Low-Carbohydrate Diets

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Low-Carbohydrate Diets

Postby malernee » Sun Jan 29, 2006 6:15 pm

Low-Carbohydrate Diets
Stephen Barrett, M.D.
Many promoters of dietary schemes would have us believe that a special substance or combination of foods will automatically result in weight reduction. That's simply not true. To lose weight, you must eat less, or exercise more, or do both.

There are about 3,500 calories in a pound of body weight. To lose one pound a week, you must consume about 500 fewer calories per day than you metabolize. Most fad diets, if followed closely, will result in weight loss—as a result of caloric restriction. But they are invariably too monotonous and are sometimes too dangerous for long-term use. Moreover, dieters who fail to adopt better exercise and eating habits will regain the lost weight—and possibly more.

The most drastic way to reduce caloric intake is to stop eating completely. After a few days, body fats and proteins are metabolized to produce energy. The fats are broken down into fatty acids that can be used as fuel. In the absence of adequate carbohydrate, the fatty acids may be incompletely metabolized, yielding ketone bodies and thus ketosis. Prolonged fasting is unsafe, because it causes the body to begin to digest proteins from its muscles, heart, and other internal organs.

Low-carbohydrate diets also produce ketosis. As it begins, large amounts of water will be shed, leading the dieter to think that significant weight reduction is taking place. However, most of the loss is water rather than fat; the lost water is regained quickly when eating is resumed. Appetite, often reduced during ketosis, also returns when a balanced diet is resumed.

Most low-carbohydrate diets do not attempt to limit the intake of proteins, fats, or total calories. (In other words, their fat content tends to be very high.) Promoters claim that unbalancing the diet will lead to increased metabolism of unwanted fat even if the calories are not restricted. This is not true, but calorie reduction is likely to occur because the diet's monotony tends to discourage overeating.

The most widely used low-carbohydrate diet is the one advocated by the late Robert C. Atkins, M.D., of New York City. His 1972 book Dr. Atkins' Diet Revolution sold millions of copies within the first two years. His 1992 update, Dr. Atkins' New Diet Revolution, has sold even more. The current plan has four steps: a 2-week "induction" period, during which the goal is to reduce carbohydrate intake to under 20 grams per day, and three periods during which carbohydrate intake is progressively raised but kept below what Atkins calls "your critical carbohydrate level" for losing or maintaining weight [1]. The dieter is permitted to eat unlimited amounts of noncarbohydrate foods "when hungry," but ketosis tends to suppress appetite. The plan calls for checking one's urine for ketone bodies to ensure that the desired level of ketosis is reached. Atkins also recommended large amounts of nutritional supplements.

Research Findings
The AMA Council on Foods and Nutrition [2], Consumer Reports [3], and many individual experts have warned that the unlimited intake of saturated fats under Atkins' food plan can increase the dieter's risk of heart disease. In 2000, experts at the University of Kentucky did a computer analysis of a week's worth of sample menus and reported:

The diet contained 59% fat.
The diet provided fewer servings of grains, vegetables, and fruits than recommended by the U.S. Dietary Guidelines.
Although the diet can produce short-term weight loss, long-term use is likely to increase the risk of both cardiovascular disease and cancer [4].
Another study was done by researchers at the Bassett Research Institute in Cooperstown, New York, who followed 18 Atkins dieters for a month. During the 2-week induction period, the dieters consumed 1,419 calories a day, compared with 2,481 calories a day before starting the diet, and lost an average of about 8 pounds. In the next phase, dieters averaged 1,500 calories a day and lost an additional 3 pounds in two weeks. Dieters in both phases cut back on carbohydrates by more than 90%, but the actual amounts of fat and protein they ate changed little. Some patients felt tired, and some were nauseated on the plan. Most indicated that they were eager to go back to their regular diet [5].

Another study found that (a) 41 overweight people who followed the Atkins diet for six months lost an average of 10% of their initial body weight; (b) most lowered their blood cholesterol level by 5%; (c) some increased their cholesterol level; and (d) 20 subjects who continued the program had maintained their weight loss at the end of a year [6].

