The number of individuals in North America that are being diagnosed with diabetes mellitus has been steadily rising for the past decade. According to the Dietary Prevention Program (DPP, 2002), it is estimated that almost 8% of North American’s have some form of diabetes. In fact, according to the Centres for Disease Control and Prevention, diabetes is the number seven leading cause of death in North America, a list that it wasn’t even considered for just a couple decades ago. Scientists expect this epidemic to continue to rise, as it is estimated that one in three American’s living today will eventually develop diabetes, and by 2050 that number will increase by 165 percent (DPP).
Type 1 diabetes mellitus, or insulin dependent diabetes (previously known as “juvenile-onset diabetes”), is a form of diabetes that is mostly misunderstood by scientists and researchers today. However, it is generally accepted that this type of diabetes is affected mostly by genetics, and therefore is widely considered un-curable, although manageable (DPP, 2002). Type 2 diabetes mellitus, on the other hand, is not believed to be genetic. This form of diabetes (previously termed “adult-onset diabetes”) is believed to be highly dependent on lifestyle choices and weight management. Type 2 diabetes, which accounts for the majority of diabetes cases, can be prevented or, when diagnosed, regulated (DPP). Additionally, due to the rising prevalence of diabetes in North America, many individuals are being classified as “pre-diabetic”. These individuals show biomarkers that indicate a trend towards obtaining type 2 diabetes, and therefore should adopt intervention strategies to avoid it. For most individuals diagnosed with diabetes, these types of interventions often manifest as pharmacological ones. However, as Gillies et al. (2007) was able to show, lifestyle intervention strategies are as effective as pharmacological ones.
Behavioral scientists have been working diligently to determine different behavioral intervention strategies that may help an individual that is diagnosed with Type 2 diabetes, or determined to be pre-diabetic. It is their hope that these strategies will help educate and inform these individuals on certain ways to help avoid or lessen the effects of diabetes. It is generally accepted that adopting an exercise program can help regulate the symptoms of Type 2 diabetes. However, as evidence by the rising obesity rates in North America, the majority of adults don’t meet the daily needs of physical activity (ACSM standards: 150 minutes of moderate-vigorous activity per week). Because of this, behavioral interventions should be focused on developing an appropriate action plan for adopting or adhering to an exercise program. Therefore, the purpose of this review is to understand and examine the useful intervention strategies, and provide a framework for adopting a physical activity intervention strategy for individuals classified as pre-diabetic or diagnosed with Type 2 diabetes.
Diabetes mellitus is a group of metabolic diseases in which an individual’s blood sugar levels (blood glucose) are increased for an extended period of time. Acutely, a rise in blood sugar can cause excessive thirst, increased urine output, blurred vision, tingling or numbness (especially in the feet and toes) and fatigue. If left untreated, regular increased blood sugar due to diabetes can cause many health complications such as hypertension, nerve damage, kidney disease, heart disease, loss of vision, or loss of circulation in the extremities leading to amputation in extreme cases, among others. As Mensink, Feskens, Saris, De Bruin, & Blaak (2003) highlight, regulating the blood sugar of individuals diagnosed with diabetes is important for symptom control.
The diagnosis of diabetes relates to the ability of the pancreas to produce the hormone insulin. Insulin is responsible for shuttling glucose from the blood into the body’s cells. A normal acting pancreas will secrete insulin when blood sugars get too high, causing a pathway to open and glucose to leave the blood and enter the cell. Subsequently, this drops blood sugar (glucose) levels. In diabetics, however, there is a biological error in either the production or transport of insulin. Generally, there are two main classifications of diabetes: Type 1 and type 2.
In type 1 diabetes, the pancreas fails to produce enough insulin to offset the rise in blood sugar levels. For these individuals, exogenous insulin needs to be injected in to the body. As previously mentioned, the cause of type 1 diabetes is widely unknown, but it is believed that genetics plays a vital role.
Type 2 diabetes, on the other hand, is diagnosed when there is an insulin resistance at the cell, and the pathway for glucose to leave the blood (and enter the cell) is stunted. Individuals diagnosed with type 2 diabetes may or may not need exogenous insulin injections depending on the severity and progression of the disease. According to the World Health Organization (WHO), the primary cause of type 2 diabetes is excessive body weight and a lack of exercise.
Because of the rising prevalence of diabetes, a third classification has been termed as a way to foresee and avoid possible diagnosis. Pre-diabetes is a condition where blood sugar levels are higher than normal, but not high enough to clinically diagnose diabetes. Individuals who are classified as pre-diabetic are at an increased risk of developing type 2 diabetes.
