Exercise as it relates to Disease/The Importance of Physical Activity in reducing the risk of Type 2 Diabetes

The following is an analysis of the journal article "Physical Activity in the Prevention of Type 2 Diabetes: The Finnish Diabetes Prevention Study" by Laaksonen et al (2005).

Type 2 diabetes is caused when the body becomes resistant to the effects of insulin or the pancreas doesn't produce enough insulin.

What is the background to this research?

Type 2 Diabetes is a progressive condition meaning it develops over a long period of time. It is diagnosed when the pancreas does not produce enough insulin and/or the body becomes resistant to the normal effects of insulin.

Prevalence

In 2011-2012, it was estimated that 849,000 individuals over the age of 18 reported that they had Type 2 Diabetes. Type 2 Diabetes represents 85-90 percent of all cases of diabetes. There is no single known cause of Type 2 Diabetes, however there are many risk factors involved. An individual with a family history of diabetes is at a higher risk of developing it. It usually develops in adults over the age of 45 and is more prevalent in men than women. Research on Type 2 Diabetes is important as it is an issue that is increasing significantly in many populations around the world.

Where is this research from?

This study was conducted by researchers for the Finnish Diabetes Prevention Study Group and was supported by:

• The Academy of Finland
• The Ministry of Education
• The Novo Nordisk Foundation
• The Yrjö Jahnsson Foundation
• The Finnish Diabetes Research Foundation
• The EVO fund of the Kuopio University Hospital
• The Juho Vainio Foundation.

What kind of research was it?

The Finnish Diabetes Prevention Study (DPS) is a multicenter, randomized, controlled trial designed to test the hypothesis that lifestyle changes can prevent Type 2 Diabetes in high-risk individuals. Post hoc analyses were carried out on the role of Leisure-time physical activity (LTPA) in preventing Type 2 Diabetes. These type of analyses are used to examine the difference between pairs or groups after the global analysis. Two-sided t tests and x tests were then used to analyze the differences between the intervention and control groups.

What did the research involve?

The research involved 522 men and women with impaired glucose tolerance (IGT) from five study centers who were randomly assigned to the intervention or control group. Of the 522 subjects, 487 completed a questionnaire at baseline and at least once during a 12-month follow-up. The validated Kuopio Ischemic Heart Disease Risk Factor Study (KIHD) 12-month LTPA questionnaire was used. The study lasted 4.1 years, where subjects completed the questionnaire every 12 months during that time.

What were the basic results?

The results indicated that of the 522 initial subjects who participated, 107 developed diabetes during the 4.1-year follow-up period. As a result of the questionnaire, it was reported that participation in <1h/week of moderate-to-vigorous LTPA was 37% in the intervention group and 39% in the control group. Involvement in ≥2.5h/week of moderate-to-vigorous LTPA was 41% in the intervention group and 40% in the control group. After the initial baseline questionnaire, men engaged in more total LTPA and moderate-to-vigorous LTPA than women, but amounts of low-intensity LTPA did not differ significantly between men and women. In the combined groups, an increase in structured, strenuous LTPA seemed to decrease the risk of diabetes by 57% for the upper verses the lower third after adjusting for dietary changes, but further adjustment for changes in BMI attenuated the reduction to 47%. Also in the combined groups an increase in moderate-to-vigorous LTPA in the upper third was associated with a 40% lower risk of incident diabetes even after further adjustment for diet, BMI and their changes. Those who increased the intensity and frequency of walking for exercise during follow-up had a 48% lower risk of diabetes than others. However with further adjustment for baseline dietary factors and their changes and BMI and its changes the association attenuated again. Compliance to the CDC/ACSM physical activity recommendation (≥2.5h/week) during follow-up was 62% in the intervention group but only 46% in the control group. Men and women whose average levels of moderate-to-vigorous LTPA were in compliance with current CDC/ACSM recommendations were 44% less likely to develop diabetes than those remaining sedentary. There were weakened associations, however, when adjusting for dietary variable and BMI.

What conclusions can you take from this study?

The conclusion that we can draw from the results that were obtained from this study is that more vigorous LTPA has greater benefits for reducing the risk of diabetes. Low-intensity LTPA, nonetheless, offers benefits to incident diabetes also, however they are not as strong. It is suggested that strenuous, structured LTPA would have likely mediated the decrease in diabetes due to the weight loss and weight maintenance that was a result of this kind of LTPA. Weight loss is a strong factor contributing to improved insulin sensitivity and plays an important role in diabetes prevention. These findings are consistent with other similar studies that have investigated the effects of exercise in reducing the risk of diabetes.

Physical activity is known to be a factor involved in reducing the risk of type 2 diabetes.

Limitations

Although this study was effective in its aim, there were a few limitations that could affect the results slightly. As previously discussed, after adjusting the models for such things as dietary variables and BMI, many of the results and associations were weakened and therefore presented a slightly smaller relationship between LTPA and the risk of diabetes. Furthermore, although the study used a validated questionnaire (which the study argues is one of the strengths of its research), there is a high chance that participants overestimated the amount of LTPA they were involved in, therefore affecting the accuracy of the results.

Practical advice

To decrease the risk of developing diabetes in high-risk individuals it is important to combine regular physical activity with healthy eating, therefore resulting in weight lose and weight maintenance. Compliance with current physical activity recommendations may significantly decrease the incidence of Type 2 Diabetes, especially in high-risk individuals. In women with Type 2 Diabetes, combining resistance and aerobic training enhances insulin resistance, decreases abdominal subcutaneous and visceral adipose tissue and increases muscle density more than aerobic training alone. Therefore a balance of several training types will be most beneficial in reducing the risk of developing Type 2 Diabetes.

Further reading

For further information on Type 2 Diabetes and the effects that physical activity has on reducing its risks please see the following documents:

• Wei, M., Gibbons, L., Mitchell, T., Kampert, J., Lee, C., & Blair, S. (1999). The Association Between Cardiorespiratory Fitness and Impaired Fasting Glucose and Type II Diabetes Mellitus in Men. Journal Of Cardiopulmonary Rehabilitation, 19(4), 263. http://dx.doi.org/10.1097/00008483-199907000-00009
• Pan, X., Li, G., Hu, Y., Wang, J., Yang, W., & An, Z. et al. (1997). Effects of Diet and Exercise in Preventing NIDDM in People With Impaired Glucose Tolerance: The Da Qing IGT and Diabetes Study. Diabetes Care, 20(4), 537-544. http://dx.doi.org/10.2337/diacare.20.4.537
• Reduction in the Incidence of Type 2 Diabetes with Lifestyle Intervention or Metformin. (2002). New England Journal Of Medicine, 346(6), 393-403. http://dx.doi.org/10.1056/nejmoa012512
• Physical Activity. (2016). American Diabetes Association. Retrieved 18 September 2016, from http://www.diabetes.org/are-you-at-risk/lower-your-risk/activity.html?referrer=https://www.google.com.au/