Atkins Diet Alert: A Physician's Committee for Responsible Medicine (PCRM) site
AtkinsDietAlert.org is brought to you by the Physicians Committee for Responsible Medicine, a leading advocate for preventive medicine, especially good nutrition. PCRM has been speaking out about the dangers of high-protein diets since its founding in 1985. Studies show that meat-heavy, high-protein eating patterns are, over the long run, linked to osteoporosis, heart disease, colon cancer, and renal disease, and pose particular dangers for people with diabetes.
Given the seriousness of these health risks, and the strength of the scientific evidence currently available, PCRM hopes this Web site will encourage people to be wary of high-protein diets and to choose healthier options. PCRM is also concerned about possible legal liability for doctors who prescribe these diets....
Health Risks of High-Protein Diets
Recent media reports have publicized the short-term weight loss that sometimes occurs with the use of very-high-protein weight-loss diets. Some of these reports have distorted medical facts and have ignored the potential risks of such diets. Past experience with the fen-phen drug combination and other weight-loss regimens has shown that some people may disregard even serious long-term health risks in hopes of short-term weight loss.
We would like to notify you of (1) risks from the long-term use of high-protein diets, (2) currently circulating misunderstandings and deceptive statements made in support of such diets, and (3) the establishment of a registry for individuals who have followed such diets.
Despite press accounts of seemingly dramatic weight loss, the effect of high-protein diets on body weight is similar to that of other weight-reduction diets. Three recent studies (one at Duke University, a second at the University of Pennsylvania and a third at a medical center in Philadelphia) suggest that the average weight loss with high-protein diets during the first six months of use is approximately 20 pounds, or about half a pound per week. This is not demonstrably greater than that which occurs with other weight-loss regimens or with low-fat, vegetarian diets.
There is nothing special about high-protein, very-low-carbohydrate diets. In fact, a recent review of 107 research studies on high-protein, low-carbohydrate weight-loss diets concluded that weight loss was associated with longer diet duration and restriction of calories, but not with reduced carbohydrate intake.
High-protein, very-low-carbohydrate weight-loss diets are designed to induce ketosis, an abnormal state that also occurs in uncontrolled diabetes mellitus and starvation. Over the long run, ketosis can contribute to a variety of physical problems, including calcium losses, increased risk of osteoporosis, and an increased propensity to form kidney stones.
High-protein diets typically contain higher-than-recommended amounts of dietary cholesterol, fat, saturated fat, and protein, and very low levels of fiber and some other important dietary constituents. The Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association states, “High-protein diets are not recommended because they restrict healthful foods that provide essential nutrients and do not provide the variety of foods needed to adequately meet nutritional needs. Individuals who follow these diets are therefore at risk for compromised vitamin and mineral intake, as well as potential cardiac, renal, bone, and liver abnormalities overall.”...
High-protein, high-fat dietary patterns, when followed over the long term, are associated with increased risk of the following conditions:
1. Colorectal cancer. Colorectal cancer is one of the most common forms of cancer and is among the leading causes of cancer-related mortality. Long-term high intake of meat, particularly red meat, is associated with significantly increased risk of colorectal cancer. The 1997 report of the World Cancer Research Fund and American Institute for Cancer Research, Food, Nutrition, and the Prevention of Cancer, reported that, based on available evidence, diets high in red meat were considered probable contributors to colorectal cancer risk. In addition, high-protein diets are typically low in dietary fiber. Fiber appears to be protective against cancer.
2. Heart disease. Typical high-protein diets are extremely high in dietary cholesterol and saturated fat. The effect of such diets on blood cholesterol levels is a matter of ongoing research. However, such diets pose additional risks to the heart, including increased risk for heart problems immediately following a meal. Evidence indicates that meals high in saturated fat adversely affect the compliance of arteries, increasing the risk of heart attacks.
3. Impaired kidney function. High-protein diets are associated with reduced kidney function. Over time, individuals who consume very large amounts of protein, particularly animal protein, risk permanent loss of kidney function. Harvard researchers reported recently that high-protein diets were associated with a significant decline in kidney function, based on observations in 1,624 women participating in the Nurses’ Health Study. The good news is that the damage was found only in those who already had reduced kidney function at the study’s outset. The bad news is that as many as one in four adults in the United States may already have reduced kidney function, suggesting that most people who have renal problems are unaware of that fact and do not realize that high-protein diets may put them at risk for further deterioration. The kidney-damaging effect was seen only with animal protein. Plant protein had no harmful effect.
The American Academy of Family Physicians notes that high animal protein intake is largely responsible for the high prevalence of kidney stones in the United States and other developed countries and recommends protein restriction for the prevention of recurrent kidney stones.
4. Osteoporosis. Very high protein intake is known to encourage urinary calcium losses and has been shown to increase risk of fracture in research studies.
