A Study of Niacin Regulation

Inclusion Criteria: * Males and females between 18 and 65 years of age who are able to comprehend instructions, follow study procedures, willing to sign an informed consent form, and consume an isoenergetic diet eating all meals from Mayo CRTU for at least 3 days prior to study. * Overweight/Obese volunteers will have a BMI 29.0 - 40.0 kg/m2. * Upper body/visceral obesity (UBO) in women will be defined as those with a waist-hip ratio (WHR) \> 0.85 and/or increased visceral fat by single slice CT scan, usually with \> 120 cm2 of visceral fat by CT scanning or a visceral fat/total fat ratio of \> 0.30, and/or biochemical evidence of metabolic syndrome as defined by ATP III criteria (fasting plasma triglycerides ≥ 150 mg/dL, HDL-cholesterol \< 50 mg/dL for women and \< 40 mg/dL for men, fasting plasma glucose ≥ 100 mg/dL). Upper body obesity in men will be defined as a waist-hip ratio of \> 0.95 and/or increased visceral fat (visceral fat area \> 180 cm2 or a visceral/total fat abdominal ratio by CT of \> 0.40) by single slice CT scan and/or biochemical evidence of metabolic syndrome as defined by ATP III criterial. These visceral fat values are based upon the data collected at Mayo Clinic using our methods, and are correlated with dyslipidemia and hyperinsulinemia. * Female subjects are eligible if they meet the following criteria: are not pregnant or nursing; all women of childbearing potential will have a negative urine pregnancy test at screening and a negative urine pregna…