Effectiveness of Popular Weight Loss Diets on Cardiovascular Risk Reduction

Your patients are excited to tell you they are ready to work on weight loss in an effort to reduce their risk for heart disease. They are planning to follow a popular weight loss diet promoted in a best-selling book or offered by a commercial vendor. How likely are they to be successful in achieving and maintaining their desired healthy weight? Will the diet they plan to embark on likely result in cardiovascular risk reduction as measured by improvements in blood pressure, lipids, glucose, and hemoglobin A1c levels? Do you cheer them on and support their efforts? Or, try to steer them in a different direction? Recent data from the National Health and Nutrition Examination Surveys estimate that 69% of adults in the United States are obese or overweight with approximately 35% obese.1Overweight is defined as a body mass index (BMI) of 25 kg/m2 to 29.9 kg/m2; and obesity, as a BMI of 30 kg/m2 or greater. The high rates of overweight and obesity raise public health concerns because of their strong association with chronic diseases. Hypertension, dyslipidemia, type 2 diabetes mellitus, coronary heart disease, stroke, osteoarthritis, sleep apnea, and some cancers are linked to obesity.2,3 In addition, obesity is associated with higher cardiovascular disease (CVD) and all-cause mortality when compared with those considered to be at normal weight (BMI, 18.5–24.9 kg/m2).2,3 One of the clinical questions addressed in the 2013 American Heart Association/American College of Cardiology/The Obesity Society Obesity Guideline was “Among overweight and obese adults, does achievement of reduction in body weight with lifestyle and pharmacologic interventions affect CVD risk factors, CVD events, and morbidity and mortality?”3 The writers of the Guideline completed a comprehensive review of the scientific literature and determined that sustained weight loss of 3% to 5% of body weight would likely result in meaningful reductions in several CVD risk factors including triglycerides, blood glucose, hemoglobin A1c, and the risk for developing type 2 diabetes mellitus. Weight loss greater than 5% will reduce blood pressure, improve low-density lipoprotein cholesterol, and high-density cholesterol.3 Given the benefits of weight loss on CVD risk reduction, healthcare providers are tasked with prescribing dietary strategies and other lifestyle interventions that will be safe and effective for patients. The writers of the Obesity Guideline recommend a variety of dietary approaches to weight loss including general caloric restriction to restriction of certain food types (high-carbohydrate, low-fiber, or high-fat foods) to create an energy deficit. In addition, the writers of the Guideline recommend commercial-based weight loss lifestyle interventions, particularly if there is peer-reviewed published evidence of their safety and efficacy.3 The challenge is to find quality evidence, with outcome data, to endorse or prescribe popular weight loss diets to patients as a strategy for weight loss and CVD risk reduction. The long-term effects of 4 popular diets (Atkins, South Beach, Zone, and Weight Watchers) were the subject of a recently published, systematic review of randomized controlled trials by Atallah and colleagues4 at McGill University and the Jewish General Hospital in Montreal, Quebec, Canada. Atkins5 is a low-carbohydrate diet with unlimited protein and fat; South Beach6 is a low-carbohydrate diet that focuses on lean proteins, monounsaturated or polyunsaturated fats, and low-glycemic index carbohydrates. The Zone7 is a low-carbohydrate diet that recommends the consumption of low-fat proteins, low-glycemic load carbohydrates, and small amounts of “good” fat. Weight Watchers is a lifestyle intervention program that uses a point system to provide caloric restriction while supporting participants in weekly weigh-in and group educational sessions.8 All 4 popular diets produced similar, modest short-term (<12 months) weight loss; however, Weight Watchers was more effective at long-term (≥12 months) weight loss (average weight change of −3.5 to −6.0 kg vs −0.8 to 5.4 kg). Limited data regarding maintenance of weight loss suggested that the modest short-term weight loss at 12 months was at least partially regained at 24 months. Moreover, there was a paucity of data regarding the effects of these popular diets on CVD risk factors. Available data showed no significant differences among the diets in improving CVD risk. The investigators of an older (2005) systematic review of commercial weight loss diets including Weight Watchers but not the book-based, Atkins, South Beach, or Zone similarly reported that, with the exception of 1 randomized controlled trial of Weight Watchers, the evidence to support the use of major commercial weight loss programs is limited.9 The investigators of an radomized controlled trial of Atkins, Ornish (very low fat),10 Weight Watchers, and Zone demonstrated similar modest weight loss and improved CVD risk factors at 1 year for all of the diets, but they noted an important and well-documented association between level of adherence to the diet and the overall benefit. They concluded that, whereas adherence to all of the diets was low, increased adherence was associated with greater weight loss and CVD risk factor reductions for each diet group.11 Although the writers of Obesity Guideline recommend the use of commercial weight loss diets when there is solid scientific evidence regarding their efficacy, limited evidence exists in the literature to date. Although Weight Watchers appears to be the more effective with regard to weight loss, more evidence is needed to strongly recommend Weight Watchers or other diets for CVD risk reduction. Adherence to any particular diet may be the most important aspect of their effectiveness. Therefore, it is critically important that cardiovascular nurses and other healthcare providers become familiar with and use accepted behavior change strategies and individualize their approach to weight management based on each patient’s goals, values, and beliefs as well as their level of motivation and self-efficacy.12 The writers of the Obesity Guideline endorse a variety of dietary approaches to a reduction in dietary energy and advise participation in comprehensive lifestyle programs that assist participants in adhering to a lower calorie diet as well as increased physical activity. The use of new technology such as electronic medical records and personal health monitoring devices provides new opportunities for delivery of weight loss interventions, but more research is needed to determine their effectiveness.13 Counseling patients regarding weight loss and CVD risk reduction is an increasingly important role for cardiovascular nurses given the high prevalence of overweight and obesity and associated CVD risk factors. As such, nurses need to be familiar with evidenced-based recommendations for weight loss as well as behavior change strategies to improve long-term adherence to diets and other treatments that result in meaningful weight loss and cardiovascular risk reduction.

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