5. Complications of diabetes. In diabetes, kidney and heart problems are particularly common. The use of diets that may further tax the kidneys and may reduce arterial compliance is not recommended.
In people with diabetes, the safest approaches to preventing or slowing kidney problems include controlling blood glucose levels, blood pressure, and cholesterol and decreasing protein intake to low normal levels.
While high-protein diets may carry potential health risks for anyone if maintained for more than a few weeks, they are especially risky for people with recurrent kidney stones, kidney disease, diabetes, osteoporosis, colon cancer, or heart disease.
Misunderstandings and Deceptive Statements
Recent prominent news stories have encouraged the circulation of significant misunderstandings among members of the public, sometimes further encouraged by inaccurate statements in the course of media interviews. Some patients may be confused or misled about important dietary issues based on the following inaccurate notions:
1. "High-protein diets cause dramatic weight loss." As noted above, the weight loss typically occurring with high-protein diets—approximately 20 pounds over the course of six months—is not demonstrably different from that seen with other weight-reduction regimens or with low-fat, vegetarian diets. People adopting vegetarian diets, which have a much more healthful nutrient pattern than high-protein diets, tend to lose approximately 10 percent of their body weight. Anecdotal accounts of greater weight loss with high-protein diets are atypical and may represent the additional effects of exercise or other factors.
2. "Fatty foods must not be fattening, because fat intake fell during the 1980s, just as America's obesity epidemic began." Some news stories have encouraged the public to discount health warnings about dietary fat and saturated fat, suggesting that fat intake declined during the 1980s, an era during which obesity became more common. However, food surveys from the National Center for Health Statistics from 1980 to 1991 show that daily per capita fat intake did not drop during that period. For adults, fat intake averaged 81 grams in 1980 and was essentially unchanged in 1991. While the American public added sodas and other non-fat foods to the diet, forcing the percentage of calories from fat to decline slightly, the actual amount of fat in the American diet did not drop at all.
A notable contributor to fat intake during that period was cheese consumption. Per capita cheese consumption rose from 15 pounds in 1975 to more than 30 pounds in 1999. Typical cheeses derive approximately 70 percent of energy from fat and are a significant source of dietary cholesterol.
3. "Fat and cholesterol have nothing to do with heart problems." Abundant evidence has established the ability of dietary fat and cholesterol to increase cardiovascular disease risk. Nonetheless, some popular-press articles have suggested that evidence supporting this relationship is weak and inconsistent. In addition, widely circulated news reports of a cardiac arrest suffered by the late diet-book author Robert Atkins have suggested that neither diet nor arteriosclerosis played any role in the unfortunate event. The net result of such reporting may be to suggest that individuals may disregard well-established contributors to heart disease.
4. "Meat doesn't boost insulin; only carbohydrates do that, and that's why they make people fat." Popular books and news stories have encouraged individuals to avoid carbohydrate-rich foods, suggesting that high-protein foods will not stimulate insulin release. However, contrary to this popular myth, proteins stimulate insulin release, just as carbohydrates do. Clinical studies indicate that beef and cheese cause a bigger insulin release than pasta, and fish produces a bigger insulin release than popcorn.
Also, it is important to realize that different carbohydrate-rich foods have very different effects. Most cause a gradual, temporary, and safe rise in blood sugar after meals. Beans, green leafy vegetables, and most fruits are in this healthful category. The main exceptions are large baking potatoes, white bread, and sugary foods, which can cause an overly rapid rise in blood sugar.
5. "People who eat the most carbohydrates tend to gain the most weight." Popular diet books point out that a carbohydrate restriction may induce ketosis as well as a reduction in energy intake, resulting in temporary weight loss. This has been misinterpreted as suggesting that carbohydrate-rich foods are the cause of obesity. In epidemiological studies and clinical trials, the reverse has been shown to be true. Many people throughout Asia consume large amounts of carbohydrate in the form of rice, noodles, and vegetables and generally have lower body weights than Americans—including Asian Americans—who eat large amounts of meat, dairy products, and fried foods. Similarly, vegetarians, who generally follow diets rich in carbohydrates, typically have significantly lower body weights than omnivores.
If you're looking to lose weight but want to avoid the hazards of the high-protein fad diets, consider replacing animal products with low-fat plant foods.
Research shows that vegetarians are not only, on average, 10 percent slimmer than omnivores, but they are also at dramatically lower risk of heart disease, diabetes, colon cancer and a host of other diseases. Plus, the food is delicious and easy to prepare.
For a step-by-step guide to healthy weight loss, see A Guide to Healthy Weight Loss, which shows you how three weeks on a low-fat vegan diet can get you on the road to your healthy weight goal.
For more information, see our fact sheet on permanent weight control and a summary of our latest weight-loss study.
For recipes, please visit www.pcrm.org/health/recipes/ and www.healthyeatingseries.com/recipes.html.