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• Isganaitis E, Lustig RH. Fast food, central nervous system insulin resistance, and obesity. 2005;25:2451–2462.
• Levine JA, Vander Weg MW, Hill JO, Klesges RC. Non-exercise activity thermogenesis: the crouching tiger hidden
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• Basu A, Devaraj S, Jialal I. Dietary factors that promote or retard inflammation. 2006;26:995–1001.
The Changing Roles of Dietary Carbohydrates
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From Simple to Complex
Amy E. Griel, Elizabeth H. Ruder, Penny M. Kris-Etherton
Abstract—The dietary recommendations made for carbohydrate intake by many organizations/agencies have changed over
time. Early recommendations were based on the need to ensure dietary sufficiency and focused on meeting micronutrient
intake requirements. Because carbohydrate-containing foods are a rich source of micronutrients, starches, grains, fruits,
and vegetables became the foundation of dietary guidance, including the base of the US Department of Agriculture’s
Food Guide Pyramid. Dietary sufficiency recommendations were followed by recommendations to reduce cholesterol
levels and the risk for cardiovascular disease; reduction in total fat (and hence saturated fat) predominated. Beginning
in the 1970s, carbohydrates were recommended as the preferred substitute for fat by the American Heart Association
and others to achieve the recommended successive reductions in total fat and low-density lipoprotein cholesterol
(LDL-C). Additional research on fats and fatty acids found that monounsaturated fatty acids could serve as an alternative
substitution for saturated fats, providing equivalent lowering of LDL-C without concomitant reductions in high-density
lipoprotein cholesterol and increases in triglycerides witnessed when carbohydrates replace saturated fat. This research
led to a sharper focus in the guidelines in the 1990s toward restricting saturated fat and liberalizing a range of intake
of total fat. Higher-fat diets, still low in saturated fatty acids, became alternative strategies to lower-fat diets. As the
population has become increasingly overweight and obese, the emergence of the metabolic syndrome and its associated
disruptions in glucose and lipid metabolism has led to reconsiderations of the role of carbohydrate-containing foods in
the American diet. Consequently, a review of the evidence for and against high-carbohydrate diets is important to put
this controversy into perspective. The current dietary recommendations for carbohydrate intake are supported by
the evidence. (Arterioscler Thromb Vasc Biol. 2006;26:1958-1965.)
Key Words: carbohydrates 䡲 dietary patterns 䡲 nutrition 䡲 cardiovascular risk
D
49.0% kcal for men and from 44.8% kcal to 49.7% kcal for
women.1 The increase in carbohydrate intake has been
accompanied by an apparent increase in energy intake (2450
kcal to 2618 kcal for men and 1542 kcal to 1877 kcal for
women; P⬍0.01), and a corresponding decrease in the
percentage of calories from total fat (36.9% to 32.8%;
P⬍0.01 for men and 36.1% to 32.8%; P⬍0.01 for women).1
ata from the National Health and Nutrition Examination
Surveys have been collected by the Centers for Disease
Control since the 1970s to track dietary habits of Americans.
Careful comparison of these surveys, taking into account
improved methodologies for collecting intake data,1–3 indicate that over the past 25 years, the consumption of carbohydrate in the United States has increased from 42.4% kcal to
Original received February 22, 2006; final version accepted June 9, 2006.
From the Department of Nutritional Sciences (A.E.G., E.H.R., P.M.K.-E.) and Department of Integrative Biosciences (A.E.G., P.M.K.-E.), the
Pennsylvania State University, University Park, Pa.
Correspondence to Penny Kris-Etherton, the Pennsylvania State University, University Park, PA 16802. E-mail [email protected]
© 2006 American Heart Association, Inc.
Arterioscler Thromb Vasc Biol. is available at http://www.atvbaha.org
1958
DOI: 10.1161/01.ATV.0000233384.97125.bd
Griel et al
Based on our best estimates, Americans consume more
calories and more carbohydrates than ever before.
