PHILADELPHIA — For years diet doctors have criticized Americans for yo-yo dieting. But looking at the protein advice given by nutrition specialists over the past year or two, it seems instead that it’s the experts who’ve been bouncing back and forth with no clear advice for confused consumers.
At one time or another, protein, carbohydrates and fats have all been vilified. These days, when you sit down to a meal it seems as if you’re facing a traitor in every bite.
A prime example of recommendation flip-flopping is the experts’ advice on protein. Back in the 1960s, Americans were told they would be healthy if they ate lots of meat. But over the next two decades, health experts began to promote high-carbohydrate diets and to warn Americans against eating too much protein.
When the low-carbohydrate, high-protein Atkins’ diet first came out 30 years ago, and again after its recent resurgence in popularity, mainstream experts came out strongly against it: protein — along with fat — is what is killing Americans, they intoned.
In fact, in 2000, the American Heart Association published several statements critiquing the regimen. The association insisted that there was no evidence showing that high-protein meals could lead to weight loss and they might even hurt the dieter’s kidneys and rob strength from the bones.
A year later, the heart association backed off these statements a bit and simply argued that weight loss seen by those following the protein gurus was simply “fluid loss.” And still they warned against deviations from the USDA’s Food Pyramid.
NEW PROTEIN RANGES
But the tide seems to be turning yet again.
The latest nutrition guidelines seem to reflect confusion even among the experts. No longer are there hard and fast numbers for the percentages of major food groups. Now protein can range from 10 percent to 35 percent of daily intake. At the annual meeting of the American Dietetic Association this week, nutritionists basically admitted that they really don’t know how much protein Americans need.
And several new studies have shown that diets that have moderately high levels of protein can lead to weight loss that targets fat and spares muscle, said Donald Layman, a professor in the department of food science and human nutrition at the University of Illinois, Urbana-Champaign.
While all low-calorie diets lead to weight loss, recent research has shown that not all calories are created equal, Layman said at the meeting. For example, one new study looked at two groups of dieters: one with a high-protein regimen — 125 grams of protein and 171 grams of carbs — and one with a high-carbohydrate regimen — 68 grams of protein and 246 grams of carbs. Both groups were also required to exercise.
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At the end of four months, people who ate more protein lost more weight — 22 pounds versus 15 pounds. Further, people on the high-protein diet had lost more fat and less muscle than the group on the high-carb diet.
Another important finding: higher levels of protein may also help dieters stick with their plans.
Studies have shown that protein, more than carbohydrates or fat, leads to feelings of fullness and satiety, said Richard Mattes, a professor of foods and nutrition at Purdue University. People given a high-protein breakfast feel full longer than those who eat a carbohydrate-rich breakfast, Mattes said.
Mattes also cautioned that the form of protein consumed makes a difference. Solid protein is satisfying. Protein in liquid form is not.
Ultimately, the percentage of protein you need will depend on whether you are dieting or not, said Cathy Nonas, of the New York Obesity Research Center in New York City. “If you’re on a 1,200 calorie a day diet and want to lose weight and you’re only eating 10 percent protein, you’re not getting enough protein to support lean tissue. Even 20 percent isn’t enough to support lean tissue. Studies have shown that you need to get at least 76 grams of protein, so that means you have to go to the upper ranges of the protein recommendations for a 1,200 calorie diet.”
But Nonas and the other experts stopped short of recommending the very high levels of protein suggested by eating plans like the Atkins’ diet because these plans so drastically cut carbohydrates — the initial phase of the Atkins’ diet limits carbohydrates to 20 grams a day.
That’s because carbohydrates are the major source of fiber in the diet.
Just cutting carbohydrates back to 50 percent of your diet would be enough, Nonas said, and that would still allow for enough carbs to be within the range recommended by the ADA.
“You can increase lean protein and decrease carbohydrates and still have a really healthy mix,” she said.
Linda Carroll is a freelance reporter based in New Jersey. Her work has appeared in The New York Times, Health and Smart Money.
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