SNAP Trial: Weight Gain Prevention Strategies Work Well

Pam Harrison

May 03, 2016

Young adults who weigh themselves daily and who make small diet and activity changes to prevent weight gain are less likely to gain weight or become obese compared with those who make no changes during 3 years of follow-up, according to a new study.

Furthermore, young adults who initially lose weight to buffer against future weight gain and who also monitor their weight and maintain high levels of physical activity are even less likely than those who make no changes to gain weight or become obese during the same follow-up interval.

The study was published online May 2 in JAMA Internal Medicine.

"Until now, we didn't have clear guidance on what the message and recommendations should be for preventing weight gain," Deborah Tate, PhD, professor of health behavior and nutrition, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, said in a journal [TB1]news release. "This study showed that frequent weighing and either initial weight loss or daily small changes to diet and activity are useful weight gain prevention approaches."

SNAP Randomized Trial

The study of novel approaches to weight gain prevention (SNAP) was a 3-group randomized trial in which researchers compared a self-regulation group that made small daily diet and activity changes (small-changes group), a self-regulation group that made large behavioral changes (large-changes group), and a control group of participants in whom no behavioral change was introduced. A total of 599 young adults between 18 and 35 years of age with a body mass index of between 21.0 and 30.0 kg/m2 participated in the trial.

"The small- and large-changes interventions both began with 10 face-to-face group meetings over 4 months," lead author Rena Wing, PhD, from the Warren Alpert Medical School of Brown University, Providence, Rhode Island, and colleagues observe.

As the authors note, they chose 4 months as an initial treatment interval to give the large-changes group time to lose between 2.3 and 4.5 kg as a buffer against future weight gain.

After the initial 4-month intervention, the remaining interventions were delivered primarily online. "To encourage self-regulation, participants were instructed to weigh themselves daily and submit their weight via the study website, text message, or email," the authors explain. The participants also received feedback on their progress every month by email and were either congratulated on their success or were given additional strategies to get their weight back under control.

Small-changes participants whose daily weigh-in showed their weight inching upward were asked to drop 100 calories a day from their diet and increase their physical activity levels, whereas those in the large-changes group were asked to increase physical activity levels to 250 minutes a week after initially losing weight.

Weight Change at 3 Years

At a mean of 3 years' follow-up, participants in the small-changes group had lost 0.56 kg, whereas those in the large-changes group had lost 2.37 kg (P < .001). In comparison, those in the control group had gained a modest 0.26 kg at study endpoint (P < .001 for large-changes vs controls; P = .02 for small-changes vs controls).

The proportion of those who had gained 0.45 kg or more from baseline along with the proportion of those who became obese also went up over time, with the largest proportion in both categories being among the control participants.

Table. Secondary Outcomes at 3 Years' Follow-up

  Control Small Changes Large Changes P Value
Participants who gained ≥0.45 kg 40.8% 32.5% 23.6% <.001
Participants who became obese at least once 16.9% 7.9% 8.6% .008
Change in weight from baseline to 2 years 0.54 kg −0.77 kg −1.5 kg <.001

As the authors point out, the initial weight loss in the large-changes group produced by a calorie-restricted diet during the first 4 months of the study was followed by a gradual regaining of that weight, such that by year 2, large-changes subjects had regained 2.1 kg, or 58% of their initial weight loss.

"In contrast, participants in the small-changes group lost less weight initially (a mean of 1.48 kg at 4 months) but had a more stable trajectory, gaining only 0.7 kg between month 4 and year 2," they note. Although longer-term follow-up is needed, findings at year 2 of the SNAP study thus suggest that tinkering with diet and activity levels based on fluctuations in daily weight may be the more successful strategy to prevent weight gain over a lifetime.

"[W]eight gain is a serious health risk, and approaches to prevent or reduce it are urgently needed," Dr Wing said in the news release. "These new self-regulation approaches, which can easily and cost effectively be shared to help prevent weight gain in young adults, could have a significant impact on our public health."

Effective Interventions

In an invited commentary, Tannaz Moin, MD, from the David Geffen School of Medicine, University of California, Los Angeles, points out that more than one third of the population in the United States is obese, "so it is critical to disseminate effective interventions to tackle this epidemic." Because the study involved relatively young healthy adults, many of whom were not overweight at baseline, "weight loss interventions that buffer against possible weight gain may play an important role in the growing obesity epidemic," Dr Moin observes. "This approach would be akin to the primary prevention of many other chronic diseases, which is standard of care."

She adds, "Ultimately, to be able to move the needle on the obesity epidemic, we need effective interventions that are also scalable and sustainable," which, given the nature of the largely online delivery of both self-regulatory behavioral strategies used in the current study, could deliver on both counts, Dr Moin suggests.

The authors and Dr Moin have disclosed no relevant financial relationships.

JAMA Intern Med. Published online May 2, 2016. Article full text, Editorial full text

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