per day of a dietary supplement containing 500 mg of chitosan (3 g per day) and one mg of each of the following: beta-glucan, snowhite oat fiber, betaine HCL and aloe saponins. The formulation was supplied by the Rexall-Sundown Company of Boca Raton, FL. Because of the small concentration of the accompanying ingredients, it is assumed that any major action of the dietary formula was derived from the chitosan [13].
Statistical Analyses
The effects of treatment were analyzed using one-way analysis of variance. Analyses of changes were adjusted for the baseline value (if available) and age. Analyses of the body composition improvement index (BCI), the total cholesterol, LDL, HDL, and total cholesterol to HDL ratio were adjusted only for age. Average reported fat intake (g), number of steps (as measured by the pedometer), and weekly average caloric intake among subjects in the TRT group were analyzed for weekly trends using repeated measures linear models. All statistical testing was two-sided with a significance level of 5%. Contrasts with a p-value less than or equal to 0.05 were called statistically significant. All statistical analyses were carried out with SAS (version 8.2) software (SAS Institute, Cary, North Carolina).
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSCONCLUSIONACKNOWLEDGMENTSREFERENCES |
|---|
Table 1 summarizes the baseline characteristics of study participants who completed the study in each of the three groups. There were no statistically significant differences between the three groups on any of the baseline body composition measures. While no statistically significant differences were found between the TRT and CTL groups, the mean HDL was significantly lower and the mean Total Chol/HDL ratio was significantly higher in TRT as compared to the PLA (p = 0.01 and p = 0.03 respectively).
|
|
No significant differences were seen among groups in changes in total cholesterol, HDL, Chol/HDL Ratio, LDL or bone mineral density (BMD). Although not shown here, an examination of the 38 other chemistries also revealed no significant changes in any of the three study groups.
Thirty-nine of the 46 subjects in the TRT group recorded their average fat intake each week for eight weeks. Of these 39 subjects, 28 had complete data for all 8 weeks. The data were analyzed using repeated-measures linear models to assess the significance of trends in fat intake week to week. The model found a trend toward a beneficial decrease in fat of 1.6 g per week (p = 0.06). However, these differences in fat intake, although statistically significant, were small so as to have essentially no effect on changes in fat mass using the standard formula of 9 calories per g of fat and the 3,500 calories needed to gain or deplete a pound of fat.
Analyses of the average number of steps and average caloric intake each week found no significant trends and no interpretable interactions, suggesting that the changes in weight and fat mass were attributable to the supplement rather than to changes in diet and physical activity levels.
|
DISCUSSION |
|---|
Theoretically, how does chitosan accomplish loss of fat mass? As a soluble fiber, chitosan has the potential to lower the glycemic index of foods, thus creating a slower and more sustained calorie uptake, and thereby reducing acute insulin demand. The latter favors energy utilization over energy storage [14–22]. Fiber can also produce a bulking effect that increases satiety and compliance with reduced calorie diets [23,24]. However, chitosan may have an added benefit of trapping fats in the gut, i.e., limiting absorption, via distinct mechanisms.
The latter possibility led some researchers to show that chitosan can effectively absorb fat in a water medium [25,26]. In the acidic environment of the stomach, it is postulated that chitosan acts as a soluble fiber, readily dispersing in the digestive secretions and food particles [8]. Binding several times its weight in water, chitosan is thought to form a gel that traps and encapsulates dietary fats. As it passes in the small intestine, it encounters an environment that is no longer acidic. In a non-acidic environment, chitosan becomes insoluble and forms its gel-like complex with bound fats and bile acids leaving the fat indigestible with no caloric value. This insoluble complex passes undigested through the large intestine and is naturally eliminated. In addition, chitosan carries a positive charge, and the positive charge of chitosan has been postulated to attract negatively charged fatty and bile acids. A decrease in bile activity would indirectly slow fat absorption.
In vitro studies [25,26] and in vivo animal studies [27–29] are especially strong in showing the fat trapping capabilities of chitosan. The human studies, while less convincing, still suggest fat trapping capabilities. Of the reported studies examining stool fat directly, many support the ability of chitosan to decrease gastrointestinal fat absorption [26,30,31]; others do not [32,33]. The differences may be due to the poor correlation some direct fecal fat assays show with fecal energy excretion [34]. The question arises whether chitosan-bound fat in the feces is measured completely by standard assays.
