We studied the seasonal fluctuations in the eviscerated body weight, liver, fat bodies, and volume of food eaten in a population of viviparous lizard Sceloporus torquatus torquatus inhabiting the southern part of the Valley of Mexico. Observed changes in the mass of fat bodies of females suggest that most of the stored lipids in these structures are used for maintenance during the two driest months of the year. During the dry season, females consumed nearly seven times less food than during the rainy season, and their physical condition (mean eviscerated weight) was much lower in April (the driest month) than in May (start of the rainy season). Liver mass in females was higher during the rainy season than in the dry period. Males stored fewer lipids in the fat bodies than did females. However, the stored energy in these structures may be important at the beginning of the dry season to support activities related with their reproductive behavior and to survive during the driest months of the year. There were no significant monthly changes in carcass mass or quantity of food eaten by males. In contrast, the liver mass of males changed significantly during the study year although the biological significance of these changes is unclear.