The widely held belief that we’re less likely to regain weight when we lose it gradually rather than quickly is not true, according to an Australian study published last week.
The study found that keeping off the pounds over the long haul is difficult regardless of how quickly the weight is initially lost, although people are more likely to achieve their target weight — and to do so more rapidly — when calories are severely restricted.
In other words, as a commentary that accompanies the study puts it, “a slow and steady approach does not win the [weight-loss] race, and the myth that rapid weight loss is associated with rapid weight regain is no more true than Aesop’s fable.”
This study thus appears to shatter yet another diet myth — one that is at the center of weight-loss guidelines worldwide.
Phase I: weight loss
The study had two phases. In the first phase, the researchers randomly assigned 200 adults, aged 18 to 70, to either a 12-week rapid weight-loss program or a 36-week gradual one. All of the participants were obese, with a body mass index (BMI) between 30 and 45. Those in the rapid weight-loss group were put on a very low-calorie diet that restricted their food intake to 450 to 800 calories per day. Those in the gradual weight-loss group were put on a low-calorie diet that reduced their food intake by 400 to 500 calories per day. All participants were also instructed to undertake at least 30 minutes of mild- to moderate-intensity exercise (such as a brisk walk) daily.
The goal of both diets was for participants to reduce their body weight by 15 percent.
At the end of the first phase of the study, 81 percent of the participants in the rapid weight-loss program had achieved a weight loss of at least 12.5 percent of their body weight compared to 50 percent of the participants in the gradual weight-loss program.
In addition, significantly fewer people had dropped out early in the rapid program than in the gradual one (3 percent versus 18 percent).
Phase II: maintenance
The participants who had lost at least 12.5 percent of their weight in phase I of the study were then put on an individualized weight-maintenance diet (as recommended by the Australian Guide to Healthy Eating) for 144 weeks (more than two-and-a-half years). To help with this adherence, they met periodically with a dietitian and were advised to continue their daily exercise.
Keeping the weight off was a struggle for both groups. At the end of the 144 weeks, 71.2 percent in the gradual diet group and 70.5 percent in the rapid diet group regained most of the weight they had earlier lost.
“These findings are not consistent with present dietary guidelines which recommend gradual over rapid weight loss, based on the belief that rapid weight loss is more quickly regained,” the study’s authors conclude.
Furthermore, they point out, “achievement of a weight loss target was more likely and attrition was lower when weight loss was undertaken rapidly rather than gradually.”
There are several possible explanations for why a very low-calorie diet might be initially more effective, note the authors of the accompanying commentary. These include the fact that very low-calorie diets are simpler to follow. They require fewer decisions about food choices and don’t demand that you measure or estimate portion size. And because the weight loss occurs quickly, people may be more motivated to stick with the diet — at least, initially.
Warnings and conflicts
It’s important to point out that all participants in this study were carefully supervised by medical professionals — and for good reason. Very low-calorie diets are associated with a variety of health risks, most notably, fatigue, constipation, the formation of gallstones and kidney damage. Indeed, one participant in this study’s rapid weight-loss group developed acute cholecystitis and had to have her gallbladder removed — an event that the study’s authors acknowledge was probably related to the diet.
One other important caveat: Although the study was funded by the Australian National Health and Medical Research Council and the Sir Edward Dunlop Medical Research Foundation, one of the authors has a past financial tie to Nestle, which sells Optifast products for rapid weight loss. Those products were given free to the participants in the study who were in the rapid weight-loss group. The study’s authors say, however, that Nestle had no role in the design of the study or in the interpretation of its results. In addition, the authors of the commentary have several financial connections with weight loss companies (such as Jenny Craig) and with pharmaceutical companies that are promoting obesity-related drugs.
Although the study seems well designed and conducted, such financial conflicts-of-interest are troubling.