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In a trial of weight loss approaches, the rate at which people dropped excess pounds was not linked to their success in keeping the weight off over the next three years.
Researchers say the small study shows that current guidelines advising slow and steady weight loss should be revised, and the focus should be instead on improving methods for helping people maintain their weight over the long term.
The long-held belief that losing weight gradually produces better long-term outcomes seems to stem from the perception that obesity is a behavioural problem and that gradual weight loss allows more time for habits to change, the Australian study team writes in The Lancet Diabetes & Endocrinology.
"Obesity is not just a lifestyle disease as it is commonly believed but is largely genetic," senior author Joseph Proietto, Sir Edward Dunlop Professor of Medicine at the University of Melbourne, told Reuters Health.
Scientific evidence also does not support the superiority of a gradual approach in achieving or maintaining weight loss, he said. Regardless of how pounds are lost, many individuals have difficulty staying at their new weight and often gain it all back.
To test whether the rate of weight loss affects whether people regain weight, Proietto and his colleagues designed a two-part trial.
Read: How I lost weight - Part 1
How the study was conducted
In the first part, 200 obese adults were randomly assigned to either a 12-week rapid weight loss program on a very-low-calorie liquid meal-replacement diet of 450 to 800 calories a day, or to a 36-week program of gradual weight loss. The gradual diet was based on current Australian healthy eating dietary recommendations and included one or two liquid meal replacements per day, with a goal of reducing the participants' calorie intake by 400 to 500 a day.
In part two, people who had lost 12.5 percent or more of their body weight were able to continue into a weight maintenance program that would run for about three years. The maintenance program included an individualized eating plan and meetings with a dietician every 12 weeks.
In the first part of the study, the researchers found, participants who lost weight faster were more likely to achieve their target weight loss. Overall, 81 percent of those in the rapid weight loss group lost 12.5 percent or more of their body weight, compared to 50 percent in gradual weight loss group.
And in part two, the speed at which individuals had lost weight did not appear to play a role whether they regained weight or how much. Both groups gained back about 71 percent of the weight that they had initially lost.
Read: How I lost weight - Part 2
Low calorie diets should be supervised
As observed in this study, very low calorie diets can lead to robust weight loss in a very short time, but this type of diet should only be undertaken with medical supervision, said Dr. Kishore M Gadde, from the Pennington Biomedical Research Centre in Baton Rouge, Louisiana. He was not involved in the study, but wrote an accompanying editorial in the same issue of the journal.
Keeping the weight off is all too frequently the problem, Gadde said. "Once desired weight loss is achieved, individuals need to make intensive efforts to maintain their lost weight."
The study showed that seeing a nutrition counsellor every three months is not adequate support for weight maintenance, Gadde noted.
"Exercise can help prevent weight regain to some extent, but the intensity of exercise needed to prevent regain is difficult to incorporate into our daily lives," he told Reuters Health.
Medication may be needed for some
Using diet and exercise, unfortunately only about 15 percent may be able to successfully lose weight and keep it off, he said. "Pharmacotherapy could be a consideration for those regaining weight," he said. "But, we do not have solid evidence at this time that pharmacotherapy confers long-term success."
Proietto and his colleagues had also measured hunger-related hormones and appetite among participants in their study to see how the rate of weight loss might affect changes in feelings of hunger, both long- and short-term.
"The rate of weight loss also did not influence the changes in hunger controlling hormones that occur with weight loss," said Proietto, who also heads the weight control clinic at Austin Health in Melbourne.
From 2005 to 2010, Proietto chaired the Optifast Medical Advisory Committee for Nestlé Healthcare Nutrition Australia Ltd. But the company did not fund the current study.
Proietto feels that while appetite suppression after weight loss should be considered, the problem is that there are not many effective agents and none of them have been tested for long-term safety.
"Our study shows again that drugs are not essential for achieving weight loss but they are probably important for assisting with weight maintenance," he said.
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