Prevention of type 2 (non-insulin-dependent) diabetes mellitus by diet and physical exercise. The 6-year Malmö feasibility study

Loss of abdominal fat and improvement of the cardiovascular risk profile by regular moderate exercise training in patients with NIDDM

Non-insulin-dependent diabetes mellitus (NIDDM) is associated with an increased cardiovascular risk. Glycaemic control alone is often insufficient to control diabetic dyslipidaemia and other cardiovascular risk factors associated with NIDDM. The present trial was designed to evaluate the effects of physical activity as an adjunct to standard diabetes therapy on the lipid profile, blood pressure, glycaemic control, weight and body fat. Sixteen well-controlled (HbA1c 7.5%) patients with NIDDM participated in a regular aerobic exercise training programme at 50-70% maximal effort over 3 months. Thirteen age- and sex-matched patients with NIDDM served as a control group. The 3-month intervention with an increase in physical activity from 92 (mean +/- SD) +/- 79 to 246 +/- 112 min per week (p < 0.001) by means of a structured activity programme resulted in significant improvement of plasma lipids with a 20% decrease in triglycerides (p < 0.05), unchanged total cholesterol and increases in high-density lipoprotein and high-density lipoprotein-3 subfraction of 23% (p < 0.001) and 26% (p < 0.001), respectively. Systolic and diastolic blood pressure decreased significantly from 138 +/- 16 to 130 +/- 17 mm Hg (p < 0.05) and 88 +/- 10 to 80 +/- 10 mmHg (p < 0.001), respectively. Resting heart rate decreased from 81 +/- 13 to 74 +/- 14 beats per minute (p < 0.001), waist-hip circumference ratio decreased from 0.96 +/- 0.11 to 0.92 +/- 0.10 (p < 0.001) and body fat decreased from 35.3 +/- 7.2 to 33.0 +/- 8.0% (p < 0.001). These effects occurred independently of changes in body weight and glycaemic control, which did not change during the study. This study shows that improvement in physical fitness by introducing regular physical exercise as part of the treatment programme in patients with NIDDM results in a significant amelioration of their cardiovascular risk profile.

Splanchnic and muscle metabolism during exercise in NIDDM patients

To characterize splanchnic and muscle metabolism during exercise in non-insulin-dependent diabetes mellitus (NIDDM), eight male nonobese patients and seven healthy control subjects (CON) were studied during 40 min of bicycle exercise at 60% of maximal oxygen uptake. Biopsies were obtained from the quadriceps femoris muscle at rest and immediately after exercise. Arterial glucose concentration in NIDDM had declined by 10% (P < 0.01) at the end of exercise, whereas in CON it had risen by 21% (P < 0.05). Leg glucose uptake rose from 0.19 +/- 0.06 mmol/min at rest to 2.25 +/- 0.61 mmol/min at the end of exercise in NIDDM and from 0.13 +/- 0.05 to 1.17 +/- 0.34 mmol/min in CON. Splanchnic glucose output increased from 0.52 +/- 0.06 to 2.37 +/- 0.26 mmol/min in NIDDM and from 0.79 +/- 0.12 to 2.44 +/- 0.38 mmol/min in CON. Leg lactate output during exercise was twofold higher in NIDDM. Muscle contents of lactate and glycogen were similar in both groups at rest, whereas after exercise lactate tended to be higher (19.5 +/- 1.7 vs. 12.7 +/- 5.9 mmol/kg dry wt) and glycogen lower (154 +/- 35 vs. 251 +/- 41 mmol glucosyl units/kg dry wt) in NIDDM. Whole body respiratory exchange ratio during exercise was higher in NIDDM (0.84 +/- 0.02 vs. 0.78 +/- 0.02, P < 0.05). Exercise-induced changes in other muscle metabolites were similar in NIDDM and CON. These data indicate that the decline in blood glucose during exercise in nonobese NIDDM is due to enhanced peripheral glucose utilization rather than to an attenuated increase in splanchnic glucose output.

Effects on glucose tolerance, insulin secretion, insulin-like growth factor 1 and its binding protein, IGFBP-1, in a randomized controlled diet and exercise study in healthy, middle-aged men

OBJECTIVES

To study the effects of advice on diet, exercise and their combination on oral glucose tolerance (OGTT), insulin secretion, insulin-like growth factor-1 (IGF-1) and its binding protein, IGFBP-1.

DESIGN

A 6-month, randomized, controlled intervention study.

