Influence of protein intake and training status on nitrogen balance and lean body mass

The present study examined the effects of training status (endurance exercise or body building) on nitrogen balance, body composition, and urea excretion during periods of habitual and altered protein intakes. Experiments were performed on six elite bodybuilders, six elite endurance athletes, and six sedentary controls during a 10-day period of normal protein intake followed by a 10-day period of altered protein intake. The nitrogen balance data revealed that bodybuilders required 1.12 times and endurance athletes required 1.67 times more daily protein than sedentary controls. Lean body mass (density) was maintained in bodybuilders consuming 1.05 g protein.kg-1.day-1. Endurance athletes excreted more total daily urea than either bodybuilders or controls. We conclude that bodybuilders during habitual training require a daily protein intake only slightly greater than that for sedentary individuals in the maintenance of lean body mass and that endurance athletes require daily protein intakes greater than either bodybuilders or sedentary individuals to meet the needs of protein catabolism during exercise.     

Body mass, body composition and sleeping metabolic rate before, during and after endurance training

Metabolic rate, more specifically resting metabolic rate (RMR) or sleeping metabolic rate (SMR), of an adult subject is usually expressed as a function of the fat-free mass (FFM). Chronic exercise is thought to increase FFM and thus to increase RMR and SMR. We determined body mass (BM), body composition, and SMR before, during, and after an endurance training programme without interfering with energy intake. The subjects were 11 women and 12 men, aged 37 (SD 3) years and body mass index 22.3 (SD 1.5) kg · m^–2. The endurance training prepared subjects to run a half marathon competition after 44 weeks. The SMR was measured overnight in a respiration chamber. Body composition was measured by hydrostatic weighing. Measurements were performed at 0, 8, 20, 40, and 90 weeks after the start of the training. The BM had decreased from a mean value of 66.6 (SD 6.9) to 65.6 (SD 6.7) kg (P<0.01), fat mass (FM) had decreased from 17.1 (SD 3.9) to 13.5 (SD 3.6) kg (P<0.001), and FFM had increased from 49.5 (SD 7.3) to 52.2 (SD 7.6) kg (P<0.001) at 40 weeks. Mean SMR before and after 40 weeks training was 6.5 (SD 0.7) and 6.2 (SD 0.6) MJ · day^–1 (P<0.05). The decrease in SMR was related to the decrease in BM (r=0.62,P=0.001). At 90 weeks, when most subjects had not trained for nearly a year, BM and SMR were not significantly different from the initial value while FM and FFM had not changed since week 40 of training. In conclusion, it was found that an exercise induced increase in FFM did not result in an increase in SMR. There was an indication of the opposite effect, a decrease in SMR in the long term during training, possibly as a defence mechanism of the body in the maintenance of BM.     

Effect of long-term leisure time physical activity on lean mass and fat mass in girls during adolescence

The purpose of this 7-yr prospective longitudinal study was to examine if the level and consistency of leisure-time physical activity (LTPA) during adolescence affected the quantity and distribution of lean mass (LM) and fat mass (FM) at early adulthood. The study subjects were 202 Finnish girls who were 10-13 yr old at baseline. LM and FM of the total body (TB), arms, legs, and trunk were assessed by dual-energy X-ray absorptiometry. Muscle cross-sectional area (mCSA) of the left leg was assessed by peripheral quantitative computed tomography. Scores of LTPA were obtained by questionnaire. Girls were divided into four groups comprising those with consistently low (G(LL)) or consistently high (G(HH)) physical activity, or those whose physical activity changed from low to high (G(LH)), or from high to low (G(HL)), over the 7 yr of follow-up. At baseline, no differences were found in LM, FM, and FM% among the groups in any of the body segments. By the end of the study G(HH) and G(LH) had higher values of LM of the TB, arms, legs, and trunk than that of the G(HL) and G(LL) groups (P < 0.05, respectively). High FM% of the TB was associated with low level of LTPA, but no significant differences were found in the absolute amount of FM and mCSA among the LTPA groups. Our results suggest that a consistently high level of LTPA during the transition from prepuberty to early adulthood has a positive effect on lean mass gain in girls. Participating in 5 h of LTPA per week had a significant effect on FM% but not on the absolute amount of fat mass.     

