Exercise as it relates to Disease/Effects of diet and exercise intervention for patients with type 2 diabetes

This paper is a critique on the article: Vanninen E, Uusitupa M, Siitonen O, Laitinen J, Länsimies E. Habitual physical activity, aerobic capacity and metabolic control in patients with newly diagnosed type 2 (non-insulin-dependent) diabetes mellitus: effect of 1-year diet and exercise intervention. Diabetologia. 1992 Apr 1;35(4):340-6.

This is an assignment created for the unit 'Health Disease and Exercise' at the University of Canberra. Semester 2, 2020

What is the background to this research?
Self-report data collected from 2017 to 2018, revealed that 5.3% of Australians over the age of 18 (and inclusive) had Type 2 diabetes. This value equates to almost 1 million people diagnosed and furthermore, approximately 16,700 associated deaths.

Supporting literature has shown that exercise is beneficial for Type 2 diabetes patients. With regular exercise, 3x< per week, there is an increased insulin resistance effect coupled with an enhanced glucose tolerance post-exercise. If sustained, exercise can also increase high-density lipoprotein (HDL) cholesterol, and reduce low-density lipoprotein (LDL) cholesterol. High levels of LDL can be dangerous as they are associated with atherosclerosis.

During the time period of this study, there was limited evidence of large studies on habitual physical activity in patients with Type 2 diabetes, and its effects. Furthermore, education on diet, physical activity and diabetes in general was near to none in the affected population. Therefore, the present study aimed to investigate the effects of a 1-year intensified diet and exercise intervention on obese, Type 2 diabetics. There was a strong focus on assessing the effects of aerobic capacity and its implications on metabolic function, as well as compliancy to exercise in the selected participants.

Where is the research from?
The intervention group of this study visited the outpatient centre at the Department of Medicine, Kuopio University Hospital where they were treated. The conventional group completed their treatment at the community clinics from which they were referred in Kuopio, Finland. Participants were referred if they were between 40 and 64 years inclusive and had a fasting blood glucose level >6.7 mmol/l. As the highest prevalence of Type 2 diabetes in Finland is from the ages of 55–59, the selected age range for this study is adequate. However, ages 64–75 years are closely followed, perhaps showing a need to increase the selected age range.

The percentage of adults (18-64yrs) reaching the guidelines for physical activity in Finland is currently 34%, with 76% of the population exhibiting sedentary behaviour per day. With a large amount of the population already not physically active, it may be difficult to encourage diabetic patients into regular bouts of exercise/physical activity. This statement is also taking into consideration that on average, females and males were classified as obese on observation of their BMI from this study.

The primary author of this study, Dr. Esko Vanninen, is a professor in the Department of Clinical Physiology and Nuclear Medicine in Kuopio, Finland. He has participated in multiple other studies that similarly investigate insulin-resistance or impaired glucose-control patients. However, these papers have no focus on exercise and its effects on insulin resistance or glucose control.

There is little to no conflicting evidence to that of the findings in this study. However, literature does show an increase in aerobic capacity in patients with Type 2 diabetes with supervised exercise programs, not self-administered.

What kind of research was this?
The design of this study was a randomised control trial (RCT) in which the participants were referred from physicians if they fit the selected criteria. This type of study can prevent any bias selection of participants, which may have altered the results. After elimination of participants due to various factors, only 78 were analysed for the results. As this number can be considered relatively low for the study, different factors such as sex, disease state, exercise history could have skewed the results. This would be considered a downfall to the design of this particular study.

What did the research involve?
After a 3-month diabetic education programme, participants were randomly divided into two groups, the intervention and conventional groups. The intervention group were instructed to visit the outpatient clinic every 2-months for a 12-month period. During these visits they received treatment from a physician, dietitian, and a specialised diabetes nurse. The professionals held a responsibility to motivate patients to exercise, educate them on diet as well as metabolic control. The conventional group did not visit any specialists, instead they attended the community health centres.

All participants used exercise records to note down their duration, intensity and mode of exercise (occupational and recreational) for the 12-month period. Self-report measures, such as the one used in this study, have shown to overestimate physical activity/exercise levels in other studies. Although this method is cost effective, it tests the reliability of the data presented in this study.

Even though there were 2-month check-ups in the intervention group, exercise was unsupervised during the entire 12-month period (except for the initial and post aerobic capacity test). This meant participants were to exercise with a goal of achieving a frequency of 3-4x/week, duration of 30-60 mins and mean heart rate of 110-140 bpm (for which they were not supplied with heart rate monitors). To improve the aerobic capacity of these participants, supervised exercise training may have induced this effect. Results would then have been similar to that of the supported literature noted in the introduction of the study.

As only baseline and 12-month (post-intervention) measures were taken for this study, there is no indication of acute-response to the intervention. Perhaps, this missing data could have provided further motivation for the participants, and a comparison of initial and post-treatment effects.

What were the basic results?
The intervention group reported a 14% increase in the men, and a 41% increase in the female's habitual physical activity at the end of the study. Compared to the conventional group, the men did not significantly increase their habitual physical activity. Aerobic capacity did not significantly improve in either groups, neither did the associated markers (serum-lipid profile). However, among the participants that did increase their VO2 max (n=37), there was also a greater increase in HDL-cholesterol levels than compared to the conventional group. There was a statistically significant inverse correlation between aerobic capacity and HbA 1c (marker for diabetes), even though aerobic capacity did not improve.

The researchers interpreted the results in a manner that was clearly demonstrated in the statistical findings. No over-emphasis on their findings was implied.

What conclusions can we take from this research?
Through thorough analysis of this research article, the main finding is that encouraging increases in habitual physical activity in Type 2 diabetics is not sufficient to improve aerobic capacity. Furthermore, intensified diet education did not induce a significant response in the participants to increase aerobic capacity. Although HDL-cholesterol levels increased and HbA 1c levels decreased with improved aerobic function, evidence is not sufficient enough to state that these metabolic changes are due to increases in aerobic capacity. Increases in physical activity and a reduction in sedentary time in general may have induced these responses, perhaps in conjunction with other variables (better diet, smoking habits, weight loss).

In a more recent review, structured aerobic exercise coupled with resistance exercise demonstrated the largest reduction in HbA 1c levels in Type 2 diabetics. Additionally, a combined effort of more than 150 minutes per week showed further reductions which is in align with the current recommendations of this study. Pedometer-registered physical activity in Type 2 diabetic patients for a short period (12-week intervention), showed an increase in aerobic capacity as well as positive changes to metabolic function and weight loss. Perhaps this method could be substituted for the self-report exercise logs utilised in this study in order to increase motivation for physical activity.

Practical advice
Regular physical activity is beneficial for patients with Type 2 diabetes as it has demonstrated an improvement in metabolic function (HbA 1c, HDL- cholesterol). With the use of pedometers, further increases in regular physical activity are administered. Aerobic capacity can be increased in these patients with supervised exercise sessions that also incorporate resistance training.

When combined, effective diet and exercise can improve serum lipid profiles in that of patients with Type 2 diabetes. These two methods can ultimately improve the quality of life in this affected population.

Further information/resources
The following links provide further information:


 * Relationship between pedometer‐registered activity, aerobic capacity and self‐reported activity and fitness in patients with type 2 diabetes
 * Physical activity advice only or structured exercise training and association with HbA1c levels in type 2 diabetes: a systematic review and meta-analysis
 * Exercise and Diabetes Mellitus
 * Diabetes Australia