SETTING

Primary health care centres in Sollentuna, Stockholm and the Department of Medicine, Karolinska Hospital, Stockholm, Sweden.

SUBJECTS

One hundred and fifty-seven normoglycaemic healthy men, mean age 46 years, range 35-60 years, with slightly to moderately raised cardiovascular risk factors.

INTERVENTIONS

Advice on diet (D, n = 40), exercise (E, n = 39) a combination of both (DE, n = 39) and a control group (C, n = 39).

MAIN OUTCOME MEASURES

An OGTT, insulin secretion, IGF-1 and its binding protein, IGFBP-1.

RESULTS

The number of pathological OGTTs in the intervention groups decreased from 42/118 to 33/118 whilst the number in the control group did not change. Fasting insulin levels decreased in groups E and DE from 8.8-7.4 mU L-1 (P < 0.01) and from 8.3-6.7 mU L-1 (P < 0.01), respectively. Accordingly, the insulin area under the curve decreased from 5278 to 4828 (P < 0.05) in group E, and from 5482 to 4809 (P < 0.01) in group DE. IGF-1 only increased in group D. The most prominent changes were noted for IGFBP-1, which increased in all three intervention groups and to the highest degree in group DE (from 33.7-42.6 micrograms L-1, P < 0.001).

CONCLUSIONS

A combination of increased exercise and improved diet, as well as increased exercise alone, favourably affect glucose and insulin homeostasis in middle-aged men with moderately elevated cardiovascular risk factors. The most marked changes were noted for IGFBP-1, possibly suggesting a decreased insulin secretion and an enhanced insulin sensitivity.

Nutrition and health practices of diabetic and nondiabetic men and women from two southeastern New England communities

Diabetes occurs in at least 13 million persons in the United States and is a major cause of morbidity and premature mortality. Diet is the cornerstone of diabetes management, and the purpose of this investigation was to examine dietary intakes and health practices among diabetic and nondiabetic individuals from a recently surveyed population-based sample from two communities in southeastern New England. Data were collected during cross-sectional home health surveys conducted in random population samples of two New England communities during 1987-1988, 1989-1990, and 1992-1993. A food frequency questionnaire was completed by 1,897 of 2,077 eligible respondents who made up our study sample. Statistical analyses suggest that diabetic individuals do not appear to be adhering to measures known to improve metabolic control (i.e., weight reduction and physical activity). Furthermore, both diabetic and nondiabetic individuals alike should be targeted for educational programs aimed at improving dietary intakes which lead to a reduction in consumption of total and saturated fatty acid.

Diabetes and Canada's aboriginal peoples: the need for primary prevention

The high prevalence of non-insulin-dependent diabetes mellitus (NIDDM) in Canada's native communities corresponds with high diabetes prevalence rates in other populations of indigenous peoples that have undergone changes associated with acculturation. Behavioural risk factors can be particularly amenable to public health action. There exists a need to develop, implement and test in collaboration with native people, interventions aimed at reducing the incidence and impact of NIDDM, by reducing the risk of its onset, and by early detection and treatment. Intervention programmes should be conceived with sensitivity to the overall health, social, economic, educational and cultural environment within a community. Although this review focuses specifically on diabetes in Canada, many of the points relating to the need for primary prevention of the disease will be appropriate in other situations.

Quality of life is not negatively affected by diet and exercise intervention in healthy men with cardiovascular risk factors

Health-related quality of life was assessed in a diet and exercise intervention study among 157 healthy men aged 35-60 years (mean +/- s.d.; 46.2 +/- 5.0) with moderately raised cardiovascular risk factors. The men were randomized to four groups, diet (D, n = 40), exercise (E, n = 39), diet plus exercise (DE, n = 39), and no active intervention (controls (C) n = 39). Quality of life was measured with two self-administered questionnaires; Subjective Symptoms Assessment Profile and Minor Symptom Evaluation Profile, at baseline and after 1.5, 3 and 6 months. Cardiovascular risk factors were investigated at baseline and after 6 months. As a result of changes in dietary habits and physical exercise in the three intervention groups, several important cardiovascular risk factors were significantly reduced. The quality of life/well-being did not differ between the four groups and did not change significantly in any of the groups during the study. There was, however, a tendency towards fewer gastrointestinal symptoms in group D and fewer cardiac symptoms in group DE. We conclude that advice on lifestyle changes in the form of diet and exercise reduce risk factors in middle-aged men without negative effects on their quality of life.

