Q: WHAT DOES “PREDIABETES” REALLY MEAN? FOR INDIVIDUALS WITH PREDIABETES, IS DIABETES THE INEVITABLE OUTCOME OR CAN LIFESTYLE CHANGES MAKE A DIFFERENCE?
A: Lifestyle factors can have a major impact! Being physically active and embracing a healthy diet are habits recommended for everyone, and this is particularly true for individuals with prediabetes (see Box 1 for prevalence data). To fully understand the benefits of these lifestyle behaviors, this article will review what prediabetes is and how both activity and nutrition are valuable tools to decrease one’s risk of developing type 2 diabetes (T2D).
With prediabetes, blood glucose levels are higher than normal but are not elevated to the level resulting in a diagnosis of T2D (13). Various measures are used to assess glucose status; Box 2 includes specific measures associated with normal, prediabetes, and diabetes for fasting plasma glucose (FPG), 2-hour plasma glucose after a 75-g oral glucose tolerance test (75g-OGTT), and hemoglobin A1c. “Prediabetes” is a term used for those with impaired fasting glucose and/or impaired glucose tolerance (1). The American Diabetes Association (ADA) does not consider these markers to be clinical entities but rather risk factors for T2D and cardiovascular disease (1). Recognizing the continuous nature of these measures, risk is described as “extending below the lower limit of the range and becoming disproportionately greater at higher ends of the range” (1). As a result, individuals with prediabetes are at a relatively high risk of developing T2D in the future (13). Thus, the concept of a “slippery slope” is often applied to help visualize glucose levels that gradually increase across time, progressing from normal, to prediabetes, and then to diabetes if no interventions are made. Without interventions to improve health, 15% to 30% of individuals with prediabetes will develop T2D within 5 years (3). Risk factors for the development of T2D are shown in Box 3. A simple risk assessment tool can be found at http://www.diabetes.org/risktest.
Central to recommendations related to lifestyle factors is confidence that lifestyle-based interventions actually are effective. A number of research studies have shown that T2D can be delayed or prevented. Two studies that demonstrate the benefits of lifestyle modification are the Finnish Diabetes Prevention Study (14) and the Diabetes Prevention Program (9).
The Finnish Diabetes Prevention Study included subjects recruited from screenings of high-risk groups (e.g., first-degree relatives of those with T2D) who had a body mass index of more than 25 kg.m−2, were 40 to 65 years of age, and had impaired glucose tolerance (14). Subjects were assigned randomly to one of two conditions: 1) control group, oral and written information related to diet and activity but no individualized programming, or 2) intervention group, individualized lifestyle modification related to diet and exercise. Those in the lifestyle modification group received detailed advice on weight loss that focused on reducing weight by 5% or more, nutrition (including reduction in total fat intake to less than 30% of energy consumed, reduction in saturated fat intake to less than 10% of energy consumed, and increase in fiber intake to at least 5 g per 1,000 kcal), and physical activity. The physical activity program focused on aerobic exercise and also included supervised individually tailored resistance training. The risk of T2D was reduced by 58% in the lifestyle intervention group. The authors conclude that, even in women and men at high risk for T2D, changes in lifestyle can prevent T2D (14). A recent review and meta-analysis confirm the potential benefits for both males and females; lifestyle interventions resulted in a lower rate of progression to T2D, greater weight reduction, and greater reduction in FPG, among other benefits (4).
The Diabetes Prevention Program included individuals at high risk of developing T2D, with elevated FPG and 75g-OGTT, who were assigned randomly to one of three conditions: 1) placebo group, standard lifestyle recommendations plus placebo tablets; 2) metformin group, standard lifestyle recommendations plus metformin, a common medication used by individuals with T2D; or 3) intensive lifestyle modification group (9). The lifestyle modification group engaged in a 16-week curriculum with subsequent individualized and group sessions focused on helping participants achieve and maintain weight loss of at least 7% initial body weight by means of a healthy diet (low calorie, low fat) and physical activity (at least 150 minutes per week). Incidence of diabetes was reduced in both the group that was treated with metformin (31% lower than the placebo group) and the group that received intensive lifestyle intervention (58% lower than the placebo group). Note that the lifestyle intervention was more effective than the medication; the lifestyle intervention group also had a 39% lower incidence of T2D than the metformin group (9).
