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Diabetes: Combined Diet and Physical Activity Promotion Programs to Prevent Type 2 Diabetes Among People at Increased Risk

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What the Task Force Found

About The Systematic Review

The CPSTF finding is based on evidence from a systematic review of 53 studies that described 66 programs (search period January 1991 - February 2015). The review was conducted on behalf of the CPSTF by a team of specialists in systematic review methods, and in research, practice and policy related to diabetes prevention and control.

Context

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Summary of Results

  • Among populations at increased risk of type 2 diabetes, combined diet and physical activity promotion programs led to improvements in health outcomes and risk factors for type 2 diabetes and cardiovascular disease compared with usual care.
    • The proportion of people who developed type 2 diabetes decreased by a median of 11 percentage points (interquartile interval [IQI]: 5 to 16; 16 studies).
    • The proportion of people who achieved normal blood sugar (normoglycemia) increased by a median of 12 percentage points (IQI: 6 to 14; 6 studies).
    • Body weight was reduced by an average of 2.2% (95% confidence interval [CI]: 1.4 to 2.9; 24 studies).
    • Fasting blood glucose was reduced (improved) by an average of 2.2 mg/dL (95% CI 0.9 to 3.6; 17 studies) and hemoglobin A1c (a measure of long-term glucose levels) was reduced (improved) by an average of 0.08 percentage points (95% CI 0.04 to 0.12; 8 studies).
    • Blood pressure (17 studies) and cholesterol levels (13 studies) also were improved.
  • The effect on mortality was unclear. Mortality was reduced by 2 to 10 percentage points (2 studies) or by 0.6 per 1000 person-years (1 study) over 3 to 23 years of follow-up. However, this benefit was statistically significant in only one study, and in that study only among women.
  • Regardless of program features, almost all programs led to weight loss, reduced risk of diabetes, or both. However, among 12 studies with direct comparisons, more intensive programs (based on features such as number of sessions, individual sessions, and additional personnel) resulted in greater weight loss and lower rates of diabetes than less intensive programs. Across studies, more effective programs provided:
    • Individual (vs. group) exercise sessions,
    • Individual (vs. group) diet sessions, or
    • Diet counselors
  • In studies of programs that used protocols outlined by the U.S. Diabetes Prevention Program (DPP) study or Finnish Diabetes Prevention Study (DPS), or modifications of them, participants lost more weight (3% of initial body weight) than participants in programs not based on DPP or DPS (1.6% of initial body weight; P=0.051), but reductions in risk of developing diabetes were similar between studies of different programs.

Summary of Economic Evidence

An economic review of 28 studies (search period January 1985 - April 2015) shows that combined diet and physical activity promotion programs for people at increased risk for type 2 diabetes are cost-effective. All monetary values reported are in 2013 U.S. dollars.

Cost of the programs:

  • All programs: median $653 per participant (IQI: $383 to $1,160; 12 studies)
  • Group-based programs: median $417 per participant (IQI: $341 to $600; 8 studies)
  • Programs that translated the U.S. DPP into community or primary care settings: median $424 per participant (IQI: $340 to $793; 8 studies)

Cost-effectiveness of the program (from the health system perspective, which included only the direct medical costs of the programs and healthcare costs averted, based on either data collected in actual programs or estimates from simulation models):

  • Cost per quality-adjusted life year (QALY) saved:
    • All programs: median $13,761 (IQI: $3,067 to $21,899; 16 studies)
    • Group-based programs: median $1,819 (IQI: −$5,027 to $16,443; 5 studies)
    • Individual-based programs: median $15,846 (IQI: $7,980 to $72,723; 5 studies)
  • Cost per disability-adjusted life year (DALY) averted:
    • $21,195 and $50,707 (2 studies)
  • Cost per life year gained (LYG):
    • Median $2,684 (IQI: −$2,444 to $17,410; 6 studies)

The variation in program costs per participant is partly explained by the number of sessions, delivery mode of the core sessions (individual vs. group), setting (clinical trial vs. community or primary care), and type of personnel used (health professionals vs. trained laypeople). The variation in cost-effectiveness is partially explained by variation in cost and effectiveness of the programs, program delivery modes, patient follow-up times, and delivery settings.

Applicability

Based on results for programs in different settings and populations, findings are applicable to the following:

  • Adults at increased risk of type 2 diabetes
    • Older adults were shown to have greater benefits
  • Adolescents (based on two studies)
  • Women and men
  • All racial and ethnic groups
  • All socioeconomic levels
  • Urban and rural environments
  • Healthcare and community-based settings in the United States

Evidence Gaps

Each CPSTF review identifies critical evidence gaps—areas where information is lacking. Evidence gaps can exist whether or not a recommendation is made. In cases when the Task Force finds insufficient evidence to determine whether an intervention strategy works, evidence gaps encourage researchers and program evaluators to conduct more effectiveness studies. When the Task Force recommends an intervention, evidence gaps highlight missing information that would help users determine if the intervention could meet their particular needs. For example, evidence may be needed to determine where the intervention will work, with which populations, how much it will cost to implement, whether it will provide adequate return on investment, or how users should structure or deliver the intervention to ensure effectiveness. Finally, evidence may be missing for outcomes different from those on which the Task Force recommendation is based.

