Direct comparisons of commercial weight-loss programs on weight, waist circumference, and blood pressure: a systematic review

The age-adjusted prevalence of obesity in adults in the United States is estimated to be 35 % [1]. The general prevalence of obesity has not decreased over the last 10 years, and it has increased among some groups. For example, obesity has increased by approximately 4 % among individuals aged 60 years and older [1]. Obesity has been associated with elevated blood pressure, dyslipidemia, elevated glucose level, and insulin resistance [2]. Wildman and colleagues found that 68 % of obese adults in the U.S. have two or more of these cardiometabolic abnormalities [3]. Clinically, even moderate weight loss of 5–10 % of body weight has been shown to significantly improve cardiovascular and endocrine disease risk factors [4, 5].

Among overweight and obese individuals, comprehensive lifestyle intervention alone or with adjunctive therapies is typically recommended as the initial management strategy [6]. Many individuals choose to participate in various commercially available weight-loss programs. In the U.S., these commercial programs constitute a $2.5 billion dollar industry, with Weight Watchers (45 %), Nutrisystem (14 %) and Jenny Craig (13 %) representing the largest market share [7]. A recent systematic review examined the efficacy of commercial weight-loss programs and found that individuals participating in Weight Watchers and Jenny Craig achieved significantly greater weight losses as compared to participants randomized to control/education or behavioral counseling interventions at 12 months [8]. Other programs like Nutrisystem, Medifast, and the Biggest Loser Club were also included in this review, but did not have any long-term studies of their programs. Guidelines from the American Heart Association/American College of Cardiology/The Obesity Society (AHA/ACC/TOS) state that clinicians can consider referring patients to commercial programs with demonstrated efficacy [6].

A limitation of previous reviews is that head-to-head comparisons between commercial weight-loss programs were not reported [8, 9]. Only head-to-head trials are appropriate to compare effectiveness between programs. Because participants are recruited and randomized using the same criteria, this study design reduces the potential influence of confounders that might contribute to differences in effect. Understanding whether one commercial program performs better than another is an important clinical question, as patients and clinicians are often faced with the dilemma of choosing between these weight-loss programs. Therefore, our objective in this study was to directly compare weight loss outcomes between commercially available weight-loss programs and compare changes in waist circumference and blood pressure between programs.

We examined 4,212 citations, and identified seven articles [12‐18] representing three RCTs reporting head-to-head comparisons that met our eligibility criteria (Additional file 1: Figure S1). Table 1 displays the population characteristics and risk of bias of each trial. Across all trials, participants’ mean age ranged from 39 to 49 years and most participants were women. Race was reported in only one trial [13], in which over three-fourths were Caucasian. All trials were rated as high risk of bias.

Three studies reported multiple head-to-head comparisons (Weight Watchers vs. Atkins [12‐14], Curves [15‐18], Jenny Craig [15‐18], Nutrisystem [15‐18], and SlimFast [13, 14]; Jenny Craig vs. Curves [15‐18], Nutrisystem [15‐18]; Nutrisystem vs. Curves [15‐18]; and Atkins vs. SlimFast [13, 14]). Of the fourteen head-to-head comparisons of mean weight change available, only one showed a significant difference (Fig. 1) where Curves participants lost 1.8 kg (95%CI: 0.1, 3.5 kg) more than Weight Watchers participants at three months [15]. There was no significant difference between programs for mean waist circumference change at any time point, among the eleven available comparisons (Fig. 2). Two trials reported data for the difference in SBP and DBP changes between programs (Fig. 3) [12, 13]. A comparison of Atkins versus SlimFast showed that SlimFast participants had an average of 4.5 mmHg (95 %CI: 0.4, 8.6 mmHg) lower systolic blood pressure after six months of follow-up [13]. There was no significant difference in diastolic blood pressure change among the reported data.

While previous literature has shown that Weight Watchers, Jenny Craig and Nutrisystem are effective in facilitating weight loss as compared to control/education or behavioral counseling [8], clinicians and patients may want to directly compare available commercial weight-loss programs when discussing the options for losing weight. In the present study, we found that most commercial programs perform similarly with respect to short-term changes in weight, waist circumference, and blood pressure among eligible head-to-head RCTs included in this review. Our findings build upon a recent review that compared named diets like Ornish and Atkins, and found that weight loss differences between individual strategies were small [19]. We considered commercial programs such as SlimFast and Curves not included in the review by Johnston and colleagues [19], and examined other outcomes beyond weight.

