The effect of different dietary fats on fat cell size and number in rat epididymal fat pad.

I. Rats were given diets containing different fats (200 g/kg) from weaning to 8 months of age. The fats were sunflower-seed oil (SFO), lard (L) and an equal mixture of sunflower-seed oil and lard (mixed-fat diet; MF). A control group was given the basal diet unsupplemented with fat. Energy intake and bodyweight of individual animals were recorded weekly. 2. Three animals from each dietary group were killed after 5, 13, 17 and 29 weeks on the experimental diets. At slaughter epididymal fat pads were excised, weighed and the number and size of fat cells in the pad was determined. 3. There were no significant differences between the energy intake in the whole experimental feeding period for rats given the different fat diets. However, when energy intakes were examined on a monthly basis animals given MF had a significantly higher energy intake in the first z months of feeding than those animals given SFO. In the third month of feeding (when animals were over 12 weeks old) the group given L had a significantly higher intake than the group given SFO. 4. Bodyweight , epididymal-fat-pad weight, cell size and cell number did not differ significantly between the ' fat-fed' animals at any individual slaughter period. Analysis of pooled values from the four slaughter periods revealed that animals given M F had significantly more fat cells than those given SFO. 5. We conclude that the nature of the dietary fat has no effect on the cellularity of developing adipose tissue but that the number of fat cells formed is sensitive to energy intake before IZ weeks of age in the rat. Certain diseases prevalent in affluent countries have been attributed to changes in dietary patterns (see Vergroesen, 1975). Particular emphasis has been placed on dietary fats and vascular disease and where recommendations have been made by governmental or medical organizations these invariably include a paragraph advising modification of the fat composition of the diet. In the Netherlands, for example, it is recommended that saturated fat intake should be replaced to a considerable extent by polyunsaturated fat, of which linoleic acid is the major component. It was recently reported by Widdowson and her colleagues (Widdowson, Dauncey, Gairdner, Jonxis & Pelikan-Filipkova, I 975) that the depot fat of Dutch babies had a very high linoleic acid content compared with their British counterparts. This difference might be attributed to the different fatty acid composition of …