For most of the last half century, reduction in fat intake has been the primary nutritional approach for the prevention and treatment of obesity and cardiovascular disease (CVD). Over the last few years, very low carbohydrate (Atkins'-type) diets have achieved great popularity, with publication of several studies suggesting greater weight loss and improvements in CVD risk factors over 3 to 6 months. Recently, a third dietary approach focusing on glycemic index (Gl) has generated interest. However, few studies have compared the effects of these diets on body weight regulation and risk for CVD. The primary hypotheses of this study are that any diet that lowers the postprandial rise in blood glucose (very-low-carbohydrate or low- Gl) will have beneficial effects on the physiological adaptations to weight loss and on some CVD risk factors. However, other CVD risk factors will be adversely affected by a very-low-carbohydrate vs. a low-GI diet. Preliminary data provide strong support for these hypotheses, by showing that resting energy expenditure declines less and CVD risk factors improve more with weight loss on a low-glycemic load diet compared to a conventional low-fat diet. This application proposes a cross-over feeding design to study the effects of three diets following 12.5% weight loss in obese young adult subjects (n = 24, age 18 to 35 years). The diets are: 1) conventional low-fat, with 65% carb, 20% fat, 15% protein; 2) low-fat/low-GI, also with 65% carb, 20% fat, 15% protein; and 3) very-low-carbohydrate, with 10% carb, 60% fat, 30% protein. The primary outcome is resting energy expenditure (indirect calorimetry). Secondary outcomes include total energy expenditure (doubly labeled water), thermic effect of food (indirect calorimetry), physical activity (accelerometry), insulin resistance and beta-cell function (frequently-sampled IVGTT), blood lipids, measures of systemic inflammation and coagulopathy, and blood pressure. This study should have major public health implications to the millions of Americans currently following diets to decrease body weight and risk for CVD.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK072428-04
Application #
7468427
Study Section
Special Emphasis Panel (ZRG1-CICS (01))
Program Officer
Staten, Myrlene A
Project Start
2005-09-15
Project End
2010-07-31
Budget Start
2008-08-01
Budget End
2010-07-31
Support Year
4
Fiscal Year
2008
Total Cost
$511,269
Indirect Cost
Name
Children's Hospital Boston
Department
Type
DUNS #
076593722
City
Boston
State
MA
Country
United States
Zip Code
02115
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