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:
Dairy products and dairy substitutes:
- Nonfat milk and milk products
- Unsweetened nonfat yogurt
- Soy beverages
Fats and oils:
- 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
Protein (meat, poultry, fish,
eggs, nuts, and beans):
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
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Brehm BJ, Seeley RJ, Daniels SR, D'Alessio DA. A randomized trial
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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
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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
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Fleming RM. The effect of high-protein diets on coronary blood flow.
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Sondike SB, Copperman N, Jacobson MS. Effects of a low-carbohydrate
diet on weight loss and cardiovascular risk factor in overweight adolescents. J
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Copyright © 2009 Truestar Health & Healthnotes, Inc. All rights reserved.
www.truestarhealth.com
The information presented in Truestar Healthnotes is for informational
purposes only. It is based on scientific studies (human, animal, or in vitro),
clinical experience, or traditional usage as cited in each article. The results reported may
not necessarily occur in all individuals. For many of the conditions discussed, treatment with
prescription or over-the-counter medication is also available. Consult your doctor,
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before making any changes in prescribed medications. Information expires September 2010.
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