Effects of agar (kanten) diet on obese patients with impaired
glucose tolerance and type 2 diabetes
H. Maeda,1,2 R. Yamamoto,1 K. Hirao1 and O. Tochikubo2
1HEC Science Clinic, Isogo-ku, Yokohama-shi, Kanagawa, Japan
2Department of Public Health, Yokohama City University, Kanazawa-ku, Yokohama-shi, Japan
Aim: The aim of this study was to evaluate the efficacy of agar diet in combination with a conventional diet
(traditional Japanese food) for obese patients with impaired glucose tolerance and type 2 diabetes.
Methods: After a 4-week run-in period on their habitual diets, 76 patients were randomly assigned to have conven-
tional diet or conventional diet with agar. Both groups were on these diets for 12weeks. Body weight, body mass index
(BMI), glycaemic control, blood pressure, insulin resistance, total body fat, fat distribution and lipids were assessed
before and after the experimental period.
Results: In both groups, after 12weeks, mean body weight, BMI, fasting glucose levels, homeostasis model assessment-
insulin resistance, and systolic and diastolic blood pressures had decreased significantly from their baseline values.
HbA1c, visceral fat area, subcutaneous fat area, total body fat, insulin area under the curve after oral glucose tolerance
test and total cholesterol decreased significantly in the agar-diet group. After 12weeks, mean changes of body weight
(
2.8 2.7 kg vs.
1.3 2.3 kg, p¼ 0.008), BMI values (
1.1 1.1 kg/m2 vs.
0.5 0.9 kg/m2, p¼ 0.009) and total
cholesterol (
7.6 27.5mg/dl vs.þ 2.4 23.4mg/dl, p¼ 0.036) were significantly greater in the agar-diet group than in
the conventional diet group.
Conclusions: The agar diet resulted in marked weight loss due to the maintenance of reduced calorie intake and to an
improvement in metabolic parameters.
Keywords: agar, diabetes, diet, IGT, obesity
Received 3 January 2004; returned for revision 4 March 2004; revised version accepted 5 March 2004
Introduction
Obesity is considered a major risk factor in diabetes [1].
There are ethnic differences in the relation to obesity
and the development of diabetes. For example, in the
West, body mass index (BMI) of diabetic subjects aver-
age 29.4 kg/m2, but in Japan, the corresponding average
is 23.1 kg/m2, indicating less severe obesity [2]. None-
theless, in these cases as well, the cluster of metabolic
disorders including impaired glucose tolerance (IGT),
hypertension, and hyperlipidaemia readily causes
atherosclerotic disorders. As is well known, insulin
resistance contributes to these disorders [3].
Treatment for diabetes is based on maintaining diet
control and an appropriate exercise regimen. The results
of the Diabetes Prevention Program (DPP) have clearly
shown that improved life style and sustained weight loss
delayed the development of diabetes [4]. Guidance in
dietary control plays a major part. Weight loss has
been reported to improve not only IGT [5,6] but also
Correspondence:
Hajime Maeda, MD, HEC Science Clinic, 4-1-4-102 Yokodai, Isogo-ku, Yokohama-shi, Kanagawa 235-0045, Japan.
E-mail:
hec@asahi-net.email.ne.jp
OR I G I N A L A R T I C L E doi: 10.1111/j.1463–1326.2004.00370.x
40 Diabetes, Obesity and Metabolism, 7, 2005, 40–46 # 2004 Blackwell Publishing Ltd

hyperlipidaemia [7,8], hypertension [6–9] and insulin
resistance [10]. In obese diabetic subjects, achieving
and maintaining ideal body weight, control of blood
glucose and dietary fibres reduce the onset of diabetes
[11,12] and of insulin resistance [13]. Long-term sus-
tained intake of soluble dietary fibres has been reported
to bring about improvements in hyperinsulinaemia and
plasma lipids in type 2 diabetic subjects [14].
Agar, long a popular food in the traditional Japanese
diet, is high in dietary fibre. This study investigates its
effectiveness in treating type 2 diabetic subjects and
subjects with IGT accompanying obesity in individuals
who find weight-control difficult. Fixed portions of agar
prepared in tasty ways were added to the diet of one
group of individuals. Comparisons were made between
this group and another group kept on a conventional diet
to study the efficacy of agar diet.
Patients and Methods
Subjects
Subjects were 76 outpatients (28 males and 48 females;
age 58.6 6.4 years) undergoing diet and exercise ther-
apy at the HEC Science Clinic for obese patients with
IGT and type 2 diabetes who were not taking medicines
known to alter glucose tolerance. The entrance criteria
for enrolment into the study was glycosylated haemo-
globin (HbA1c) < 8.0%. Their BMIs were all above the
standard of 25 kg/m2, because criteria for ‘Obesity
Disease’ in Japan recommended by the Japan Society
for the Study of Obesity (2000) was BMI> 25 kg/m2
[15]. None of the patients had micro or macrovascular
complications of diabetes. The protocol of the study was
explained to them. IGT and diabetes were judged by the
new guidelines of the American Diabetes Association
standards for the diagnosis of diabetes [16].
The study was conducted with the approval of the
ethics committee of the HEC Science Clinic, and all
subjects gave written informed consent to the protocol.
Study Design
After the baseline measurements were completed, the 76
subjects were randomly assigned to either conventional
diet therapy (nine IGT subjects and 29 type 2 diabetic
subjects) or conventional diet therapy with agar (eight
IGT subjects and 30 type 2 diabetic subjects). All sub-
jects were observed for a preliminary 4weeks, during
which they followed their habitual weight-maintaining
diet. They then underwent 12 weeks of the experimental
diet regimens. We assessed the measurements per-
formed before and after the experimental period.
All subjects were maintained on a nutritionally
balanced calorie-reduced diet that contained approxi-
mately 25% of calories as fat, 60% as carbohydrate,
15% as protein and a maximum of 300mg of cholesterol
per day. In both groups, daily energy intake was limited
to 400 kcal less than energy output. Energy output was
assessed by calorie counter (Kenzmedico, Saitama,
Japan). The agar-diet subjects received 180 g (30 kcal,
4.5 g dietary fibre) of agar, pleasantly seasoned with con-
diments, each day 15min before the evening meal. Two
types of packaged agar products were used in this study
(figure 1,figure 2). The agar was a gel produced from
powder and sold in packets under the Japanese name
Slim Kanten (Choshiya, Yokohama, Japan). All subjects
were instructed moderate intensity exercise for 30min at
least three times a week. Once or twice a month special-
ists in weight control provided both groups guidance in
topics like menus and nutritional balance. Each partici-
pant in the study kept a personal record of kinds and
Fig. 1 The product called Slim Kanten comes in firm jelly-
like blocks, which are cut into bite-size pieces and served
with variously flavoured sauces (strawberry, honey,
orange, apricot and peach).
# 2004 Blackwell Publishing Ltd Diabetes, Obesity and Metabolism, 7, 2005, 40–46 41
H. Maeda et al. Effects of agar diet on obese patients OA