Changing Habits to Delay Diabetes
Editorial
The New England Journal of Medicine -- May 3, 2001 -- Vol. 344, No. 18
For centuries, fatter and more sedentary people have been considered more likely to get
diabetes. More recently, many prospective studies have established that obesity and physical
inactivity are risk factors for type 2 diabetes mellitus (1) and that weight loss and exercise
improve insulin sensitivity and insulin secretion in the short term. Two studies, in subjects in
Sweden and China, have indicated that changes in diet and in exercise habits might delay the
onset of diabetes. (2,3) However, because these studies had methodologic weaknesses (one
was not randomized, and in the other, clinics rather than individual subjects were randomized), it
has remained uncertain whether changes in lifestyle can delay the onset of diabetes.
In this issue of the Journal, Tuomilehto and colleagues report the results of the Finnish Diabetes
Prevention Study, (4) which examined the effect of changes in lifestyle on the development of
type 2 diabetes in high-risk subjects. All subjects had impaired glucose tolerance -- an
intermediate stage in the natural history of type 2 diabetes characterized by a lesser degree of
hyperglycemia. Impaired glucose tolerance is associated with an annual rate of progression to
diabetes of 1 to 10 percent. (5) A total of 523 overweight subjects with impaired glucose
tolerance were randomly assigned to either a control group, which received general information
on changes in lifestyle, or an intervention group.
Subjects in the intervention group met with a nutritionist seven times during the first year and
every three months thereafter; the visits were designed to encourage specific changes in their
lifestyles. Goals for changes were established in five categories: a reduction in weight (by 5
percent or more), a reduction in fat intake (to less than 30 percent of energy intake), a reduction
in saturated fat intake (to less than 10 percent of energy intake), an increase in fiber intake (to at
least 15 g per 1000 kcal), and an increase in exercise (to at least 30 minutes per day).
Although the average weight loss in response to the intervention was small (4.2±5.1 kg), the
effect of these changes in lifestyle on the incidence of diabetes was substantial: the risk of
diabetes was 58 percent lower in the intervention group. Tuomilehto et al. found a lower
incidence of diabetes among persons who achieved more of the goals for changes in lifestyle,
regardless of the group to which they had been assigned. This finding supports the authors' claim
that the reduction in the incidence of type 2 diabetes was due largely to the changes in lifestyle.
These results demonstrate that modifying the risk factors for type 2 diabetes reduces the risk of
disease. This was not a foregone conclusion. The sustained positive energy balance (a higher
intake than expenditure of energy) that promotes obesity and type 2 diabetes results from an
interaction between genetic and environmental factors. (6) It was not certain that an outpatient
intervention program could successfully influence long-term habits of diet and activity when
subjects had easy access to calorically dense foods and only minimal exercise was required for
the activities of daily living. Whether the remarkable success of this study was a result of changes
in habits of diet, activity, or both is not clear, however, since this type of analysis was not
performed.
Will the same interventions for the primary prevention of type 2 diabetes work in the United
States or in other populations? Tuomilehto and colleagues believe that the pessimism that
surrounds the difficult task of inducing change in the lifestyles of overweight, sedentary persons is
not warranted. Their optimism may be justified by the low dropout rate in their study (less than 9
percent in the intervention group and less than 7 percent in the control group). However, it is
difficult to predict how the dropout rates among persons enrolled in a clinical trial in Finland will
translate into clinical practice elsewhere. Different populations may also be more or less willing
to accept the changes in lifestyle recommended in the study.
Pharmacologic interventions to decrease insulin resistance have also been proposed as a means
of preventing type 2 diabetes. The Diabetes Prevention Program is an ongoing multicenter,
randomized trial in the United States that involves more than 3000 men and women with
impaired glucose tolerance. The program is evaluating whether the risk of type 2 diabetes can be
reduced through substantial changes in diet and exercise or a pharmacologic intervention (850
mg of metformin twice daily), as compared with the risk among subjects assigned to receive
typical recommendations about lifestyle. (7) Results are anticipated in the fall of 2002.
How long can lifestyle changes be sustained? The Finnish study was not designed to address this
question. However, most people do not maintain their weight loss after participating in
weight-control programs. (8) Despite the convincing demonstration that type 2 diabetes was
delayed in the short term, it is uncertain how long the reduced incidence of diabetes will last.
