Importance: Unhealthful dietary patterns, low levels of physical activity, and high sedentary time increase the risk of cardiovascular disease.

Objective: To systematically review the evidence on the benefits and harms of behavioral counseling for the primary prevention of cardiovascular disease in adults without known cardiovascular risk factors to inform the US Preventive Services Task Force.

Data Sources: MEDLINE, PubMed, Cochrane Central Register of Controlled Trials, and PsycINFO for studies published in the English language between January 1, 2013, and May 25, 2016, and ongoing surveillance in targeted publications through March 24, 2017. Studies included in the previous review were reevaluated for inclusion.

Study Selection: Randomized clinical trials of behavioral interventions targeting improved diet, increased physical activity, decreased sedentary time, or a combination of these among adults without known hypertension, dyslipidemia, diabetes, or impaired fasting glucose.

Data Extraction and Synthesis: Independent critical appraisal and data abstraction by 2 reviewers.

Main Outcomes and Measures: Cardiometabolic health and intermediate outcomes, behavioral outcomes, and harms related to interventions.

Results: Eighty-eight studies (N = 121,190) in 145 publications were included. There was no consistent benefit of the interventions on all-cause or cardiovascular mortality or morbidity (4 trials [n = 51,356]) or health-related quality of life (10 trials [n = 52,423]). There was evidence of small, statistically significant between-group mean differences for systolic blood pressure (−1.26 mm Hg [95% CI, −1.77 to −0.75]; 22 trials [n = 57,953]), diastolic blood pressure (−0.49 mm Hg [95% CI, −0.82 to −0.16]; 23 trials [n = 58,022]), low-density lipoprotein cholesterol level (−2.58 mg/dL [95% CI, −4.30 to −0.85]; 13 trials [n = 5554]), total cholesterol level (−2.85 mg/dL [95% CI, −4.95 to −0.75]; 19 trials [n = 9325]), and body mass index (−0.41 [95% CI, −0.62 to −0.19]; 20 trials [n = 55,059]) at 6 to 12 months as well as small-to-modest associations with dietary and physical activity behaviors. There was no evidence of greater incidence of serious adverse events, injuries, or falls in intervention vs control participants.

Conclusions and Relevance: Diet and physical activity behavioral interventions for adults not at high risk for cardiovascular disease result in consistent modest benefits across a variety of important intermediate health outcomes across 6 to 12 months, including blood pressure, low-density lipoprotein and total cholesterol levels, and adiposity, with evidence of a dose-response effect, with higher-intensity interventions conferring greater improvements. There is very limited evidence on longer-term intermediate and health outcomes or on harmful effects of these interventions.

Despite evidence that healthful dietary patterns, physical activity, and limited sedentary time are associated with reduced cardiovascular morbidity and mortality,^1-4 most US adults are not meeting national recommendations for these behaviors.⁵ Counseling within primary care and interventions referred through primary care may be one strategy to improve these behaviors and subsequently prevent poor cardiovascular outcomes.

The US Preventive Services Task Force (USPSTF) has several recommendations related to cardiovascular disease (CVD) prevention, including guidance on healthy lifestyle counseling^6,7; screening and treatment for obesity,⁸ hypertension,⁹ and abnormal blood glucose levels¹⁰; aspirin¹¹ and statin¹² use; and tobacco cessation interventions.¹² The purpose of this review was to update the USPSTF review on the benefits and harms of behavioral counseling interventions for healthful diet, physical activity, and/or sedentary behavior for the primary prevention of cardiovascular disease among adults without known CVD or those with known hypertension, dyslipidemia, diabetes, or impaired fasting glucose. This review will help the USPSTF update its 2012 C grade recommendation that clinicians may choose to selectively counsel adults about healthful diet and physical activity.⁷

Scope of Review

This review addressed 4 key questions (KQs) as shown in Figure 1. Methodological details (including study selection, a list of excluded studies, and description of data analyses), as well as more detailed results (including detailed descriptions of all of the interventions and data on effect modification and subpopulation results), are publicly available in the full evidence report.

