Excess fetal adipose tissue growth during intrauterine development increases future obesity risk. Development of brown adipose tissue, a highly thermogenic organ in utero, may affect postnatal energy expenditure, thus influencing obesity risk. This pilot research study is designed to understand the developmental origins of energy balance by examining maternal and neonatal factors that influence neonatal brown adipose tissue and to quantify its physiological relevance to energy expenditure in human neonates.

The developmental origins of obesity begin in utero with growth and differentiation of adipose tissue. Fetal white adipose tissue accretion is highly variable and dependent on the maternal intrauterine environment. Unlike white adipose tissue, brown adipose tissue has a high capacity for thermogenesis. Brown adipose tissue is present at birth and it is believed to support the critical function of thermoregulation in early postnatal life. Therefore, Brown adipose tissue may also influence the development of neonatal energy balance. Similar to white adipose tissue, it is hypothesized that development of Brown adipose tissue in utero is also influenced by maternal factors such as prepregnancy body mass index and gestational weight gain. The research aims of this study to 1) identify maternal and neonatal factors that contribute to neonatal Brown adipose tissue and 2) to identify changes in neonatal Brown adipose tissue and to energy expenditure in response to a mild cold exposure. To achieve these aims, we will conduct a pilot and feasibility study that is cross-sectional, observational study in up to 60 infants 0-3 weeks of age. Using state-of-the-art methodology, we will assess brown adipose tissue, body composition, and resting metabolic rate under thermoneutral and mild-cold stimulated conditions.

Inclusion Criteria:

• aged 0 weeks to less than 3 weeks at visit 1
• be willing to complete MRI procedures

Exclusion Criteria:

• Unable to complete two clinic visits within 14 days
• Born with health conditions that would render the procedures unsafe
• Born earlier than 36 and 0 days gestation
• Taken a steroid drug since birth
• Implanted metal or electronic objects that render MRI unsafe

This study will enroll neonates from two mechanisms: 1) recruited from the greater Baton Rouge area, and 2) recruited from an ongoing prenatal weight maintenance intervention randomized controlled trial (R01DK099175).