Table of Contents
All food is comprised of three essential components or macronutrients: fat, protein, and carbohydrate. High-fat/low-carbohydrate or low-carb diets emphasize increased consumption of proteins and fats and a severe reduction of carbohydrates These diets are based on research that indicates high carbohydrate consumption increases levels of insulin in the blood. Insulin is a hormone that helps the body covert food into energy in the form of glucose or sugar. High insulin levels have been linked to medical conditions such as diabetes mellitus type II, cardiovascular disease, and obesity. These diseases are all part of a syndrome called Insulin Resistance Syndrome or Syndrome X.
The most popular and well-known of the current high fat/low carb diets is the Atkins diet first published in 1972 by cardiologist, Dr. Robert Atkins. However, some anthropologists believe this way of eating is as old as humanity and have called it the Paleolithic Diet.
The earliest recognized publication of a high-fat/ low-carb diet was William Banting’s Letter on Corpulence, published in 1863, in which Banting reported weight loss and improved health by following a low carbohydrate diet prescribed by his doctor, William Harvey. Banting suffered from obesity and hearing loss caused by fat compressing his inner ear. After following a low carb diet, he lost weight and his hearing improved.
In the 1920s the Epilepsy Center at Johns Hopkins Hospital began to use a high fat/low carbohydrate diet called the Ketogenic Diet to treat children with intractable, or hard to control, seizures. Johns Hopkins Epilepsy Center continues to use this diet program today. Also in the 1920s explorers Vilhjalmur Stefansson lived for many years with the Inuit people of artic Canada. His diet consisted exclusively of meat and fish. Since it was a virtually carbohydrate-free diet and high in fat, it was expected that his health would suffer. Once Stefansson returned home, Dr. Clarence Lieb of Bellevue Hospital in New York, examined him and found, to his surprise, that Stefansson was in perfect health. Dr. Lieb was able to duplicate these results later in a year long controlled study.
(Illustration by GGS Information Services/Thomson Gale.).
High-fat/low-carb diets vary in the number of grams of carbohydrates to be consumed each day. Most plans include three or more phases or stages. The earliest stages allow the fewest grams of carbohydrate to be eaten per day and typically last for two weeks. The middle stage is the weight loss stage and the carbohydrate grams may be slightly increased and then maintained at that level until the desired weight loss has been achieved. During the final phases, carbohydrates are gradually increased until weight loss stops or weight gain begins. At this point, the dieter reduces the amount of carbohydrate consumed until weight has stabilized.
The number of carbs allowed varies according the plan, but most plans consider the range of carbohydrates that will allow an individual to lose weight to be between 25 and 45 grams per day. The daily number of grams of carbohydrate consumed after ideal weight has been achieved will depend on the age, gender, and size of the individual, but Dr. Atkins reports that an individual of healthy weight who exercises should be able to eat between 45 and 100 grams of carbohydrate a day and still maintain a healthy weight and enjoy the health benefits of a low carb lifestyle.
Many high-fat/low-carb diets recognize that not all carbohydrates are bad. Some carbohydrates digest more slowly than others, causing a gradual rise in blood sugar after eating. Researchers have developed a glycemic index to rank carbohydrates and other foods according to the effect they have on blood sugar. It is called the glycemic index because the term “glycemia” refers to the presence of glucose or sugar in the blood.
The glycemic index is a scale of 0-100. Foods with higher glycemic index ratings break down quickly and cause a sharp spike in blood sugar. When blood sugar rises quickly, the body produces a surge of insulin to lower the amount of glucose in the blood. Insulin is a hormone that helps the body take sugar (glucose) out of the bloodstream and put it into cells, where it can be used for energy or stored in fat. Foods with lower glycemic index ratings break down more slowly. They cause a more gradual rise in blood sugar, which means less insulin will be needed. Lower blood sugar and insulin levels have been shown to prevent or treat type II diabetes and heart disease. They have also been shown to improve weight loss.
