Dietary Obesity in Rats: Body Weight and Body Fat Accretion in Seven Strains of Rats

Abstract

Ten male and 10 female rats from each of seven strains were fed a grain ration for 10 or 20 weeks from weaning. Body weight and body fat of these rats were compared with those of 20 rats of the same age and sex fed a ration containing 60% hydrogenated fat. Also, five male and five female rats of the same seven strains were killed at weaning. Mean weanling weights and the percentage of body fat for the seven strains of rats were similar. Mean weights of five male rats fed grain for 20 weeks ranged from 304 g for S 5B/Pl rats to 445 g for Osborne-Mendel rats; for five female rats, mean weights ranged from 163 g for S 5B/Pl to 301 g for Osborne-Mendel rats. Male rats fed the high fat ration ranged in weight from 346 g for S 5B/Pl to 693 g for Osborne-Mendel males. Females fed the high fat ration ranged in weight from 170 g for S 5B/Pl to 452 g for Osborne-Mendel rats. After 20 weeks of experiment (at 23 weeks of age), carcasses of both male and female rats fed grain contained from 10 (S 5B/Pl) to 16% fat (Sprague-Dawley). Rats fed high fat ranged from 14 (S 5B/Pl) to 40% (Osborne-Mendel) body fat. For rats of the same sex and age, body weight was influenced nearly equally by genetics (strain differences) and ration, but the percentage of body fat was influenced largely by the ration (74% of variation due to ration difference).