Many currently popular diets are designed to lower carbohydrate consumption, but they frequently differ from each other in important ways. Some (e.g., Atkins, Protein Power) restrict carbohydrate to the point that a condition of ketosis is reached (ketosis is a condition wherein the body breaks down fats into ketones, which can either be used either as energy, or eliminated from the body via the breath or urine. Other low carbohydrate diets (e.g., Zone, Life Without Bread) are less restrictive, and some (e.g., Sugar Busters) seek to eliminate only sugars and foods that raise blood sugar levels excessively (e.g., high-glycemic-index foods). When total carbohydrate intake is reduced, protein and fat intake represent a larger proportion of the diet. Some low carbohydrate diets (e.g., Zone, Insulin Resistance Diet) recommend replacing carbohydrate with healthful sources of protein and fat; others do not restrict any type of protein or fat sources (e.g., Atkins, Protein Power).
Why do people follow this diet?
Many people expect to have better success with weight loss and control of blood pressure, blood sugar, and blood cholesterol levels by following a low-carbohydrate diet.
What do the advocates say?
Advocates contend that the high amount of carbohydrates in typical modern diets is unnatural for humans, who evolved for hundreds of thousands of years while eating a low-carbohydrate diet. They say that the current overconsumption of carbohydrates has led to increasing problems with obesity, diabetes, and other health problems. High-carbohydrate diets are presumed to result in higher insulin levels, which may lead to insulin resistance and related metabolic disorders such as high triglycerides, low HDL ("good") cholesterol, and high blood pressure.
Some scientific authorities do recommend that people with the insulin resistance syndrome (IRS) or type 2 diabetes avoid high-carbohydrate diets, and some recommend a diet lower in carbohydrate than current public health guidelines suggest. Researchers have demonstrated that replacing carbohydrate in the diet with either fat or protein lowers blood triglycerides and raises HDL ("good") cholesterol, and a few studies have also reported improved blood sugar control and increased loss of weight and body fat resulting from these dietary changes.
What do the critics say?
Many nutrition experts disagree with the basic premise of low-carbohydrate diets—the notion that high-carbohydrate, low-fat diets cause obesity and other health problems. In one argument, some nutritionists point to the traditional Japanese diet that is very high in carbohydrates, low in protein, and very low in fat, yet is associated with good health and normal weight in people who follow that diet. Rather than attributing obesity and other problems to carbohydrate intake, these critics blame the overconsumption of calories (from any source) and lack of physical activity as the primary causes of these health disorders.
Critics concede that low-carbohydrate dieters often experience significant weight loss during the initial stages of the diet. However, these critics argue that these diets often have a diuretic effect (i.e., promote water loss) and that the initial weight loss is due to water loss, not fat loss. Recent research suggests that some people may lose more weight over the course of several months on a low-carbohydrate diet than on one that is equal in calories but higher in carbohydrates, but few studies have been done to determine the long-term effects, good or bad, of low-carbohydrate diets.
In addition, many authorities are concerned that a lower-carbohydrate diet may result in higher calorie intake from fat, which could lead to more difficulties with overweight, insulin resistance, high cholesterol levels, and heart disease risk. Studies of low-carbohydrate diets that are also low in calories and promote weight loss often do not support these concerns, but research on the effects of higher calorie versions of these diets is scarce and conflicting. Increased protein intake as a result of avoiding carbohydrates is also a concern for some critics, since some high-protein diets may increase the risk of osteoporosis, kidney stones, and some cancers.
Critics also express concern that the lack of grains, fruits, and vegetables in low-carbohydrate diets may lead to deficiencies of key nutrients, including fiber, vitamin C, folic acid, and several minerals.
Best bets
The human body works best with a diet that includes some carbohydrate. Recently a Recommended Dietary Allowance for carbohydrate was set at a minimum of 130 grams per day. This would represent 26% of the calories in a 2,000-calorie-per-day diet, which would still be considered a low-carbohydrate diet, but would avoid the potential hazards of more restrictive diets, including symptoms of ketosis (nausea, weakness, dehydration, light-headedness, and irritability) and loss of body protein.
Certain dietary fats and their food sources are associated with good health and reduction of disease risks. Foods high in unsaturated fats that are free of trans fatty acids have been associated with protection from atherosclerosis, heart disease, insulin resistance, and other health concerns. Examples of these foods include olive oil, fatty fish, flaxseeds, and nuts. However, replacing high-carbohydrate foods with these foods may increase calorie intake if portion sizes are not kept moderate.