Data Sources and Searches

This review was designed as an extension of 2 prior systematic reviews conducted by the Kaiser Permanente Research Affiliates Evidence-based Practice Center for the USPSTF that focused on healthful diet and physical activity counseling for cardiovascular disease prevention among individuals with¹⁴ and without¹⁵ known CVD risk factors (ie, hypertension, dyslipidemia, diabetes, or impaired fasting glucose). As such, relevant studies from those reviews were reevaluated for potential inclusion. Then, the following databases were searched for new relevant English-language literature published between January 1, 2013, and May 25, 2016: MEDLINE, PubMed (publisher-supplied records only), PsycINFO, and the Cochrane Central Register of Controlled Trials (eMethods in the Supplement). Collectively, the literature searches encompassed literature published from 1966 through May 25, 2016. The database searches were supplemented by reviewing bibliographies from other relevant literature and from expert suggestions. ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials. Since May 2016, ongoing surveillance was conducted using searches of a subset of core clinical journals identified by the USPSTF to identify major studies published in the interim that may affect the conclusions or understanding of the evidence and therefore the related USPSTF recommendation. The last surveillance was conducted on March 24, 2017, and identified no new studies.

Study Selection

Two reviewers independently reviewed all identified titles and abstracts and relevant full-text articles against prespecified inclusion and exclusion criteria (eTable 1 in the Supplement). Discrepancies were resolved through discussion and consensus. Eligible studies were fair- and good-quality randomized clinical trials that evaluated the effectiveness of primary care–relevant interventions focused on improving dietary habits, increasing physical activity, and/or reducing sedentary time with the primary aim of CVD primary prevention among adults 18 years or older. Studies were excluded from this review if they (1) targeted persons with known CVD, hypertension, dyslipidemia, diabetes, impaired fasting glucose or glucose tolerance, or a combination of these factors; (2) targeted persons categorized as high risk based on a cardiovascular risk–assessment tool; or (3) generically stated that participants must have 1 or more CVD risk factors to be included. In contrast, studies in adults who may be at elevated risk for CVD based on factors such as age, race/ethnicity, family history of CVD, overweight or obesity, high-normal blood pressure, or history of gestational diabetes, as well as those conducted among unselected samples or samples selected because of suboptimal behavior (eg, did not meet national physical activity guidelines) were included. Eligible interventions were those conducted in primary care or referred from primary care, or those deemed feasible for primary care or referral given the nature of the intervention delivery (eg, face-to-face counseling, telephone support), behavior change techniques (eg, goal setting, self-monitoring), or setting (eg, home, community). Studies had to report a behavioral outcome (ie, diet-, physical activity–, sedentary time–related measure), intermediate outcome (eg, blood pressure, lipid levels, weight, incidence of hypertension), or health outcome (ie, morbidity, mortality, health-related quality of life) or report adverse events related to the intervention.

Data Extraction and Quality Assessment

Two reviewers independently assessed the methodological quality of all eligible studies, using criteria outlined by the USPSTF (eTable 2 in the Supplement).¹³ Each study was assigned a final quality rating of good, fair, or poor; disagreements between the investigators were resolved through consensus after discussion and consultation with additional investigators. Studies were rated as poor quality and excluded if they had several important major risks of bias, including very high attrition at 6 to 12 months (eg, greater than 40%), differential attrition between intervention groups (eg, greater than 20%), lack of baseline comparability between groups without adjustment for those variables, or other issues in the conduct, analysis, or reporting of results of the trial that were judged to considerably bias the results (eg, possible selective reporting, inappropriate exclusion of participants from analyses, and questionable validity of randomization and allocation concealment procedures). One reviewer completed primary data abstraction, and a second reviewer checked all data for accuracy and completeness.

Data Synthesis and Analysis

Summary tables were created for study characteristics, population characteristics, intervention characteristics, and outcomes. The data on health outcomes (KQ1) and adverse events (KQ4) did not allow for pooled analyses and so were summarized descriptively. For intermediate health outcomes (KQ2) and behavioral outcomes (KQ3), random-effects meta-analyses using the method of DerSimonian and Laird were run to calculate the pooled differences in mean changes (for continuous data) and pooled odds ratio (for binary data).¹⁶ The between-group difference for each outcome as reported by each respective study was pooled favoring adjusted over unadjusted reported effect estimates. If a between-group effect estimate and variance were not provided, a crude effect estimate was calculated. Within each study, 1-year outcome data were chosen for meta-analyses if available; otherwise, the point closest to 1 year was chosen. If a trial had more than 1 active intervention group, data for the most intensive group or the group that was the most similar with other interventions included in the analysis were plotted. Methods consistent with the previous review¹⁵ were used to estimate and categorize the intensity (total contact in minutes) of each intervention group as low (30 minutes), medium (31-360 minutes), or high (>360 minutes). Results at all other points and for all intervention groups within each trial were reported in tabular format.