The clinical diagnosis of diabetes involves not only taking measurements of blood glucose but also administering an HbA1c test. This simple procedure requires your doctor to take a blood sample, which is then used to determine your blood sugar levels by analyzing the amount of what is called glycated hemoglobin (or HbA1c). The more glucose that is digested and enters the blood, without the appropriate amount of insulin to offset it, the more glycated hemoglobin will be present. This test provides a more accurate overview of an individual’s overall blood sugar levels, and the American Diabetes Association recommends that an individual who is classified as pre-diabetic or with type 2 diabetes take the HbA1c test twice a year. A HbA1c level below 5.7 percent is considered normal whereas an HbA1c level between 5.7 and 6.4 percent signals pre-diabetes. Type 2 diabetes is diagnosed when the HbA1c is over 6.5 percent. Regardless of the HbA1c classification, physical activity is important for blood sugar control and symptom regulation of type 2 diabetics (Tuomilehto et al., 2001). Therefore, it is important to understand the intervention strategies that are observed in the literature that best help individuals diagnosed with Type 2 diabetes adopt and adhere to exercise.
For the literature review of this report, online database searches using a combination of the following keywords were used to gather a depth of knowledge on the intervention strategies for both diabetics (type 2) and pre-diabetics: Diabetes, behavioral intervention, Type 2 Diabetes Mellitus, pre-diabetes, and behavior. The majority of the peer-reviewed journal articles in this review were found on the online databases PubMed, or SportDiscus.
Inclusion criteria for articles to be reviewed were ones that specifically looked at behavioral intervention strategies for individuals classified as either Type 2 Diabetic of pre-diabetics. Emphasis was given to randomized control trials, of which five articles were found (see Table 1). However, other articles were also used to further explain or provide a framework for behavioral intervention strategies. Exclusion criteria included any article that didn’t fit the inclusion criteria, articles that didn’t present data, or studies that showed null findings. Additionally, because of its genetic nature, articles that looked at Type 1 diabetes mellitus specifically were not included in the literature review.
For studies that fulfilled the inclusion criteria, the primary reviewer abstracted relevant population and behavioral intervention characteristics that related to diabetics (type 2) or pre-diabetics. Outcomes examined include: blood glucose levels, HbA1c levels, blood pressure, weight reduction, glucose tolerance, and cholesterol – all things related to risk of increased blood glucose levels. Additionally, because of its profound effect on weight management and also blood glucose and HbA1c levels, exercise adoption and adherence was also examined. For most studies, observations were calculated using p-values.
Five eligible randomized control trial articles were identified in the literature (Balducci et al., 2010; Block et al., 2015; Page, Harnden, Cook, & Turner, 1992; Tuomilehto et al., 2001; Mensink, Feskens, Saris, De Bruin, & Blaak, 2003; see Table 1). Three of which were focused on individuals classified as pre-diabetic (Block et al.; Page, Harnden, Cook, & Turner; Tuomilehto et al.), while two others included both pre-diabetics and individuals with type 2 diabetes (Balducci et al.; Mensink, Feskens, Saris, De Bruin, & Blaak). Of the five eligible articles, three were centred on goal setting interventions (Mensink, Feskens, Saris, De Bruin, & Blaak; Tuomilehto et al.; Balducci et al.). Additionally, one article assessed the usefulness of technological interventions (Block et al.). All eligible articles included an experimental group who were given a specific intervention, as well as a control group which were given a different form of intervention. Besides the technological intervention (Block et al.), the underlying variable in the experimental groups were either additional lifestyle advice or added supervision. Two of the five eligible articles analyzed the effects of additional counseling on physical activity (Balducci et al.; Tuomilehto et al.) while two additional articles looked at dietary advice to improve biomarkers for diabetes such as cholesterol and blood glucose concentration (Mensink, Feskens, Saris, De Bruin, & Blaak; Page, Harnden, Cook, & Turner). The average follow up time looking at the effectiveness of the intervention strategies was 6 months.
On top of the randomized control trials, two study’s were identified as non-RCT trials looking at the usefulness of intervention strategies based on the social cognitive theory (Plotkinoff, Lippke, Courneya, Birkett, & Sigal, 2008) or qualitative analysis such as surveys (Plotkinoff, Brez, & Hotz, 2000). Both of these articles used individuals that were already diagnosed with type 2 diabetes and were used to provide a framework for behavioral intervention strategies (to be discussed).
After analyzing the themes from the different types of intervention strategies, it was found that supervised aerobic or resistance training programs plus exercise counseling was more effective than exercise counseling alone (Balducci et al., 2010). In this case, the mean (SD) volume of physical activity was significantly higher (p<0.001) in the experimental group (supervised training plus counseling) compared to the control group (counseling alone). Additionally, the experimental group also had significant improvements in their HbA1c levels (P<0.001) over the control. Tuomilehto et al. (2001) further supported the benefits of additional counseling by showing that individual exercise counseling could reduce the risks of diabetes and increase physical activity. In this study, they were able to show that individual counseling was more beneficial than general oral and written information about exercise. Their results indicated that the risk of diabetes was reduced by 58% (p<0.001) in the experimental group compared to the control group at a 1 year follow-up.