In yet another study, researchers who compile the National Weight Control Registry analyzed the diets of 2,681 members who had maintained at least a 30-pound weight loss for a year or more. Because the Atkins diet has been used for more than 30 years, the researchers reasoned that, if it worked, its followers would be well represented. However, they found that only 25 (1%) of these successful people had followed a diet with less than 24% of their daily calories in the form of carbohydrates. The mean duration of successful weight maintenance in this low-carbohydrate group was 19 months, whereas the mean duration of dieters who consumed more than 24% of their daily calories as carbohydrates was 36 months. Because so few Atkins dieters were found in the Registry, the researchers concluded that the Atkins diet may not create the favorable "metabolic advantage" claimed for it [7].

The nutrition committee of the American Heart Association has issued a science advisory warning that high-protein diets have not been proven effective and pose health risks. The report covered the Atkins, Zone, Protein Power, Sugar Busters, and Stillman diets. The committee stated:

Such diets may produce short-term weight loss through dehydration.
Weight loss may also occur through caloric restriction resulting from the fact that the diets are relatively unpalatable.
The high fat content may be harmful to the cardiovascular system in the long run.
Any improvement in blood cholesterol levels and insulin management would be due to weight loss, not the change in composition.
A very high-protein diet is especially risky for patients with diabetes because it can speed the progression of diabetic kidney disease [8].
In 1999. Atkins set up a foundation to provide "funding for research and education on the role of controlled carbohydrate nutritional protocols in treating and preventing a wide range of medical conditions." [9] In 2002, a 6-month study funded by Atkins found that followers of the Atkins diet lost more weight than comparable people on a high-carbohydrate diet and improved their blood cholesterol and triglyceride levels [10]. However, the dropout rate was much higher in the low-carbohydrate group and the improved lipid levels did not necessarily mean that the diet would have a cardioprotective effect in the long run [11]. In response to publicity about the study, the American Heart Association cautioned:

A high intake of saturated fats over time raises great concern about increased cardiovascular risk. The study did not follow participants long enough to evaluate this.
The study did not actually compare the Atkins diet with the current AHA dietary recommendations [12].
In 2003, experts who evaluated reports indexed since 1966 in MEDLINE found that weight loss was associated with longer diet duration and calorie restriction but not with reduced carbohydrate content. The researchers concluded:

There is insufficient evidence to make recommendations for or against the use of low-carbohydrate diets, particularly among participants older than age 50 years, for use longer than 90 days, or for diets of 20 g/d or less of carbohydrates. Among the published studies, participant weight loss while using low-carbohydrate diets was principally associated with decreased caloric intake and increased diet duration but not with reduced carbohydrate content [13].

In July 2003, researchers at the University of Pennsylvania reported the results of a controlled study of 63 people who were randomly assigned to either the Atkins diet or a conventional diet. The low-carbohydrate (Atkins) group lost about 4% more weight for the first 6 months, but there was no significant difference between two groups at 1 year. The low-carbohydrate diet appeared to improve risk factors for heart disease, but the authors concluded that more research is needed on the safety and effectiveness of this regimen [14]. In June 2004, Philippe O. Szapary, M.D., an assistant professor who is part of the University of Pennsylvania team, told me:

Although Atkins had published no research, he successfully challenged the notion that one type of diet is good for everyone.
The best type of diet may be determined by heredity factors. With good luck, during the next ten years, genetic research will clarify which diets are best for which people.
Because carbohydrates can raise triglyceride levels, a low-carbohydrate might be good for obese individuals with abnormally high triglyceride levels.
Carbohydrates, expecially simple carbohydrates, are also associated with low HDL levels. Some studies have found that a low-carbohydrate diet can raise the HDL level.
Low-carbohydrate diets are unsuitable for people with coronary artery disease, gout, or kidney disease. Before a low-carbohydrate diet is started, measurements should be made of the blood levels of creatinine (which reflects kidney function), uric acid (related to gout), and glucose (may detect diabetes, which can elevate triglyceride levels).
Low-carbohydrate dieters should also have their blood lipid levels monitored. If the three-month total or LDL-cholesterol level skyrockets, the diet should probably be discontinued [15].
The importance of careful monitoring is illustrated by the case of Jody Gorran, a 53-year-old Florida business executive who is suing Atkins Nutritionals, Inc. and Atkins's estate for negligent misrepresentation, product liability, and deceptive and unfair trade practices. The suit, filed in 2004, charges that Gorran's total and LDL-cholesterol levels shot up from very low to abnormally high within two months after he began following the Atkins diet, but he continued using it because passages in Atkins's book and Web site reassured him that it was safe to do so. About two years later, he developed angina and required angioplasty to unblock a coronary artery that had nearly closed. His suit seeks damages plus a court order to force Atkins's books, Web sites, and product promotions to warn that low-carbohydrate diets can be hazardous to health and increase the blood level of LDL-cholesterol [16].