Foods that have a high glycemic index rating include: white bread, white rice, white potatoes, beer, corn products and products containing refined sugars. Foods with moderate glycemic index ratings include: whole grain breads and pastas, brown rice, sweet pota-totes, green peas, many fruits (especially when eaten alone) and yogurt. Low glycemic index foods include: rye grain, nuts, legumes such as black beans and lentils, green vegetables, apricots and cherries.
Foods that are high in fiber tend to have lower glycemic index numbers, because fiber takes longer to digest. Studies have shown that fats like olive oil and acidic products like vinegar, can also slow digestion and keep blood sugar from rising too quickly. The glycemic index can be used along with a high fat/low carb diet, to help choose which carbohydrates can be eaten with the least effect on blood sugar.
Other high fat/low carb diets include:
- Protein Power (Michael Eades, MD and Mary Dan Eades, MD.)—This diet plan emphasizes adequate protein consumption and limiting carbs to between 20 to 40 grams per day in the initial phase, increasing carb consumption to 50 grams per day during the middle phase, and once ideal weight is achieved, maintaining carb consumption at between 70 to 130 grams per day afterwards. Fat is considered neutral, but the authors admit that accessive fat consumption will make weight loss difficult.
- Eat Fat Get Thin diet (Barry Groves, MD)—This plan allows up to 60 grams of carbohydrate per day until ideal weight is reached and then the dieter is advised to gradually increase the grams of carbohydrates until weight loss stops. Unlimited amounts of meat, fish, poultry, cheese and eggs are allowed. Sugar, most grains, and breads are eliminated. Fruits are allowed, but not extremely sweet fruits. All vegetables are allowed except starchy vegetable, and green leafy vegetables are encouraged.
- The Schwarzbein Principle (Diana Schwarzbein, M.D. and Nancy Deville)—Life Without Bread (Wolfgang Lutz, MD)— Dr. Lutz is an early proponent of high fat/low carb eating. His plan deals primarily with the heath benefits of the diet. He recommends a carbohydrate limit of no more than 72 grams per day and encourages unlimited meat, non-starchy vegetables, cheese and natural fats. He advices moderation when eating nuts and whole dairy products.
- The Diet Cure (Julia Ross, MD)—This plan advises eating 20 grams of protein at each meal and limiting carbohydrates to 20 grams per meal. The plan is called “undieting” and stresses the importance of breakfast, avoiding hunger, and avoiding white flour, sugar, and refined products.
- Neanderthin (Ray Audette)—Nutritionist, Ray Audette advises that it is modern technology and overly processed food that make people ill and fat. His plan advises to eat as close to natural as possible asking the simple question, “Could I eat this if I were naked with a sharp stick on the savanna?” It is a Spartan plan that forbids all grains, all beans, all dairy products, and sugar. It has been called low carb dieting in its purest form.
- The Stone Age diet (Richard Mackarness, MB, BS, DPM)—One of the earliest books espousing the benefits of high fat/low carb diets. The author suggests that refined sugar should come with a warning label, encourages high fat and high protein consumption, and restricing carbohydrates to 60 or fewer grams per day.
The macronutrients in foods, fat, protein, and carbohydrate are converted to energy during digestion in a process called metabolism. The human body needs fat and protein to survive. Both fats and proteins are converted into energy as they are digested. Carbohydrate is converted to glucose as the body produces the hormone insulin. Insulin stimulates the body to store excess energy as fat. Unless the energy generated by these carbohydrates is used immediately, the excess is stored in the form of fat within the body.
The human body does not actually need carbohydrate to survive, though other important nutrients such as vitamins are found in fruits and vegetables which are primarily carbohydrates with little or no fat or protein. Many cultures live healthy lives and consume only meat and water. These cultures, such as the Inuit or Eskimos, live long, healthy lives on diets essentially carbohydrate free.
In high fat/low carb dieting weight loss occurs because reducing carbohydrate intake causes the human body to convert fat stores into energy. This process is called ketosis. Ketosis is a very efficient form of energy production that does not involve the production of insulin. When insulin levels remain constant, excess energy is not stored as fat. Combining the fat-burning of ketosis and the stabile insulin levels created in the absence of carbohydrates, high fat/low carb diets generally lead to rapid weight loss. The rationale is that it is not fat or even calories that cause people to be overweight, but rather inefficient or unhealthy insulin cycles.
