Diet-induced thermogenesis is lower in rats fed a lard diet than in those fed a high oleic acid safflower oil diet, a safflower oil diet or a linseed oil diet.
Diet-induced thermogenesis is lower in rats fed a lard diet than in those fed a high oleic acid safflower oil diet, a safflower oil diet or a linseed oil diet.
Year: 1995
Authors: H Takeuchi, T Matsuo, K Tokuyama, Y Shimomura, M Suzuki.
Publication Name: J. Nutr.
Publication Details: Volume 125; 920.
Abstract:
Diet induced thermogenesis (DIT) plays an important role in the regulation of energy balance and occurs primarily in brown adipose tissue (BAT). DIT is increased following over-feeding and reduced by starvation. Dietary fats and oils have also been shown to affect DIT with beef fat and safflower oil diets reducing and increasing thermogenesis, respectively. The effects of specific FAs on DIT are not known. The objective of the present study was to compare dietary fats differing in their FA profiles on sympathetic activity of BAT, DIT and body fat accumulation in rats. Rats were fed for 12 weeks an isoenergetic diet based on lard (high SFA), high oleic safflower oil (high MUFA), safflower oil (high LA) or flaxseed oil (high ALA). Norepinephrine turnover rates in BAT were then estimated. The intake of lard promoted body fat accumulation by significantly decreasing DIT, as shown by a significant reduction in whole-body oxygen consumption. The high ALA diet resulted in the highest incremental oxygen consumption although values did not differ significantly from the safflower oil diets. A significant decrease in sympathetic activity in BAT, specifically norepinephrine turnover rate, was observed in the lard fed rats in comparison with animals fed the vegetable oils. These results are consistent with previous research by these investigators in which rats fed a high SFA diet (beef fat) exhibited significantly lower norepinephrine turnover rates in liver, heart, soleus muscle and subcutaneous adipose tissue in comparison to rats fed a safflower oil diet. Although the rats consumed a similar amount of metabolizable energy, the carcass fat content was significantly higher in the lard fed rats than in the other diet groups. Abdominal adipose tissue weights were the same in all diet groups. The authors speculated that the differential effect of fat accumulation in carcass and abdominal tissue may be due to site-specific alterations in the FA composition of the plasma membranes. The authors concluded that the intake of animal fats rich in SFAs decreases DIT through a reduction in sympathetic activity in BAT resulting in the promotion of body fat accumulation. In addition, MUFAs, ALA and n-6 PUFAs appear to have similar effects on DIT and fat accumulation. Further research is suggested to ascertain the mechanism(s) responsible for the decrease in sympathetic activity following the consumption of high SFA diets.