The increase in carbohydrate content of the diet brings the
dietary intake of carbohydrates well within the range of
current dietary guidelines. Specifically, the Institute of Medicine of the National Academies recommends a diet that
provides 45% to 65% kcal from carbohydrates, 10% to 35%
kcal from protein, and 20% to 35% kcal from total fat, while
keeping saturated fat, trans fat and dietary cholesterol low.4
These recommendations are consistent with the Dietary
Guidelines for Americans 2005.5 The American Heart Association and the National Cholesterol Education Program
recommend a diet that provides 50% to 60% kcal from
carbohydrates. Irrespective of total calories, Americans are
consuming the recommended percent calories from carbohydrates, but how does the quality of these carbohydrates affect
lipids and lipoproteins?
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Lipid Modifying Effects of Carbohydrate
Rich Diets
It has been universally documented that when carbohydrates
are substituted for saturated fat, a reduction in total and
low-density lipoprotein cholesterol (LDL-C) is observed.6 –18
These observations led to the development of a 3-step
American Heart Association diet for the treatment of hypercholesterolemia, in which successive reductions in total fat
were recommended for control of lipids. High-carbohydrate
diets remained the diet of choice until research on monounsaturated fatty acids, a more ubiquitous fatty acid than
polyunsaturated fatty acids, found that monounsaturates were
neutral in their effect on LDL-C.19 Moderate-fat, moderatecarbohydrate diets could achieve LDL-C reductions equivalent to high-carbohydrate, low-fat diets.20 As the monounsaturated fat findings were replicated, later versions of the
American Heart Association dietary guidelines appropriately
focused on diets for reducing LDL-C via restrictions in
saturated fat, rather than total fat.
An additional consequence to fat restricted diets is their
propensity to increase fasting triglycerides (TG) and reduce
high-density lipoprotein cholesterol (HDL-C). Within the
range of total fat (18% to 40% kcal) evaluated in controlled
feeding studies, there is a linear dose-response relationship
between total fat content of the diet and the changes in
HDL-C and TG.4 Weighted least-squares regression analysis
revealed that for every 5% decrease in total fat, HDL-C levels
would be expected to decrease by 2.2% and TG levels would
be expected to increase 6%. Levels of Lp(a), a lesser studied
atherogenic lipoprotein, also increase in a stepwise manner as
levels of dietary total and saturated fat are reduced.21,22
Results from several recent clinical trials are highlighted in
Table 1. The reduction in total fat in the recently published
Women’s Health Initiative would have been expected to elicit
⬇4.4% reduction in HDL-C and ⬇12% increase in TG levels.
The actual changes observed in this study were a 1.2%
decrease in HDL-C and a 0.7% increase in TG levels.23 The
investigators attribute this more favorable lipid change to the
quality of the carbohydrate emphasized in the diet (fruits,
vegetables, and whole grains). Similarly, in the OmniHeart
Trial, a diet rich in carbohydrates resulted in only a modest
Dietary Carbohydrates
1959
decrease in HDL-C (⫺2.8%) and a negligible increase in TG
(0.1%), compared with baseline.24 In the OmniHeart Trial, 3
diets were compared: high-carbohydrate, high-protein, and
high-unsaturated-fat. As expected, the high-carbohydrate diet
was associated with higher TG than the other diets; however,
the high-protein diet resulted in a lower HDL-C than the
high-carbohydrate diet. In the Portfolio Diet Study25 TG were
decreased (⫺16.8 mg/dL) and the HDL-C decrease was
blunted (⫺3.1 mg/dL), compared with the reduction observed
on the control diet. The TG response observed in the DASH
diet study (⫹3.5%) was much less than would have been
predicted (⫹12%) given the 10% reduction in total fat,
compared with the control diet. In these 4 newer trials,
high-carbohydrate diets continued to improve the total cholesterol (TC)/HDL-C ratio, as observed in earlier trials. Thus,
new data consistently support the current range for carbohydrate intake.