While increased exercise was an important factor in reducing the risk and symptoms of type 2 diabetes, so too was dietary advice. Two eligible papers were identified for their effects of dietary lifestyle interventions on certain biomarkers for developing diabetes in individuals classified as pre-diabetic (Mensink, Feskens, Saris, De Bruin, & Blaak, 2003; Page, Harnden, Cook, & Turner, 1992). One study (N=102) looked at the use of regular dietary advice versus only brief information about the effects of a healthy diet on blood glucose concentration (Mensink, Feskens, Saris, De Bruin, & Blaak). Results of this particular study showed that regular dietary advice (experimental group) was more beneficial than brief information (control group) on decreasing blood glucose concentration (p<0.05) – a biomarker for type 2 diabetes. Additionally, Page, Harnden, Cook, & Turner (1992) were able to support the benefits of dietary advice. In their study, they were able to show that receiving advice to improve diet and physical activity is indicative to adhering to that advice which results in reduced biomarkers for type 2 diabetes. In this case, the experimental group (n=23) was given advice to improve their diet while the control group (n=8) was given no advice. As expected, the experimental group who were given advice significantly lowered their cholesterol levels (p<0.01) compared to the control group. Additionally, at a 2 year follow-up, 9 of 17 participants from the experimental group had continued to exercise. These results indicate that dietary advice is helpful in reducing the biomarkers for diabetes as well as continuing exercise (Mensink, Feskens, Saris, De Bruin, & Blaak; Page, Harnden, Cook, & Turner).
Of the eligible articles included in this review, 4 of the 5 studies looked at behavioral intervention strategies based on exercise counseling or dietary advice. The problem with this, as Block et al. (2015) suggests, is that these strategies involve face-to-face interactions in order to facilitate health improvements or reduction in certain biomarkers for type 2 diabetes. In a recent study, however, Block et al. looked at the use of technology on reducing similar type 2 diabetes biomarkers in individuals classified as pre-diabetic. Using a fully-automated algorithm-driven technological intervention called Alive-PD, they were able to show that improvements can be made without face-to-face interventions. In their study, participants (N=339) were randomly assigned to either the intervention group (n=163) that received the Alive-PD program, or the control group (n=176) which were placed on a 6-month waiting list with usual care. The Alive-PD intervention group would be sent weekly emails that suggested small-step goals which were then linked to individual web sites with tools for tracking, coaching, social support and health information. Additionally, a mobile phone app and automated phone calls were also provided for further support. What they found was that the experimental group given the Alive-PD program had significant reductions in fasting blood glucose, HbA1c levels, and body weight (p<0.001). These findings suggest that technological interventions may be a useful tool to use for individuals classified as pre-diabetic, or diagnosed with diabetes, to help lessen the effects of their respective conditions.
The prevalence of diabetes is on the rise and, especially in North America; it can be argued that diabetes is becoming an epidemic. However, most individuals who are classified as pre-diabetic or diagnosed with type 2 diabetes tend to rely on medication prescribed from a general practitioner to treat their symptoms and lower their blood sugar. Regardless of this, as Gillies et al. (2007) was able to show, lifestyle intervention strategies are as effective as pharmacological ones.
As evidenced from the review of the literature, it can be argued that both exercise counseling as well as dietary advice can be beneficial for the improvements in biomarkers leading to type 2 diabetes (Balducci et al., 2010; Page, Harnden, Cook, & Turner, 1992; Tuomilehto et al., 2001; Mensink, Feskens, Saris, De Bruin, & Blaak, 2003). Additionally, recent research suggests that the use of technology may be a useful tool for similar benefits (Block et al., 2015). However, these studies have all focused on applying interventions by the use of counseling or the addition of certain variables such as advice or supervision. While these approaches have proved to be beneficial, they don’t necessarily improve behavior, only work to make adjustments on daily living. While these studies have all used randomized control trials to support their findings, certain qualitative researchers have been able to use behavioral interventions to help provide a different framework to improving physical activity in individuals with diabetes. Ronald Plotkinoff is one of those researchers.
Plotkinoff and colleagues (2008) suggest that, by using the self-determination theory outlined by Bandura (2004), the behavior of individuals with type 2 diabetes can be changed for the better. He believes that the promotion of health behavior in individuals with diabetes should focus on improving self-efficacy, or the belief they can improve, to set goals and change behavior. He further adds that social support and outcome expectancies are important factors for setting goals (Plotkinoff, Lippke, Courneya, Birkett, & Sigal). The problem with the RCT trials that were outline in this report is that they didn’t have very large reach. For the most part, individuals had to identify themselves (or by their doctors) to be at risk. Furthermore, these individuals often would have to seek out additional help that sometimes their doctors were unable (or unwilling) to provide. Therefore, Plotkinoff, Brez, & Hotz (2000) wanted to provide a framework that could be applied in community samples with a larger reach. They were able to show that by using a population and community based survey, behavioral changes in individuals with diabetes (or pre-diabetics) could be administered. This indicates that behavioral changes can be applied not only by clinical trials, but also by applying psychological theories and utilities that may have a larger reach to more individuals. In conclusion, by combining these factors, individuals diagnosed with type 2 diabetes may be able to set and reach goals aimed at improving their health, and ultimately their diabetes symptoms.
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