Sympathetic activity is lower in rats fed a beef tallow diet than in rats fed a safflower oil diet.

Effects of dietary fats consisting of different fatty acids on sympathetic activity and body fat accumulation were studied in rats. Rats were meal-fed an isoenergetic diet based on either beef tallow or safflower oil for 8 weeks. Carcass fat content was greater (P < .05) in rats fed the beef tallow diet than in rats fed the safflower oil diet. Norepinephrine (NE) turnover rate was significantly lower (P < .05) in interscapular brown adipose tissue (IBAT) and pancreas in rats fed the beef tallow diet than in rats fed the safflower oil diet, resulting in a decreased (P < .05) diet-induced thermogenesis (DIT) and an increased (P < .05) serum insulin concentration in the former. To confirm the effects of dietary fats on sympathetic activity in relation to body fat accumulation, rats were chemically sympathectomized. Sympathectomy abolished the differences in body fat accumulation, DIT, and serum insulin concentration between the two dietary groups. These results suggest that the beef tallow diet promotes body fat accumulation by reducing sympathetic activity as compared with intake of the safflower oil diet.