Type 2 diabetes is increasingly common; it affected about 6 percent of persons in developed
countries in 1995. (9) If the results reported by Tuomilehto et al. are confirmed in other
populations, physicians and policymakers may wish to consider whether such intervention
programs should be routinely covered by insurance companies and made more broadly available
in primary care settings. Such decisions will probably require evidence that the complications of
diabetes can be delayed or prevented. It is reasonable to expect, however, that the onset of
microvascular complications will be delayed, since the frequency of these complications is
closely correlated with the duration of diabetes. (10,11,12)
In the future, it is anticipated that the molecular basis of many complex human diseases, including
type 2 diabetes, will be identified. Eventually, it may be possible to target intervention programs
at genetically susceptible persons before they become overweight and sedentary. At present, the
results of the Finnish Diabetes Prevention Study should encourage physicians and other health
care providers to persevere in the difficult task of promoting a healthy lifestyle, since by doing so
they will give patients a better chance at a life less burdened by many diseases, including type 2
diabetes.
P. Antonio Tataranni, M.D.
Clifton Bogardus, M.D.
National Institutes of Health
Phoenix, AZ 85016
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Related article....
Prevention of Type 2 Diabetes Mellitus by Changes in
Lifestyle among Subjects with Impaired Glucose
Tolerance
Jaakko Tuomilehto, Jaana Lindstrom, Johan G. Eriksson, Timo T. Valle, Helena Hamalainen, Pirjo
Ilanne-Parikka, Sirkka Keinanen-Kiukaanniemi, Mauri Laakso, Anne Louheranta, Merja Rastas, Virpi
Salminen, Matti Uusitupa, for the Finnish Diabetes Prevention Study Group
Abstract
Background. Type 2 diabetes mellitus is increasingly common, primarily because of increases
in the prevalence of a sedentary lifestyle and obesity. Whether type 2 diabetes can be prevented
by interventions that affect the lifestyles of subjects at high risk for the disease is not known.
Methods. We randomly assigned 522 middle-aged, overweight subjects (172 men and 350
women; mean age, 55 years; mean body-mass index [weight in kilograms divided by the square
of the height in meters], 31) with impaired glucose tolerance to either the intervention group or
the control group. Each subject in the intervention group received individualized counseling
aimed at reducing weight, total intake of fat, and intake of saturated fat and increasing intake of
fiber and physical activity. An oral glucose-tolerance test was performed annually; the diagnosis
of diabetes was confirmed by a second test. The mean duration of follow-up was 3.2 years.
Results. The mean (±SD) amount of weight lost between base line and the end of year 1 was
4.2±5.1 kg in the intervention group and 0.8±3.7 kg in the control group; the net loss by the end
of year 2 was 3.5±5.5 kg in the intervention group and 0.8±4.4 kg in the control group
(P<0.001 for both comparisons between the groups). The cumulative incidence of diabetes after
four years was 11 percent (95 percent confidence interval, 6 to 15 percent) in the intervention
group and 23 percent (95 percent confidence interval, 17 to 29 percent) in the control group.
During the trial, the risk of diabetes was reduced by 58 percent (P<0.001) in the intervention
group. The reduction in the incidence of diabetes was directly associated with changes in
lifestyle.
Conclusions. Type 2 diabetes can be prevented by changes in the lifestyles of high-risk
subjects. (N Engl J Med 2001;344:1343-50.)
Source Information
From the Diabetes and Genetic Epidemiology Unit, Department of Epidemiology and Health
Promotion, National Public Health Institute, Helsinki (J.T., J.L., J.G.E., T.T.V.); the Department
of Public Health, University of Helsinki (J.T.); the Research and Development Center, Social
Insurance Institution, Turku (H.H., M.R.); the Department of Internal Medicine, Finnish
Diabetes Association and Tampere University Hospital, Tampere (P.I.-P.); the Department of
Public Health Science and General Practice, University of Oulu, and the Unit of General
Practice, Oulu University Hospital, Oulu (S.K.-K., M.L.); the Department of Clinical Nutrition,
University of Kuopio, Kuopio (A.L., M.U.); and the Institute of Nursing and Health Care,
Tampere (V.S.) -- all in Finland. Address reprint requests to Professor Tuomilehto at the
National Public Health Institute, Department of Epidemiology and Health Promotion, Diabetes
and Genetic Epidemiology Unit, Mannerheimintie 166, FIN-00300 Helsinki, Finland, or at
jaakko.tuomilehto@ktl.fi.
Other authors were Sirkka Aunola, Ph.D., Research and Development Center, Social Insurance
Institution, Turku; Zygimantas Cepaitis, Dipl.Eng., and Vladislav Moltchanov, Ph.D., Diabetes
and Genetic Epidemiology Unit, Department of Epidemiology and Health Promotion, National
Public Health Institute, Helsinki; Martti Hakumaki, M.D., Ph.D., Department of Clinical
Nutrition, University of Kuopio, Kuopio; Marjo Mannelin, M.S., and Vesa Martikkala, M.S.,
Department of Sports Medicine, Oulu Deaconess Institute, Oulu; and Jouko Sundvall, M.S.,
Department of Biochemistry, National Public Health Institute, Helsinki -- all in Finland.
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