Undiagnosed glucose intolerance in the community: the Isle of Ely Diabetes Project

The Isle of Ely Diabetes Project is a prospective population-based study of the aetiology and pathogenesis of Type 2 diabetes mellitus. Between 1990 and 1992, 1156 subjects aged between 40 and 65 years underwent a standard 75 g oral glucose tolerance test (OGTT). A total of 1122 individuals who were not known to have diabetes completed the test and were classified according to WHO criteria; 51 subjects (4.5%) had previously undiagnosed diabetes and 188 (16.7%) had impaired glucose tolerance. The subjects with newly diagnosed glucose intolerance were significantly older, more obese, and shorter than those with normal glucose tolerance. Blood pressure, cholesterol, triglyceride, and LDL-cholesterol concentrations were elevated and HDL-cholesterol levels were lower among those with abnormal rather than normal glucose tolerance. In multiple regression analyses stratified by gender and including age, body mass index, and the waist-hip ratio as covariates, there were significant differences between those with normal and abnormal glucose intolerance in blood pressure, triglyceride, and HDL-cholesterol, but not total or LDL-cholesterol. In both male and female subjects, height had a significant independent negative association with the plasma glucose at 120 min after administration of oral glucose (standardized beta coefficient = -0.12, p < 0.01).

Dietary factors in the aetiology of diabetes

Quite different nutrition-related environmental factors influence the development of type 1 insulin-dependent diabetes (IDDM) and type 2 non-insulin-dependent diabetes (NIDDM). IDDM is characterized by progressive beta-cell destruction which leads to complete insulin deficiency; at the time of diagnosis 80-90% of beta cells have been destroyed. In children there is epidemiological evidence that high intake of nitrites and N-nitroso compounds, early introduction of cow's milk to the diet and short duration or absence of breastfeeding increase the risk of IDDM. Studies in experimental animals suggest that cow's milk and soy proteins may be diabetogenic. There is current interest in the effects of free radical scavengers, particularly niacin and natural and synthetic antioxidants on the incidence of IDDM. These findings from ecological, animal, and human case-control studies remain to be evaluated in prospective cohort studies covering infancy and childhood and finally in human intervention trials. NIDDM is characterized by insulin resistance which is complicated by impaired insulin secretion at the time of appearance of hyperglycaemia and clinical diabetes. Its preclinical development is insidious and poorly defined, and there is little direct evidence that the same factors which influence metabolic control in clinical diabetes also affect the preclinical development of the disorder. Obesity, particularly of the abdominal type, is common in people who develop NIDDM, and weight control by appropriate diet and physical activity is probably the most important measure for preventing NIDDM. High (saturated) fat intake seems to be associated with insulin resistance, obesity and increased risk of NIDDM, and diets high in carbohydrate seem to protect from glucose intolerance and diabetes, mainly owing to their high fibre content.

Oral glucose tolerance and its relationship to overweight and other cardiovascular risk factors in men aged 33-42. A study in the community of Habo, Sweden

OBJECTIVE

To study the prevalence of family history of diabetes, overweight, and glucose intolerance in a defined general population, and the associations between these variables and others involved in the so-called metabolic syndrome (blood pressure, obesity, serum lipids).

DESIGN

An oral glucose tolerance test (OGTT) was done on all participants in a population study who reported a family history of diabetes or had a body mass index (BMI) > or = 27.

SETTING AND PARTICIPANTS

A population study of men aged 33-42 was carried out at Habo in southwestern Sweden (participation rate 86.1%). An OGTT was done on 170 men who fulfilled the criteria stated above.

RESULTS

Overweight was a risk factor for impaired glucose tolerance and was more strongly associated with this state than was a family history of diabetes. Glucose intolerance was also associated with increased blood glucose concentration during the OGTT and with other metabolic disturbances such as increased serum lipids, increased blood pressure, and physical inactivity.

CONCLUSIONS

The combination of overweight and impaired glucose tolerance is already common at a rather young age in men and is often combined with impairment of arterial blood pressure and serum lipids. The results indicate that it is urgent to start preventive measures early in life.

