Exercise as it relates to Disease/Does being physically active lower the risk of diabetes in adolescents?

This work is a critic of the journal article "Physical Activity May Facilitate Diabetes Prevention in Adolescents" by Thomas et al. (2009).

What is the background to this research?[edit | edit source]

The authors of this research were concerned with the sudden increment of cases of type 2 diabetes among adolescent populations, an "epidemic" growing at the same rate of an outburst of child obesity. According to the first extensive population-based investigation of incidents of diabetes in American youth, SEARCH for Diabetes in Youth Study (SEARCH)   in 2001, 3.5% of the 10 -19-years-old participants had type 2 diabetes. In addition, the American Diabetes Association disclosed that one in six overweight adolescents has pre-diabetes. However, by far the type I diabetes continues to be the most common amongst adolescents.

Supported by high-quality evidence in adult prevention trials, the benefits of increasing Physical Activity (PA) to avert and slow down the development of type 2 diabetes. For example, in the Diabetes Prevention Program and the Finnish Diabetes Prevention Group, rigorous lifestyle modifications, inclusive of exercise, were 58% more successful in slowing down advancement to diabetes from an impaired glucose tolerance. In another study conducted in China, the Da Qing IGT and Diabetes study demonstrated that exercise decreased diabetes incidence by 46% amongst those with IGT. However, it is unclear if the same result would be achieved in an adolescent population.

This study set out to examine the relationship of PA with glucose tolerance (K_g) and Resting Energy Expenditure (REE) in an adolescent population and hypothesised a positive association between time and intensity of PA and glucose tolerance and REE. These are important because of the lack of prevention trials in pediatric populations and the impending "epidemic" of type 2 diabetes and obesity in children and adolescents.

Where is the research from?[edit | edit source]

A multidisciplinary team of professionals from the University of Alabama at Birmingham, United States of America (USA) conducted this study. The team comprised professionals from the Department of Nutrition Science, Department of Medicine, and General Clinical Research Center (GCRC).

This manuscript was published by https://care.diabetesjournals.org/ in 2008 and by the American Diabetes Association in 2009. The authors appeared to be experienced researchers with a minimum of three research works under their belt.     

This work has a significant role to play not only in the discovery of new knowledge but also as an educational and propagation tool of the SEARCH for Diabetes in Youth Study that was launched in 2000 to tackle vital "knowledge gaps in the understanding of childhood diabetes" .

The study population consisted of 32 males and females, African American and Caucasian adolescents, aged 12 to 18 years. The study was approved by the Institutional Review Board for Human Use at the University of Alabama at Birmingham. Participants and guardians signed a consent form before registration.

This research was funded by the General Clinical Research Center (GCRC) and the Clinical Nutrition Research Unit, University of Alabama, Birmingham, and no likely conflicts of interest pertinent to this work were reported.

What kind of research was this?[edit | edit source]

The research was part of an original longitudinal study: "Intra-abdominal fat and risk of disease in adolescent". A cross-sectional study (a variety of observational study design) that measure the association between Physical Activity with K_g and REE in an adolescent population at a specific point in time.

It has been said that cross-sectional study design has its merits for being comparatively quick and inexpensive. It can be carried out prior to designing a cohort study or a baseline in a cohort study . Furthermore, these research designs can serve as a framework to plan, monitor and evaluate public health . Nevertheles, these studies have their limitations (see what did the research involve?).

According to the Level of Evidence ranking, Cross-sectional study designs are level IV and categorised as the most biased across the clinical domains .

What did the research involve?[edit | edit source]

The participants were 32 male and female adolescents aged 12-18 years admitted overnight to the GCRC and instructed to fast for 12 hours. Upon admission, body composition was assessed. The morning after the admission, their REE was measure via indirect calorimetry and K_g by an Intravenous glucose tolerance test. In addition, daily PA was assessed with fitted accelerometers that measure vertical acceleration and deceleration. The subjects wore the accelerometer 24 hours a day for 8.5 days, except when swimming and bathing.

As the authors stated, one of the strengths of this study was the estimation of Intravenous glucose tolerance and time involved in moderate to vigorous PA. Nonetheless, one major limitation of this study is the size and diversity of the population; the sample was very small and may not represent the characteristics of the targeted population. For example, there are no representations of various ethnic and races, that is, Asian-non Hispanic, Hispanic and American Indian participants. This is important because it has been reported that type 2 diabetes is inequitably impacting the minority races and ethnic groups and from low socio-economic backgrounds .

Furthermore, it may be difficult for the layman to interpret the data if one does not have normal values or ranges to compare the data. For instance, in the current paper, on the design and methods section, under the subheading -Intravenous glucose tolerance test, the authors wrote the following about the values for K_g: " a higher number implies higher (better) glucose tolerance", but does not provide a classification table to compare these values with. In contrast, in a study by Nathan and colleagues, "Impaired fasting glucose and impaired glucose tolerance, implications for care , the authors had included a table with the classification of glucose tolerance states.

Finally, a limitation of using a cross-sectional study design to measure PA and the association with glucose tolerance and REE is that it would be difficult to discriminate cause and effect from simple association. Thus, further work needs to be done to establish if a PA intervention is associated with changes in REE and K_g.

What were the basic results?[edit | edit source]

The main findings of this study were:

• Female subjects had considerably higher fat mass, a higher percentage of fat, lower Free Fat Mass( FFM), lower REE and higher intravenous glucose tolerance (K_g).
• Males were more physically active in terms of Total PA (TPA), Moderate PA (MPA), and Hard PA (HPA)than females participants. African American youth engaged in substantially higher TPA.
• Minutes spent in TPA, MPA, HPA and Very Hard PA (VHPA) was not determined by race.

• PA was positively associated with normal glucose metabolism and REE. However, HPA and VHPA did not significantly contribute to glucose tolerance, nor did VHPA have an independent relationship with REE.

The researchers emphasised that this work revealed new knowledge about Glucose metabolism in adolescents, suggesting that the information was relevant when diseases related to obesity, namely diabetes, are significantly increasing in this population. It also suggested that adolescents benefit by participating in exercise training programs and boosting leisure-time participation.

What conclusions and practical advice can we take from this research?[edit | edit source]

This manuscript was written in 2009; Thomas and her team pioneered the assessment of glucose uptake in an adolescent population related to PA. Many other researchers follow suit from testing the effectiveness of a Healthy Lifestyle Program to testing different intensities of exercise and the effect in insulin sensitivity and glucose uptake, such as Savoye et al. 2014 , Rohling et al. 2015 , and Bird et al. 2016 . Interestingly, from all the literature reviewed, I found The Consensus Report from Diabetes Care 2016, the most thorough and informative manifest in children and adolescents onset type 2 diabetes .

Some of the organisations in the U.S and Australia currently working and supporting research in prevention, cure and treatment of diabetes are:

• The SEARCH for Diabetes in Youth

• Diabetes Australia

• Juvenile Diabetes Research Foundation
• Australasian Paediatric Endocrine Group
• State and Territory Diabetes Organisations
• National Diabetes Service Scheme

• American Diabetes Association (ADA)
• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
• National Institutes of Health (NIH)
• National Diabetes Education Program (NDEP)

Policymakers, academia and the world of science and research have become aware of the growing trends in chronic diseases across populations and the burden they constitute for any country's health system and economy. For example, in Australia, the Institute of Health and Welfare generated the number 15 Australian Burden of Disease Study Series, including the Impact of physical inactivity as a risk factor for chronic conditions report .