Sexual Dimorphism of Brown Adipose Tissue Function.

OBJECTIVE: To determine whether brown adipose tissue (BAT) activity in school-age children differs between the sexes and to explore the impact of dietary intake, sedentary behavior, and picky/fussy eating. STUDY DESIGN: Children aged 8.5-11.8 years of age (n = 36) underwent infrared thermography to determine the temperature of the skin overlying the main superficial BAT depot in the supraclavicular region before and after 5 minutes of mild cold exposure (single-hand immersion in cool tap water at about 20°C). The relationships between the supraclavicular region temperature and parental reports of food consumption, eating behavior, and inactivity were explored. RESULTS: The supraclavicular region temperature was higher in boys (n = 16) at baseline, and after cold exposure. Boys displayed a greater thermogenic response to cold. Strong negative correlations were observed between the supraclavicular region temperature and body mass index percentile, and differences in supraclavicular region temperature between girls and boys persisted after adjustment for body mass index percentile. A negative linear relationship was observed between protein and vegetable intake and supraclavicular region temperature in girls only, but did not persist after adjustment for multiple comparisons. There was no difference in the adjusted supraclavicular region temperature between active or inactive children, or picky and nonpicky eaters. CONCLUSIONS: These findings indicate sexual dimorphism in BAT thermogenic activity and a sex-specific impact of diet. Future studies should aim to quantify the contribution of BAT to childhood energy expenditure, energy imbalance, and any role in the origins of childhood obesity.

Body mass index as a determinant of brown adipose tissue function in healthy children.

OBJECTIVE: To determine whether body mass index (BMI) percentile and ethnicity influence skin temperature overlying brown adipose tissue (BAT) depots in the supraclavicular region in healthy children. STUDY DESIGN: Infrared thermography measured supraclavicular region temperature (T(SCR)) at baseline and after exposure to a mild cool stimulus (single hand immersion in water at 20.1 °C) for 5 minutes in children aged 6-11 years (n = 55). The studies were undertaken in a normal school environment. RESULTS: BMI percentile and ethnicity were significant predictors of baseline T(SCR), with an inverse relationship between BMI percentile persisting after adjustment for ethnicity. Twenty-four children demonstrated a significant rise in T(SCR) after exposure to the cool stimulus. BMI percentile was a significant predictor of T(SCR) response, although there was no effect of ethnicity on T(SCR) change after exposure to the cool stimulus. CONCLUSION: We have demonstrated a negative relationship between BMI percentile and both baseline T(SCR), colocating with the primary region of BAT, and the change in T(SCR) in response to the cool stimulus. Future studies aimed at determining the primary factors regulating BAT function in healthy children should be targeted at the goal of maintaining a healthy BMI trajectory during childhood.