When it comes to dieting, the conventional wisdom holds that losing weight gradually is more sustainable in the long run than losing weight quickly. But new results from a long-term clinical trial show that this is just another dieting myth.
Both fast and slow weight loss produced pretty modest results over the long term. But in some respects, the rapid weight-loss regimen tested in the study worked better than its slow-but-steady counterpart, according to a report published Thursday by the journal Lancet Diabetes and Endocrinology.
The study involved 200 obese Australian adults between the ages of 18 and 70. Ninety-seven of them were randomly assigned to a strict diet that replaced breakfast, lunch and dinner with Optifast shakes. By consuming only 450 to 800 calories per day, their goal was to lose 15% of their body weight in 12 weeks. The other 103 volunteers were asked to drink Optifast shakes once or twice a day and prepare their remaining meals according to the recommendations in the Australian Guide to Healthy Eating. This plan was supposed to lead to a 15% reduction in body weight over 36 weeks.
Volunteers in both groups also had meetings with dietitians and received educational materials about healthful eating.
Despite its austerity, the extreme diet worked better for more people than the gradual diet, according to the study. Among the volunteers who made it to the end of the weight-loss portion of the study, 81% of those on the rapid plan lost at least 12.5% of their body weight. For volunteers on the gradual diet, only 62% achieved the same goal.
One of the reasons for this success was that the extreme diet was more tolerable than the gradual one (perhaps because it lasted for only three months instead of nine). Only 3% of those assigned to the rapid weight-loss regimen dropped out of the study, compared with 18% of those in the gradual program.
Volunteers who followed the rapid plan were getting more exercise (2,291 extra steps per day, on average) than their counterparts on the gradual diet (an average of 1,300 extra steps per day). However, the gradual dieters saw bigger improvements in both waist and hip circumference. The drop in BMI was virtually the same in both groups: 5.3 points lower for those fueled only by Optifast and 5.2 points lower for those who got to eat at least some real food.
But losing weight isn't the hardest part of a diet -- the bigger challenge is keeping it off. So the researchers tracked the volunteers who were still part of the study for 144 more weeks. During that time, all of them were advised to follow an "individualized diet for weight maintenance," according to the study.
Of the 127 volunteers who completed the study, all but six -- five who lost weight rapidly and one who lost weight gradually -- started to gain back some of the pounds they had shed. Those who started with the extreme diet lost a little more than 32 pounds after the initial 12-week period but gained back 23 of them. And those who lost weight gradually dropped 31.5 pounds after 36 weeks but gained back 22 of them.
The net result after more than three years: Those who followed the gradual diet ended up losing 0.44 pounds more, on average, than those who followed the rapid diet.
The researchers found several reasons to endorse the all-Optifast diet: It is simpler to follow than a gradual diet that requires people to prepare some of their own meals. It produces results more quickly, which may encourage people to exercise more. The hormone changes detected in those on the rapid diet seemed to make them feel less hungry than their counterparts on the gradual diet. And it is probably cheaper.
But in the end, both approaches ultimately did a poor job of helping obese people lose weight in a sustainable way.
"A strategy to suppress hunger after weight loss and therefore prevent weight regain ... is still awaited," the researchers concluded.