Diabetes affects over 9% of Americans and is expected to double in prevalence in the next 25 years. In a country where 37% of adults are at risk for developing type 2 diabetes, programs to prevent diabetes are necessary to address the costs, morbidity, and mortality associated with this disease. Diet and exercise programs to prevent diabetes are targeted to patients with a glycosylated hemoglobin A1c level between 5.7% and 6.4% or a fasting blood glucose of 100-125 mg/dL. Many studies have shown the benefit of intensive diet and exercise programs in preventing progression to diabetes and improving weight reduction. Based on the results of a systematic review published in Annals of Internal Medicine in July 2015, the Community Preventive Services Task Force published a clinical guideline recommending the use of combined diet and exercise programs for all patients at increased risk of developing type 2 diabetes (Ann Intern Med. 2015 Jul 14. doi: 10.7326/M15-0452.).

Description of diet and exercise programs

The task force identified several critical components of successful programs: a minimum of 3 months’ duration; well-trained providers and facilitators; a mix of counseling, coaching, and extended support outside of scheduled sessions; and multiple sessions of varied content and delivery methods.

Interventions commonly featured at least one of a few other components. Most programs set a clear goal for weight loss, and many programs included goals for physical activity and diet. Many programs used a variety of different team members such as doctors, nurses, dietitians, diabetes educators, personal trainers, trained health coaches, and physiotherapists. A series of maintenance sessions after the initial intervention was noted in many of the studies. Often times, the studies modeled their intervention based upon the well-known National Diabetes Prevention Program curriculum. These materials are available free on the Centers for Disease Control and Prevention’s website. Of the 66 programs reviewed, all were live programs using some combination of individual and group sessions. Seven programs were virtual programs using a variety of modalities such as websites and apps. Two studies were conducted with groups of adolescents.

Program outcomes

The task force recommendation was based upon a systematic review of 53 studies that evaluated 66 intensive diet and exercise education programs from 1991 to 2015. The studies were conducted over 3 months to 6 years with an average length of 12 months. Only five were less than 6 months. They included randomized controlled trials, prospective nonrandomized comparison trials, and prospective single-group studies. Some were compared with usual care and some with less intensive counseling.

The systematic review supported a decrease in the risk of developing type 2 diabetes and improved hyperglycemia, blood pressure, and lipid panels. The data were not sufficient to directly comment on long-term outcomes like cardiovascular disease, diabetic compilations, or death.

It was clear that more intense programs that included more sessions, more personnel, and more individual sessions had better weight loss and diabetes prevention outcomes.

Economics

A review of 28 studies showed that these programs are cost effective. Twelve programs provided program costs, including identifying patients at risk and program costs. The average cost per participant was $653, with a range of $383-$1,160. Group-based programs were more cost effective.

Next steps

There is a large amount of evidence to support the recommendation of diet and exercise programs in the prevention of type 2 diabetes. The cost of such programs is small in comparison with the costs incurred from the long-term health effects of type 2 diabetes, but we do not yet know which components of these programs are most important. The data support that higher-intensity programs are more successful, but, at the same time, more expensive. In an era in which virtual tools are prevalent, data are currently insufficient to support their use. Identifying a structure for maintenance visits, causes of program attrition, and long-term follow-up of existing programs also may help to craft the ideal program for diabetes prevention.

The Bottom Line

Combined programs of diet and exercise promotion are very successful and cost effective in preventing patients with prediabetes from progressing to type 2 diabetes. Higher-intensity programs with more sessions, more personnel, and individual counseling are more effective but also are more expensive. All patients with an increased risk for type 2 diabetes should participate in a combined diet and exercise program.

Dr. Skolnik is associate director of the family medicine residency program at Abington (Pa.) Memorial Hospital and professor of family and community medicine at Temple University in Philadelphia. Dr. Fidler is a resident in family medicine at Abington Memorial Hospital.

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