The experimental obesity by high-fat feeding--a model for evaluation of the biological value of fats.

The experimental obesity by high-fat feeding of rats, introduced after weaning, was found to be a suitable model for evaluation of the biological value of nutritional fats with different fatty acid composition: butter (group B), lard (L), partially hydrogenated oil (H), lard + sunflower oil 2:1 (LS). The differences in the fatty acid composition of these regimens affect: the efficiency in creating the model of obesity; the hormonal pattern of blood plasma; some metabolic pathways in liver and adipose tissue (especially in group H); the fatty acid composition of some structural, reserve and transport lipids; some biological tests indicative of membrane's phospholipid and fatty acid composition, i.e. the rate of platelets aggregation. A special attention should be paid to the striking differences in the cellularity and morphogenesis of adipose tissue in group B (hyperplastic obesity) in comparison with all other high-fat groups (hypertrophic obesity), irrespective of the identical energy and protein content of the diets. Thus, the early administration of a diet with butterfat (50% of energy) promoted a model of hyperplastic obesity, while the isocaloric diet with lard + sunflower oil caused a hypertrophic type of obesity. The authors have proved the regenerating capacity of the periepididymal fat pad in adult rats after partial lipectomy. The relative contribution of endogenic and exogenic (nutritional) factors in this process is discussed and the modifications in the cellularity of adipose tissue on these conditions are evaluated.