Weight Loss During the Intensive Intervention Phase of the Weight-Loss Maintenance Trial

Background

To improve methods for long-term weight management, the Weight Loss Maintenance (WLM) trial, a four-center randomized trial, was conducted to compare alternative strategies for maintaining weight loss over a 30-month period. This paper describes methods and results for the initial 6-month weight-loss program (Phase I).

Methods

Eligible adults were aged ≥25, overweight or obese (BMI=25–45 kg/m²), and on medications for hypertension and/or dyslipidemia. Anthropomorphic, demographic, and psychosocial measures were collected at baseline and 6 months. Participants (n=1685) attended 20 weekly group sessions to encourage calorie restriction, moderate-intensity physical activity, and the DASH (dietary approaches to stop hypertension) dietary pattern. Weight-loss predictors with missing data were replaced by multiple imputation.

Results

Participants were 44% African American and 67% women; 79% were obese (BMI≥30), 87% were taking anti-hypertensive medications, and 38% were taking antidyslipidemia medications. Participants attended an average of 72% of 20 group sessions. They self-reported 117 minutes of moderate-intensity physical activity per week, kept 3.7 daily food records per week, and consumed 2.9 servings of fruits and vegetables per day. The Phase-I follow-up rate was 92%. Mean (SD) weight change was −5.8 kg (4.4), and 69% lost at least 4 kg. All race–gender subgroups lost substantial weight: African-American men (−5.4 kg ± 7.7); African-American women (−4.1 kg ± 2.9); non–African-American men (−8.5 kg ± 12.9); and non–African-American women (−5.8 kg ± 6.1). Behavioral measures (e.g., diet records and physical activity) accounted for most of the weight-loss variation, although the association between behavioral measures and weight loss differed by race and gender groups.

Conclusions

The WLM behavioral intervention successfully achieved clinically significant short-term weight loss in a diverse population of high-risk patients.

Introduction

The U.S. Surgeon General's recent call to action has highlighted the epidemic rise in obesity, as overweight and obesity affect about 65% of adults in the U.S.1, 2 Obesity increases cardiovascular disease (CVD) risk factors3, 4, 5 and overall mortality.6, 7, 8 The prevalence of these risk factors—hypertension, dyslipidemia, and type 2 diabetes—is generally 1.5–2.9 times higher among overweight adults than normal-weight adults.⁹ Modest weight loss significantly improves CVD risk factors, including lowering blood pressure (BP)10, 11 and hypertension risk¹²; reducing total cholesterol, low-density lipoprotein (LDL) cholesterol, and total triglycerides; and raising high-density lipoprotein (HDL) cholesterol.¹³ Similarly, weight loss lowers blood glucose in both diabetic and nondiabetic individuals and reduces risk of type 2 diabetes.14, 15 In response to this overwhelming evidence, clinical treatment guidelines for hypertension, dyslipidemia, and type 2 diabetes include weight control as a core component.2, 16, 17, 18, 19

A combined emphasis on dietary intake and physical activity is important to both short- and long-term weight-loss goals.3, 20, 21, 22, 23 Behavioral strategies to modify these health behaviors are important components of weight-loss interventions because they emphasize the individual's ability to monitor and regulate behavior,24, 25, 26 and target the barriers to both initial weight loss²⁰ and long-term maintenance. Weight loss is difficult, however, and in the Trials of Hypertension Prevention (TOHP-II)¹² only 43% of participants lost ≥4 kg during a 6-month intensive behavioral intervention. Unfortunately, regain following weight loss is also common, and few trials have implemented interventions for longer than 18 months or have explicitly tested alternative strategies to sustain weight loss.27, 28, 29, 30

This paper describes results from the 6-month Phase I of the Weight-Loss Maintenance (WLM) trial. This controlled trial examined three approaches for maintaining weight loss for 30 months following initial weight loss in a large, diverse adult population at high risk for CVD. Phase I of the WLM provided a nonrandomized intensive behavioral intervention10, 11, 31, 32, 33, 34, 35 to all participants to help them reduce caloric intake, promote a DASH (dietary approaches to stop hypertension) dietary pattern, and increase moderate-intensity physical activity to lose ≥4 kg of weight. Those who lost ≥4 kg during Phase I were eligible for Phase II and were randomized to a self-directed control group, a personal contact intervention providing brief monthly phone or face-to-face contacts, or an interactive technology intervention. The technology intervention provided support almost exclusively through an interactive website with self-monitoring tools, a bulletin board, problem-solving modules, up-to-date information, and other resources. Given the high prevalence of overweight in African Americans,⁹ and the burden of CVD in that population,³⁶ a major trial goal was to recruit about 40% African Americans. Adequate representation of both men and women was also an important recruitment goal.

Described here are the overall Phase-I weight-loss results and demographic and behavioral measures associated with weight loss in this large and diverse cohort. Race- and gender-specific weight-loss outcomes are presented, along with other demographic and behavioral modifiers of outcome.