Research
& Study
International Journal of Obesity
( 1984) 8, 289293
Received 9 March 1983 ; accepted 7 July, 1983.
EFFECT OF GLUCOMANNAN ON OBESE PATIENTS: A CLINICAL STUDY
David E. WALSH Vazgen YAGHOUBIAN and Ali BEHFOROOZ*.
Research Department General Nutrition Mills, Box 349, Farge North Dakota; and
*Computer Science Department,, Moorhead State University MoorAcad, Minnsota, USA.
An eight-week double-blind trial we, conducted to test purified glucomannan fiber
as a food supplement m 20 obese subjects Glucomannan fiber (from konjac root)
or placebo was given in i-g doses (two 500 mg capsules) with 8 oz water, 1 h prior
to each of three mcais per d. Subjects were instructed not to change their cating
or excrcise patterns. Results showed a significant mean weight loss (5.5 Ibs)
using glucomannan over an eight-week period. Serum cholesterol and low-density
lipoprotein cholesterol were significantly reduced (21.7 and 15.0 mg/dl respectively
in thc glucomannan treated group. No adverse reactions to ghcomannan were reported.
Introduction
Fiber in the diet is essential for good health'.2'. Consumption of fiber has been
shown to reduce the occurrence of obesity'," by acting as a bulking agent 2,4,22
High intake of dietary fiber is also reported to reduce caloric consumption, food
ingestion rate, and nutrient abs orp tion 6,19,20,21
The type of fiber eaten is also important". Cellulose fiber does not effect serum
cholesterol levels 9,17 but pectin gel fiber has been shown to reduce blood serum
cholesterol in a number of studies 3,7,8,15 Glucomannan is a pectin-like gel fiber
composed of a polysaccharide chain of repeating units of ,ß1,4-linked glucose
and mannose 16. Glucomannan is a natural component of konjac root, which has been
safely consumed as food for over 1000 years in the Orient 16.
Studies of human subjects and rats have indicated that glucomannan forms a gel
and greatly increases the moisture content of the food bolus during digestion
Terasawa et al.~5 reported a 23 mg/dl drop in cholesterol over a two-week period
while their human subjects were on glucomannan. Kiriyama et aL 10 observed similar
results in experiments with rats on hypercholesterolemic diets. One gram of glucomannan
will absorb about 100 ml of water in vitro. Studies with rats showed that the
gel forms around the food particles, causing digestive enzymes to release sugars
and fats at a slow rate10.
The objectives of the present study were: (1) To determine the effect of glucomannan
as a weight reduction aid in obese patients, and (2) To determine the effect of
glucomannan on serum cholesterol, triglycerides, lowdensity lipoprotein cholesterol,
and high-density lipoprotein cholesterol.
Subjects and methods
A total of 20 obese women were randomly selected from a larger group of obese
females who responded to a newspaper advertisement. Those who responded and were
20 percent or more 289 over their ideal weight'' formed a group from which 20
subjects were randomly selected The 20 subjects were randomly placed into two
groups of ten with Little difference in weight and height distribution. This was
achieved by repeatedly selecting two random groups and comparing them with respect
to their weight and height distribution. When two groups with similar weight and
heights distribution were found, one was named the placebo group and the other
the glucomannan group.
The glucomannan group took two capsules of a supplement containing 5 00 mg of
purified glucomannan, three times per day, with 8 oz of water, 1 h before each
meat The placebo group took two capsules containing 500 mg starch under the same
conditions. Both supplement were identical in shape, color, and appearance, Neither
patients nor researchers knew in which group each subject wet entered.
Prior to the experiment, both groups were advised that they were participants
in a clinical study and that the objective of the study was to determine the effectiveness
of the supplement as a weight-loss diet aid. All patients were instructed not
to deviate from their previous established eating and exercise patterns.
Each patient's weight and height, without shoes, were recorded using a Health-O-Meter
scale, model DQF400. The same scale was used for all weighings. Starting weight
(pounds), height (inches), and blood samples were obtained for each person at
the beginning of the study; and weight and blood samples were taken after four
and eight weeks. The blood sam pies were analyzed for total scrum cholesterol
total triglycerides (TG), and high-density lipoprotein (HDL) cholesterol using
an enzymatic method 14 Low-density Lipoprotein cholesterol (LDL) was calculated
by difference from cholesterol, high-density lipoprotein cholesterol, and triglycerides
using the following common formula: CLDL = CScrum &emdash; (CHDL + TC/5), were
CLDL = Low-Density Lipoprotein Cholesterol, CSerum = Total Serum cholesterol,
CHDL = High-Density Lipoprotein Cholesterol, and TC = Serum Triglycerides 5. Neither
subjects nor investigator' were advised of the blood chemistry results until after
the study we, completed.
Results
Table 1 shows weight and height distribution for the two groups. The average weight
in the glucomannan group was 185 lb, in a range from 132 lb to 218 lb. The average
percentage overweight of this group was 54.5 percent. The placebo group, by design,
had similar characteristics. The average weight in the placebo group was 183 lb
and thc weight range and percentage overweight were 133 to 214 lb and 51.2 percent
respectively.
Acceptance of the food supplement was very good. Many subjects indicated that
they had a 'full' feeling after taking glucomannan. Observations of satiety were
made occasionally in patient interviews, but no complete survey was done. In the
future, investigators might measure satiety to determine it there is a statistical
significance to this observation. No adverse effects were reported by subjects
in either the glucomannan group or the placebo group. There were, however, several
in the glucomannan group who reported that the food supplement had relieved mild
constipation.
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