Statistical heterogeneity among the pooled studies was examined using standard χ² tests, and the proportion of total variability in point estimates was approximated using the I² statistic.¹⁷

Visual displays were first used to investigate whether the heterogeneity among the results was associated with any prespecified population or intervention characteristics; meta-regression was then used when indicated. To evaluate small-study effects, funnel plots and the Egger test¹⁸ (for continuous outcomes) or Peters test¹⁹ (for dichotomous outcomes) were used. Stata version 13.1 (Stata Corp) was used for all quantitative analyses. All significance testing was 2-sided, and results were considered statistically significant at P < 0.05

The strength of the overall body of evidence for each KQ was graded as high, moderate, low, or insufficient based on established methods²⁰ and addressed the consistency, precision, reporting bias, study quality, and dose response related to each outcome.

A total of 10,045 titles and abstracts and 351 articles were reviewed to determine if they met the prespecified inclusion criteria, and 88 trials (87 randomized clinical trials [n = 121,106] and 1 nonrandomized clinical trial [n = 84]) reported in 145 publications were included (Figure 2).^21-165 Fifty trials were carried forward from the previous review^{22,26,31,33,34,38,42,47,49,50,52,56,57,61,63,64,66,69,72,76,79,82,85,86,88,90,95-98,102,104,109,112,114,118,119,121,126-128,130,132,136,143,146,147,149,151,159} and were synthesized with 38 newly identified trials.^{21,24,27,32,35,39,41,43,44,53,54,58,60,67,71,73,78,83,89,91,94,103,106,108,111,123,131,139,140,145,150,152-154,156,160-162} The included trials were highly variable in terms of their study populations, interventions, and specific outcome measures (Table 1). The majority of the trials took place in the United States and were conducted within or recruited from a primary care setting. There was great diversity in the interventions tested: 23 trials focused on healthful diet and physical activity, another 24 on healthful diet only, and 44 on physical activity only. Intervention intensity (total minutes of contact) ranged from 3 minutes to 2340 minutes (39 hours), with a mean of 6 hours and 11 minutes. Low-intensity interventions were mostly mailed, print-based interventions, whereas medium- and high-intensity interventions involved one-on-one individual and telephone counseling and group sessions.

Effects of Interventions on Health Outcomes

Key Question 1. Do primary care behavioral counseling interventions to improve diet, increase physical activity, and/or reduce sedentary behavior improve health outcomes in adults?

Twelve of the 88 included trials reported health outcomes.^{52,63,69,76,82,96,97,121,146,147,151,154} Only 2 of these trials^62,154 were identified as part of the update, and both reported quality-of-life outcomes. Four trials (n = 51,356) reported all-cause or CVD-related mortality,^{82,146,147,151} of which 3 also reported cardiovascular events.^146,147,151 All 4 of these trials focused on high-intensity diet interventions. Overall, few deaths were reported, and no differences were observed between treatment and control groups over 3 to 15 years of follow-up. The 3 trials that reported cardiovascular events or composite CVD outcomes showed some beneficial results, although results were mixed. The Women's Health Initiative dietary modification trial (n = 48,835) showed no difference in major coronary heart disease events (ie, nonfatal myocardial infarction [MI] or coronary heart disease death) (adjusted hazard ratio [HR], 0.93 [95% CI, 0.83 to 1.05]) or fatal and nonfatal stroke (adjusted HR, 1.02 [95% CI, 0.90 to 1.17]) among women without a history of CVD between those randomized to low-fat diet counseling and those in a usual-care diet group over 8.1 years of follow-up.⁸¹ Similarly, a broader composite CVD outcome comprising nonfatal MI, coronary heart disease death, and coronary artery bypass graft surgery/percutaneous coronary intervention showed no significant difference between treatment groups (adjusted HR, 0.94 [95% CI, 0.86 to 1.02]).⁸¹ In contrast, long-term observational follow-up from the Trial of Hypertension Prevention (TOHP) phase I and II (n = 2415) showed a significant difference in CVD (defined as MI, stroke, revascularization, or CVD death) between treatment groups over 10 to 15 years of follow-up (HR, 0.70 [95% CI, 0.53 to 0.94]).⁴⁸ When revascularization was excluded from the definition, however, significance was lost (adjusted HR, 0.72 [95% CI, 0.50 to 1.03]). Ten trials reported quality-of-life outcomes and reported modest improvements at 6 and 12 months among intervention participants but no consistent benefit of the intervention compared with control conditions.^{30,52,62,69,76,96,97,121,146,155}

