Theories on fast or slow diets carry little weight

It’s advice that’s been peddled forever to dieters, but now medics have blown a hole in the theory — research has found whether you lose weight quickly or slowly does not reduce the amount or rate of weight you regain.

The findings have led those who conducted the research to describe “the myth that rapid weight loss is associated with rapid weight regain” as “no more true than Aesop’s fable”.

The study, carried out by Australian researchers, runs contrary to current dietary recommendations.

The findings, published in The Lancet Diabetes & Endocrinology journal, involved 200 obese adults randomly assigned to either a 12-week rapid weight-loss programme on a very low calorie diet (450–800 kcal/day) or a 36-week gradual weight loss programme. Participants who lost more than 12.5% of bodyweight were then placed on a weight maintenance diet for three years.

Participants who lost weight faster were more likely to achieve target weight loss: 81% of participants in the rapid weight loss group lost greater than or equal to 12.5% of their bodyweight versus just 50% in the gradual weight-loss group.

The researchers found that the initial rate of weight loss did not affect the amount or rate of weight regain in the patients who entered the subsequent weight maintenance period, as similar amounts of weight were regained after three years by participants who had lost weight on either diet programme. Weight regain was around 71% in both groups after three years.

Katrina Purcell, dietician and the first author on the paper from the University of Melbourne, said across the world, guidelines recommend gradual weight loss for the treatment of obesity, “reflecting the widely held belief that fast weight loss is more quickly regained”.

“However, our results show that achieving a weight loss target of 12.5% is more likely, and drop-out is lower, if losing weight is done quickly,” Ms Purcell said.

Dietitian Richelle Flanagan, a spokesperson for the Irish Nutrition and Dietetics Institute, said she was not surprised at the latest research findings, that other emerging studies were showing similar results.

“They are right in terms of the evidence coming out that actually the rate of weight loss is not as indicative as the rate of weight regain as originally thought,” Ms Flanagan said.

She said there were good programmes running now in the UK, including the Counterweight programme which the NHS has embraced, and a number of Ireland-based dietitians have trained in, as a surgical alternative to tackling obesity.

This 12-week programmes involves total diet replacement where participants are given nutritionally complete soups and drinks and food is gradually reintroduced.

A study had been carried out by the Universities of Glasgow and Newcastle evaluating the success of the Counterweight Plus weight-loss programme and 52% of those who followed it properly had kept the weight off after a year.