Masters Theses

Date of Award

12-1986

Degree Type

Thesis

Degree Name

Master of Science

Major

Nutrition

Major Professor

Roy E. Beauchene

Committee Members

Betsy Haughton, Edward T. Howley

Abstract

Growth, feed consumption, body composition and hepatic lipogenesis were studied in male Wistar rats that were exercised or feed restricted. The study consisted of 5 groups, with 10 animals per group: Sedentary, ad libitum-fed control group (A); Exercised by swimming for 3 hours/day, ad libitum fed (E3.0); Exercised by swimming for 1.5 hours/day, ad libitum fed (E1.5); Sedentary, diet restricted to match weight of E3.0 (R3.0); Sedentary, diet restricted to match weight of E1.5 (R1.5).

The body weights and feed consumption of the two exercised groups were never significantly different. Therefore, it became unnecessary to treat the two diet-restricted groups separately in an effort to match their body weights to those of the exercised groups. Thus, R1.5 and R3.0 were combined into one group (R) for statistical purposes. It was also observed that the test responses for the 2 exercised groups were not significantly different, hence, these 2 groups were also combined for statistical comparisons (E = E1.5 + E3.0).

Hepatic lipogenesis was estimated by tritium (3H20) uptake of hepatic fatty acids and glucose-6-phosphate dehydrogenase activity (G6PD). Exercise resulted in enhanced fatty acid synthesis as seen by increased G6PD activity (p < 0.05) and tritium uptake. Diet restriction produced a non-significant increase in estimated lipogenesis. This was probably due to a meal-feeding effect.

Exercise significantly decreased body weight, in spite of the fact that the feed consumption of E was approximately the same as A. To maintain the same body weight as E, feed intake of R animals was decreased by 30%. Growth curves for all the experimental groups were of similar shape, though R and E were at a lower level than A.

Body composition measurements were performed in which protein, fat, moisture and ash were analyzed separately. These analyses were expressed in absolute and relative amounts. Exercised rats had a significant decrease in both absolute and relative amounts of body fat as compared to A, and significantly less relative amounts than R, even though E and R were weight-matched. Diet restricted animals also had less absolute and relative amounts of fat than A, though not significantly so. Exercise and caloric restriction produced no significant differences between any of the groups in absolute amounts of protein. Surprisingly, R did have a significantly greater percent protein than E and A.

E had more absolute and relative amounts of moisture than any of the other groups. Though increased body moisture is usually indicative of increased lean body mass, this was not true in this study. Ash showed no significant differences among groups.

In general, exercise resulted in increased hepatic lipogenesis and affected body size and body composition, mainly by decreasing body fat. Diet restriction caused similar alterations, though not to the same degree. Since exercised animals had approximately the same feed consumption, but increased liver lipogenesis and less body fat as compared to control rats, it was concluded that exercise altered lipid metabolism by increasing overall mobilization and utilization of body fatty acids.

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