EPR study of iron status in human body during intensive physical activity

The iron metabolism was studied in serum blood samples collected from 26 professional sportsmen undergoing intensive physical exercises using EPR combined with hematological and biochemical laboratory tests. Only 23% of EPR spectra (n = 6) were practically normal while in the rest spectra additional abnormal absorption lines were detected. Presumably, the significant portion of new signals may be caused by different cytochromes. Moreover, the anisotropic signals with g ₁ ? 2.02; g ₂ ? 1.94 and g ₃ ? 1.86 registered in some spectra pointed to the sulfur-iron centers. There was nearly linear correlation between the concentration of Fe³⁺ in transferrin (Fe³⁺-Tf) obtained from the EPR spectra and the serum iron concentration measured by absorption photometry both for sportsmen and controls (healthy individuals and patients with different diseases). At equal serum iron concentrations the Fe³⁺-Tf level was higher in sportsmen than that in controls. The Pearson correlation coefficient (r) for Fe³⁺-Tf and serum iron values was equal to 0.89 in sportsmen versus r = 0.97 in controls. Additional new lines in serum EPR spectra of professional sportsmen prove the suitability of EPR assay for scheduled medical exams since routine biochemical and hematological tests are insufficient to discover all abnormalities in iron metabolism under intensive physical exercises.     

The influence of physical activity on lean mass accrual during adolescence: a longitudinal analysis.

During childhood, physical activity is likely the most important modifiable factor for the development of lean mass. However, the effects of normal growth and maturation must be controlled. To distinguish effects of physical activity from normal growth, longitudinal data are required. One hundred nine boys and one hundred thirteen girls, participating in the Saskatchewan Pediatric Bone Mineral Accrual Study, were repeatedly assessed for 6 yr. Age at entry was 8-15 yr. Stature, body mass, and physical activity were assessed biannually. Body composition was assessed annually by dual-energy X-ray absorptiometry. Physical activity was determined using the physical activity questionnaires for children and adolescence. Biological age was defined as years from age of peak height velocity. Data were analyzed using multilevel random-effects models. In boys, it was found that physical activity had a significant time-dependent effect on lean mass accrual of the total body (484.7+/-157.1 g), arms (69.6+/-27.2 g), legs (197.7+/-60.5 g), and trunk (249.1+/-91.4 g) (P<0.05). Although the physical activity effects were similar in the girls (total body: 306.9+/-96.6 g, arms: 31.4+/-15.5 g, legs: 162.9+/-40.0 g, and trunk: 119.6+/-58.2 g; P<0.05), boys for the same level of activity accrued, depending on the site, between 21 and 120% more absolute lean mass (g). In conclusion, habitual physical activity had a significant independent influence on the growth of lean body mass during adolescence, once biological maturity and stature were controlled.     

Hormonal reactions during heavy training stress and following tapering in highly trained male rowers.

The purpose of this study was to determine whether fasting plasma leptin, cortisol, testosterone and growth hormone concentrations were altered with a heavy increase in training stress followed by a reduced stress in highly trained male rowers. Twelve male national standard rowers (age 20.5 +/- 3.0 years, height 187.9 +/- 6.1 cm, body mass 87.1 +/- 8.3 kg, percent body fat 10.4 +/- 3.2 %) underwent a three-week period of maximally increased training stress followed by a two-week tapering period. The fasting blood samples were obtained every week after the rest day. In addition, the maximal 2000-meter rowing ergometer performance time was assessed before and immediately after the exhaustive training period as well as after the tapering period. A 22 % increase in training stress caused a significant decrease (by 8 %) and increase (by 9 %) in leptin and testosterone, respectively. A further increase in training volume by 25 % significantly reduced leptin further by 35 %. At the same time, no changes were observed in testosterone. Growth hormone was significantly elevated only after the first week of heavy training stress compared to the pretraining level. In the first tapering week, where the physical stress was reduced by 50 %, leptin only significantly increased by 29 %. Testosterone and growth hormone were significantly reduced to almost pretraining levels by the end of the second tapering week. Leptin was further significantly increased during the second tapering week. Cortisol remained relatively constant during the whole study period. Similarly, rowing performance was not significantly changed. We conclude that leptin is more sensitive to the rapid and pronounced changes in training stress compared to measured stress hormones in athletes. In addition, fasting plasma leptin could be regarded as a key signal for metabolic adaptation to exhaustive training stress in highly trained male rowers.     

Age changes in skinfolds, body fat and lean body mass in Jat-Sikh and Bania females during 20 to 80 years

The present paper reports the changes in body fat and lean body mass during 20 to 80 years. The data consist of 502 Jat-Sikh and 510 Bania females. The body fat has been calculated by applying Durnin & Womersley's (1974) formulae. The body fat reaches a maximum value of 20.06 kg at age-group 60-64 in Jat-Sikh females and 22.15 kg at age-group 45-49 in Bania females followed by a decline, reaching a value of 15.28 kg in Jat-Sikhs and 14.93 kg in Banias in the 70+ age group. The redistribution of fat with ageing has also been observed from skinfold measurements and changing body contours. The lean body mass reaches a maximum value of 35.64 kg in Jat-Sikhs and 36.22 kg in Bania at age-group 35-39 followed by a steady decrease reaching a value of 30.47 kg in Jat-Sikhs and 28.27 kg in Banias at age-group 70+. The females of the present study possess significantly lesser body fat and lean body mass as compared to American and British females. But in terms of percentages the Jat-Sikh females of the present study possess the largest lean body mass and the least body fat.     