Enter the Metabolic Syndrome
Approximately 47 million US residents have the metabolic
syndrome (MetS). It is estimated that the MetS soon will
surpass cigarette smoking as the number one risk factor for
cardiovascular disease risk in the US population. The National Cholesterol Education Adult Treatment Panel III defined the MetS as the presence of three or more of the
following 5 factors: (1) abdominal obesity (waist circumference ⬎102 cm for males and ⬎99 cm for females); (2)
elevated triglycerides ⬎150 mg/dL; (3) low HDL-C (⬍40
mg/dL for men and ⬍50 mg/dL for women); and (4)
hypertension (⬎130/⬎85 mm Hg for systolic blood pressure/
diastolic blood pressure) and elevated fasting glucose (⬎110
mg/dL).27a Lipid abnormalities that are present in the MetS
but not included in its definition are small, dense LDL
particles. Often referred to as the “lipid triad” (high triglycerides, low HDL-C and small, dense LDL particles) these
lipid abnormalities are associated with elevated blood pressure, insulin resistance, and a prothrombotic state.
Aside from lowering LDL-C, diets enriched in carbohydrate are expected to have 2 adverse effects in patients with
MetS.26 First, high carbohydrate intakes require higher insulin levels for postprandial metabolism. In the insulin-resistant
state of MetS, the high carbohydrate load will raise postprandial glucose levels and in some patients raise fasting glucose
levels if the carbohydrate load exceeds insulin secretion
capacity. Second, if patients with MetS can compensate with
greater insulin secretion, the increased magnitude of hyperinsulinemia would be expected to worsen the TG/HDL-C
abnormalities already present in MetS.26
Feeding studies support this hypothesis. Carbohydrateenriched diets have been shown to induce atherogenic dyslipidemia,27a,27b which is characterized by small dense LDL
particles, high TG levels, and low HDL-C levels. An analysis
of several short-term feeding studies indicate that across a
wide range of dietary carbohydrate (40% to 80% kcal) and fat
(5% to 45% kcal) intake there is a strong linear relationship
(r⫽0.93; P⬍0.0001) between the prevalence of LDL phenotype B (small dense LDL) and the percentage of calories from
dietary carbohydrates.28 This dyslipidemia appears more
pronounced in sedentary, overweight or obese populations.29
1960
Arterioscler Thromb Vasc Biol.
TABLE 1.
Recent Clinical Trials Evaluating Reduced-Fat/High-Carbohydrate Diets
Study
September 2006
Study Design
Length of Intervention
Subject Population
Diet
Women’s Health Initiative
Trial (2006)23
Randomized, controlled
free-living study
Mean follow-up: 8.1 year;
CVD risk markers assessed
at 3 years
48 835 postmenopausal
women
Reduction in total fat (target:
20% en) rich in fruits,
vegetables and whole grains
OmniHeart Trial (2005)24
Randomized, crossover,
controlled feeding study
Three 6-week feeding
periods
164 men and women with
pre-HTN or stage I HTN
Diet rich in carbohydrates
Control diet
Diet rich in protein
Diet rich in unsaturated fat
Portfolio Diet Study (2003)25
Randomized, controlled
feeding study
1 month
46 men and women with
elevated cholesterol
Low-fat, high-fiber vegetarian
diet
Control diet
67
DASH diet Trial (2001)
Randomized, controlled
free-living study
8 weeks
436 men and women with
pre-HTN or stage I HTN
Low-fat diet rich in fruits,
vegetables, whole grains and
low-fat dairy
Control diet
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CHO indicates dietary carbohydrate; HDL, high-density lipoproteins; HTN, hypertension; LDL, low-density lipoproteins; MUFA, monounsaturated fatty acids; PUFA,
polyunsaturated fatty acids; SFA, saturated fatty acids; TC, total cholesterol; TG, triglycerides.
a
% Total energy; bMean change from baseline; cMean change from control diet.
*P⬍0.0001 when compared to control diet; †P⬍0.005 when compared to control diet; ‡P⬍0.05 when compared to control diet, §P⬍0.001 when compared to
carbohydrate-rich diet; ¶P⬍0.05 when compared to carbohydrate-rich diet; 储P⬍0.001 when compared to protein-rich diet; **P⬍0.05 when compared to protein-rich
diet.