During a 10-year follow-up to the Diabetes Prevention Program (Diabetes Prevention Program Outcomes Study), researchers investigated whether the benefits could be sustained and if there were long-term effects on health (10). Reduction in diabetes incidence persisted after 10 years, and onset of diabetes was delayed by approximately 4 years for the lifestyle group and 2 years for the metformin group compared with the placebo group. Other benefits noted for the lifestyle intervention group include improved blood pressure and lipid levels as well as long-term weight loss (10). In addition, in a 10-year economic analysis, the lifestyle intervention has been found to be cost-effective compared with placebo from both a health system and societal perspective (7).
In light of these studies, and others, the ADA recommends that individuals with prediabetes be referred to a support program targeting weight loss of 7% body weight and physical activity of at least 150 minutes per week of moderate activity (1). The use of prescription medication (i.e., metformin) also is a consideration to prevent development of T2D for those with prediabetes, especially if body mass index is greater than 35 kg.m−2, the individual is younger than 60 years, and prior gestational diabetes mellitus for women (1).
CONSIDERATIONS FOR LIFESTYLE CHANGES
Although the benefits of physical activity are well documented, health and fitness professionals must develop programs within the limitations of the individual. Individuals with prediabetes have been found to have more physical limitations and comorbidities than those with normal glucose status, although fewer than individuals with diabetes (11). Thus, there is a continuum, with the least limitations and comorbidities noted for those with normal glucose status and the most observed for those diagnosed with diabetes (11). In one research report, those with prediabetes reported chronic pain (one third), arthritis (one fourth), and difficulty walking several blocks or climbing a flight of stairs (one third) (11). Mobility-related limitations create challenges to fully embracing physical activity recommendations and need to be addressed individually within a tailored exercise prescription.
In addition to an individualized exercise prescription, a personalized nutritional plan is valuable. Medical nutrition therapy by a registered dietician or registered dietitian nutritionist is recommended for those diagnosed as having diabetes (12). In addition, diabetes educators and other health care team members with appropriate training can provide nutrition therapy as determined by scope of practice and state regulations (12).
Although the benefits of lifestyle modifications related to nutrition and physical activity provide much promise, actually making and maintaining lifestyle changes can be a challenge. The National Diabetes Education Program published a helpful document, “Guiding Principles for the Care of People With or at Risk for Diabetes,” that identifies and summarizes areas of agreement among existing guidelines to help health care providers give optimal care (12). The 10 principles are listed in Box 4. In particular, note the focus on nutrition (principle 4) and physical activity (principle 5).
When promoting change, the recognition of the need for self-management is included in principle 3. Self-management is a process that evolves across time in response to individual needs, priorities, and situations (6,12). Although no one ideal approach is identified, strategies may include self-directed goal setting, problem solving, improving health literacy, and engaging family support (12). Others also have identified self-efficacy enhancement and relapse prevention strategies (6). Understanding the individual is key to developing effective interventions, including an assessment of the following: medical history, age, cultural influences, health beliefs and attitudes, diabetes knowledge, emotional response to diabetes, physical limitations, family support, financial status, readiness, literacy, and self-management skills and behaviors (6).
Self-management can be promoted through programs, trained peers, community programs, support groups, and even information technology (6). As an example, care4life provides health information via text messaging, web, and mobile apps, including tracking goals related to weight loss, healthy eating, and exercise, as well as other features such as medication reminders and nutrition tips (content developed in collaboration with the ADA). See https://www.care4life.com/ for more information.
A continuum exists from normal glucose regulation to a diagnosis of T2D. Prediabetes falls midway on this continuum and reflects increased glucose levels above normal but not yet at the level for a diagnosis of diabetes. To prevent or delay the progression from prediabetes to diabetes, lifestyle modifications are recommended, including weight loss and physical activity. Developing individualized exercise prescriptions as well as nutritional plans are potential areas of modification to prevent or delay the development of T2D. For a visual summary of prediabetes, see Box 5 (infographic from the U.S. Centers for Disease Control and Prevention also available at http://www.cdc.gov/diabetes/pubs/statsreport14/prediabetes-infographic.pdf).
