Set of nine strains bred as parallel strains from a single outbred colony maintained by B. Houssay in 1948. All strains were selected for large body weight and high fertility. One strain designated Beta IIM (RGD:40924649) derived from line 'b' became obese with mild glucose intolerance and glycosurea in older obese rats (Calderari et al 1987). Alpha IIM (RGD:40924650) was used as a control strain in study.