Dietary-induced permanent changes in brown and white adipose tissue composition in rats.

We have previously observed that feeding rats a cafeteria diet causes excess weight gain and changes in tissue composition. The object of this study was to assess whether these alterations were sustained after withdrawal of the palatable diet in the rat. The results showed that the obesity was not reversed by feeding a standard diet ad libitum for five months after withdrawal of the cafeteria diet. Body weight was 26 per cent greater than in control rats and tissue composition showed permanent alterations. The excess weight of lumbar white adipose tissue was due mainly to lipid content (86 per cent) and this was also true, but to a less extent, for interscapular brown fat (59 per cent). Increased brown fat mass was a result of hyperplasia and hypertrophy, whereas increased lumbar white fat was mainly a result of hyperplasia alone. In conclusion, changes in tissue composition, particularly in fat depots, were permanent and could be ascribed to the obesity per se, and not to the diet composition.