Previous surveys have found that 10 to 15 % of patients are using commercial programs to lose weight [20, 21]. Participating in these programs has been associated with greater likelihood of achieving a clinically significant weight loss of 10 % or greater [22]. While the AHA/ACC/TOS guidelines recommend that clinicians refer obese patients to high-intensity, comprehensive lifestyle interventions that include a moderately reduced calorie diet, increased physical activity, and use of behavioral strategies to enhance adherence [6], a recent study found that few programs in the community meet these recommendations [23]. In contrast, commercial weight-loss programs are widely available across the U.S. and some programs’ practices are consistent with the AHA/ACC/TOS suggested elements. Four programs included in this review (Weight Watchers, Curves, Jenny Craig, Nutrisystem) have practices consistent with these elements. In fact, the AHA/ACC/TOS guidelines suggest that commercial programs with demonstrated efficacy may be acceptable [6]. While counseling programs that promote healthy diet and physical activity have a role in treating obesity, evidence also suggests that a role exists for commercial programs in weight management.

While this review reported multiple head-to-head comparisons, we identified only three studies that met our inclusion criteria – one of which was an unpublished trial. Additional head-to-head RCTs would benefit clinicians and patients, as these data would provide clear information to determine whether one program is superior or similar to another. Health insurers might be considering offering a commercial weight-loss program as a benefit [24]. Direct comparisons of these programs would also help better inform policymakers’ selection of a program. Given the costs of these programs, patients and insurers may not be able to afford more than one option, thus rigorous comparative effectiveness research is needed to inform these decisions. Trials that directly compare commercial weight-loss programs head-to-head are the most appropriate methodology to compare effectiveness. Individuals may be tempted to use the recent review reporting comparisons of commercial weight loss programs to control/education or counseling to compare programs; however, they might draw inappropriate conclusions. For example, as compared to control at 3 months, Weight Watchers achieved 2.5–5.9 % greater weight loss whereas Nutrisystem had a 6.7 % greater loss [8]. Some may subsequently interpret this finding as Nutrisystem resulting in greater weight loss than Weight Watchers. However, we found that the direct comparison of these two programs were not significantly different at 3 months. While we would not make definitive conclusions based on one trial, the finding does illustrate the importance of direct comparisons to understand whether one commercial program is superior to another and the need for more head-to-head trials. In addition, such trials should extend to 12 months or beyond to provide a comparison of programs’ long-term effectiveness.

The limited information available for blood pressure outcomes is also critical, as some programs used prepackaged, processed foods that may contain higher levels of sodium than recommended [25]. Future studies should include lipids, glucose and hemoglobin A1c as outcomes, as dyslipidemia and diabetes mellitus are conditions where weight loss is often indicated.

Our study has several strengths. We considered a comprehensive list of commercial weight-loss programs when searching the evidence, and focused only on RCTs to capture evidence that has the greatest scientific rigor. Some commercial weight-loss programs may only conduct prospective or retrospective case series studies to describe their effect, which are subject to biases including selection bias. While limiting our synthesis to only RCTs increases the scientific rigor, some comparative studies may have been excluded. We also considered other outcomes beyond weight loss, which have not been considered in other reviews [8, 9, 19]. The present study also has several limitations. We used two databases to conduct our searches and obtained references from the commercial programs themselves; however, we might have missed citations listed only in other databases such as EMBASE or Web of Science. We included only RCTs of commercial weight-loss programs available throughout the United States. The evidence base also has several limitations. The risk of bias was high for all three of the included studies. Most trials reported only short-term results at three months; therefore, we cannot comment on between-program differences in maintenance of outcomes.

Overall, our results provide preliminary evidence of little differences in short-term benefits with respect to mean weight change, mean waist circumference change, and mean blood pressure change between commercial weight-loss programs in head-to-head comparisons. Additional long-term head-to-head trials of commercial programs would help clinicians who may be considering referring patients to these programs to achieve and maintain clinically significant weight loss.

AHA/ACC/TOS, American Heart Association/American College of Cardiology/The Obesity Society; CDSR, cochrane database of systematic reviews; DBP, diastolic blood pressure; RCT, randomized controlled trial; SBP, systolic blood pressure