Effects of Interventions on Intermediate Health Outcomes

Key Question 2. Do primary care behavioral counseling interventions to improve diet, increase physical activity, and/or reduce sedentary behavior improve intermediate outcomes associated with cardiovascular disease (CVD) in adults?

Thirty-four of the included trials (n = 75,793) reported the effects of behavioral interventions on at least 1 intermediate outcome (ie, blood pressure, lipid levels, glucose levels, or adiposity measures); nearly half of the trials were of good quality.^{21,26,31,32,38,39,47,52,63,67,71,76,78,79,82,85,86,88,89,91,96,98,102,118,130,132,136,146,147,149-151,153,161} When trials were pooled, healthful diet, physical activity interventions, or both were associated with small but statistically significant improvements in systolic blood pressure (22 trials), diastolic blood pressure (23 trials), low-density lipoprotein cholesterol (LDL-C) level (13 trials), total cholesterol level (19 trials), and adiposity measures (20 trials), compared with controls at 6 months or more (Table 1). Pooled between-group mean differences were −1.26 mm Hg (95% CI, −1.77 to −0.75) for systolic blood pressure, −0.49 mm Hg (95% CI, −0.82 to −0.16) for diastolic blood pressure, −2.58 mg/dL (95% CI, −4.30 to −0.85) for LDL-C level, and −2.85 mg/dL (95% CI, −4.95 to −0.75) for total cholesterol level—all in favor of intervention vs control groups with follow-up times of 6 months or more. For adiposity outcomes, interventions were associated with improvements in body mass index (mean difference, −0.41 [95% CI, −0.62 to −0.19]; calculated as weight in kilograms divided by height in meters squared), weight (mean difference, −1.04 kg [95% CI, −1.56 to −0.51]), and waist circumference (mean difference, −1.19 cm [95% CI, −1.79 to −0.59]), with considerable statistical heterogeneity (I² > 90%) in all analyses. There was no evidence of an association between healthful diet, physical activity counseling, or both and levels of high-density lipoprotein cholesterol, triglycerides, or fasting glucose in pooled analyses (Table 2). Among the intermediate outcomes showing a positive association, dose-response effects were evident, with increasing intervention intensity associated with larger improvements in intermediate outcomes (Table 2). High-intensity interventions were consistently associated with statistically significant benefit on intermediate outcomes, and the effect sizes were slightly higher in analyses limited to the subset of high-intensity interventions (6-12 trials per outcome), compared with the results of combining trials of all intensities. The associations between medium-intensity interventions (5-9 trials per outcome) and intermediate outcomes were less consistent and generally showed no benefit, with the exception of the outcome of weight. There was insufficient evidence (only 1-4 trials per outcome) to assess the association between low-intensity interventions and intermediate outcomes.

Meta-analyses stratified by diet-only messages, physical activity–only messages, or combined diet and physical activity messages were consistent with those seen in analyses stratified by intensity (results available in the full evidence report). Healthful diet interventions (with or without physical activity messages) (7-16 trials per outcome), which were mostly high-intensity interventions, consistently showed statistically significant favorable associations with intermediate outcomes. No such benefit was seen when limiting the analyses to physical activity–only trials, which were largely of low intensity, although there were far fewer trials included in these analyses (4-8 trials per outcome). There was no evidence of effect modification based on whether the intervention was linked to primary care (independent of intervention intensity), the number of intervention sessions, the duration of the intervention, whether the intervention included group sessions, the focus of the intervention message (eg, specific dietary message), the population risk for CVD, or study quality. Very few trials reported longer-term effects (ie, greater than 12 months of follow-up) on intermediate outcomes, and there was no consistent pattern in the effects over time among those that did. In addition, there was no evidence of small-study effects for any of the intermediate outcomes.

