| Rodent studies have shown that a diet rich in omega 3 fatty acids found in fish oil (FO) results in significantly less total body fat accretion during growth compared to isoenergetic diets containing other types of dietary fats. The purpose of this dissertation was to explore the effects of FO on body composition (BC) and metabolism in adults.; Study 1 characterized the reliability of BC assessment using air displacement plethysmography. Men and women (n=980) completed two body composition assessments separated by 15-30 min. There was a significant correlation (r=0.992; p=0.001) between trial 1 and 2 for body fat%, and a paired t-test revealed no significant differences. The observed CV (3.09%) and technical error of the measurement (1.07 fat%) compare favorably with other established methods of BC analysis.; Study 2 examined the effects of supplemental FO on resting metabolic rate (RMR) and BC in young inactive men. Subjects (37.5+/-8.4% body fat, n=14) received 10g/d of safflower oil (SO) or FO for 6 wk. RMR and lean mass (LM) increased significantly for FO. There was a significant increase in serum leptin at 6wk for SO.; Study 3 examined the effects of supplemental FO in a heterogeneous group of men and women, and used varying doses of FO. Subjects (50+/-16 y, n=36) were given SO, Low (LFO), Medium (MFO) or High (HFO) doses of FO for 4 wk. There was a significant increase in RMR, and a significant reduction in serum glucose and triglycerides in the LFO. There was a significant reduction in 24h urinary creatinine excretion in the SO. BC changes were not significant, however the correlation between LM changes and RMR changes approached significance (p=0.07), suggesting this is the mechanism responsible for increasing RMR.; Study 4 examined the effects of dietary FO on BC in rats fed either a typical modern diet or the same diet with FO as the fat source for 6wk (n=19). FO resulted in a significantly lower daily energy intake, with no difference between groups for body mass. However, FO had a significantly higher LM and bone mineral density at 6 wk.; Taken together, these data show that dietary fish oil raises RMR, at least in part by increasing LM. |