Not All Carbohydrates Are Created Equal
As with dietary fat, all carbohydrates are not chemically
equivalent. Carbohydrates can be classified into the broad
categories of simple or complex carbohydrates. Simple carbohydrates can be further broken-down into monosaccharides
(eg, glucose and fructose) and disaccharides (eg, sucrose and
lactose). Complex carbohydrates are either starch or fiber;
fiber has several possible categorizations (eg, soluble versus
insoluble, nondigestible versus lignan versus functional fiber
provided from nondietary sources). Thus, the term carbohydrate describes a diverse macronutrient and recommendations
regarding total carbohydrate intake reveal little about how the
recommendations should be implemented using foods. Because processed foods containing added sugars are replacing
other foods in the American diet, simple carbohydrate intake
has increased to a greater extent than complex carbohydrates
in the diet and now provides nearly one-third of total dietary
carbohydrate intake (Figure).30
The Institute of Medicine of the National Academies has
been acutely aware of differences within the carbohydrate
subset and has set additional guidelines for fiber and added
sugar at 14 g per 1000 kcal and 25% or less of energy from
added sugars.4,31 In addition, practical advice issued by the
US Dietary Guidelines, 2005, identifies a category of “discretionary calories” (13% of intake), which could be consumed as added sugars.5 These recommended amounts are
not specific amounts to achieve, but rather an amount that
should not be exceeded.
Simple Carbohydrates and Added Sugars:
Fructose Versus Glucose
Simple carbohydrates, or sugars, are not all equivalent in their
biologic effects. Sucrose, the carbohydrate found in table
sugar, is sugar easily refined from sugar beets and sugar cane.
As a disaccharide composed of fructose and glucose, sucrose
has been used as a sweetener for centuries and until the 1990s
was the major source of per capita sweetener in the American
diet. Fructose is a monosaccharide named for the sweetener
found in fruit. In the 1970s an inexpensive process was
developed to convert cornstarch into high-fructose corn
syrup. This syrup is a mixture of fructose and glucose
monosaccharides. With the introduction of high-fructose corn
syrup, American diets have become sweeter. Specifically, per
capita consumption of sugar in the United States is 46.4
pounds, compared with 55.7 pounds for corn sweeteners
(high-fructose corn syrup, glucose syrup, and dextrose). Food
products which contribute the most to this increase in simple
sugar consumption are grain products, including cakes, cookies, and cereals at 42.3%, and sugar, sweets, and beverages at
38.2% of total sugar consumption.32 According to data from
the US Department of Agriculture’s Continuing Survey of
Food Intakes of Individuals (CSFII) 1994 to 1996 and 1998,
added sugars currently contribute 24% to 30% of dietary
carbohydrates; the contribution of added sugar intake from
fructose per se is estimated at 7% to 8% of calories, whereas
fructose consumption from both added sugars and naturally
occurring sugars in fruit and fruit juices is ⬇12% calories.33
Fructose metabolism differs from that of sucrose and
glucose, and consequently has different implications for
health. The majority of fructose metabolism occurs in the
hepatic cytoplasm,34 where it is phosphorylated by fructokinase to fructose-1-phosphate. Fructose-1-phosphate is then
catalyzed by aldolase B to form the dihydroxyacetone-3
phosphate and glyceraldehyde. These triose phosphates continue through the Emden-Meyerhof pathway yielding pyruvate, which enters the mitochondria for the citric acid cycle,
or glycerol-3-phosphate, which provides the glycerol moiety
for triacylglycerol synthesis. Compared with glucose metab-
Griel et al
TABLE 1.
