Dietary intervention and other strategies to prevent unhealthy weight gain and the development of obesity should be based on knowledge of dietary, physiological, genetic and behavioral determinants and their contributing interactions. Identifying these determinants is difficult because physiological susceptibility to specific dietary and behavioral factors implicated in unhealthy weight gain differs between populations and individuals within the populations. The research challenge is identifying specific determinants in a free-living, adult population.

Understanding the interaction between diet and the underlying susceptibility factors such as physiologic, genetic and epigenetic, and behavioral factors mandate an integrated approach.

This integrated approach should include understanding the interplay of physiological factors (genetics, epigenetics, taste preferences, susceptibility to energy excess, etc.) and behavioral factors (food cravings, restraint, disinhibition, physical activity) as each of these domains is a potential driving force in energy expenditure, food preference, dietary choices, and food intake.

Which of these factor(s) is most important? The investigators propose that by examining dietary, physiological, genetic, and behavioral factors in an integrated fashion we will gain insight into the obesity epidemic and identify the most important determinants of weight gain. As a secondary aim, the investigators will identify a single parsimonious collection of factors and develop strategies to mitigate the risks of developing obesity.

This is a prospective, longitudinal, clinical study using an epidemiological approach. The sample consists of 90 free-living participants aged 20-35 years. The participants will undergo a series of assessments in the domains of diet, physiological factors, and behavioral factors at baseline and every 12 months for 2 years.

OBJECTIVES

1. Identify dietary, physiological, genetic and behavioral determinants of unhealthy weight gain in healthy, young, ethnically-mixed men and women.
2. Identify relationships between genetic measures of taste perception and the determinants of unhealthy weight gain in the said population.
3. Identify relationships among the determinants of unhealthy weight gain that contribute to an individual's susceptibility to obesity.

Inclusion Criteria:

• Inclusion criteria will be healthy men and women between the ages of 20-35, with BMI < 27.5 kg/m2, and fasting blood glucose < 126 mg/dl.

Exclusion Criteria:

• History of diabetes, history of obesity (BMI > 30).
• History of known inherited medical conditions that might influence future health status.
• Current or planned medication usage that might influence future health status.
• Prior serious injuries/surgeries that might influence future health status.
• Women who are pregnant or breastfeeding (once enrolled, pregnancy will not cause subjects to be terminated from the study).
• Women who are < 6 months postpartal, or women who have discontinued breastfeeding < 3 months prior to screening.
• History of cancer (including skin cancer) within 5 years.
• History or organ transplant.
• Previous diagnosis with HIV, Hepatitis B or C, or tuberculosis.
• Abuse of alcohol or illegal drugs.
• Abnormal EKG.
• Presence of pacemaker, defibrillator, or implanted metal.
• History of eating disorders and abnormal psychological scores for the screening measures described under Psychological Assessment Measures in the Appendix. This psychological screening will be conducted approximately two weeks prior to outpatient testing.

The sample includes 90 free-living participants aged 20-35 years.