Food Restriction Causes Low Bone Strength and Microarchitectural Deterioration in Exercised Growing Male Rats

Abstract

SummaryThe pathogenesis of bone disorders in young male athletes has not been well understood. We hypothesized that bone fragility is caused by low energy availability, due to insufficient food intake and excessive exercise energy expenditure in young male athletes. To examine this hypothesis, we investigated the influence of food restriction on bone strength and bone morphology in exercised growing male rats, using three-point bending test, dualenergy X-ray absormetry, and micro-computed tomography. Four-week-old male SpragueDawley rats were divided randomly into the following groups: the control (Con) group, exercise (Ex) group, food restriction (R) group, and food restriction plus exercise (REx) group after a 1-wk acclimatization period. Thirty-percent food restriction in the R and REx groups was carried out in comparison with that in the Con group. Voluntary running exercise was performed in the Ex and REx groups. The experimental period lasted 13 wk. At the endpoint of this experiment, the bone strength of the femurs and tibial BMD in the REx group were significantly lower than those in the Con group. Moreover, trabecular bone volume and cortical bone volume in the REx group were also significantly lower than those in the Con group. These findings indicate that food restriction causes low bone strength and microarchitectural deterioration in exercised growing male rats.

The Interaction of Voluntary Running Exercise and Food Restriction Induces Low Bone Strength and Low Bone Mineral Density in Young Female Rats

“…2). Our group reported that the combination of voluntary running exercise and food restriction resulted in low bone strength in young male rats [29], similar to finding in the present study with young female rats. Moreover, in the present study, the two-way ANOVA statistical methods, revealed that an interaction occurred as a result of combination of conditions.…”

Influence of exercise and sports on bone

“…Epidemiological studies have reported that bone disorders are less frequent in male athletes than in female athletes. On the other hand, our data suggested that food restriction decreases bone strength due to cortical bone loss, although mechanical loading adds to bone strength in growing male rats 57) . Therefore, these data imply that low energy availability caused trabecular bone loss even though the experimental group underwent exercise training.…”

“…Therefore, these data imply that low energy availability caused trabecular bone loss even though the experimental group underwent exercise training. In this study, low energy availability caused low BMD and microarchitectural deterioration in the growing male rats 57) . <Fig.…”

Calorie restriction in rodents: Caveats to consider

“…This TRF regimen reduced body and liver weight gains (but not fat) and improved glucose tolerance. Similarly Hatori et al (2012) also limited feeding of a HFD (61%) to 8 hr during the dark period in B6 mice and noted reduced evidence of obesity, hyperinsulinemia, hepatic steatosis, and improved motor coordination with no differences in caloric intake (Hattori et al, 2014). The period of restricted feeding appears to be a critical element in the benefits of these regimens.…”

“…Hattori et al investigated exercise initiated at 4 wk in male SD rats with and without 30% CR for 13 wks. They noted a reduction in femoral bone strength in rats in the exercised group on CR compared to control rats (Hattori et al, 2014). …”