Prevalence of diabetes, hypertension, and ischemic heart disease in former elite athletes

Diabetes, hypertension, and ischemic heart disease are less frequent among physically active subjects. The aim of the present national population-based study was to compare the prevalence of these three diseases between former Finnish elite athletes and referents. The subjects consisted of surviving former male athletes who represented Finland between the years 1920 and 1965 at least once in international competitions and referents who at the age of 20 were classified as completely healthy at a medical examination, and who responded to a questionnaire in 1985 (athletes, n = 1,282; referents n = 777). In 1985, they completed a questionnaire with medical, life-style, and psychosocial items; at that time, the leisure physical activity was greater in previous athletes than in referents. The presence or absence of the three diseases was identified from the questionnaire or from at least one of three registers: Finnish hospital inpatient discharge register, reimbursable medication register, and disability pension register. When compared with referents, both endurance and mixed-sports athletes had lower age-adjusted odds ratios (ORs) for all studied diseases. Compared with referents, power-sports athletes had a higher risk for high body mass index (BMI) but a lower risk for ischemic heart disease. Subjects with high BMI had an increased risk for all three diseases. Smokers had a higher risk for diabetes and ischemic heart disease compared with those who were never smokers. After adjustments for age, BMI, smoking history, and occupational group, compared with referents, former endurance athletes had the lowest ORs for diabetes (OR 0.24; 95% confidence interval, 0.07 to 0.81) and ischemic heart disease (OR 0.33; 0.18 to 0.61).(ABSTRACT TRUNCATED AT 250 WORDS)

Low-intensity endurance exercise training, plasma lipoproteins and the risk of coronary heart disease

Physically active individuals generally show a reduced risk of coronary heart disease (CHD) compared to the sedentary population. However, whether such reduction in CHD risk mainly results from the concomitant improvement in cardiorespiratory fitness or from the alterations in CHD risk factors has yet to be clearly established. Furthermore, there is still some controversy regarding the potential associations between endurance training-induced changes in metabolic variables considered as CHD risk factors (plasma glucose, insulin and lipoprotein levels) and the magnitude of improvement in cardiorespiratory fitness. From the results of several studies discussed in this article, it is proposed that prolonged endurance exercise of low intensity (approximately 50% VO2max), performed on an almost daily basis, seems to significantly improve metabolic variables considered as CHD risk factors through mechanisms that are likely to be independent from the training-related changes in cardiorespiratory fitness. The notion of 'metabolic fitness' is introduced and can be defined as the state of a ste of metabolic variables relevant to CHD risk and affected by the level of physical activity. Evidence available suggests that these metabolic variables are not closely related to the adaptation of cardiorespiratory fitness in response to exercise training. The concept of metabolic fitness has several implications for the prescription of exercise and for the primary and secondary prevention of CHD. Indeed, emphasis should not be placed on aiming at increasing VO2max through high-intensity exercise, but rather on producing a substantial increase in daily energy expenditure that will eventually lead to weight loss and related improvements in carbohydrate and lipid metabolism. Therefore, from a practical standpoint, although a 1 h daily walk may not have marked effects on cardiorespiratory fitness, it probably represents an exercise prescription that is likely to substantially improve 'metabolic fitness', thereby reducing the risk of CHD.

Diabetes mellitus but not impaired glucose tolerance is associated with dysfunction in peripheral nerves

To clarify whether long-term impaired glucose tolerance (IGT) is associated with dysfunction of peripheral and autonomic nerves, age-matched men with IGT and diabetes mellitus were followed prospectively for 12-15 years, when peripheral and autonomic nerve function was assessed. The patients comprised four subgroups: (1) 51 IGT subjects (duration of IGT at least 12-15 years); (2) 35 diabetic patients, with IGT 12-15 years ago, who later developed diabetes; (3) 34 diabetic patients, duration of diabetes at least 12-15 years; and (4) 62 age-matched non-diabetic control subjects. Mean age of the whole study population was 61 +/- 2 years (mean +/- SD), not different in the four groups. Peripheral nerve function tests included nerve conduction velocities, amplitudes, distal latencies, F-reflexes, and sensory perception thresholds for heat, cold, and vibration. Autonomic nerve function tests included the heart rate reaction during deep breathing (expiration to inspiration ratio) and to tilt (acceleration and brake indices). Despite 12-15 years of IGT, peripheral nerve function did not differ between IGT and control subjects, whereas autonomic nerve function deviated; an abnormal expiration to inspiration ratio (a sign of vagal nerve dysfunction) was significantly more common (15/51 versus 5/62; p < 0.01) in IGT than in control subjects. Diabetic patients (groups 2 and 3) showed lower conduction velocities (in general 2-4 m s-1 lower) than IGT and control subjects in all tested nerves. In conclusion, diabetes but not IGT, is associated with peripheral nerve dysfunction.