Identified Evidence Gaps

Several areas would benefit from additional research on the effectiveness of combined diet and physical activity promotion programs. Future research should aim to do the following:

  • Assess potential differences in the effectiveness of specific programs in different populations (e.g., by race, SES, educational attainment, age, cognitive or physical disabilities)
  • Study the effectiveness of programs delivered via the Internet, email, apps, or social networking
  • Assess the relative effectiveness of individual and group sessions
  • Identify effective structures for the maintenance phase of these programs to help participants continue their improvements to diet and physical activity following completion of the core phase
  • Conduct long-term follow-up of community-based programs to evaluate the durability of program effects on diabetes incidence, weight loss, other diabetes risk factors, morbidity, and mortality
  • Determine recruitment and attrition rates. Understand reasons referred clients don't follow-up and reasons why participants drop out. Develop methods to recruit and retain clients.

Economic Review

Several areas would benefit from future research on the economics of combined diet and physical activity promotion programs.

  • Additional studies should examine programs implemented in community and primary care settings. Evaluations should include group-based programs delivered by trained laypeople.
  • Costs of identifying and recruiting eligible individuals to participate should be evaluated and incorporated into future economic assessments.
  • More rigorous research is needed to better understand costs associated with program implementation and ways to lower them in community or primary care settings. Costs include start-up costs, costs of program delivery (by program duration and setting), and costs to different stakeholders and society as a whole.
  • To better understand long-term economic benefits of the program, research should assess actual heath care expenditures averted in total, by expenditure category. Ideally this would be done by following an intervention cohort and its comparison group for a longer period of time.

Study Characteristics

  • Programs lasted between 3 months and 6 years, with a median of 12 months (IQI: 10 to 27 months).
    • The core period lasted between 1 month and 5 years, with a median of 6 months (IQI: 5 to 12 months).
    • Maintenance periods (in 28 programs) lasted between 4 and 68 months, with a median of 12 months (IQI: 7 to 18 months).
  • Programs provided between 0 (virtual sessions only) and 72 sessions, with a median of 15 sessions (IQI: 6.5 to 24.5 sessions).
    • During the core period, there were between 0 (virtual only) and 72 sessions, with a median of 10 sessions (IQI: 6 to 16 sessions).
    • During the maintenance period (in 28 programs), there were between 0 (virtual only) and 24 sessions, with a median of 6 sessions (IQI: 1.5 to 12 sessions). In some programs, the maintenance period contacts were by telephone or email only.
  • Programs used individual face-to-face meetings (40 programs included individual diet sessions, 41 programs included individual exercise sessions), group meetings (diet: 41 programs, exercise: 39 programs), or both (diet: 24 programs, exercise: 24 programs). Five programs were conducted via web-tools, social networking, email, text messaging, video (or a combination of these) with no in-person sessions.
  • Sessions were led by different combinations of trained diet counselors including dietitians, nutritionists, or others (37 programs); trained exercise counselors including physical trainers or others (26 programs); nurses (15 programs); physicians or psychologists (8 programs); and trained laypeople (13 programs).
  • Programs included specific weight loss goals (42 programs), diet goals (19 programs), and physical activity goals (32 programs).
  • Programs included individually tailored plans for diet (16 programs) and physical activity (23 programs).
  • Studies were conducted in the United States (21 studies), Europe (17 studies), and other countries.

Publications

Balk EM, Earley A, Raman G, Avendano EA, Pittas AG, Remington PL. Combined diet and physical activity promotion programs to prevent type 2 diabetes among persons at increased risk: a systematic review for the Community Preventive Services Task Force. Annals of Internal Medicine. 2015;163. Available at: http://annals.org/aim/article/2395729/combined-diet-physical-activity-promotion-programs-prevent-type-2-diabetes.
Li R, Qu S, Zhang P, et al. Economic evaluation of combined diet and physical activity promotion programs to prevent type 2 diabetes among persons at increased risk: a systematic review for the Community Preventive Services Task Force. Annals of Internal Medicine. 2015;163. Available at: http://annals.org/aim/article/2395730/economic-evaluation-combined-diet-physical-activity-promotion-programs-prevent-type.
Pronk NP, Remington PL, Community Preventive Services Task Force. Combined diet and physical activity promotion programs for prevention of diabetes: Community Preventive Services Task Force recommendation statement. Annals of Internal Medicine. 2015;163. Available at: http://annals.org/aim/article/2395731/combined-diet-physical-activity-promotion-programs-prevention-diabetes-community-preventive.
Ackermann RT. Diabetes prevention at the tipping point: aligning clinical and public health recommendations. Annals of Internal Medicine. 2015;163. Available at: http://annals.org/aim/article/2396440/diabetes-prevention-tipping-point-aligning-clinical-public-health-recommendations.
Pronk NP. Systematic review with meta analysis: structured diet and physical activity programmes provide strong evidence of effectiveness for type 2 diabetes prevention and improvement of cardiometabolic health. Evidence-Based Medicine. 2015.

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