You’ve probably heard that a slow and steady approach to weight loss improves the odds that you’ll stay slim in the long run. Easy go, easy come back—or so the conventional wisdom holds.
Historically, some public health authorities even championed the superiority of gradual weight loss plans. The thinking was that a slow reduction in body weight is more likely to be the result of healthy and sticky lifestyle changes, while rapid weight loss tends to stem from get-slim-fast tactics that are ultimately unsustainable.
While this line of thinking makes sense, the research says otherwise.
In a 2013 New England Journal of Medicine report titled “Myths, Presumptions, and Facts about Obesity,” the belief that quick weight loss is inferior to gradual weight loss is highlighted as false. “To date, the totality of evidence does not support the myth that gradual weight loss improves long-term outcomes,” says Krista Casazza, first author of the report and an associate professor at the University of Alabama at Birmingham.
That’s not to say one approach is obviously superior to the other. But the old adage that “the faster you lose weight, the faster you’ll regain it” is clearly wrong, says Joseph Proietto, chair of obesity clinical care at the nonprofit World Obesity Federation.
For a 2014 study, Proietto and his colleagues divided volunteers into two groups. One group adhered to a “rapid weight loss” program that involved severe calorie restriction for 12 weeks. A second group aimed to lose the same amount of weight by taking a less extreme approach to calorie reduction during a 36-week period.
While just 50% of people in the gradual weight loss group achieved the targeted level of weight loss, 81% of people in the rapid weight loss group hit the mark. After roughly two years of follow-up, Proietto and colleagues found that the people who had lost weight rapidly hadn’t gained back more than those who’d lost weight slowly. “The rate of weight regain is the same irrespective of the rate of weight loss,” Proietto says. Unfortunately, both groups tended to gain back most of the weight, he adds.
Whether you drop pounds quickly or slowly, research shows time and again that your body tends to fight back in response to lost weight. “After you change your lifestyle and the weight gradually starts to come off, the body senses this and physiological adaptations are initiated to get you back to your set point,” Proietto explains.
In an earlier study, Proietto and colleagues found that levels of hunger-stimulating hormones—the kinds that encourage weight regain—usually rise in response to pounds lost. Levels of these hormones also remain elevated even a year later, which suggests that the body doesn’t stop pushing back against attempts to lose weight, even after an initial adjustment period. More research suggests metabolism tends to slow down when people eat less and lose weight, which also counteracts attempts to stay svelte.
“This is why diets fail,” Proietto says. “Some people prefer gradual change, while some want to change right now and to have a turning point. Our research shows there is no right way.”
Why does your body resist your efforts to slim down?
“It’s a survival mechanism,” says Luzia Hintze, a weight loss researcher at the University of Ottawa in Canada. For most of human history, sustenance was scarce. “The human beings who survived were the ones whose bodies were more efficient at preserving energy,” Hintze explains.
While food is no longer hard to come by, “we still carry those mechanisms that help us maintain our fat level,” she adds.
Hintse’s study, published this year in the journal Physiology & Behavior, found that the speed of weight loss doesn’t make any difference when it comes to your body’s unhelpful fat-saving mechanisms. “There is no difference,” she explained. “Those adaptations are going to happen independent of rate of weight loss.”
She says more research has examined the rate of weight loss among people on diets that involve a rebalancing of macronutrients—cutting carbs in favor of fat or protein, for example—as opposed to diets that focus on calorie restriction.
But again, losing weight quickly or slowly doesn’t seem to make much difference. “Even when playing with macronutrients, the compensatory mechanisms regarding appetite and energy expenditure were the same,” she says.
When it comes to rapid versus gradual weight loss plans, Hintze says people should adopt an approach that suits their personal preferences. “Some people prefer gradual change, while some want to change right now and to have a turning point,” she says. “Our research shows there is no right way.”