Low Carbohydrate Diets: Are They Effective



Low Carbohydrate Diets: Are They Effective? Are They Safe?

by Amy Scholten, MPH

[pic]Obesity is a growing epidemic, and many promoters of popular weight-loss diets are placing the blame on carbohydrates. Promoters of The Zone, Dr. Atkin’s New Diet Revolution, Sugar Busters, and other low carbohydrate diets claim that eating carbohydrates causes overeating and that a high protein, low carbohydrate diet is the way to “fight fat.”

However, this claim is quite controversial. Although some studies have compared low carbohydrate diets (most of which involve relatively high fat intake) against low fat diets, most were flawed, and no consistent findings have emerged to support either one of these diets—or any one particular diet, for that matter—as better than another for causing weight loss for all people.

Some experts believe it is simply a matter of calories: eat fewer calories than you burn up and the net result will be weight loss. The source of these calories, whether it is protein, carbohydrate, or fat, may not matter much at all. The real deciding factor is individual to each person—which type of low-calorie diet are you more likely to stick with?

Despite the uncertainly over which diet is best, many professional associations, including the American Dietetic Association and the American Heart Association, caution against the use of low carbohydrate diets. Here is an explanation of their position.

A Glimpse of Some Popular Low Carbohydrate Diets

Dr. Atkin’s New Diet Revolution

Theory: Excessive carbohydrates prevent the body from burning fat efficiently. A high intake of carbohydrate produces excessive amounts of insulin (a hormone that helps lower blood sugar), which can lead to overeating and obesity. Drastically reducing carbohydrate consumption causes the body to burn reserves of stored fat for energy.

• Carbohydrates are limited to 20 grams per day for the first two weeks and 0 to 60 grams per day during the ongoing weight loss phase. In the maintenance phase, carbohydrate intake ranges from 25 to 90 grams per day.

• Carbohydrates such as breads, pasta, most fruits, starchy vegetables, milk, and yogurt are avoided or limited.

• Unlimited amounts of protein and fat from meat, eggs, chicken, fish, butter, and vegetable oil are allowed

• If this diet is followed properly, all vitamin and mineral needs are met.

The Zone

Theory: The right combination of foods reduces levels of insulin and eicosanoid (a substance that’s involved in a variety of regulatory processes in the body), which reduce hunger and weight, increase mental relaxation and focus, and induce optimal health, high energy, and improved athletic performance.

• Rigid quantities of foods are eaten at specific times, and in a distribution of 40% carbohydrate, 30% protein, and 30% fat.

• Carbohydrates such as bread, pasta, and certain fruits and vegetables, are avoided or limited. Saturated fat and arachidonic acid are also avoided. The diet suggests eating lots of egg whites, nuts, olives, monounsaturated fats, and large amounts of low-glycemic-index* fruits and vegetables.

• The calorie level of the diet varies from person-to-person. But the key is that all meals should provide nutrients in the 40-30-30 proportion.

• When followed properly, this diet is low in saturated fat and meets vitamin and mineral needs.

*Glycemic index is a ranking given to a single food based on its effect on blood sugar levels. Foods with a high glycemic index tend to increase blood sugar levels and therefore increase the production of insulin.

Sugar Busters

Theory: Sugar and certain carbohydrates (those that have a high glycemic index) increase insulin levels, leading to fat storage and weight gain.

• Refined and processed carbohydrates, such as sugar, white flour, and all foods made from these ingredients, are eliminated. The diet also prohibits foods such as corn syrup, molasses, honey, soft drinks, and beer as well as starchy vegetables such as potatoes, corn, white rice, beets, and carrots.

• The diet encourages consuming lean meats, whole grains, and low-glycemic-index carbohydrates, such as high fiber vegetables and fruits. There are no restrictions on protein foods.

• When followed properly, this diet meets vitamin and mineral needs.

• Average daily caloric intake is 1200 calories per day.

The Seductiveness of Low Carbohydrate Diets

Despite the allure of carbohydrates, many people trying to lose weight are willing to abandon them at the beck and call of low carbohydrate diets. According to Cornell University Cooperative Extension, these diets attract followers for the following reasons:

They are often effectively marketed.

Weight loss gurus who are “health authorities,” such as doctors, have developed many of these diets, gaining the confidence of consumers. These diet gurus take grains of truth from scientific literature and use them to support the diets. For example, they use facts such as “ Americans are getting fatter” and “Americans are consuming more carbohydrates,” and turn it into “Americans are getting fatter because they are eating more carbohydrates,” which is only half of the truth (see Rise in Obesity, below). What they don’t mention is that people are eating more calories overall, which may be why they are gaining weight.

