Lipoprotein lipase (LPL) activities of skeletal muscles, heart and adipose tissue were investigated during feeding, prolonged food restriction, and refeeding. The influence of the duration of starvation on adipose tissue LPL activity was to cause it to decrease throughout starvation, whereas heart LPL activity increased during the first 24 hours of fasting and then declined for the remainder of the fast. Starvation of 10-week-old female, lean and obese rats to 80% of initial body weight required 5 and 9 days, respectively. In fed controls, no differences between phenotypes were found for any tissue in the LPL activities expressed per gram tissue. However, obese rats exhibited significantly smaller muscle mass and a resulting 29% lower total skeletal muscle LPL activity. No phenotype differences were detected for tissue LPL activities during starvation or refeeding. During caloric restriction, the LPL activities were reduced in heart (-18%) and adipose (-52%) tissues, but skeletal muscle was unchanged except for the slow-twitch, oxidative soleus muscle, which was increased approximately two-fold. After refeeding to initial body weight, the LPL activity of heart returned to normal, but adipose tissue was dramatically increased (+300%) for both lean and obese Zucker rats. These data suggest that reduced skeletal muscle mass with normal LPL activity per gram tissue may contribute to an increased availability of plasma triglyceride fatty acids to adipose tissue of the genetically obese rat.