Effects of Interventions on Behavioral Outcomes

Key Question 3. Do primary care behavioral counseling interventions to improve diet, increase physical activity, and/or reduce sedentary behavior improve associated health behaviors in adults?

All but 2^32,153 of the 88 included studies (n = 117,589) reported the effects of a behavioral intervention on dietary, physical activity, and/or sedentary behavior outcomes. More than one-third of the studies that reported behavioral outcomes (36/86 studies) were newly identified as part of this update. Almost all of the behavioral outcomes were based on self-report; 3 trials measured urinary sodium excretion, and 11 trials used accelerometers or pedometers to capture objective measures of physical activity. The instruments, modes of administration, and summary measures were highly variable across trials that measured behavioral outcomes through self-report.

Overall, there was evidence that behavioral interventions generally improved participants' dietary intake and physical activity levels. Mean between-group differences for dietary outcomes showed consistent benefit for healthful diet interventions (with or without physical activity messages) vs control groups at 6 months' or greater follow-up, but the precision in the magnitude of effects was highly variable across trials; thus, pooled results are not presented. Between-group differences for dietary outcomes were in the magnitude of 65 kcal/d (favoring the control group) to −500 kcal/d (favoring the intervention group) in total energy intake (11 trials), 0.8 to −11 percentage points in the percentage of calories from fat (15 trials), and −0.3 to −4.1 percentage points in the percentage of calories from saturated fat (9 trials). Effects on fruit and vegetable intake ranged from between-group differences of −0.2 serving/d (favoring the control group) to 2.2 servings/d (favoring the intervention group) (16 trials); between-group differences in grams of fiber per day ranged from 1 g to 2.5 g in favor of the intervention group (6 trials). Reductions in sodium (urinary sodium excretion or self-reported dietary intake) ranged from −380 mg/d to −1380 mg/d (6 trials). Only 9 trials reported the effects of the interventions on dietary outcomes at greater than 12 months of follow-up (ie, 1.5 to 6 years of follow-up), with a lack of effect or slightly attenuated effect being seen over time.

Physical activity interventions (with or without dietary messages) were associated with a 35-minute (95% CI, 22.0 to 47.0) increase in physical activity per week compared with controls in pooled analyses at 6 to 12 months of follow-up (27 trials). The standardized effect size when pooling 46 trials that reported any continuous measure of physical activity (eg, minutes per day, minutes per week, metabolic-equivalent minutes per week, score) was a mean difference of 0.20 (95% CI, 0.14 to 0.26) in favor of the intervention group. Additionally, meta-analysis indicated that intervention group participants had an odds ratio of 1.32 (95% CI, 1.12 to 1.56) for meeting physical activity recommendations, compared with those in the control group (16 trials). Data on physical activity outcomes beyond 12 months were sparsely reported. Studies that limited their inclusion to participants with suboptimal levels of physical activity at baseline (eg, below the recommended level of 150 minutes per week) resulted in greater increases in physical activity compared with those that did not limit inclusion based on baseline physical activity levels. In contrast to findings for intermediate outcomes, there was no evidence of effect modification based on intervention intensity. Likewise, there was no evidence of a difference in effects for interventions focused only on physical activity messages vs those focused on both physical activity and healthful diet messages.

Only 4 trials reported measures of sedentary behavior independent of physical activity behavior. Of these 4 trials, 2 found statistically significant group × time effects on self-reported minutes of sitting, including 1 trial that specifically targeted reductions in daily television viewing and total sitting time.

Harms of Interventions

Key Question 4. What adverse events are associated with primary care behavioral counseling interventions to improve diet, increase physical activity, and/or reduce sedentary behavior in adults?

Harms of included interventions were sparsely reported and were inconsistently defined. Fourteen of the included trials (n = 8220) specifically mentioned the occurrence of harms or lack of harms.^{22,32,35,41,44,52,73,78,95,97,102,121,132,150} Across these studies, there were no serious adverse events related to the interventions reported, although none were hypothesized. Seven physical activity–focused trials (n = 3565) reported the incidence of injuries, fractures, or falls; only 1 trial among women aged 40 to 74 years reported significantly more injuries (19% vs 14%, P = 0.03) and falls (37% vs 29%, P < 0.001) among participants in the intervention group than in the control group, respectively, over 24 months of follow-up.¹⁰²

This systematic review was conducted to assist the USPSTF in updating its 2012 recommendation on healthful diet and physical activity counseling for the primary prevention of CVD in persons without CVD risk factors (ie, hypertension, dyslipidemia, diabetes, or impaired fasting glucose). Eighty-eight unique trials, nearly one-half of which (38 trials) were published since the previous USPSTF review, were included. The pooled estimates found in this updated systematic review were generally consistent in magnitude with the 2010 review on this topic¹⁵ and slightly lower in magnitude compared with the associations seen in the 2014 review among persons at high risk for CVD¹⁴ (eTable 3 in the Supplement).

