Low-carbohydrate diets are notorious for their panacean promises: Lose weight fast! Eat what you want! But a new scientific review suggests it takes at least a year, and a strict interpretation of “low-carb,” to see lasting results from this particular diet regime.
Low-carb diets promise to both burn fat and reduce sugar intake, while being flexible when it comes to non-carb foods. The popular Atkins Diet—the first phase of which restricts carbohydrate intake to 20 grams per day—is a great example of this approach. But these diets are also restrictive: An apple alone has 25 grams of carbs.
So is it worth it? A recent scientific review says yes, if you are willing to suffer. The review broke a number of weight-loss studies down by how long they lasted (longer or shorter than a year) and by how much they restricted calories from carbs; some restricting carbs to 40% of their daily caloric intake, and others restricting carbs to 10%. Low-carb dieters were compared to people who went on weight-loss diets but didn’t restrict their carbs. Systematic reviews like this one are among the best evidence science can provide because they combine the results of many studies on the same topic.
First, the good news: Researchers found that either type of low-carb diet was more effective than a regular weight-loss plan, at least in the short term. But participants who stayed on the 10% diet for at least a year lost more weight, and more fat, than people on either other diet. Those on the low-carb diets also lost more body fat, versus just weight, than people on a normal weight-loss diet. Unfortunately, for people who stick to their diets for more than a year, only the 10% diet still outperforms normal weight-loss plans when it comes to reducing body fat. If you want to get the best results possible, this research suggests you have to cut your carbs to almost nothing for at least a year.
Cutting carbs is no easy feat. Americans typically get around 50% of their calories from carbohydrates; reducing that to 10% is likely to leave them feeling “symptomatic, starved, and deprived,” says Sarah Currie, a New York-based dietician who specializes in low-carb diets. Moreover, changing eating habits that drastically, Currie says, “takes a good 1 to 3 years to be permanent.”
A more traditional combination of eating fewer calories and getting more exercise may seem preferable, until you factor in recent research on contestants from the US reality show The Biggest Loser. That study found that people who succeed in using diet and exercise to lose weight end up burning many fewer calories than those who never shed pounds in the first place. In other words, dieting makes it easier to gain weight.
It’s understandable if all this makes dieting seem hopeless. But keep in mind that most measures of body weight are actually bad proxies for health. The benefits of exercise extend well beyond weight loss, and having an “overweight” Body Mass Index (BMI) is associated with a lower risk of death. But of course, if you can severely restrict your carbohydrate intake every day—and take a year-plus sabbatical from bread, potato chips, pizza and ice cream—you will see better weight- and fat-loss results than by following a typical reduced-calorie or less restrictive low-carb diet.