Dietary Carbohydrates
1961
Continued
Lipid Responseb
Diet Composition
CHOa
Proteina
Total Fata
SFAa
MUFAa
PUFAa
54
18
29
10
11
6
48
17
35
12
13
7
58
15
27
6
13
8
48
25
27
6
13
8
48
15
37
6
21
10
48
22
30
6
13
53
22
25
5
10
TC (mg/dL)
TC/HDL
TG (mg/dL)
⫺0.2
1.0
⫺0.3
⫺0.1
1.0
⫺1.4
⫺0.14
0.1
⫺14.2¶
⫺2.6¶
⫺0.20
⫺13.1
⫺0.3¶储
⫺0.29
⫺58.7†
⫺52.5†
⫺3.1†
⫺1.05
8
⫺15.4
⫺14.3
⫺4.6
0.25
⫺0.27
⫺10.2‡
LDL (mg/dL)
HDL (mg/dL)
⫺9.7‡
⫺0.7
⫺6.9
⫺6.2
⫺12.4
⫺11.6
⫺19.9§
⫺15.4¶储
10
58
18
27
7
10
8
⫺14.2
⫺11.0
⫺3.8
50
14
37
14
13
7
—
—
—
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olism, where citrate produced by mitochondria inhibits the
enzyme phosphofructokinase, shutting off additional catabolism of glucose to fructose-1-phosphate, fructose catabolism
proceeds without feedback regulation. Thus, when large
quantities of fructose are consumed, the system can be
flooded with intermediates including acetyl coenzyme A for
lipogenesis and triglyceride synthesis. Clinical studies have
demonstrated that fructose consumption results in substantial
increases in lipogenesis compared with consumption of eucaloric amounts of glucose.35
Several studies have compared the effects of glucose
versus fructose on lipid metabolism. Bantle et al36 compared
the effects of consuming 17% of calories from either fructose
or glucose for 6 weeks. Plasma TG levels significantly
increased in men (P⬍0.001) but not women (P⬍0.72) after
the fructose period. LDL-C was higher at the 4-week time
point during fructose feeding, but this difference was no
c*
c*
c*
⫺16.4§
⫺9.3¶**
⫺16.8†
16.8
3.3c*
—
longer apparent at 6 weeks.36 Havel et al37,38a evaluated the
effects of consuming a chronic diet of either 25% kcal as
fructose or glucose on the postprandial triglyceride concentrations of overweight or obese women with normal triglycerides. Postprandial triglyceride concentration increased in
the area under the curve over 14 hours in the subjects
consuming the 25% fructose diet compared with their baseline complex carbohydrate diet. The magnitude of the increase was greater at 10 weeks on the fructose treatment
compared with 2 weeks. At 10 weeks, apolipoprotein B levels
increased 11.7⫹3.7% among subjects consuming 25% fructose but no such increase was observed on the glucose
treatment. Postprandial triglycerides were not significantly
altered from the baseline diet at 10 weeks for either glucose
or fructose treatments.
In summary, simple carbohydrates are, by their namesake
rapidly absorbed. The predominant effect on serum glucose
Availability of added sugar for Americans 2 years of age and older.
1962
Arterioscler Thromb Vasc Biol.
TABLE 2.
Dietary Recommendations for Carbohydrate-Rich Foods at the 2000-Calorie Level31
Food Groups and Subgroups
Fruit Group
September 2006
USDA Food Guide Amount
2 cups (4 servings)
Equivalent Amounts
Half cup equivalent is:
Nutrients
Potassium, folate, vitamin C, dietary fiber
Half cup fresh, frozen, or canned fruit
1 medium fruit
One-quarter cup dried fruit
Half cup 100% fruit juice
Vegetable Group
Dark green vegetables
2.5 cups/day
3 cups/wk
Orange vegetables
Half cup equivalent is:
Half cup of cut-up raw or cooked vegetable
Potassium, vitamin A, vitamin C, vitamin E,
folate, dietary fiber
1 cup raw leafy vegetable
Legumes (dry beans)
2 cups/wk
Starchy vegetables
3 cups/wk
Other vegetables
3 cups/wk
Half cup vegetable juice
6.5 cups/wk
Grain Group
6-oz equivalents
1-oz equivalent is:
1 slice bread
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Whole grains
3-oz equivalents
Other grains
3-oz equivalents
Milk Group
3 cups
1 cup dry cereal
B vitamins (thiamin, riboflavin, niacin, and
folate), and minerals (iron, magnesium, and
selenium), dietary fiber
Half cup cooked rice, pasta, cereal
1 cup equivalent is:
Calcium, potassium, vitamin D
1 cup low-fat/fat-free milk, yogurt
● 1.5 oz low-fat or fat-free natural cheese
2 oz low-fat or fat-free processed cheese
The USDA Food Guide recommendation for the meats and beans group is 5.5-oz equivalents/day; 27 grams (6 tsp)/day of oil are recommended.31
and lipid metabolism depends on the type of simple carbohydrate and the insulin resistant state of the individual
ingesting the food or beverage. Simple carbohydrates such as
glucose may raise postprandial glucose in patients with MetS;
high-fructose corn syrup may improve postprandial glucose
at the expense of increasing postprandial triglycerides. Neither effect should be touted as an improvement in cardiovascular risk. Moreover, chronic fructose consumption substantially increases lipogenesis, resulting in increases in
triglycerides compared to consumption of eucaloric amounts
of glucose.38b
Complex Carbohydrates: A Focus on Fiber
In contrast to the deleterious effects of simple carbohydrates
on lipid and glucose metabolism, dietary fiber has demonstrated consistent beneficial effects on lipid metabolism.