Table 3 summarizes the findings for this evidence review. Healthful diet and physical activity behavioral interventions in persons without traditional CVD risk factors were associated with modest reductions in blood pressure, levels of total cholesterol and LDL-C, and adiposity measures at approximately 6 to 12 months of follow-up, compared with control conditions. The interventions varied considerably across the studies, such as in their behavioral focus (diet only, physical activity only, or diet plus physical activity messages), their delivery mode (group and individual in-person counseling, telephone counseling, print-based, or technology-based), and their intensity (number of sessions, length of sessions, and duration of the intervention). There was evidence of a dose-response relationship, with increasing intervention intensity being associated with larger improvements in intermediate outcomes, but there was insufficient evidence to assess the effects of low-intensity interventions alone on intermediate outcomes. There was considerably more evidence for behavioral outcomes, with 86 trials reporting the effects of counseling interventions on dietary intake, physical activity, and/or sedentary behaviors. The direction of effects for all behavioral outcomes were reasonably consistent and suggested generally a small benefit for dietary outcomes and a moderate benefit for physical activity. However, there was substantial variation in outcome measures and insufficient evidence on the effects of interventions on sedentary behaviors.

The evidence for the effects of interventions on longer-term health outcomes, including all-cause and CVD-specific mortality, CVD events, and health-related quality of life, as well as intermediate cardiometabolic outcomes past 1 year, was sparse and inconsistent, precluding a robust conclusion. Likewise, a limited number of trials reported on harms of the interventions, and none of these studies found any serious adverse events related to the interventions.

In the context of sparse randomized clinical trial evidence for the effect of healthful diet and physical activity interventions on health outcomes, observational evidence from very large, individual participant–data meta-analyses of prospective cohort studies can be used to estimate and bound the potential benefit of proportional differences in intermediate outcomes on the risk of morbidity and mortality. Such evidence suggests that small differences in blood pressure, blood cholesterol levels, and body mass index can translate into small differences in important health outcomes (see full evidence report).^166-168

This review represents only a subset of the literature on dietary and physical activity counseling. Trials focused on dietary or physical activity counseling in persons with known cardiovascular risk factors or to prevent or manage other health risks and conditions (eg, falls, cognitive impairment, cancer), as well as those focused on weight loss or weight management, were excluded. Many of these topics are the focus of other USPSTF reviews and recommendations.^169-173

Limitations

With complex interventions such as these, describing and synthesizing intervention characteristics is difficult. The included interventions varied considerably in terms of the nature of the advice, mode of delivery, and delivery schedule. Details of each intervention were abstracted, and an established taxonomy for describing the behavior change techniques used in the interventions¹⁷⁴ was used. Consistent rules were used to estimate the total minutes of contact and to categorize each intervention group by intensity. Despite these attempts, there is a need for better reporting of intervention characteristics to facilitate evaluation and dissemination of evidence-based practices. As outlined by Krist et al,¹⁷⁵ research on behavioral counseling interventions such as the type synthesized here would benefit from an application of checklists and frameworks, such as the Template for Intervention Description and Replication (TIDierR); Research, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM); and the Pragmatic-Explanatory Continuum Indicator Summary (PRECIS), to assess the feasibility and applicability of interventions as well as to improve replication and dissemination.

This review found no evidence of a difference in effects by the focus of the message, but analyses were highly confounded by the intensity of interventions. Also, only 1 of the included studies targeted reductions in sedentary behavior (ie, sitting time) as the main focus of the trial, and only 3 trials reported the outcomes of sedentary behavior. More research on the effects of counseling to reduce sedentary behavior in adults on behavioral and intermediate health outcomes is warranted. Very few studies explored whether effectiveness of the intervention varied among important subpopulations (older adults, racial and ethnic minority groups, and those with lower socioeconomic status). Such a priori analyses could assist in identifying groups of adults who might benefit more from such interventions.

