What does it take to keep weight off? Apparently more than $665

EBM Focus - Volume 17, Issue 2

Reference: Obesity (Silver Spring). 2022 Jan;30(1):106-116

Many a New Year’s weight loss resolution has lived and died by the sword of the “diet.” The body of evidence on dieting overwhelmingly shows that most diets work while you do them. Maintaining that weight loss after the diet ends, however, is most often a losing battle. Despite the yearly advent of new and improved fad diets and wonder pills, unrealized weight loss resolutions continue to pile up while rates of obesity steadily climb. What is it going to take to actually help people achieve sustained weight loss? Money? A group of researchers in the US recently conducted a trial to evaluate just that.

Four hundred eighteen adults (72% White and 91% female) self-enrolled into an online group-based behavioral weight control program for 18 months where half were randomized to receive a financial incentive for the first 12 months. The online program involved free access to educational materials, personalized feedback, group lessons, and individualized dietary (1,200-1,800 kcal per day) and exercise (up to 200 minutes/week) goals. Incentives were both behaviorally-based (keeping a daily food log, daily weights, etc.) and outcome-based (% body weight lost), with a maximum possible benefit of $665. Drop-out rates were similar between groups, with 74% following up at 12 months and 71% at 18 months. All participants were included in the analysis, with missing data treated as indicating nonadherence.

Results indicated significantly higher percent body weight loss in the financially-incentivized group at 6 and 12 months, but not at 18 months. Comparing those who received financial incentives vs. online weight loss program alone, ≥ 5% weight loss was achieved in 55% vs. 40% at month 6 (p = 0.01, NNT 7), 45% vs. 32% at month 12 (p = 0.02, NNT 8), and 33% vs. 25% at month 18 (not significant). At least 10% weight loss was achieved in 28% vs. 16% at month 6 (p = 0.02, NNT 9), 25% vs. 15% at month 12 (p = 0.03, NNT 10), and 17% vs. 13% at month 18 (not significant). Mean weight loss at 18 months was 4.4 kg (9.7 lbs) in the financially incentivized group and 3.5 kg (7.7 lbs) in the online-only group, with nearly 75% in both groups regaining weight between months 6 and 18 (1.4 kg [3 lbs] / 0.7 kg ([1.5 lbs], respectively). The average payment for participants in the incentivized group was $324.

The bottom line is that neither the diet nor the financial incentive worked in the long term. Shocking. It’s been hypothesized that more people have success with commercial diets like Weight Watchers or Jenny Craig because they have a vested interest in the diet working, namely, the ‘good money’ they paid for these programs. So while the idea to look at the flip-side of this coin—actually paying people to lose weight—may not exactly be grounded in reality, it is certainly an interesting approach. Unfortunately, these data suggest that the difficulty maintaining weight loss which is seen consistently with other diets is encountered even when a financial incentive is provided (and then goes away). And this was in a population set up for success! The self-selected enrollment process for this study recruited participants through responses to flyers and emails, meaning that participants were already motivated to lose weight and had access to the internet, transportation, and daytime availability for group chats. This form of selection bias leads to likely overestimation of benefit in favor of the intervention, which is saying a lot for an intervention that didn’t seem to work. If money didn’t help people with weight control, maybe the next trial should see if vitamin D would do the trick.

For more information, see the topic Obesity in Adults in DynaMed.

DynaMed EBM Focus Editorial Team

This EBM Focus was written by Katharine DeGeorge, MD, MS, Deputy Editor at DynaMed and Associate Professor of Family Medicine at the University of Virginia. Edited by Alan Ehrlich, MD, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School; Dan Randall, MD, Deputy Editor at DynaMed; Carina Brown, MD, Assistant Professor at Cone Health Family Medicine Residency; Nicole Jensen, MD, family physician at WholeHealth Medical; Vincent Lemaitre, PhD, Senior Medical Writer at DynaMed; and Sarah Hill, MSc, Associate Editor at DynaMed.