Randomized trial of a commercial weight loss program

Nutrition Research Newsletter,  May, 2007  

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The prevalence of obesity among US adults has increased dramatically over the last few decades and approximately one third of adults are considered obese. Numerous studies have tested a number of strategies and interventions to promote weight loss and maintenance in the general population of overweight and obese women. One of the most consistent observations is that successful weight loss with maintenance is characterized by regular physical activity, in addition to some effort to regulate food choices.

Some research suggests that commercial weight loss programs have the potential to promote a greater degree of weight loss than traditional counseling or medical interventions. One commercial program, the Jenny Craig (JC) program includes individual counseling, low-energy density diet, prepackaged goods, and increased physical activity. However, this multifaceted intervention has not been previously tested in a randomized trial. Therefore, a group of researchers tested whether the JC program promotes greater weight loss in overweight or obese women compared with control condition and described the effect of plasma lipids, carotenoids, hormones, and fitness. Seventy overweight or obese women (initial BMI > 25 kg/[m.sup.2] and < 40 kg/[m.sup.2]) were randomized to a commercial weight loss program or control conditions. All of the women completed a baseline and 6 month clinic visit, and 65 women completed a 12 month clinic visit. The intervention portion consisted of referral to a community-based JC facility. The core components of the JC weight loss program are described as addressing food, body, and mind. Interactions between corporate-trained and supervised staff and the clients consist of weekly one-to-one contacts with a counselor who is described as a consultant, with follow-up telephone and e-mail contacts and Web site/message board availability. The food component consists of prescribing an energy-reduced diet (typically 1200 kcal/d to 2000 kcal/d, individualized based on energy requirements) that includes prepackaged prepared food items that incorporate (and are accompanied by) increased vegetables, fruit, and other additional strategies to reduce the energy density of the diet. Subjects assigned to the usual care control group were provided consultation, at baseline and again at 16 weeks, with a research staff dietitian, who also provided publicly available print material that described dietary and physical activity guidelines to promote weight loss and maintenance. The dietitian discussed the participant's anthropometric data and the concepts of healthy weight and energy balance. Baseline energy requirements for weight maintenance were then calculated, and an energy intake level (accompanied by a menu plan based on food groups) to achieve a weight loss of 10% over a 6 month period was prescribed, involving a deficit of 500 kcal/d to 1000 kcal/d, as per current recommendations. Anthropometric measures were taken and included height, weight, and waist and hip circumferences. The 3 minute step test was used to detect possible changes in aerobic fitness of study participants. Lab tests were also performed and plasma lipids, carotenoids, and hormones were measured.

At randomization, the women were 41.1 years with a BMI of 34. At six months, weight loss was 7.2 kg and 7.8% in the intervention group and 0.3 kg and 0.3% in the control group. One year analysis showed a significantly greater change in weight, percent weight, BMI and waist and hip circumferences in the intervention versus control group. HDL cholesterol concentration increased significantly in the intervention group. Fasting serum insulin decreased in the intervention but increased in the control group at six months. Total carotenoids, alpha-carotene, and beta-carotene increased more in the intervention group than in the usual care control group between baseline and six months, but the difference was not sustained over the year.

The findings from this study showed that a commercial diet and lifestyle modification program that includes individual counseling, low-energy density diet, prepackaged foods, and increased physical activity successfully facilitated weight loss, which was notably maintained at one year. The program also promoted favorable changes in plasma lipid and hormone concentrations. One limitation of this study was the choice of control group. A more intensive intervention for the control group, particularly one with more frequent contact and counseling, may have resulted in a similar degree of weight change in the two study arms. The control group in this study was provided an intervention that would be a likely first step for the overweight or obese individual seeking guidance for weight loss and could be covered by health insurance programs. Therefore, a comparison of the commercial weight loss program to a more intensive intervention that does not incorporate prepackaged foods would be of interest.

Cheryl L. Rock, Bilge Pakiz, Shirley W. Flatt, et al. Randomized Trial of a Multifaceted Commercial Weight Loss Program, Obesity Research 15(4):939-949 (April 2007). [Address correspondence to Cheryl L. Rock, University of California, San Diego, 9500 Gilman Drive, Dept. 0901, La Jolla, CA 92093-0901. E-mail: elrock@uesd.edu].

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