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The effect of rate of weight loss on long-term weight management: a randomised controlled trial

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Summary

Background

Guidelines recommend gradual weight loss for the treatment of obesity, indicative of a widely held opinion that weight lost rapidly is more quickly regained. We aimed to investigate the effect of the rate of weight loss on the rate of regain in obese people.

Methods

For this two phase, randomised, non-masked, dietary intervention trial in a Melbourne metropolitan hospital, we enrolled 204 participants (51 men and 153 women) aged 18–70 years with a BMI between 30 and 45 kg/m2. During phase 1, we randomly assigned (1:1) participants with a block design (block sizes of 2, 4, and 6) to account for sex, age, and BMI, to either a 12-week rapid weight loss or a 36-week gradual programme, both aimed at 15% weight loss. We placed participants who lost 12·5% or more weight during phase 1 on a weight maintenance diet for 144 weeks (phase 2). The primary outcome was mean weight loss maintained at week 144 of phase 2. We investigated the primary outcome by both completers only and intention-to-treat analyses. This study is registered with the Australian New Zealand Clinical Trials Registry, number ACTRN12611000190909.

Findings

200 participants were randomly assigned to the gradual weight loss (n=103) or rapid weight loss (n=97) programme between Aug 8, 2008, and March 9, 2010. After phase 1, 51 (50%) participants in the gradual weight loss group and 76 (81%) in the rapid weight loss group achieved 12·5% or more weight loss in the allocated time and started phase 2. At the end of phase 2, both gradual weight loss and rapid weight loss participants who completed the study (n=43 in gradual weight loss and n=61 in rapid weight loss) had regained most of their lost weight (gradual weight loss 71·2% regain, 95% CI 58·1–84·3 vs rapid weight loss 70·5%, 57·8–83·2). Intention-to-treat analysis showed similar results (gradual weight loss 76·3% regain, 95% CI 65·2–87·4 vs rapid weight loss 76·3%, 65·8–86·8). In phase 1, one participant in the rapid weight loss group developed cholecystitis, requiring cholecystectomy. In phase 2, two participants in the rapid weight loss group developed cancer.

Interpretation

The rate of weight loss does not affect the proportion of weight regained within 144 weeks. These findings are not consistent with present dietary guidelines which recommend gradual over rapid weight loss, based on the belief that rapid weight loss is more quickly regained.

Funding

The Australian National Health and Medical Research Council and the Sir Edward Dunlop Medical Research Foundation.

Introduction

During the past decade, the prevalence of obesity has increased significantly, and it now represents a major health problem in both low-income and high-income countries.1 Dietary weight loss is generally unsuccessful in the long-term,2, 3 and optimum non-invasive methods to achieve and maintain weight loss remain elusive. Guidelines worldwide recommend gradual weight loss for the treatment of obesity,4, 5, 6 reflecting a widely-held opinion that rapid weight loss is associated with poorer long-term outcomes than is gradual weight loss. This notion probably stems from the belief that obesity is caused by bad social habits and that gradual weight loss allows more time to change such habits.

The widespread belief in the superiority of gradual over rapid weight loss has recently been questioned,7, 8 and scientific evidence does not support the superiority of a gradual approach in achieving or maintaining weight loss.9 Findings of a non-randomised study10 showed that participants who lost weight rapidly achieved and maintained greater weight loss than did those who lost weight gradually. However, individuals who chose rapid weight loss might have been more motivated than those who did not.

We aimed to investigate whether the rate of weight loss affects the rate of regain, and whether weight loss-induced changes in circulating appetite-mediating hormones and subjective appetite are affected by the rate of weight loss.

Section snippets

Study design and participants

We did a two-phase, randomised, non-masked, dietary intervention trial between August, 2008, and July, 2013, in a Clinical Research Unit at a Melbourne metropolitan hospital.

We recruited volunteers using radio and newspaper advertisements and by word of mouth. Eligible patients at screening were obese (BMI 30·0–45·0 kg/m2), otherwise healthy, and aged between 18 and 70 years. Key exclusion criteria included use of a very low energy diet or weight loss drugs in the previous 3 months, pregnancy

Results

204 participants were randomly assigned to either the rapid weight loss or gradual weight loss group; 200 participants started the diet (figure 1). Table 1 shows baseline characteristics of the two groups.

179 (89·5%) participants completed phase 1. Significantly more participants discontinued the gradual weight loss programme than the rapid weight loss programme (18 [18%] vs three [3%], p=0·002). The main reason given for withdrawal in both groups was difficulty adhering to the diet.

Figure 2

Discussion

By contrast with the widely-held belief that weight lost rapidly is more quickly regained,16, 17 our findings show that regain is similar after gradual or rapid weight loss. Moreover, achievement of a weight loss target was more likely and attrition was lower when weight loss was undertaken rapidly rather than gradually in phase 1. Several possible reasons exist for this finding. Rapid weight loss might motivate participants, which could explain why participants in the rapid group spontaneously

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