Numerous studies have shown that diets rich in soluble fiber
lower blood cholesterol levels, whereas diets rich in insoluble
fiber have no effect on lipids and lipoproteins, but benefit
laxation.39 – 45 The major soluble fibers are ␤-glucan (found in
oats, barley, and yeast), psyllium (found in husks of blonde
psyllium seed), and pectin (found in fruit). Several properties
of soluble fiber, viscosity, bile acid binding capacity, and
potential cholesterol synthesis-inhibiting capacity after fermentation in the colon,46,47 contribute to its cholesterollowering effect.48
A meta-analysis of 8 studies reported that 10 g per day of
psyllium reduced TC and LDL-C levels by 4% and 7%,
respectively.49 Another meta-analysis of 67 controlled dietary
studies50 found that for each gram of soluble fiber from oats,
psyllium, pectin, or guar gum, TC concentrations decreased
by 1.42, 1.10, 2.69, and 1.13 mg/dL, respectively. Similarly,
LDL-C levels decreased by 1.23, 1.11, 1.96, and 1.20 mg/dL,
respectively, demonstrating comparable cholesterol-lowering
effects of these soluble fibers. In a study of normolipidemic
and normotensive subjects (n⫽53), an increase in dietary
fiber intake (30.5 g/d total fiber and 4.11 g/d soluble fiber)
significantly reduced LDL-C (12.8%), but did not affect TG
or HDL-C levels.51 The addition of 3 or 6 g/d ␤-glucan from
barley to a Step I diet (55% carbohydrate, 16% protein, 31%
total fat) has been shown to lower TC (4% and 9%, respectively) and LDL-C (13.8% and 17.4%, respectively) concentrations in mildly hypercholesterolemic men and women.52
Translating the disparate effects of simple versus complex
carbohydrates, easily shown in experimental feeding studies,
into dietary choices has been difficult because most foods
contain both simple and complex carbohydrates. Two measures to combine the overall food effect, glycemic index (GI)
and glycemic load (GL), have been proposed. The GI is
defined as the area under the 2-hour glycemic curve after
consumption of a food containing 50 grams of carbohydrate,
divided by the area under the curve for a standard food (white
bread or glucose) that also contains 50 grams of
carbohydrate.53,54a The GL is defined as the product of the GI
of that food multiplied by its carbohydrate content. Classification of carbohydrate by GI and GL may be superior to
classification by the type or source of carbohydrate for
elucidating the effects of carbohydrate-rich foods on glucose
and lipid metabolism, although dietary recommendations
have not yet been established.54b Clinical studies generally
show that when the amount of carbohydrate is held constant,
foods with a higher GI increase fasting TG levels.55 Low-GI
Griel et al
diets also may protect against HDL-C–lowering associated
with traditional high-carbohydrate diets.56 The large variability in response to specific foods and mixed meals composed
of foods with different GI/GL has led to somewhat unwieldy
consideration of this index in dietary recommendations.
Simple food descriptions continue to predominate in dietary
carbohydrate guidelines (eg, whole grains, no added sugars,
etc).
