Measurement of oxygen consumption and locomotor activity in monosodium glutamate-induced obesity.

Oxygen consumption and locomotor activity were studied in mice developing obesity after neonatal administration of monosodium glutamate (MSG) and in untreated controls. MSG-treated mice became obese in the absence of increased food intake. Locomotor activity was significantly less in MSG-treated mice 2, 10, and 20 wk after weaning. Oxygen consumption expressed in terms of the Lee index was not significantly different at 2 wk after weaning although at 10 and 20 wk it was significantly lower in MSG-treated mice. Plasma thyroxine was not different between MSG-treated and control mice. It is suggested that diminished energy expenditure is the major factor in the etiology of obesity after neonatal administration of MSG.