• American Diabetes Association – prediabetes
•American Diabetes Association – print-on-demand resources
•American Diabetes Association – slide sets
•Centers for Disease Control and Prevention – diabetes
•Guide to Community Preventive Services – guide to diabetes prevention and control
•Guiding principles for the care of people with or at risk for diabetes
•Diabetes HealthSense: resources for living well
•National Diabetes Prevention Program
•Prevent Diabetes STAT: Screen, Test, Act, Today (American Medical Association and the Centers for Disease Control and Prevention):
1. American Diabetes Association. Standards of medical care in diabetes — 2014. Diabetes Care. 2014; 37: S14–80.
2. Centers for Disease Control and Prevention. National Diabetes Statistics Report: Estimates of Diabetes and Its Burden in the United States, 2014. Atlanta (GA): U.S. Department of Health and Human Services; 2014 [cited 2014 Nov 19]. Available from: http://www.cdc.gov/diabetes/pubs/statsreport14/national-diabetes-report-web.pdf
3. Centers for Disease Control and Prevention Web site [Internet]. Prediabetes. Atlanta (GA): Centers for Disease Control and Prevention [cited 2014 Dec 3]. Available from: http://www.cdc.gov/diabetes/basics/prediabetes.html
4. Glechner A, Harreiter J, Gartlehner G Sex-specific differences in diabetes prevention: a systematic review and meta-analysis. Diabetologia. 2014 [cited 3 Dec 2014]. Available from: http://www.diabetologia-journal.org/
5. Gregg EW, Zhuo X, Cheng YJ, Albright AL, Narayan KV, Thompson TJ. Trends in lifetime risk and years of life lost due to diabetes in the USA, 1985–2011: a modelling study. Lancet Diabetes Endocrinol. 2014; 2: 867–74.
6. Haas L, Maryniuk M, Beck J, et al, for 2012 Standards Revision Task Force. National standards for diabetes self-management education and support. Diabetes Care. 2014; 37 (Suppl. 1): S144–53.
7. Herman WH, Edelstein SL, Ratner RE, et al, for the Diabetes Prevention Program Research Group. The 10-year cost-effectiveness of lifestyle intervention or metformin for diabetes prevention: an intent-to-treat analysis of the DPP/DPPOS. Diabetes Care. 2012; 35 (4): 723–30.
8. International Diabetes Federation. IDF Diabetes Atlas.
6th ed. Brussels, Belgium [cited 2014 Nov 20]. Available from: http://www.idf.org/diabetesatlas/update-2014
9. Knowler WC, Barrett-Connor E, Fowler SE, et al, for the Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med. 2002; 346 (6): 393–403.
10. Knowler WC, Fowler SE, Hamman RF, et al, for the Diabetes Prevention Program Research Group. 10-Year follow-up of diabetes incidence and weight loss in the Diabetes Prevention Program Outcomes Study. Lancet. 2009; 374 (9702): 1677–86.
11. Lee PG, Murphy SL, Cigolle CT, et al Physical function limitations among middle-aged and older adults with prediabetes. Diabetes Care. 2013; 36: 3076–3083.
12. National Diabetes Education Program. Guiding Principles for the Care of People With or at Risk for Diabetes. September 2014. Bethesda (MD): National Diabetes Education Program [cited 3 Dec 2014]. Available from: http://ndep.nih.gov/hcp-businesses-and-schools/guiding-principles/
13. National Diabetes Information Clearinghouse Web site [Internet]. Diagnosis of diabetes and prediabetes [cited 2014 Nov 3]. Available from: http://diabetes.niddk.nih.gov/dm/pubs/diagnosis/
14. Tuomilehto J, Lindstrom J, Eriksson JG, et al, for the Finnish Diabetes Prevention Study Group. Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med. 2001; 344: 1342–50.