Controversy About Atkins's Health
Atkins died in April 2003 of complications of a head injury [9]. At that time, and following a hospitalization for cardiac arrest a year earlier, skeptics wondered whether his health problems could have been related to long-term use of his diet. Although one person's experience is not enough to evaluate a diet, the Atkins organization's responses have been contradictory. In April 2002, an Atkins Nutritionals news release stated:

We have been treating this condition, cardiomyopathy, for almost two years,” explains Patrick Fratellone MD, Dr. Atkins’ personal physician and cardiologist, “and during the course of diagnosis, we discovered that Dr. Atkins’ coronary arteries were normal as diagnosed by an angiogram . . . in April of 2001. Clearly, his own nutritional protocols have left him, at the age of 71, with an extraordinarily healthy cardiovascular system. Unfortunately, the infection-related cardiomyopathy is totally another matter." [17]

After Atkins's death, the coroner's report listed his weight at 258. Stuart Trager, M.D., a hand surgeon who heads the Atkins Physicians Council, said that "during his coma, as he deteriorated and his major organs failed, fluid retention and bloating dramatically distorted his body." [18]. Trager also claimed that Atkins was 6 feet tall and had weighed 195 at the time of his admission [19]. That would have given him a body mass index (BMI) of 26.4, which is classified within the "overweight" range. However, Michael Fumento, an investigative reporter who interviewed Trager, has disclosed that the "admission weight" was an estimate made during a test procedure and was not based on an actual weighing, and that the publicly released report had covered his blood pressure numbers [19].

On February 16, 2004, on "Larry King Live," Atkins's widow Veronica repeated that Atkins had not been overweight and did not have coronary artery disease [20]. However, in April, in a column on the Atkins Nutritionals Web site, she stated:

It is clear that Robert developed a condition called cardiomyopathy approximately three years prior to his death. It is also true that when he developed cardiomyopathy his coronary arteries showed only minimal and clinically insignificant signs of coronary artery disease, consistent with what would be expected in a 69-year old man. Cardiomyopathy is a serious and progressive condition and was, I have been told, in Robert's case, caused by a viral infection. Though this condition significantly weakened his heart, its cause was clearly related to an infection and not his diet.

All of this was well documented and openly discussed by Robert himself on national television. Additionally, as Dr. Atkins explained on "Larry King Live" and other public appearances, he did have a witnessed cardiac arrest in April of 2002. All accounts and records related to this event . . . are consistent with conditions arising from his cardiomyopathy, a lack of blood flow. Robert did have some progression of his coronary artery disease in the last three years of his life including some new blockage of a secondary artery that was remedied during this admission. He did not have a heart attack [21].

Some day, perhaps, the Atkins organization will explain how could have progression of coronary disease that he didn't have in a cardiovascular system that was "extraordinarily healthy."

The Bottom Line
Although short-range studies have found that low-carbohydrate diets can produce weight loss, no study has demonstrated that such diets are safe or effective for long-term use [11-14,22,23]. Atkins advocated his diet for more than 30 years and stated that more than 60,000 patients treated at his center had used his diet as their primary protocol. However, he never published any study in which people who used his program were monitored over a period of several years. The recent popularity of low-carbohydrate diets has encouraged food companies to market low-carbohydrate foods for people who want to "watch their carbs." Most of these foods are much higher in fat than the foods they are designed to replace. I believe that "low-carb" advertising is encouraging both dieters and nondieters to eat high-fat foods, which is exactly the opposite of what medical and nutrition authorities have been urging for decades. Following a low-carbohydrate diet under medical supervision may make sense for some people, but a population-wide increase in fat consumption is a recipe for disaster.

