Research Supporting Low Carb Diet
Research Supporting a Low-Carb Diet
Studies show that following a low-carbohydrate, high-fat diet results in
weight loss, lower cholesterol, and stable blood glucose.
The table below compares two independent studies performed by Dr. Dean
Ornish, who promotes a low-fat diet, and Dr. Robert Atkins, who supports
weight loss through carbohydrate restriction.
Ornish and Atkins Diets ComparedINITIAL CONDITIONSORNISH
(low fat)ATKINS
(low carbohydrate)
Age5655
Starting weight201195
Body Mass Index28.428.1
DIET RESULTSORNISH
(low fat)ATKINS
(low carbohydrate)
Cholesterol change-24%-13%
HDL (GOOD) Cholesterol- 3%+60%
Triglycerides (BAD)+75%-82%
Weight-12%-19%
Results of other studies…
A number of short term studies, mostly in the 50’s and 60’s, showed a marked
advantage in weight loss from high protein, low carbohydrate diets compared
to diets higher in carbohydrate. (Chuck Forsberg, “Adiposity 101″)
Compared to high carbohydrate diets, a high protein low carbohydrate diet
preserved lean body mass and improved glucose oxidation. (METABOLISM Dec
1994 43:12 1481-7)
In the presence of carbohydrate, the preferred fuel is glucose and the
capacity to mobilize fat is limited. Factors that increase blood glucose
during dieting may stimulate insulin release and all the metabolic sequelae
of circulating insulin. Fatty acid synthesis is activated and lipolysis is
profoundly inhibited by insulin even at very low concentrations of the
hormone. (Am J or Clin Nut 1992;56;217S-23S)
In the obese NIDDM (Type II diabetes patients), ketones generated by low
carbohydrate diets suppress hepatic glucose output and fasting blood sugar.
(O619, IJO 1994 165)
A Scottish study found lowering carbohydrate intake doubled weight loss,
increased fat oxidation, and reduced metabolic slowdown compared to lowering
fat intake.
“We treated obese subjects with high fat, low carbohydrate diets. If the
carbohydrate content of the diet was not more than 50 to 60 g/day and the
fat content approximately 150 g/day, an average daily weight reduction of 0
3 kg was achieved. The cholesterol and triglyceride concentrations in the
serum, which had been raised at the beginning of the experiment, invariably
showed a tendency towards normalization under this dietary program.” (1973
American Journal of Clinical Nutrition, “Response of body weight to a low
carbohydrate, high fat diet in normal and obese subjects”)
As reported in Newsday, (March, 2000), researchers at Schneider Children’s
Hospital in New Hyde Park, NY, found that overweight teens on a high-fat,
high-protein diet lost more weight than adolescents on a traditional low-fat
diet. The study, which included 22 people ages 12-18 who were 20-100 pounds
overweight, found that those on the high-fat, high-protein diet lost an
average of 19 pounds in 12 weeks, compared to those on a low-fat diet who
lost an average of 8.5 pounds. The teens’ cholesterol levels also improved,
according Dr. Marc Jacobson, lead researcher and director of the Center for
Atherosclerosis Prevention at the hospital. Overall cholesterol levels
dropped in both groups, according to Nancy Copperman, the nutritionist who
designed the diets. But triglycerides — a kind of blood fat — fell 33
percent in the high-fat, high-protein diet group, compared to 17 percent in
the low- fat diet group, Copperman said. And levels of HDL, the so-called
good” cholesterol, also improved. Kidney and liver functions were not
affected.