Nutritionists argue that, as with any weight loss plan, weight loss on high fat/low carb diets is caused by the reduction in calories caused by essentially eliminating an entire food group from the diet and not from a particular metabolic change.
Many of today’s modern health concerns such as type II diabetes, heart disease, and obesity may be linked directly to improper insulin metabolism. Modern diets are high in carbohydrates. This excess carbohydrate consumption leads the body to be in a constant state of insulin production causing high levels of insulin to remain in the blood stream. This excess insulin may leads to a condition called Insulin Resistance Syndrome which causes illnesses such as diabetes, heart disease, and obesity.
Proponents of high fat/ low carb diets suggest that following these plans will lead to rapid weight loss, lower blood cholesterol levels, and increased energy.
While following a High Fat/ Low Carb diet, individuals must drink plenty of water. When the body burns fat for energy it creates waste products called ketones or ketone bodies. Drinking plenty of water helps to flush these by products out of the body.
Individuals with kidney disease should not attempt high fat/low carb diets because of the risk of kidney failure. Similarly, a diet high in fats may be harmful to individuals with advanced coronary artery disease or gout. These conditions may be worsened by the increased fat consumption.
Nutritionists express concerns over the long term adherence to a diet high in saturated fats. The American Heart Association has repeatedly expressed concerns about any diet plan that encourages increased fat consumption and a reduced consumption of a variety of fruits and vegetables fearing that this diet will lead to increased risk of coronary heart disease, stroke, and cancer.
There have been individual case reports of individuals who experienced severe metabolic acidosis or too much acid in the blood, after following a high fat/ low carb diet. However, this appears to an isolated and rare complication of this diet, and many doctors argue that in individuals with normal kidney and liver function, high fat/low carb diets will not cause this condition. At least two long term studies with significant numbers of participants reported no cases of metabolic acidosis.
In 2007, the Journal of the American Medical Association (JAMA) published the results of a Stanford University study comparing the Adkins diet with the Zone, LEARN, and Ornish diets. The study followed 311 over-weight women for a period of two years and eight months. The women were randomly assigned to one of the four diet plans. At the end of 12 months, participants who followed the high fat/low carb diet (Atkins) had lost the most amount of weight and had either comparable or better screenings for cholesterol, glucose and insulin, and blood pressure.
In 2004 researchers compared the effects of low carbohydrate diet and low fat diet on over weight individuals with high cholesterol. 120 over weight individuals with high cholesterol were randomly assigned to either a low carb diet or a low fat/calorie restricted diet. Both groups were given exercise recommendations, and the low carb group was also given supplements. At the end of 24 weeks the low carb group had lost more weight and had a greater reduction in cholesterol levels than the low fat/ low calorie group. Additionally, fewer participants dropped out of the low carb group than dropped out of the low fat/ low calorie group.
Doctors Atkins and Eades who have published books about high fat/low card diets have many case histories of patients they have treated in their individual practices who have experienced significant weight loss and improvement of medical conditions such as diabetes, high cholesterol, and coronary artery disease.
As far back as 1863, published reports support the efficacy and benefits of a high fat/low carb diet. Anthropologists have examined the remains of many cultures that ate diets consisting almost exclusively of meat and water with few if any carbohydrates. These cultures such as the Inuit of the Artic, Pacific Island tribes, and African tribes such as the Maasai, had virtually no incidence of obesity, heart disease, cancers, and other diseases that plague our society today. However, when these groups begin to eat a diet similar to diets in the United States, they develop the same obesity related illnesses prevalent in modern Western culture.
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Atkins & Low Carbohydrate Weight-Loss Support, A website dedicated to low carbohydrate eating that contrasts and compares various low carbohydrate diet plans and provides a forum and support group http://www.lowcarb.ca/
Deborah L. Nurmi, MS