Additionally, most of the trials relied on self-reported dietary and physical activity measures, with variable levels of evidence of the reliability and validity of the measures. Dietary intake was most often measured by food frequency questionnaires (such as the full-length or shorter versions of the Block food frequency questionnaire),^176,177 entries in food diaries, or 24-hour food recalls. The tools and summary variables used to measure physical activity were even more inconsistent. Physical activity was summarized in terms of total physical activity, leisure-specific physical activity, moderate- and/or vigorous-intensity physical activity, walking behaviors, and multiple other indicators; in addition, the results were expressed in different units across studies (eg, minutes per week, metabolic equivalent task–minutes per week, steps per day, summary "scores"). Each of these methods can be prone to bias.¹⁷⁸ While researchers must fit the specific measurement instruments and summary variables to the needs of their particular study aims, research protocols, and sample characteristics, the field of research could benefit from more standardization of behavioral outcome measurement.¹⁷⁹

Studies that were heterogeneous with respect to clinical and demographic characteristics, interventions, and settings were intentionally pooled. For most outcomes, the statistical heterogeneity of pooled analyses was unimportant (I² < 40%) or moderate (I² = 30%-60%) and therefore still reasonable to allow for interpreting of pooled estimates. However, given the clinical heterogeneity, interpreting the 95% confidence intervals instead of the summary estimate helps inform the true magnitude of effects on the individual outcomes.

Conclusions

Diet and physical activity behavioral interventions for adults not at high risk for cardiovascular disease result in consistent modest benefits across a variety of important intermediate health outcomes across 6 to 12 months, including blood pressure, low-density lipoprotein and total cholesterol levels, and adiposity, with evidence of a dose response effect, with higher-intensity interventions conferring greater improvements.There is very limited evidence on longer-term intermediate and health outcomes or on harmful effects of these interventions.

Accepted for Publication: March 10, 2017.

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Funding/Support: This research was funded under contract number HHSA-290-2012-00015-I, Task Order 6, from the Agency for Healthcare Research and Quality (AHRQ), US Department of Health and Human Services, under a contract to support the USPSTF.

Role of the Funder/Sponsor: Investigators worked with USPSTF members and AHRQ staff to develop the scope, analytic framework, and key questions for this review. AHRQ had no role in study selection, quality assessment, or synthesis. AHRQ staff provided project oversight, reviewed the report to ensure that the analysis met methodological standards, and distributed the draft for peer review. Otherwise, AHRQ had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript findings. The opinions expressed in this document are those of the authors and do not reflect the official position of AHRQ or the US Department of Health and Human Services.

Additional Contributions: We gratefully acknowledge the following individuals for their contributions to this project: the AHRQ staff; the US Preventive Services Task Force; EPC staff members Keshia Bigler, MPH, Erin Coppola, BS, Smyth Lai, MLS, Elizabeth O’Connor, PhD, Ning Smith, PhD, and Elizabeth Hess, MA, ELS(D). USPSTF members, peer reviewers, and federal partner reviewers did not receive financial compensation for their contributions.

Additional Information: A draft version of this evidence report underwent external peer review from 7 content experts: David Brown, PhD (Centers for Disease Control and Prevention), Janet de Jesus, MS (National Heart, Lung, and Blood Institute), Paul James, MD (University of Iowa), Sarah Lewington, DPhil (University of Oxford), Alice Lichtenstein, DSc (Tufts University), JoAnn Manson, MD (Harvard University and Brigham and Women's Hospital), and Deborah Young, PhD (Kaiser Permanente) and 4 federal partners: the Centers for Disease Control and Prevention (CDC), the National Institutes of Health (NIH), the Indian Health Service (IHS), and the Department of Veterans Affairs (VA). Comments were presented to the USPSTF during its deliberation of the evidence and were considered in preparing the final evidence review.

Evidence reviews for the US Preventive Services Task Force (USPSTF) use an analytic framework to visually display the key questions that the review will address to allow the USPSTF to evaluate the effectiveness and safety of a preventive service. The questions are depicted by linkages that relate interventions and outcomes. A dashed line indicates a relationship between an intermediate outcome and a health outcome that is presumed to describe the natural progression of the disease. Further details are available in the USPSTF procedure manual.¹³

^a High risk of cardiovascular disease includes adults with hypertension, dyslipidemia, diabetes, impaired fasting glucose or glucose tolerance, or a combination of these factors.

Reasons for exclusion: Aim: Study aim was not relevant. Setting: Study was not conducted in a country relevant to US practice or not conducted in, recruited from, or feasible for primary care or a health system. Population: Study was not conducted in an included population. Outcomes: Study did not have relevant outcomes or had incomplete outcomes. Intervention: Intervention was out of scope. Design: Study did not use an included design. Publication Date: primary results published prior to 1990. Language: Publication not in English. Quality: Study was poor quality. USPSTF indicates US Preventive Services Task Force.

Abbreviations: BMI=body mass index; BP=blood pressure; CVD=cardiovascular disease; DASH=Dietary Approaches to Stop Hypertension; DBP=diastolic blood pressure; HD=healthy diet; HPT=Hypertension Prevention Trial; NR=not reported; PA=physical activity; PCC=primary care clinician; TOHP=Trials of Hypertension Prevention; USPSTF=US Preventive Services Task Force.
^a Quality assessed using criteria specific for randomized clinical trials outlined in the USPSTF procedure manual.^13
b Low intervention intensity indicates 30 minutes or less of total contact time; medium intensity, 31 to 360 minutes; high intensity, 360 minutes or more.
^c Conducted in or recruited from primary care setting.
^d Intervention focused on reducing sedentary time.
^e Study inclusion criteria required BMI of 25 to 34.9 (calculated as weight in kilograms divided by height in meters squared); at baseline, 36.4% with hypertension and 6.5% with diabetes.
^f Included 38.9% with hypertension and 24.5% taking medication for hypertension at baseline.
^g Included 52.4% with hypertension, 10.5% with diabetes, and 19.0% with previous CVD at baseline.
^h Included 24.4% with hypertension and 8.2% with diabetes at baseline.
ⁱ Study inclusion criteria required serum cholesterol level 5.2 to 7.8 mmol/L (200.8-301.2 mg/dL), fasting blood glucose level 6.7 mmol/L (120.7 mg/dL) or less, fasting triglycerides level 5.6 mmol/L (495.6 mg/dL) or less, and DBP 100 mm Hg or less.
^j Seven European countries (Germany, Greece, Ireland, the Netherlands, Poland, Spain, and the United Kingdom).
^k Included 39.6% with hypertension and 7.3% with diabetes at baseline.
^l Nonrandomized clinical controlled trial.
^m Included 37.7% with hypertension at baseline.

Abbreviations: BMI=body mass index; HDL-C=high-density lipoprotein cholesterol; LDL-C=low-density lipoprotein cholesterol; NA=not applicable.
SI conversion factors: To convert LDL-C, total cholesterol, and HDL-C values to mmol, multiply by 0.0259; triglyceride values to mmol/L, multiply by 0.0113; glucose values to mmol/L, multiply by 0.0555.
^a Minutes indicate total contact time for intervention.
^b Calculated as weight in kilograms divided by height in meters squared.

Abbreviations: BMI=body mass index; BP=blood pressure; CV=cardiovascular; CVD=cardiovascular disease; DBP=diastolic blood pressure; EPC=evidence-based practice center; FBG=fasting blood glucose; HDL-C=high-density lipoprotein cholesterol; HR=hazard ratio; KQ=key question; LDL-C=low-density lipoprotein cholesterol; OR=odds ratio; PA=physical activity; QOL=quality of life; RCT=randomized clinical trial; SBP=systolic blood pressure; SMD=standardized mean difference.
SI conversion factors: To convert LDL-C and total cholesterol values to mmol/L, multiply by 0.0259.
^a Inconsistent in direction and magnitude of effects for QOL outcomes.
^b Possible selective reporting or selective analysis bias.
^c Reasonably consistent and reasonably precise for SBP; reasonably consistent and imprecise for DBP and LDL-C; inconsistent and imprecise for total cholesterol, HDL-C, and triglycerides; and inconsistent and reasonably precise for adiposity outcomes.
^d All but 1 study was a randomized clinical trial; the 1 remaining study was a nonrandomized clinical trial.
^e Despite the relatively limited number of studies that reported harms related to interventions, there is moderate confidence that there are no serious harms related to behavioral counseling interventions for healthful diet and physical activity.