Other methodologies to assess fat absorption corroborate a positive effect. The radio isotopic method described by Heldeman [25] and the triglyceride method employed by Blum [35] suggest that chitosan decreases fat absorption. More evidence emanates from the study of a Japanese group [36,37] and the patents of Hoffman-La Roche [38–40]. The Japanese group measured total volatile fatty acids as well as acetic and propionic acid in feces [38]. All these values increased significantly in the feces after chitosan ingestion. Examining material from patent applications of Hoffman-La Roche provides evidence that chitosan is fat trapping [38–40]. Nevertheless, it would appear that the amount of fat trapped, at least as currently measured directly, does not explain the majority of weight lost with chitosan use [30].
Therefore, the other mechanisms mentioned in the first paragraph of the Discussion may be playing some role, major or minor, in the weight loss associated with chitosan supplementation. The influence of soluble fiber on the insulin system is especially intriguing. Slowed absorption of fats and carbohydrates in the presence of soluble fiber has a profound effect on insulin metabolism, preventing or ameliorating insulin resistance [41]. Enhancing insulin sensitivity is important in preventing and/or treating obesity and other chronic disorders [42–44]. The pattern of mass changes with chitosan, primarily loss of fat with retention of muscle, supports the possibility that chitosan works, at least in part, via its effects on the insulin system.
Although this study was not designed to distinguish the operant mechanism of action, the highly significant reductions in body fat in the TRT, as opposed to both the CTL and PLA groups, provide considerable support for the efficacy of chitosan as an adjunct to "weight loss" interventions. These changes occurred without a concomitant loss of FFM and BMD that is typically found in weight loss studies. Furthermore, the absence of self-reported significant adverse side effects or adverse changes in blood chemistries provides support for the product’s safety.
An additional contribution of this study is the finding that these results were obtained with a minimum of experimental intervention and under conditions resembling those under which consumers and/or patients are likely to use the supplement. It is also worth noting that the reductions of body fat in the TRT group were apparently independent of increases in physical activity levels and reduced caloric intakes sometimes created by experimental interventions. The study also provides support for the use of the BCI as an outcome measure as opposed to using changes in scale weight that are characteristically used in clinical trials of weight loss interventions. For example, a 4.0 lbs weight loss that consists of a loss of 2.0 lbs of fat, but a concomitant loss of 2.0 lbs of FFM receives a BCI of 0. On the other hand, the same 4.0 lbs weight loss that consists of a loss of 6.0 lbs of fat and a gain of 2.0 lbs of FFM receives a more favorable BCI of +8.0.
The examples shown in Table 3 were taken from our database of past studies and illustrate how changes in scale weights, as compared to the BCI, can lead to erroneous conclusions about the safety and efficacy of weight loss interventions. While the relative value of gaining a pound of FFM versus losing a pound of fat has yet to be determined, few would disagree that a loss of fat is a positive treatment outcome and that a gain of fat is a negative treatment outcome. Likewise, few would disagree that losses of FFM, as often seen in anorexic patients, are negative treatment outcomes. Since a gain in FFM is associated with an increased metabolic rate, this gain would also be seen as a positive treatment outcome. Thus, it is our view that the BCI is a better measure of safety and efficacy than changes in scale weight. While subject 1 had the greatest loss of scale weight (–4.3 lbs), he also had the worst BCI and, in our view, had the worst treatment outcome. Conversely, subject 4, who had the worst scale weight outcome (+0.9 lbs), had the best treatment outcome with a BCI of +5.1.
|
|
CONCLUSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSCONCLUSIONACKNOWLEDGMENTSREFERENCES |
|---|
|
ACKNOWLEDGMENTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSCONCLUSIONACKNOWLEDGMENTSREFERENCES |
|---|
Received October 14, 2004. Accepted April 17, 2006.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSCONCLUSIONACKNOWLEDGMENTSREFERENCES |
|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
