Extending weight loss programs pays dividends
medwireNews: A randomized trial supports the clinical and cost effectiveness of extending the duration of weight loss programs.
Despite only attending 28.2 sessions, on average, study participants assigned to undertake a 52-week course lost significantly more weight than those who attended a 12-week program or were given advice only, the researchers report in The Lancet.
In a linked commentary, Emily Brindal (Commonwealth Scientific and Industrial Research Organisation, Adelaide, Australia) notes that the finding “might seem obvious at first,” but says that the “widely used 12-week duration for academic study of weight loss programmes and in commercial offerings has no clear clinical basis and it is a challenge to find substantiating empirical studies.”
The 528 people in the extended program lost an average of 6.76 kg, whereas the 528 assigned to attend the routinely prescribed 12 weeks of the commercial weight-loss program (Weight Watchers) attended an average of 8.4 sessions and lost 4.75 kg by the 12-month follow-up. The difference between the two groups was statistically significant in an adjusted analysis that accounted for patients lost to follow-up – around a third of all recruited patients.
A further 211 study participants received an information booklet only, but nevertheless lost an average of 3.26 kg over the subsequent 12 months. Although their weight loss was significantly less than that achieved by patients attending the program, the researchers say the finding “highlights the importance of including a control group when evaluating the effects of weight-loss interventions.”
It is important not to extrapolate these data beyond the population studied.
The proportions of patients who lost at least 5% of their baseline bodyweight were 57%, 42%, and 25% of those assigned to the 52-week program, the 12-week program, and the information booklet, respectively. The significant differences between the groups persisted when they were reassessed 12 months later, although all three groups regained some weight during this time.
Amy Ahern (University of Cambridge, UK) and study co-authors believe that their findings are broadly applicable to the UK population, and note that the study design matched usual practice in the National Health Service, including that participants were free to continue with the program after their assigned time or to use any other weight loss intervention. Indeed, 19% of participants allocated to 12 weeks of the program were still attending it at their own expense at the 12-month follow-up.
The study participants were recruited from 23 general practices in England. At the time of enrolment, they had an average body mass index of 34.5 kg/m2, 13% had diabetes, and 50% had hypertension. Baseline glycated hemoglobin levels were around 6%, and by the 12-month follow-up these had fallen by 0.24% in the extended program group, compared with 0.13% and 0.01% in the 12-week program and brief intervention groups, respectively.
As well as encouraging more weight loss, the researchers found the 52-week program to be more cost effective than the 12-week program. Although it was more expensive over a 2-year timeframe, they calculate that, over 25 years, the number of cases of disease prevented would result in it generating significantly greater cost savings than the 12-week program.
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