Conference Report - North American Association for the Study of Obesity
from Medscape Diabetes & Endocrinology
Low-Carbohydrate, High-Protein Diets Physicians are often asked about the
safety and efficacy of low-carbohydrate, high-protein diets. Unfortunately,
very few controlled studies have evaluated these popular regimens. These
diets, which are often high in fat, raise concerns about their effects on
lipid levels. One such diet, the Atkins Diet, restricts carbohydrates and
encourages unlimited consumption of protein and fat. Preliminary results
were presented from a 3-center (University of Pennsylvania, University of
Colorado, Washington University) randomized controlled trial comparing the
Atkins Diet with a conventional low-fat, high-carbohydrate plan that
restricted daily caloric intake to 1200-1500 kcal for women and 1500-1800
kcal for men.[10] The study included 63 obese (BMI 33.8 ± 3.4 kg/m2) males
and females who were randomized to 1 of the 2 diets. Subjects received an
initial session with a dietitian to explain the assigned diet program. At 12
weeks, the researchers found that the Atkins group had a lower rate of
attrition (12%) compared with that of the conventional program (30%). In
addition, subjects in the Atkins group lost significantly more weight (8.5 ±
3.7%) compared with the conventional group (3.7 ± 4.0%). In terms of serum
lipids, the Atkins group demonstrated slight increases in total cholesterol
(TC; 2.2 ± 16.6%) and low-density lipoprotein (LDL) cholesterol (6.6 ± 20
7%), whereas the conventional group showed significant decreases in these
measures (TC -8.2 ± 11.5%; LDL -11.1 ± 19.4%). High-density lipoprotein
(HDL) cholesterol significantly increased in the Atkins group (11.5 ± 20.6%)
but did not change in the conventional group, whereas triglycerides showed a
significant decrease for the Atkins group (-21.7 ± 27.9%) and no change in
the conventional group. At 26 weeks, these changes persisted in both groups
even though the sample size was smaller. The researchers concluded that the
Atkins Diet produced favorable effects on weight, HDL, triglycerides, and
retention compared with a conventional low-fat, low-calorie program, whereas
the conventional plan was associated with more favorable effects on TC and
LDL cholesterol.
A similar randomized-controlled trial from Duke University was also
presented at the conference. The researchers in this study also compared the
effects of a low-carbohydrate (LC) diet with a low-fat, low-calorie (LF)
program This study included 120 obese (mean BMI 34 kg/m2) males and females,
who all received group treatment for their respective diet programs. At 6
months, both groups had similar rates of attrition, but the LC group lost
considerably more weight (13.3 ± 4.6%) compared with the LF group (8.6 ± 5
9%). In addition, the LC group lost significantly more fat mass than the LF
group (-9.7 kg for the LC group and -6.4 kg for the LF group). Both groups
showed decreases in triglycerides, with the LF group also showing a
significant decrease in total cholesterol (-13.5 mg/dL). The LC group showed
significant increases in HDL and a significant decrease in Chol/HDL ratio.
This pattern of results was similar to those of the 3-center study described
above.
Heart Disease Related to Glycemic Load
Simin Liu, Walter C Willett, Meir J Stampfer, Frank B Hu, Mary Franz, Laura
Sampson, Charles H Hennekens and JoAnn E Manson
From the Departments of Epidemiology and Nutrition, the Harvard School of
Public Health; the Channing Laboratory; and the Division of Preventive
Medicine, the Department of Medicine, Brigham and Women’s Hospital and
Harvard Medical School, Boston.
Background: Little is known about the effects of the amount and type of
carbohydrates on risk of coronary heart disease (CHD).
Objective: The objective of this study was to prospectively evaluate the
relations of the amount and type of carbohydrates with risk of CHD.
Design: A cohort of 75521 women aged 3863 y with no previous diagnosis of
diabetes mellitus, myocardial infarction, angina, stroke, or other
cardiovascular diseases in 1984 was followed for 10 y. Each participant’s
dietary glycemic load was calculated as a function of glycemic index,
carbohydrate content, and frequency of intake of individual foods reported
on a validated food-frequency questionnaire at baseline. All dietary
variables were updated in 1986 and 1990.
Results: During 10 y of follow-up (729472 person-years), 761 cases of CHD
(208 fatal and 553 nonfatal) were documented. Dietary glycemic load was
directly associated with risk of CHD after adjustment for age, smoking
status, total energy intake, and other coronary disease risk factors. The
relative risks from the lowest to highest quintiles of glycemic load were 1
00, 1.01, 1.25, 1.51, and 1.98 (95% CI: 1.41, 2.77 for the highest quintile;
P for trend < 0.0001). Carbohydrate classified by glycemic index, as opposed
to its traditional classification as either simple or complex, was a better
predictor of CHD risk. The association between dietary glycemic load and CHD
risk was most evident among women with body weights above average [ie, body
mass index (in kg/m2)
Conclusion: These epidemiologic data suggest that a high dietary glycemic
load from refined carbohydrates increases the risk of CHD, independent of
known coronary disease risk factors.
Some excerpts from “Adiposity 101,” by Chuck Forsberg