FREE-LIVING ENERGY-EXPENDITURE AND BEHAVIOR IN LATE INFANCY

Objectives-The energy requirements of infants are determined by body s ize, growth rate, and physical activity. Little is known of the determ inants of energy expended on activity. The relation bet cc een free-li ving energy expenditure and behaviour was investigated in infants aged 9 and 12 months. Methods-Total energy expenditure (TEE) was estimated by the doubly labelled water method and fat free mass was estimated f rom the O-18 dilution space. Behaviour was assessed by two 24 hour act ivity diaries. Subjects-Thirty four normal healthy infants. Results-TE E was negatively related to the time spent feeding and negatively rela ted to the time spent upset. Body size, represented by fat free mass, accounted for only 19% of the variation in TEE, whereas the combinatio n of fat free mass and two behavioural variables explained 36% of the variation in TEE. Conclusions-Behaviour contributed significantly to T EE. The energy requirements of individual subjects in this age group c annot be predicted with accuracy from body size alone.