Relationship between body mass index and gray matter volume in 1,428 healthy individuals

Objective: To investigate any correlation between BMI and brain gray matter volume, we analyzed 1,428 healthy Japanese subjects by applying volumetric analysis and voxel‐based morphometry (VBM) using brain magnetic resonance (MR) imaging, which enables a global analysis of brain structure without a priori identification of a region of interest. Methods and Procedures: We collected brain MR images from 690 men and 738 women, and their height, weight, and other clinical information. The collected images were automatically normalized into a common standard space for an objective assessment of neuroanatomical correlations in volumetric analysis and VBM with BMI. Results: Volumetric analysis revealed a significant negative correlation in men (P < 0.001, adjusting for age, lifetime alcohol intake, history of hypertension, and diabetes mellitus), although not in women, between BMI and the gray matter ratio, which represents the percentage of gray matter volume in the intracranial volume. VBM revealed that, in men, the regional gray matter volume of the bilateral medial temporal lobes, anterior lobe of the cerebellum, occipital lobe, frontal lobe, precuneus, and midbrain showed significant negative correlations with BMI, while those of the bilateral inferior frontal gyri, posterior lobe of the cerebellum, frontal lobes, temporal lobes, thalami, and caudate heads showed significant positive correlations with BMI. Discussion: Global loss and regional alterations in gray matter volume occur in obese male subjects, suggesting that male subjects with a high BMI are at greater risk for future declines in cognition or other brain functions.     

Changes in body composition and motor skills of young weight lifters during physical training

In the course of an intense weightlifting training of young athletes the change characteristics of the first phase was an increase in lean body mass, while in the second phase it was the improvement of motor abilities. Obviously, the improvement of weightlifting performance took place at a pace matching motor conduction development. The influence to be drawn concerning training methodology is that at least a half or one whole year of conditioning is necessary to create the somatic and functional preconditions of a possibly correct execution of the weightlifting technique. This finding warns against encouraging to take in competitions at an early age as well as against employing great weights in training, because both of these are likely to severely disturb outlined healthy sequence of morphological and functional development.     

Phytase supplementation increases bone mineral density,lean body mass and voluntary physical activity in rats fed a low-zinc diet

Phytic acid forms insoluble complexes with nutritionally essential minerals, including zinc (Zn). Animal studies show that addition of microbial phytase (P) to low-Zn diets improves Zn status and bone strength. The present study determined the effects of phytase supplementation on bone mineral density (BMD), body composition and voluntary running activity of male rats fed a high phytic acid, low-Zn diet. In a factorial design, rats were assigned to ZnLO (5 mg/kg diet), ZnLO+P (ZnLO diet with 1500 U phytase/kg) or ZnAD (30 mg/kg diet) groups and were divided into voluntary exercise (EX) or sedentary (SED) groups, for 9 weeks. SED rats were significantly heavier from the second week, and no catch-up growth occurred in EX rats. Feed intakes were not different between groups throughout the study. ZnLO animals had decreased food efficiency ratios compared to both phytase-supplemented (ZnLO+P) and Zn-adequate (ZnAD) animals (P<.01 compared to ZnLO). The ZnLO+P and ZnAD rats ran 56–75 km more total distance than ZnLO rats (P<.05), with the ZnLO+P rats running more kilometers per week than the ZnLO rats by Week 6. In vivo DEXA analyses indicate that rats fed phytase-supplemented diets had higher lean body mass (LBM) than those fed ZnLO diets; and that rats fed the Zn-adequate diets had the highest LBM. Body fat (%) was significantly lower in EX rats and was both Zn- and phytase insensitive. Rats fed phytase-supplemented diets had higher bone mineral content (BMC), bone area (BA) and BMD than rats fed ZnLO diets; and in rats fed ZnAD diets these indices were the highest. The dietary effects on BMC, BA and BMD were independent of activity level.We conclude that consuming supplemental dietary phytase or dietary Zn additively enhances Zn status to increase BMD, LBM and voluntary physical activity in rats fed a low-Zn diet. While the findings confirm that bone health is vulnerable to disruption by moderate Zn deficiency in rats, this new data suggests that if dietary Zn is limiting, supplemental phytase may have beneficial effects on LBM and performance activity.