Each recommendation has been mapped from the NHLBI grading format to the American College of Cardiology/American Heart Association Class of Recommendation/Level of Evidence (ACC/AHA COR/LOE) construct and is expressed in both formats. Because of the inherent differences in grading systems and the clinical questions driving the recommendations, alignment between the NHLBI and ACC/AHA formats is in some cases imperfect. Definitions for the NHLBI strength of recommendation (A-E, N) and quality of evidence (High, Moderate, Low) and the ACC/AHA levels of the evidence (LOE: A-C) and classes of recommendations (COR: I-III) are provided at the end of the "Major Recommendations" field.
Summary of Recommendations for Obesity
Identifying Patients Who Need to Lose Weight (Body Mass Index [BMI] and Waist Circumference)
1a. Measure height and weight and calculate BMI at annual visits or more frequently. NHLBI Grade: E (Expert Opinion); ACC/AHA COR: I; ACC/AHA LOE: C
1b. Use the current cutpoints for overweight (BMI 25.0–29.9 kg/m2) and obesity (BMI ≥30 kg/m2) to identify adults who may be at elevated risk of cardiovascular disease (CVD) and the current cutpoints for obesity (BMI ≥30 kg/m2) to identify adults who may be at elevated risk of mortality from all causes. NHLBI Grade: A (Strong); ACC/AHA COR: I; ACC/AHA LOE: B
1c. Advise overweight and obese adults that the greater the BMI, the greater the risk of CVD, type 2 diabetes, and all-cause mortality. NHLBI Grade: A (Strong) ACC/AHA COR: I; ACC/AHA LOE: B
1d. Measure waist circumference at annual visits or more frequently in overweight and obese adults. Advise adults that the greater the waist circumference, the greater the risk of CVD, type 2 diabetes, and all-cause mortality. The cutpoints currently in common use (from either National Institutes of Health [NIH]/NHLBI or World Health Organization/International Diabetes Federation [WHO/IDF]) may continue to be used to identify patients who may be at increased risk until further evidence becomes available. NHLBI Grade: E (Expert Opinion); ACC/AHA COR: IIa; ACC/AHA LOE: B
Matching Treatment Benefits with Risk Profiles (Reduction in Body Weight Effect on Risk Factors for CVD, Events, Morbidity and Mortality)
2. Counsel overweight and obese adults with cardiovascular risk factors (high blood pressure [BP], hyperlipidemia, and hyperglycemia) that lifestyle changes that produce even modest, sustained weight loss of 3% to 5% produce clinically meaningful health benefits, and greater weight losses produce greater benefits NHLBI Grade: A (Strong) ACC/AHA COR: I; ACC/AHA LOE: A.
a. Sustained weight loss of 3% to 5% is likely to result in clinically meaningful reductions in triglycerides, blood glucose, hemoglobin A1c, and the risk of developing type 2 diabetes.
b. Greater amounts of weight loss will reduce BP, improve low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C), and reduce the need for medications to control BP, blood glucose, and lipids as well as further reduce triglycerides and blood glucose.
Diets for Weight Loss (Dietary Strategies for Weight Loss)
3a. Prescribe a diet to achieve reduced calorie intake for obese or overweight individuals who would benefit from weight loss, as part of a comprehensive lifestyle intervention. Any one of the following methods can be used to reduce food and calorie intake: NHLBI Grade: A (Strong); ACC/AHA COR: I; ACC/AHA LOE: A
a. Prescribe 1,200–1,500 kcal/d for women and 1,500–1,800 kcal/d for men (kilocalorie levels are usually adjusted for the individual's body weight)
b. Prescribe a 500-kcal/d or 750-kcal/d energy deficit or
c. Prescribe one of the evidence-based diets that restricts certain food types (such as high-carbohydrate foods, low-fiber foods, or high-fat foods) in order to create an energy deficit by reduced food intake.
3b. Prescribe a calorie-restricted diet for obese and overweight individuals who would benefit from weight loss, based on the patient's preferences and health status, and preferably refer to a nutrition professional* for counseling. A variety of dietary approaches can produce weight loss in overweight and obese adults, as presented in critical question (CQ) 3, evidence statement (ES) 2. NHLBI Grade: A (Strong); ACC/AHA COR: I; ACC/AHA LOE: A
Lifestyle Intervention and Counseling (Comprehensive Lifestyle Intervention)
4a. Advise overweight and obese individuals who would benefit from weight loss to participate for ≥6 months in a comprehensive lifestyle program that assists participants in adhering to a lower-calorie diet and in increasing physical activity through the use of behavioral strategies. NHLBI Grade: A (Strong); ACC/AHA COR: I; ACC/AHA LOE: A
4b. Prescribe on-site, high-intensity (i.e., ≥14 sessions in 6 mo) comprehensive weight loss interventions provided in individual or group sessions by a trained interventionist.† NHLBI Grade: A (Strong); ACC/AHA COR: I; ACC/AHA LOE: A
4c. Electronically-delivered weight loss programs (including by telephone) that include personalized feedback from a trained interventionist† can be prescribed for weight loss but may result in smaller weight loss than face-to-face interventions. NHLBI Grade: B (Moderate); ACC/AHA COR: IIa; ACC/AHA LOE: A
4d. Some commercial-based programs that provide a comprehensive lifestyle intervention can be prescribed as an option for weight loss, provided there is peer-reviewed published evidence of their safety and efficacy. NHLBI Grade: B (Moderate); ACC/AHA COR: IIa; ACC/AHA LOE: A
4e. Use a very-low-calorie diet (defined as <800 kcal/d) only in limited circumstances and only when provided by trained practitioners in a medical care setting where medical monitoring and high-intensity lifestyle intervention can be provided. Medical supervision is required because of the rapid rate of weight loss and potential for health complications. NHLBI Grade: A (Strong); ACC/AHA COR: IIa‡ ACC/AHA LOE: A
4f. Advise overweight and obese individuals who have lost weight to participate long term (≥1 year) in a comprehensive weight loss maintenance program. NHLBI Grade: A (Strong); ACC/AHA COR: I; ACC/AHA LOE: A
4g. For weight loss maintenance, prescribe face-to-face or telephone-delivered weight loss maintenance programs that provide regular contact (monthly or more frequently) with a trained interventionist† who helps participants engage in high levels of physical activity (i.e., 200–300 min/wk), monitor body weight regularly (i.e., weekly or more frequently), and consume a reduced-calorie diet (needed to maintain lower body weight). NHLBI Grade: A (Strong); ACC/AHA COR: I; ACC/AHA LOE: A
Selecting Patients for Bariatric Surgical Treatment for Obesity (Bariatric Surgical Treatment for Obesity)
5a. Advise adults with a BMI ≥40 kg/m2 or BMI ≥35 kg/m2 with obesity-related comorbid conditions who are motivated to lose weight and who have not responded to behavioral treatment with or without pharmacotherapy with sufficient weight loss to achieve targeted health outcome goals that bariatric surgery may be an appropriate option to improve health and offer referral to an experienced bariatric surgeon for consultation and evaluation. NHLBI Grade: A (Strong); ACC/AHA COR: IIa§; ACC/AHA LOE: A
5b. For individuals with a BMI <35 kg/m2, there is insufficient evidence to recommend for or against undergoing bariatric surgical procedures. NHLBI Grade: N (No Recommendation)
5c. Advise patients that choice of a specific bariatric surgical procedure may be affected by patient factors, including age, severity of obesity/BMI, obesity-related comorbid conditions, other operative risk factors, risk of short- and long-term complications, behavioral and psychosocial factors, and patient tolerance for risk, as well as provider factors (surgeon and facility). NHLBI Grade: E (Expert Opinion); ACC/AHA COR: IIb; ACC/AHA LOE: C
*Nutrition professional: In the studies that form the evidence base for this recommendation, a registered dietitian usually delivered the dietary guidance; in most cases, the intervention was delivered in university nutrition departments or in hospital medical care settings where access to nutrition professionals was available.
†Trained interventionist: In the studies reviewed, trained interventionists included mostly health professionals (e.g., registered dietitians, psychologists, exercise specialists, health counselors, or professionals in training) who adhered to formal protocols in weight management. In a few cases, lay persons were used as trained interventionists; they received instruction in weight management protocols (designed by health professionals) in programs that have been validated in high-quality trials published in peer-reviewed journals.
‡There is strong evidence that if a provider is going to use a very-low-calorie diet, it should be done with high levels of monitoring by experienced personnel; that does not mean that practitioners should prescribe very-low-calorie diets. Because of concern that an ACC/AHA Class I recommendation would be interpreted to mean that the patients should go on a very-low-calorie diet, it was the consensus of the Expert Panel that this maps more closely to an ACC/AHA Class IIa recommendation.
§There is strong evidence that the benefits of surgery outweigh the risks for some patients. These patients can be offered a referral to discuss surgery as an option. This does not mean that all patients who meet the criteria should have surgery. This decision-making process is quite complex and is best performed by experts. The ACC/AHA criterion for a Class I recommendation states that the treatment/procedure should be performed/administered. This recommendation as stated does not meet the criterion that the treatment should be performed. Thus, the ACC/AHA classification criteria do not directly map to the NHLBI grade assigned by the Expert Panel.
NHLBI Grading of the Strength of Recommendations
|Grade||Strength of Recommendation*|
|A||Strong recommendation |
There is high certainty based on evidence that the net benefit† is substantial.
|B||Moderate recommendation |
There is moderate certainty based on evidence that the net benefit is moderate to substantial, or there is high certainty that the net benefit is moderate.
|C||Weak recommendation |
There is at least moderate certainty based on evidence that there is a small net benefit.
|D||Recommendation against |
There is at least moderate certainty based on evidence that there is no net benefit or that risks/harms outweigh benefits.
|E||Expert opinion ("There is insufficient evidence or evidence is unclear or conflicting, but this is what the Work Group recommends.") |
Net benefit is unclear. Balance of benefits and harms cannot be determined because of no evidence, insufficient evidence, unclear evidence, or conflicting evidence, but the Work Group thought it was important to provide clinical guidance and make a recommendation. Further research is recommended in this area.
|N||No recommendation for or against ("There is insufficient evidence or evidence is unclear or conflicting.") |
Net benefit is unclear. Balance of benefits and harms cannot be determined because of no evidence, insufficient evidence, unclear evidence, or conflicting evidence, and the Work Group thought no recommendation should be made. Further research is recommended in this area.
*In most cases, the strength of the recommendation should be closely aligned with the quality of the evidence; however, under some circumstances, there may be valid reasons for making recommendations that are not closely aligned with the quality of the evidence (e.g., strong recommendation when the evidence quality is moderate, such as smoking cessation to reduce cardiovascular disease [CVD] risk or ordering an electrocardiogram [ECG] as part of the initial diagnostic work-up for a patient presenting with possible myocardial infarction [MI]). Those situations should be limited and the rationale explained clearly by the Work Group.
†Net benefit is defined as benefits minus risks/harms of the service/intervention.
NHLBI Quality Rating of the Strength of Evidence
|Type of Evidence||Quality Rating*|
*In some cases, other evidence, such as large all-or-none case series (e.g., jumping from airplanes or tall structures), can represent high- or moderate-quality evidence. In such cases, the rationale for the evidence rating exception should be explained by the Work Group and clearly justified.
†"Well-designed, well-executed" refers to studies that directly address the question; use adequate randomization, blinding, and allocation concealment; are adequately powered; use intention-to-treat analyses; and have high follow-up rates.
‡Limitations include concerns with the design and execution of a study that result in decreased confidence in the true estimate of the effect. Examples of such limitations include but are not limited to: inadequate randomization, lack of blinding of study participants or outcome assessors, inadequate power, outcomes of interest that are not prespecified for the primary outcomes, low follow-up rates, and findings based on subgroup analyses. Whether the limitations are considered minor or major is based on the number and severity of flaws in design or execution. Rules for determining whether the limitations are considered minor or major and how they will affect rating of the individual studies will be developed collaboratively with the methodology team.
§Nonrandomized controlled studies refer to intervention studies where assignment to intervention and comparison groups is not random (e.g., quasi-experimental study design).
¶Observational studies include prospective and retrospective cohort, case-control, and cross-sectional studies.
Applying Classification of Recommendations and Level of Evidence
|Size of Treatment Effect|
|CLASS I |
Benefit >>> Risk
|CLASS IIa |
Benefit >> Risk
IT IS REASONABLE to perform procedure/administer treatment
|CLASS IIb |
Benefit ≥ Risk
|CLASS III No Benefit |
or Class III Harm
|COR III: |
|Not helpful||No proven benefit|
|COR III: |
|Excess cost without benefit or harmful||Harmful to patients|
|Estimate of Certainty (Precision) of Treatment Effect||LEVEL A |
Multiple populations evaluated*
Data derived from multiple randomized clinical trials or meta-analyses
| || || || |
|LEVEL B |
Limited populations evaluated*
Data derived from a single randomized trial or nonrandomized studies
| || || || |
|LEVEL C |
Very limited populations evaluated*
Only consensus opinion of experts, case studies, or standard of care
| || || || |
A recommendation with Level of Evidence B or C does not imply the recommendation is weak. Many important clinical questions addressed in the guidelines do not lend themselves to clinical trials. Even when randomized trials are unavailable, there may be a very clear clinical consensus that a particular test or therapy is useful or effective.
*Data available from clinical trials or registries about the usefulness/efficacy in different subpopulations, such as sex, age, history of diabetes, history of prior myocardial infarction, history of heart failure, and prior aspirin use.
†For comparative-effectiveness recommendations (Class I and IIa; Level of Evidence A and B only), studies that support the use of comparator verbs should involve direct comparisons of the treatments or strategies being evaluated.