The Energy Required to Synthesize Lean and Adipose Tissue in Rats.

Although the energy stored in lean tissue (LT) and adipose tissue (AT) is well known, the energy required to synthesize these tissues is less clear. While elucidating the energy required for AT synthesis may not be so important, the elucidation of the energy required for LT synthesis is important for individuals who aim to increase their skeletal muscle. Theoretically the energy at the point at which ΔLT/Δbody weight (BW) reaches 100% on a regression curve, which indicates the relationship between ΔLT/ΔBW and the energy used to accumulate body tissue, is considered to be the energy expended to synthesize LT. We therefore investigated the relationship using rats. Rats of different ages, and rats in exercised or sedentary states were used because their ΔLT/ΔBW was expected to be different. ΔLT/ΔBW was higher in the 4-wk-old group than in the 8-wk-old group and higher in the exercise group than in the sedentary group. We found a positive correlation between ΔLT/ΔBW and the energy expended to synthesize tissues that accumulated in the body. This energy was lower in the 8-wk-old group, which had a lower ΔLT/ΔBW in comparison to the 4-wk-old group, but was not affected by exercise. The regression curve revealed that the energy expended to synthesize LT was 2.9 kcal/g, while that expended to synthesize AT was 1.1 kcal/g. Therefore, combined with the energy accumulated to the tissues, the energy required to accumulate LT is approximately 4.0 kcal/g, while that required to accumulate AT is approximately 8.5 kcal/g.

Effect of the Energy Intake on the Iron Status of Resistance Exercises Performed in Rats.

In many cases, athletes compensate for nutrient deficiencies due to a reduced dietary intake by taking supplements or other means. However, in what ways nutrients are utilized by the body when it is deficient in energy and yet receives adequate amounts of the required nutrients are unclear. We therefore examined the effect of the balance between available energy and iron intake on the iron nutritional status of athletes. The experiment was conducted in two parts. Four-week-old male rats were divided into two groups based on energy and iron sufficiency: Experiment 1 was energy-sufficient and iron-sufficient (ES-FeS) and energy-sufficient and iron-deficient (ES-FeD). Experiment 2 was energy-deficient and iron-sufficient (ED-FeS) and energy-deficient and iron-deficient (ED-FeD) groups. All rats were made to perform climbing exercises 3 days a week at 5 P.M. The results showed that a significantly higher hematocrit, hemoglobin, plasma iron concentration, and TfS were found in the iron-sufficient group than in the iron-deficient group, TIBC was significantly lower in the iron-sufficient group than in the iron-deficient group, and TfS was significantly higher in the iron-sufficient group than in the iron-deficient group, irrespective of energy intake. It was suggested that restricting both iron and energy intake may significantly decrease the amount of iron in the liver and accelerate the metabolic turnover of red blood cells, while restricting iron intake but providing adequate energy intake suggested that resistance exercise-induced tissue iron repartitioning was not altered by iron sufficiency or deficiency.