Protein Is the Darling of the Dieting Set -- For Now

From the WebMD Archives

Nov. 25, 1999 (Atlanta) -- Here's some food for thought for people planning on targeting the turkey while skipping the stuffing in the hopes of losing weight this Thanksgiving: A majority of experts warn against so-called protein diets.

Although these types of diets have been around for decades, they seem to be enjoying a renaissance in popularity lately. Consider the number of diets out there -- the Atkins diet, the Zone, and the so-called "Mayo Clinic" diet -- to name a few. While the diets vary widely in what is permissible to eat, their common denominator is an emphasis on protein (meat, fish, poultry, eggs, tofu, and nuts) and a downplaying -- if not an outright elimination -- of carbohydrates (breads, cereals, rice, pasta, fruits, and vegetables).

"They are quick fixes; they are your basic magic bullet," registered dietician Kathleen Zelman, a spokesperson for the American Dietetic Association, tells WebMD. "The reason they have been around for so long is that they indeed work, in the short term, to produce weight loss. The problem is the weight loss is primarily a fluid loss [which] occurs in the first couple of weeks, [giving] people the illusion that this is a very effective diet."

Effective? Maybe. But sustainable? Maybe not. When a person embarks on a high-protein diet, their body goes into what is called ketosis. "[Ketosis] is an altered type of mechanism for your body to get fuel," explains Zelman. "Your body's preferred form of fuel is glucose; glucose is generally obtained from carbohydrates. [Without carbohydrates] your body goes into an altered metabolism and it uses protein and fat. Ketone bodies are a by-product of protein metabolism."

Zelman says fat is mobilized in this altered metabolism, but that ketosis over the long term can be dangerous. "Ketosis is a bizarre and unnatural state -- it gives you funny breath and some people have physiological problems when they are in ketosis."

There are numerous other reasons people shouldn't stay on a high-protein diet for long periods of time. "It defies all health authorities' recommendations. ... A diet that is high in protein ... is hard to keep low in fat, although there might be some that do," says Zelman, noting that meat, bacon, cheese, and cream -- things that are high in saturated fat -- are staples in some of these diets.

"All the health authorities have convincingly recommended to the nation at large that diets high in saturated fat are linked with [heart] disease and elevated cholesterol levels. So in that respect the fat is dangerous. It also lacks fiber, so it could be disconcerting to the [intestinal] tract. Also, the high protein content is taxing on the kidney, so if you have predisposition to kidney disease that could further escalate things," Zelman tells WebMD.

What troubles many experts is that some high-protein diets restrict fruits and vegetables as well as starches. "What you have in the grains and the fruits and vegetables ... are phytochemicals, and antioxidants and fiber," Zelman says. "You can't get phytochemicals in a pill. So what you are eliminating in your diet are these cancer-preventing nutrients that are found naturally in fruits and vegetables and grains."

"I think it is unfortunate because fruits and vegetables provide fiber and different nutrients than you'd get from high-protein foods," says Alice Lichtenstein, DSc, a professor of nutrition at Tufts University. "In the short term, I don't think I'd be concerned about it -- most people are not going to stay on this kind of diet as strictly as described for that long a period of time."

"First of all, I should point out that the Zone diet has no relation whatsoever to a high-protein diet; this is a very mistaken notion," Barry Sears, PhD, author of The Zone, tells WebMD. "A good definition of a 'high-protein' diet is any diet in which you are consuming a lot more protein than carbohydrates, and that is going to induce a state of ketosis. Nobody can say anything positive about ketosis." Sears is also the president of Sears Laboratories, a Chicago-based biotechnology company.

Sears says each meal should be 1/3 low-fat protein (the serving no bigger or thicker than the palm of your hand) and 2/3 fruits and vegetables, with a dash of monounsaturated fat. There is, however, little or no room for starches (like pasta and breads).

"The diet is based on two things: balance and moderation. You are balancing your plate in terms of protein and carbohydrates," says Sears. "Where I think the controversy of the Zone diet comes from is, it forces people to think of hormonal consequences, not simply calorie-counting. And that's an alien concept to nutritionists because they've been trained to think: calories in, calories out -- whereas the Zone says, even in [meals with similar caloric values] you can get these tremendous changes in hormonal responses simply by changing the balance of protein to carbohydrates within a meal." The object of the Zone diet is to keep certain measures of food metabolism, like insulin, within a target area or zone so that blood sugar levels stay constant and hunger levels stay low.

Although some nutritionists downplay the notion that eating a certain combinations of protein, fat, and carbohydrates will result in insulin control and weight loss, a study presented at the American Heart Association's annual conference earlier this month seems to show otherwise.

Australian researcher Peter Clifton, MD, PhD, presented data from a 12-week study of 49 obese men and women with insulin resistance syndrome, a condition that leaves the body with too much circulating insulin (hyperinsulinemia). Insulin resistance syndrome, sometimes called Syndrome X, has recently been linked to obesity, and is estimated to affect more than 60 million people in the U.S.

The researchers wanted to determine if a high-protein weight-loss diet (30% of calories from protein), compared to a lower-protein weight-loss diet (15% of calories from protein), was more effective in reducing the components of insulin resistance syndrome. Even though there was no difference in the amount of weight loss between the two groups after 12 weeks, the results show improved insulin sensitivity with a high-protein diet -- and the numbers were most significant in men.

Despite the promising results, Clinton doesn't think clinicians should encourage their patients who have insulin resistance syndrome to embark on high-protein diets. "We need to wait for good data to show that's the way we should go," he tells WebMD. "At this point, we aren't sure about the long-term problems with [protein] diets. I know that high-protein diets are hard to achieve over the long term. ... So while it's possible our theory might be right, we certainly want to confirm it in a much larger study."

Others remain convinced that it's the calories that count. "Generally, what we do know is that it's calories that count in weight management, not necessarily hormonal responses to energy sources," Jennifer Nelson, MS, RD, tells WebMD. Nelson is the director of clinical dietetics at the Mayo Clinic in Rochester, Minn. "Because there is so little research on this, we can't substantiate those claims. Those claims are unverified."

Somewhat similar to the Zone diet is the so-called "Mayo Clinic" diet. But dieters beware!

"Don't be fooled. This diet has been attributed to the Mayo Clinic since the 1940s," says Nelson. "We started receiving calls in the '40s about a diet that emphasizes a lot of protein, very limited, if any, starch, very few fruits, and very limited vegetables. I think the only fruit it allows is grapefruit because it supposedly 'burns' body fat. To the best of our knowledge, it never originated at the Mayo Clinic and we do not endorse its use.

"I think that one of the reasons these types of diets are popular is that they initially do result in immediate weight loss. When you eat a high-protein diet, you have a tendency to lose more water weight than body fat per se, and so you get a more immediate response," says Nelson. "But are you truly losing the type of weight you need to lose?"

"Weight management should not be short-term; it needs to be a lifelong commitment. If you go at it short-term you are going to struggle gaining and losing the same pounds over and over again," says Nelson. "And when you take the longer view of weight management, a well-balanced diet that provides all of the necessary nutrients in the amounts that are needed ends up being very important."

"The best way to lose weight is to take the long view and make sure that your diet has a wide variety of foods in it, is slightly lower in calories than what you need to maintain your present weight, [and] that you include more physical activity," says Nelson. "Achieving those two things -- a healthy diet and more physical activity -- in your day-to-day lifestyle requires behavioral changes and is difficult to do."

No magic bullets here.