According to the International Food Information Council there is a lack of scientific research to back up the theories behind most popular low carbohydrate diets. However, there is also relatively little scientific evidence to support low fat diets for weight loss.

The initial weight loss is usually rapid, and therefore impressive.

People seem to lose weight faster on a low carbohydrate diet, especially in the beginning. What they often do not realize is that the initial rapid weight loss is due to water loss, not loss of body fat. Carbohydrate is stored in the liver as glycogen, which contains large numbers of water molecules. When glycogen is lost due to low carbohydrate intake, water is lost along with it. However, this effect wears out in the first week or two, and after that weight loss tends to follow the amount of calorie restriction.

Eating a low carbohydrate/high protein diet is supposed to help reduce hunger.

According to proponents, the low carb approach reduces hunger, and therefore allows people to stick with their diets. Indeed, some people on low carbohydrate/high protein do say they feel less hungry. However, it is not clear whether this reported effect is due to the diet itself, or to the enthusiasm that surrounds it. In addition, not everyone who tries these diets has the same experience.

Diets Not Likely to Be Effective in the Long Term

The initial rapid weight loss and lack of hunger make low carbohydrate diets seem effective. In fact, a study published in the July 2002 issue of The American Journal of Medicine suggested that a very low carbohydrate diet program led to sustained weight loss during a 6-month period.

However, according to nutrition experts at Cornell University Cooperative Extension, the American Heart Association, and the American Dietetic Association, low carbohydrate diets have one major obstacle to permanent weight loss: you can’t stay on them forever. Any diet that restricts a whole food group can be difficult to maintain in the long term. Nonetheless, much the same is true for low fat diets: people have difficulty sticking with them because fatty foods are satisfying and difficult for many people to do without.

However, responses are different from person to person. Each person has different tastes and is therefore able to restrict—or not—different types of foods (and therefore, different sources of calories) based on their particular food preferences.

Safety Concerns

Are low carbohydrate diets safe? They’re probably safe for most people, but there are some potential concerns.

• By reducing grain and fruit intake, and limiting choice of vegetables, these diets may lead to inadequate intake of vitamins and minerals. However, most of the reputable low carbohydrate diet plans take care to ensure proper nutrition.

• Eating large amounts of high-fat animal foods over a sustained period is thought to increase the risk of coronary heart disease and strokes. In addition, it might increase risk of several types of cancer.

• In people with kidney disease, a high protein diet can cause severe health problems. This has led to the suggestion that high protein diets can cause kidney problems in healthy people. However, this has not been proven.

• During conditions of very low carbohydrate intake (such as occurs during the induction phase of the Atkins diet), a condition known as ketosis occurs. The majority of people who undertake such ketogenic diets don’t seem to experience any problems, and many report feeling clear-headed and energetic. Nonetheless, ketosis may occasionally cause some adverse effects, including fatigue, nausea, reduced immunity, mental confusion, dehydration, constipation, kidney stones, gallstones, and increased tendency to bruise.

The Rise in Obesity: Are Carbohydrates to Blame?

Proponents of low carbohydrate diets claim that carbohydrates are the culprits in the obesity epidemic. However, according to the Physician’s Guide to Popular Low-Carbohydrate Weight Loss Diets, the dramatic increase in obesity is actually the result of the following factors:

• Decreased physical activity at work, at home and during leisure time

• Increased consumption of calories from larger portions at home and in restaurants (“super-sizing”)

• Greater consumption of high-fat or sweet foods

• Widespread availability of low-cost, good-tasting, high-calorie foods

So what’s the key to weight loss? There is no single plan that will work for everyone. Two main components that most experts seem to agree on are eating fewer calories and exercising more. For weight maintenance, it is essential to find a healthful eating pattern that you can maintain for the long-term, and to engage in regular physical activity.

RESOURCES:

International Food Information Council Foundation



American Dietetic Association



References:

Blackburn, G, Phillips, J, and Morreale, S. Physician’s guide to popular low-carbohydrate weight-loss diets. Cleveland Clinic Journal of Medicine, 2001; 68:761-774

American Dietetic Association website. Send Fad Diets Packing. Available at: Accessed: March 28, 2003

Westman, E, Yancy W. Edman, J et al. Effect of a 6-Month Adherence to a Very Low Carbohydrate Diet Program. American Journal of Medicine, 2002; 113: 30-36

St. Jeor, S, Howard, B, Prewitt, T, et al. Dietary protein and weight reduction: a statement for healthcare professionals from the nutrition committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. Circulation, 2001; 104: 1869

Cornell Cooperative Extension website. Low-Carbohydrate Diets: Heresy or Hype. Available at:

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Last reviewed June 2005 by Larry Frisch, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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