Carbohydrates and Weight Loss
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Weight loss is the metabolic consequence of reduced caloric
intake. How dietary carbohydrate recommendations fit within
weight loss programs depends on the style of the dietary
change. Extreme diets, either very high in carbohydrates or
very low in carbohydrates in which energy intake is similarly
restricted, have been successful at achieving weight loss.57
For example, the Pritikin Program, a lifestyle intervention
program that includes a high-complex-carbohydrate, highfiber (35 to 40 g/1000 kcal), very low-fat (⬍10% kcal), and
low-cholesterol (⬍25 mg/d) diet and exercise component, has
been shown to reduce weight, TC, and TG by 5%, 21%, and
50%, respectively.58 Participants are satiated on high-fiber/
low-energy density diets that are hypocaloric. In contrast, The
Atkins Diet, a diet intervention program, produces a caloric
restriction through the elimination of carbohydratecontaining foods such as bread, pasta, and fruit, can also
produce weight loss. Participants report satiety from high
protein meals; the ketotic effect of very low carbohydrate
intakes also reduces hunger. Given the many weight loss
diets, an important question is whether there is one weight
loss program that is better than others, and does the carbohydrate content of the weight-loss diet predict its success?
A recent study compared the 1-year effects of 4 weight loss
diets (Atkins, Ornish, Weight Watchers, Zone) conducted in
an outpatient, diet counseling setting.59 The weight loss diets
varied appreciably in their carbohydrate content (high, Ornish; intermediate, Zone and Weight Watchers; very low,
Atkins); for the first few months participants followed their
assigned intakes. However, throughout the full year there was
a gradual drift in dietary intakes so that the 1-year macronutrient profiles of the four diet groups were not markedly
different (39% to 48% kcal carbohydrate; 31% to 39% kcal
total fat), but rather similar to baseline values. After 12
months there was a very modest and similar weight loss (2 to
3 kg) in subjects following the different diets, with comparable decreases in LDL-C (range, 7.1 to 12.6 mg/dL) and the
TC:HDL-C ratio observed. This study suggests that extremes
in dietary intake are not sustainable over the long term for
most individuals. It also suggests that any diet program can
achieve small but sustainable weight loss in motivated
participants.
Practical Recommendations and Conclusions
Dietary recommendations suggest moderate amounts of both
carbohydrate (45% to 65% kcal) and fat (20% to 35% kcal) in
the diet. Dietary patterns within these ranges for carbohydrate
and fat have been shown to promote weight loss,57,60,61 lower
TG levels,57,61 maintain HDL-C levels,57 and promote maintenance of reduced body weight.57,60 In overweight patients,
Dietary Carbohydrates
1963
reduced-fat, high-carbohydrate diets have proven effective
for weight loss,58,62,63 the prevention of type 2 diabetes,65 and
MetS.66 Of note, a low-fat high carbohydrate diet followed
over a period of ⬇7 years does not result in weight gain in
postmenopausal women. 64a In addition, moderate-fat
Mediterranean-style diets have also been proven effective for
weight loss67,68 and the prevention of the MetS69 and CVD.70
An important point to consider with all of these interventions
is that the reduced-fat, high-carbohydrate diets tested were
used in conjunction with other lifestyle changes, including
dietary patterns emphasizing whole grains, fruits, and vegetables and lifestyle patterns increasing daily physical activity,
consistent with new diet and lifestyle recommendations from
the American Heart Association.71 If the American dietary
pattern continues to incorporate additional low-fiber refined
carbohydrate foods, added sugars, and more high-fructose
corn syrup-sweetened foods, carbohydrate intake could contribute to an increase in cardiovascular disease risk factors.
Clinicians should not only follow the macronutrient recommendations but also pay attention to the food patterns that
meet current dietary recommendations. Recommendations for
dietary carbohydrates are only met when fruits, vegetables,
whole grains, and nonfat dairy products are included in the
daily diet (Table 2).
Disclosures
None.
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The Changing Roles of Dietary Carbohydrates: From Simple to Complex
Amy E. Griel, Elizabeth H. Ruder and Penny M. Kris-Etherton
Arterioscler Thromb Vasc Biol. 2006;26:1958-1965; originally published online June 22, 2006;
doi: 10.1161/01.ATV.0000233384.97125.bd
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