Obesity Risk in African American Women is Determined by a Diet-by-phenotype Interaction

Not Applicable

Completed

Brief Summary: The Scientific Premise of this study is that the high level of obesity displayed by African American (AA) women is due to the ability to secrete large amounts of insulin when sugary foods are consumed. When AA women eat a diet rich in starchy or sugary food (a "high-glycemic" diet that stimulates insulin secretion), the food that is eaten is stored as fat rather than being burned as fuel. The investigators previous research has suggested that AA women have an easier time losing weight and keeping it off when eating a low-glycemic diet. The proposed study will be the first randomized clinical trial to test the effect of high and low glycemic diets for weight loss and weight-loss-maintenance in obese AA women.

Recruitment & Eligibility

Inclusion Criteria

BMI 30-45 kg/m2
Sedentary to moderately active (<2 hours/wk of moderate, structured, intentional exercise.
Normal menstrual cycle

Exclusion Criteria

History of eating disorder
daily use of tobacco (>1 pack/wk)
change in weight greater than 5 pounds in previous 3 months
presence of any condition (e.g. PCOS) or use of any medication (e.g. glucocorticoid) deemed by the project physician to interfere with study outcomes
applicants will be screened with a standard oral glucose tolerance test. If a participant's 2 hour glucose if >200, they will not be able to enroll in the study.

Arm && Interventions

Group	Intervention	Description
High Glycemic Diet	High Glycemic Diet	-
Low Glycemic Diet	Low Glycemic Diet	-

Primary Outcome Measures

Name	Time	Method
Total Energy Expenditure	Baseline, Week 13	Total energy expenditure measured by doubly labeled water. The protocol is based on established procedures \[12\]. Urine samples are analyzed in duplicate for H218O and 2H2O enrichments using Thermo Scientific Delta V Advantage IRMS with GasBench. CO2 production rates are determined using a fixed assumption for the dilution space ratio (1.043), using Equation 3 of Speakman et al. \[10\], and energy expenditure is calculated with equation 5 of Speakman et al. \[10\]. \[10\] Speakman JR, Yamada Y, Sagayama H et al. A standard calculation methodology for human doubly labeled water studies. Cell Rep Med 2021; 2:100203. \[12\] Goran MI, Carpenter WH, McGloin A et al. Energy expenditure in children of lean and obese parents. American Journal of Physiology 1995; 31:E917-E924. \[13\] Wolfe RR. Measurement of Total Energy Expenditure Using the Doubly-Labeled Water Method. In: Radioactive and Stable Isotope Tracers in Biomedicine. Edited by: Wiley-Liss. 1992.

Secondary Outcome Measures