Physical activity epidemiology as applied to elderly populations

Physical activity epidemiological studies provide one of many types of research evidence that are necessary to assess the importance of physical activity to health. Available epidemiological evidence, when coupled with relevant experimental and clinical research, suggests that physical activity has the potential to favourably influence the development and progression of a variety of chronic diseases and conditions that are a burden to public health. The evidence is only beginning to emerge for elderly populations, however, thereby highlighting an important void in our scientific knowledge. Attempting to increase the level of physical activity of elderly people raises three important issues. First, improving adherence to a physically active life-style requires assistance of behavioural scientists, either through direct intervention, or through research that can help the elderly identify and overcome impediments to physical activity. Second, many elderly people have diseases that can limit their physical ability, but exercise scientists can assist by prescribing exercise that is both efficacious and safe given the level of limitation. Third, the number of injuries may increase with increased physical activity in elderly persons. Epidemiologists and exercise scientists working in the area of injury control can determine which activities are safe at specific levels of physical ability and function. To quote one of the originators of exercise physiology, Per Olaf Astrand (1992), 'As a consequence of diminished exercise tolerance, a large and increasing number of elderly people will be living below, at, or just above "thresholds" of physical ability, needing only a minor intercurrent illness to render them completely dependent'. Physical activity can help to push back that 'threshold of physical ability' and thereby improve physical functioning. As physical function improves, there is a propensity to perform even greater amounts of physical activity that may be essential to the quality and perhaps quantity of life for an elderly person.

Gestational diabetes: a challenge for the future

It is well established that pregnancy is associated with temporary changes in maternal metabolism which include a decrease in maternal insulin sensitivity to values similar to those associated with Type 2 diabetes. Fasting glucose concentrations fall throughout pregnancy, postprandial values rise. The maintenance of glucose tolerance in pregnancy requires a two- to three-fold increase in postprandial maternal insulin secretion. Glucose intolerance develops in women unable to compensate for the metabolic changes incurred by pregnancy. Increasing maternal hyperglycaemia is associated with increasing pregnancy morbidity and an increased likelihood of subsequent diabetes in the mother. In addition, maternal hyperglycaemia has a direct effect on the development of the fetal pancreas and is associated with an increased susceptibility to future diabetes in the infant, an effect which is independent of genetic factors. Gestational diabetes mellitus (GDM) is defined as glucose intolerance first recognized in pregnancy, and by definition includes a small number of women with previously unrecognized diabetes or impaired glucose tolerance (IGT). Figures on the prevalence of GDM vary between maternity units, depending on screening methods and the ethnic distribution of the populations. However, in a comprehensive study of a multi-ethnic antenatal population in inner London, UK it was found that only 2% of pregnant women develop significant glucose intolerance. Obstetricians and physicians debate the importance of identifying this 2% of women. The lack of agreed criteria for diagnosing gestational diabetes and the questionable obstetric benefits of treating all women with mild disturbances of glucose tolerance in pregnancy has resulted in few UK centres undertaking universal screening for GDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Can life-styles of subjects with impaired glucose tolerance be changed? A feasibility study

Thirty-one subjects with impaired glucose tolerance were randomly allocated to a group receiving advice to improve their diet and physical activity levels over 6 months (n = 23) or to a control group (n = 8). At 6 months, 18 of the 23 subjects receiving 'healthy living' advice were re-examined (five subjects had withdrawn). Fourteen of the 18 subjects showed an alteration in diet or an increase in exercise. The 18 subjects re-evaluated showed a reduction in systolic blood pressure (118 +/- 15 vs 124 +/- 15 mmHg, p less than 0.05) and decrease in total plasma cholesterol (4.5 +/- 1 vs 5.2 +/- 1 mmol l-1, p less than 0.01) and LDL-cholesterol levels (2.8 +/- 0.9 vs 3.2 +/- 0.9 mmol l-1, p less than 0.05). Plasma glucose levels were unchanged. One subject withdrew from the control group. At 6 months, the seven control subjects examined showed no significant change in metabolic parameters, with little measurable change in diet or exercise. At 2 years, 17 of the 23 'healthy living' subjects were reassessed. Nine of the subjects had continued to exercise or maintained a decreased weight compared to baseline. Fasting plasma glucose levels had increased (6.0 +/- 1.2 vs 5.5 +/- 0.6 mmol l-1, p less than 0.05), with the only continued improvement being a reduced LDL level (2.8 +/- 0.7 vs 3.1 +/- 0.9 mmol l-1, p less than 0.05). At 2 years, a similar proportion of the control group were taking regular exercise compared with the 'healthy living' group.(ABSTRACT TRUNCATED AT 250 WORDS)