Surprising effects of a high-protein, low-carb diet

THE TRUTH ABOUT DIETS

Surprising effects of a high-protein, low-carb diet

You may lose weight, but there's a catch

Published: February 25, 2015 06:00 AM

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Widely publicized diets, such as high protein and low carbohydrates, seem so promising. It’s no wonder so many of us have tried—or considered—them. But does science support the claims? We spoke with doctors and dietitians, and read the research. Here’s what you need to know before going on a high protein, low carb diet.

The promise

Remember the Scarsdale diet and the Stillman diet? Those high-protein, low-carb plans may have gone out of fashion, but Atkins, first published in 1972, is still hot. Protein-packed products are flooding stores, and the list of popular protein-rich diets—Paleo, Zone, and more—continues to grow. All claim that you’ll lose pounds, feel peppier, and reduce your risk of heart disease.

The truth

People lose weight on high-protein plans because they take in fewer calories, not because they focus on protein. “Diets only work by lowering calories,” says David Seres, M.D., director of medical nutrition at the Columbia University Medical Center in New York and a member of Consumer Reports’ medical advisory board. “Where the calories come from doesn’t matter.”

In addition to pushing protein, many of these plans recommend cutting back on—or completely eliminating—carbohydrates. Get less than 50 grams of carbs per day (the amount in two apples) for three to four days in a row, and your body will start tapping its own fat and muscle for fuel instead of its usual source: glucose derived from carbohydrates. That may sound like a way to shed pounds, but it can have serious health consequences. “You’re altering your metabolism away from what’s normal and into a starved state,” Seres says. “People in starved states experience problems with brain function.”

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A high-protein diet also overworks the kidneys. That’s especially worrisome for people with kidney disease and can predispose those with healthy kidneys to kidney stones. Over an extended period of time, excessive protein intake leaches calcium from your bones, which can lead to osteoporosis.

Far from increasing energy, that eating style might leave you fatigued and nauseated. Constipation can also be a problem because animal-based protein sources provide little or no fiber.

When it comes to heart disease, the saturated-fat-laden red meat that’s part of many high-protein diets may actually boost your risk. According to a Harvard study of more than 120,000 people followed for more than 20 years, a meat-based low-carb diet increased the risk of dying from cardiovascular disease by 14 percent.

Bottom line

It’s probably best to steer clear of high-protein, low-carb diets, according to our experts. They have no proven long-term benefits and are linked to a host of potential health problems.

Editor's Note:

This article also appeared in the March 2015 issue of Consumer Reports on Health.  


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