Register for High Carbohydrate, Low Fat Diets Most Beneficial Overall
Diet and NutritionMay 14, 2001
2001 MAY 14 - (NewsRx.com & NewsRx.net) -- by Susan Hasty, staff medical writer - Two new studies confirm what many doctors have been saying for years: a high-carbohydrate, low-fat diet is the best way to lose weight and improve overall health.
Researchers at the U.S. Department of Agriculture, Beltsville, Maryland, came to this conclusion when they analyzed popular diets for diet quality, as measured by a healthy eating index (HEI), food consumption, and body mass index (BMI). E.T. Kennedy and colleagues at the Beltsville Human Nutrition Research Center, Beltsville, Maryland, studied vegetarian (no meat, poultry, or fish) and several subclassifications of non-vegetarian diets. They pulled their data from the Continuing Survey of Food Intake By Individuals (CSFII) 1994-1996 of more than 10,000 adults, age 19 or older.
The non-vegetarian diets included low carbohydrate (less than 30% of energy from carbohydrates), medium (30% - 55%), and high (more than 55%). The high-carbohydrate diets were further subdivided as to how much energy intake was derived from fats: the Pyramid diet (less than 30% of energy from fats and at least one serving from the five major food groups in the USDA Food Guide Pyramid), and the non-Pyramid low fat (less then 15% of energy from fat) and moderate-fat (15%-30%) diets. Kennedy and coworkers also reviewed more than 200 related studies in the scientific literature.
The USDA researchers found that the diet that rated highest as measured by the HEI was the high-carbohydrate Pyramid diet (89.2), while the low carbohydrate diet (44.6) rated lowest in quality ("Popular diets: Correlation to health, nutrition, and obesity," J Am Diet Assoc, April 2001;101(4):411-420).
As might be expected, energy intakes were lowest in the vegetarian (1,606 kcals) and high-carbohydrates, low-fat (1,360 kcals) diets, these researchers reported. Similarly, BMIs were lowest for women who ate the vegetarian (24.6 kg/m2) and high-carbohydrate, low fat (24.4 kg/m2) diets. The smallest BMIs for men were also reported among the vegetarians and the high-carbohydrate Pyramid dieters (25.2 kg/m2 for both diets), the Kennedy group said.
Kennedy and associates noted that the literature review demonstrated that weight loss appeared to be associated almost entirely with energy restriction and was independent of the type of diet. The high-carbohydrate, low-to-moderate fat diets were low-energy diets, and the high-carbohydrate, Pyramid diet rated highest on the healthy eating index, they noted.
A high-carbohydrate, low-fat diet is a high-quality diet with low energy consumption, Kennedy and colleagues concluded.
In a related study, researchers in Hawaii studied the health effects of The Hawaii Diet, a traditional island diet of poi (made from the starchy taro root), sweet potatoes, and fish. This naturally high-carbohydrate, low-fat diet proved to have very beneficial effects on study subjects' weight, blood pressure, and cholesterol.
T.T. Shintani and colleagues at the Waianae Coast Comprehensive Health Center recruited 22 adults from various ethnic groups who then ate The Hawaii Diet for 21 days. There were no restrictions on portion sizes or caloric intake ("The Hawaii Diet: Ad libitum high carbohydrate, low fat multi-cultural diet for the reduction of chronic disease risk facts: obesity, hypertension, hypercholesterolemia, and hyperglycemia," Hawaii Med J, 2001;60(3):69-73).
Study subjects lost an average of 10.8 pounds (23.8 kg; p<000.1), the researchers reported, and their blood pressures decreased from an average of 136.0/82.7 mmHg to 125/78.9 mmHg (p<0.01). The average total serum cholesterol was reduced from 205.3 to 156.9 mg/dl (p<0.0001), and average blood glucose levels dropped from 112.2 to 91.5 mg/dL (p<0.01), Shintani and coworkers added.
While noting these short-term improvements were impressive, Sintani and colleagues recommended further "studies of longer duration with a control group should be conducted to test the effectiveness of The Hawaii Diet in maintaining these health benefits over a longer period of time."
For more information on the USDA study, contact Joseph Spence, USDA/ARS, Beltsville Human Nutrition Research Center, 10300 Baltimore Blvd., Room 326, Bldg. 308, Barc-East, Beltsville, MD 20705, USA.
For more information on The Hawaii Diet study, contact T.T. Shintani, Preventive Health Department, Waianae Coast Comprehensive Health Center, 86-260 Farrington Highway, Waianae, HI 96792, USA.
Key points reported in these studies include:
* USDA researchers studied data from a nutritional survey of more than 10,000 adults for diet quality, consumption patterns, and BMI
* The lowest caloric intakes were in the vegetarian and high-carbohydrate, low-fat diets
* The smallest BMIs for men and women were found among subjects eating the vegetarian and high-carbohydrate, low-to-medium fat diets
* The highest quality diet as measured by the HEI was the high-carbohydrate, Pyramid diet
* High-carbohydrate, low-fat diets are high quality diets with low energy consumption
* Researchers in Hawaii studied 22 adults on a 21-day traditional island diet of complex carbohydrates and low fats for health effects
* Average blood pressures and cholesterol and blood glucose levels decreased significantly, while subjects loss an average of 10.8 pounds
* Further, long-term studies will be needed to see if these short-term health benefits of The Hawaii Diet are sustainable This article was prepared by Health & Medicine Week editors from staff and other reports.
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