Certain sources of dietary protein are more healthful than others. Protein foods containing significant amounts of saturated fat and cholesterol have been associated with many diseases, including heart attacks, type 2 diabetes, insulin resistance, and gallstones; choosing low-fat and low-saturated-fat protein foods can minimize these risks. High meat intake, even of leaner cuts, may increase risk of osteoporosis and kidney stones. Well-done meat or meat that has been preserved with nitrites should be avoided, or kept to a minimum, due to links with cancer. The most healthful choices for increasing protein intake are fish and seafood, low- or nonfat dairy products, legumes (including soyfoods), nuts, and seeds.
Even a low-carbohydrate diet should emphasize healthful carbohydrate sources. Whole grains, fruits, and vegetables supply fiber and many important micronutrients. People with diabetes or insulin resistance may find that choosing carbohydrate foods with a low-glycemic index improves their blood sugar, blood cholesterol, and triglycerides; helps them better control their weight; and improves symptoms associated with their health conditions.
Bread, cereal, rice, and pasta:
- Whole wheat and whole grain breads
- Breads containing whole, intact grains and seeds (millet, flaxseed, etc)
- Whole wheat pasta and noodles
- Brown rice, basmati rice
- Barley, buckwheat
- Whole grain cereals, muesli
- Whole wheat pita, chapatis
- Oatmeal
Dairy products and dairy substitutes:
- Non-hydrogenated olive oil, canola oil, peanut oil
- Non-hydrogenated corn oil, flaxseed oil, hemp oil, pumpkin seed oil, safflower oil, sesame oil, soybean oil, sunflower oil
Are there any groups or books associated with this diet?
Life Without Bread: How a Low-Carbohydrate Diet Can Save Your Life by Christian B. Allan, PhD & Wolfgang Lutz, MD. Los Angeles: Keats Publishing, 2000.
Sugar Busters by H. Leighton Steward, Morrison C. Bethea, Sam S. Andrews, et al. New York: Ballantine Books, 2002.
The Insulin Resistance Diet: How to Turn Off Your Body's Fat-Making Machine by Cheryle R. Hart and Mary Kay Grossman. Chicago: McGraw-Hill, 2001.
The Zone by Barry Sears. New York: Harper Audio, 1998.
The Soy Zone by Barry Sears. New York: Regan Books, 2000.
Official Web site for the Atkins Diet
www.atkinsdiet.com
Zone Diet Web site
www.zoneperfect.com
The American Dietetics Association Web site provides information on eating healthy
www.eatright.org
Bibliography
Bravata DM, Sanders L, Huang J, et al. Efficacy and safety of low-carbohydrate diets: a systematic review. JAMA 2003;289:1837–50 [review].
Brehm BJ, Seeley RJ, Daniels SR, D'Alessio DA. A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. J Clin Endocrinol Metab 2003;88:1617–23.
Kennedy ET, Bowman SA, Spence JT, et al. Popular diets: correlation to health, nutrition, and obesity. J Am Diet Assoc 2001;101:411–20 [review].
Meckling KA, Gauthier M, Grubb R, Sanford J. Effects of a hypocaloric, low-carbohydrate diet on weight loss, blood lipids, blood pressure, glucose tolerance, and body composition in free-living overweight women. Can J Physiol Pharmacol 2002;80:1095–105.
Reaven GM. Do high carbohydrate diets prevent the development or attenuate the manifestations (or both) of syndrome X? A viewpoint strongly against. Curr Opin Lipidol 1997;8:23–7 [review].
Stein, K. High-protein, low-carbohydrate diets: Do they work? J Am Diet Assoc 2000;100:760–1.
Fleming RM. The effect of high-protein diets on coronary blood flow. Angiology 2000;51:817–26.
Sondike SB, Copperman N, Jacobson MS. Effects of a low-carbohydrate diet on weight loss and cardiovascular risk factor in overweight adolescents. J Pediatr 2003;142:253–8.
Westman EC, Yancy WS, Edman JS, et al. Effect of 6-month adherence to a very low carbohydrate diet program. Am J Med 2002;113:30–6.
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2006-09-07
