Koji Okamura

Effects of voluntary resistance exercise and high-protein snack on bone mass, composition, and strength in rats given glucocorticoid injections.

We examined the effects of a voluntary resistance exercise (climbing) together with high-protein snacks (60% protein) on bone mass and strength in rats given glucocorticoid-injections (2 mg/kg/day) as a model of age-related osteopenia. Fifty-two male Sprague-Dawley rats, 8 weeks age, were assigned to exercise or sedentary groups. These groups were further divided into groups that received no snack, snack during activity or a snack during rest. All groups were meal-fed 7:30-8:30 h and 19:30-20:30 h and the snack was fed 23:30-0:30 h (active) or 11:30-12:30 h (resting). Energy and protein intake were approximately equal in all groups. The exercise groups were allowed to climb a wire-mesh tower cage (φ20 cm×200 cm) to drink water from a bottle set at the top. Weight gain during the 8-week experimental period was inhibited by a glucocorticoid-injection. Bone mass and strength were increased by climbing exercise with a high-protein snack, while no effect of snack nor any effect of snack timing was observed. Bone weight, calcium content and protein content were positively correlated to maximum load or structural stiffness. These results suggest that resistance exercise and high-protein supplementation may be a preventive therapy for osteoporosis associated with aging.

Effects of rapid or slow body mass reduction on body composition in adult rats.

Whether the speed of body mass (BM) reduction influences the body composition is uncertain. To investigate the effects of rapid vs slow body mass reduction on body composition, rats were divided into three groups; fed ad libitum for 16-day (Control, C); received restricted food intake during 16-day to decrease BM slowly (Slow, S); or fed ad libitum for 13-days and fasted for the last 3 days to rapidly reach a BM comparable to that of S (Rapid, R). Drinking water was restricted for R on day 16 to rapidly decrease their BM. All rats trained during the study. Final BM and adipose tissues mass were similar for R and S, and both were lesser than C. The skeletal muscle mass did not decrease in R and S. The liver mass was lower in R and S than C, and the decrease tended to be greater in R than S. Both the stomach and small intestine masses were significantly lower in R than C, but did not differ between S and C. In conclusion, differences of the speed of BM reduction affect the splanchnic tissues, and the decrease in splanchnic tissue mass was greater with rapid than slow BM reduction.

Effects of short-term refeeding after rapid or slow body mass reduction on body composition in adult rats

SUMMARY We previously observed that digestive tract mass decreased more in rats experiencing rapid body mass (BM) reduction than in those undergoing slow BM reduction. To determine if BM reduction speed influences body composition after refeeding, rats were assigned to three groups. The control group (C) ate ad libitum, the slow group (S) received restricted food for 21 days to slowly reduce BM, and the rapid group (R) ate ad libitum for 18 days and fasted for the last 3 days to rapidly reach a BM comparable to that of S. Water was restricted for R on day 21. After the BM reduction, both R and S were re-fed ad libitum for 12 h and then were sacrificed with C 4-h later. The BM and masses of the carcass, adipose tissue, and small intestine in both R and S did not return to that of C during the 16-h recovery, although no differences were observed between R and S. The liver and stomach mass in both R and S recovered to that of C. The mass and water, protein, total lipid and glycogen content in the skeletal muscle did not differ between R and S. We concluded that body composition after short-term refeeding is not influenced by the speed of BM reduction.:

Energy Deficit Required for Rapid Weight Loss in Elite Collegiate Wrestlers

To determine energy density for rapid weight loss (RWL) of weight-classified sports, eight male elite wrestlers were instructed to lose 6% of body mass (BM) within 53 h. Energy deficit during the RWL was calculated by subtracting total energy expenditure (TEE) determined using the doubly labeled water method (DLW) from energy intake (EI) assessed with diet records. It was also estimated from body composition change estimated with the four-component model (4C) and other conventional methods. BM decreased significantly by 4.7 ± 0.5 kg (6.4 ± 0.5%). Total body water loss was the major component of the BM loss (71.0 ± 7.6%). TEE was 9446 ± 1422 kcal, and EI was 2366 ± 1184 kcal during the RWL of 53-h; therefore, the energy deficit was 7080 ± 1525 kcal. Thus, energy density was 1507 ± 279 kcal/kg ∆BM during the RWL, comparable with values obtained using the 4C, three-component model, dual energy X-ray absorptiometry, and stable isotope dilution. Energy density for RWL of wrestlers is lower than that commonly used (7400 or 7700 kcal/kg ΔBM). Although RWL is not recommended, we propose that commonly practiced extreme energy restriction such as 7400 or 7700 kcal/kg ΔBM during RWL appears to be meaningless.

Differential effects of rapid and slow body mass reduction on body composition during an equivalent weight loss in rats

SUMMARY It is unclear whether the rate of body mass (BM) reduction affects the body composition with an equivalent BM reduction and whether this is influenced by the intensity of BM reduction. To elucidate this, two experiments (Exp.) were conducted. In Exp. 1, the rats fasted for 3 days to decrease BM rapidly (R3); energy was restricted at 85% of their estimated basal metabolic rate to decrease BM slowly, until it reached the same BM as R3 (S20). In Exp. 2, the rats fasted for 7 days (R7); received a restricted diet as in Exp. 1 (S50). The BM decreased 11% in R3 and S20 showed a BM equivalent to R3 on Day 20. In Exp. 2, the BM decreased 18% in R7 and S50 reached the BM of R7 on Day 50. The mass and water and protein in the skeletal muscle and adipose tissue mass did not differ between the groups in both experiments. In contrast, the stomach mass was 12.9% lower in R3 than S20 (P < 0.05) and the liver mass was 9.9% lower in R3 (P = 0.078). In Exp. 2, the stomach and liver masses were 13.2% and 18.2% lower in R7 than S50 (P < 0.05), respectively. The differences in the rate of BM reduction were seen in splanchnic tissues than in skeletal muscles and adipose tissues regardless of BM intensity. The larger BM reduction appeared to be related to a greater difference in the liver mass between the rapid and slow BM reduction.: