【关键词】  protein

    the pision of Human Nutrition, Wageningen University, Wageningen, Netherlands

    ABSTRACT

    Background: The decrease in leptin after energy restriction is a starvation signal to the brain. Several studies have found an association between this decrease and subjective appetite; however, no solid data are available on the acute decrease in fasting leptin concentration and subsequent caloric compensation.

    Objective: The objective was to assess the effect of acute decreases in fasting leptin concentrations, induced by energy restriction, on subsequent energy intake compensation. We hypothesized that men with a large decrease in fasting leptin concentrations would have larger ad libitum energy intakes than would men with a small decrease in leptin.

    Design: Thirty-four male unrestrained eaters [age: 23 ± 3 y; body mass index (in kg/m2): 22.3 ± 1.6] participated in a semicontrolled intervention study. Fasting serum leptin and insulin concentrations were measured before and 2 d after 62% energy restriction. Energy intake was measured on the 2 following days on which food was provided ad libitum.

    Results: During energy restriction, fasting leptin and insulin concentrations decreased by 27.2% (95% CI: 34.4%, 19.9%) and 30.7% (95% CI: 41.0%, 20.4%), respectively. Subjects consumed 143 ± 27% of their estimated energy requirements (18.3 ± 2.9 MJ) on the first day and 124 ± 20% (16.0 ± 2.6 MJ) on the second day of ad libitum intake. No significant correlations were observed between decreases in fasting leptin or insulin concentrations and subsequent ad libitum energy intake; however, decreases in insulin were correlated with an increase in carbohydrate intake (r=0.49, P < 0.01).

    Conclusion: Although fasting leptin concentrations decreased significantly during energy restriction and subjects showed compensatory behavior during subsequent ad libitum food intake, no association was observed between the decrease in fasting leptin concentrations and caloric compensation.

    Key Words: Ob protein  insulin  appetite regulation  energy intake  caloric restriction  leptin

    INTRODUCTION

    Leptin is a hormone that is produced by adipose tissue and is secreted in the blood (1). Because leptin is produced by fat cells, serum leptin concentrations are positively correlated with the amount of fat mass in the body (2). However, short-term severe energy restriction causes circulating leptin concentrations to decrease to a larger extent than would be expected from the loss of fat mass alone (35). In a recent review, Flier (6) advocates that this decrease in leptin concentration serves as an important signal from fat to the brain that the body is starving. Moreover, he suggests that this function is likely to be as important as or more important than is leptin’s function to inform the brain about the amount of fat mass. Because of the low availability of glucose, insulin concentrations decrease during energy restriction. It has been suggested that this decrease in