For Additional Information
American Heart Association Statement on High Protein Diets
atkinsfacts.org: Archive of documents about the Atkins diet
Four steps to a healthy new lifestyle. Atkins Center Web site, accessed April 29, 2001.
White PL. A critique of low-carbohydrate ketogenic weight reduction regimens: A review of Dr. Atkins' diet revolution. JAMA 224:1415-1419, 1973.
Top-selling diets: Lots of gimmicks, little solid advice. Consumer Reports 63:60-61, 1998.
Anderson JW and others. Health advantages and disadvantages of weight-reducing diets: a computer analysis and critical review. Journal of the American College of Nutrition 19:578-590, 2000.
Miller BV and others. Effects of a low carbohydrate, high protein diet on renal function. Obesity Research 8(supplement 1):82S, 2000.
Hellmich N. Success of Atkins diet is in the calories. USA Today, Nov 8, 2000.
Wyatt HR and others. Long term weight loss and very low carbohydrate diets in the National Weight Control Registry. Obesity Research 8(suppl 1):87S., 2000.
St. Joer TS and others. Dietary protein and weight reduction. Circulation 104:1869-1974, 2001.
Robert C. Atkins, M.D., world-famous nutrition expert and best-selling author dies at 72. Atkins Center news release, April 17, 2003.
Westman EC and others. Effect of 6-month adherence to a very low carbohydrate diet program. American Journal Medicine 113:30-36, 2002.
Fumento M. Hold the lard: The Atkins diet still doesn't work.
American Heart Association statement on high-protein, low-carbohydrate diet study presented at scientific sessions. American Heart Association press release, Nov 19, 2002.
Bravata DM and others. Efficacy and safety of low-carbohydrate diets: A systematic review. JAMA 289:1837-1850, 2003.
Foster GD and others. A multicenter, randomized, controlled trial of a low-carbohydrate diet for obesity. New England Journal of Medicine 348:2082-2090, 2003.
Szapary P. Telephone interview by Dr. Stephen Barrett, June 24, 2004.
Complaint. Jody Gorran v. Atkins Nutritionals Inc. Palm Beach (Florida) County Court, filed May 26, 2004.
Statement on the status of Dr. Robert C. Atkins health from Dr. Atkins and from the chief executive officer/president of the Atkins Companies. Atkins Nutritionals news release, April 25, 2002.
Trager S. February 2004: The truth about Dr. Atkins’ weight. Atkins Nutritionals Web site, February 25, 2004.
Fumento M. Atkins Empire strikes back. Scripps Howard News Service, Feb 19, 2004.
Interview with Veronica Atkins. Larry King Live, CNN, Feb 16, 2004.
Atkins V. Statement by Veronica Atkins on the illegal distribution of personal medical information regarding her late husband, Dr. Robert C. Atkins. Atkins Nutritionals Web site, April 2004.
Blackburn GL. Making good decisions about diet. Weight loss is not weight maintenance. Cleveland Clinic Journal of Medicine 69:864-866, 2002.
Westman EC, Volek JS. Very-low-carbohydrate weight-loss diets revisited. Cleveland Clinic Journal of Medicine 69:849-862, 2002.
This article was revised on July 27, 2004.
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cat study on carbohydrate and time content feeding

Postby malernee » Tue Apr 11, 2006 8:55 am

Journal of feline medicine and surgery
Volume 7 | Issue 6 (December 2005)
Impact of time-limited feeding and dietary carbohydrate content on weight loss in group-housed cats
J Feline Med Surg. December 2005;7(6):349-55.
Kathryn E Michel, Amy Bader, Frances S Shofer, Claudia Barbera, Donna A Oakley, Urs Giger
Department of Clinical Studies - Philadelphia, School of Veterinary Medicine, University of Pennsylvania, 3900 Delancey Street, Philadelphia, PA 19104-6010, USA.

Twenty-four adult cats were transitioned to time-limited feeding and randomized to either a dry low carbohydrate diet (LC) or a dry reduced energy diet (HC). In Trial 1 the LC and HC groups received equal amounts of food (by weight) for 13 weeks. Both groups consumed all food offered, hence the LC group received more energy/day than the HC group. In Trial 2 all cats were fed the LC diet for 12 weeks, but each group received the energy that the opposite group had received in Trial 1. In Trial 1 only the overweight HC cats (body condition score>6/9) experienced a significant change in body weight (-0.52+/-0.08kg). In Trial 2, LC/Low Calorie overweight cats lost 0.62+/-0.10kg, whereas, the LC/High Calorie normal weight cats gained 0.68+/-0.05kg. In conclusion, body condition and energy intake but not type of diet influenced weight in this cohort of group-housed cats.
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