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PubMed1990

Diet and insulinlike growth factor I in relation to body composition in women with exercise-induced hypothalamic amenorrhea.

To assess the potential influence of diet and endogenous peptide anabolic hormone secretion on exercise-related differences in body composition, we compared levels of macronutrient intake, insulinlike growth factor I (IGF-I), and fat-free mass (FFM) and fat mass (FM) in matched groups of exercising women with and without secondary hypothalamic amenorrhea. Women were tightly matched according to somatotype and grouped into those with exercise amenorrhea (EXam, n = 6), exercise eumennorhea (EXeu, n = 5), and sedentary eumennorheic controls (SED, n = 5). Although no between-group difference was observed in FFM, the EXeu subjects had a significantly lower fat fraction and a significantly elevated FFM/FM ratio. Kilocaloric and protein intakes did not differ between groups, but dietary fat intake was lowest and carbohydrate intake highest in the EXam subjects. Dietary macronutrients were not correlated with the FFM/FM ratio. However, levels of insulinlike growth factor I were significantly correlated to the FFM/FM ratio and there was a clear trend for the hormone to be highest in the EXeu subjects. We conclude that differences in body composition between exercising women with and without exercise-induced hypothalamic-pituitary dysfunction were related to an alteration in IGF-I secretion, although differences in macronutrient intake might also be a factor. Further studies are warranted to elaborate upon the dietary and hormonal factors regulating the body composition response to exercise.

Adipose Tissue↗

PubMed2000

Effects of insulin-like growth factor I (IGF-I) therapy on body composition and insulin resistance in IGF-I gene deletion.

We have recently reported a patient with a homozygous partial deletion of the insulin-like growth factor-I (IGF-I) gene, resulting in IGF-I deficiency, insulin resistance, and short stature. Recombinant human IGF-I (rhIGF-I) therapy has been shown to improve insulin sensitivity (Si) and growth in other causes of IGF-I deficiency. We now report results of 1 yr of rhIGF-I therapy on body composition, bone mineral density (BMD), insulin sensitivity, and linear growth in this patient. rhIGF-I therapy was initiated at age 16.07 yr (bone age, 14.2 yr), at a starting dose of 40 microg/kg daily, increasing after 3 months to 80 microg/kg daily. Body composition, BMD, markers of bone mineralization, and auxological parameters (height, weight) were measured at 0, 6, and 12 months after start of therapy. Si, acute insulin response to glucose, and glucose effectiveness were determined at baseline, 3 months, and 12 months into therapy. On IGF-I therapy, body mass index increased from 17 kg/m2 to 18.6 kg/m2. Body composition studies (dual-energy x-ray absorbtiometry) revealed an initial decrease in total body fat, from 19.9% at baseline to 15.1% at 6 months; but by 12 months of therapy, this had reversed, with an increase to 21.8%. Si, calculated using Bergman's minimal model, was substantially reduced at baseline at 1.45 x 10-4 min-1 (microU/mL) [normal value, 5.1 x 10-4 min 1 (lean adult male)]. rhIGF-I therapy resulted in a dose-related improvement of Si into the normal range (NR) (rhIGF-I dose: 40 microg/kg x day, Si = 2.06 x 10-4 min-l; rhIGF-I dose: 80 microg/kg x day, Si = 4.39 x 10-4 min-1). Baseline reduction in Si was accompanied by elevated acute insulin response to glucose, which also fell in a dose-dependent manner. Baseline BMD was severely reduced when compared with age-matched controls (-4.88 SD); however, calculation of bone mineral apparent density indicated that the true reduction in BMD was minimal. rhIGF-I therapy increased BMD by 17% and bone mineral apparent density by 7%, indicating that IGF-I has a greater effect on bone growth than bone mineralization. Bone turnover markers also increased on rhIGF-I; mean serum osteocalcin: 8.3 ng/mL pretreatment, 21.7 ng/mL after 6 months of rhIGF-I (NR for adult male, 3.4-9.1 ng/mL); mean bone specific alkaline phosphatase: 36.5 U/L pretreatment, 82.2 U/L after 6 months of therapy (NR for adult male, 15-41). Height velocity increased from 3.8 cm/yr pretreatment to 7.3 cm/yr on 80 microg/kg.day of rhIGF-I. In this patient with severe insulin resistance, therapy with rhIGF-I resulted in beneficial effects on Si, body composition, bone size, and linear growth. These results have implications for IGF-I therapy in a variety insulin resistant states.

Absorptiometry, Photon↗

PubMed1998

Plasma leptin in children: relationship to puberty, gender, body composition, insulin sensitivity, and energy expenditure.

Leptin has been demonstrated to reflect body fat mass (FM) in humans, but the regulation of leptin levels during childhood growth and development is poorly understood. We studied the relation between plasma leptin, fasting insulin, insulin sensitivity, and resting energy expenditure in 22 healthy prepubertal children and 27 adolescents. Body composition was assessed by the H2(18)O-dilution principle, insulin sensitivity by a hyperinsulinemic (40 mU/m2/min)-euglycemic clamp, and energy expenditure by indirect calorimetry. Plasma leptin in prepubertal children (9.3 +/- 2.0 ng/mL) was not different from that in pubertal adolescents (10.9 +/- 2.2 ng/mL). Plasma leptin correlated with FM (r = .77, P < .001). There were no gender differences in leptin after controlling for FM differences. In prepubertal and pubertal subjects, plasma leptin correlated with fasting insulin independently of FM (r = .60, P < .001), but did not correlate with insulin sensitivity independently of body fat content. Leptin showed no relationship to resting energy expenditure after adjusting for body composition. The present cross-sectional evaluation of normal children shows that (1) plasma leptin reflects body fat content, (2) leptin concentrations are similar between prepubertal children and pubertal adolescents, (3) there are no gender differences in leptin independent of adiposity, and (4) leptin correlates with fasting insulin but not with insulin sensitivity. Contrary to animal data, our cross-sectional results in healthy children do not suggest a role for leptin in puberty or a female-related leptin resistance as reported in adults. It remains to be determined at which stage of human development the sexual dimorphism in leptin becomes evident.

Adolescent↗

PubMed1964

[BODY COMPOSITION].

Explore the source record for details and available documents.

Body Composition↗

PubMed1990

Physiologic and body composition changes in feeder pigs under simulated marketing conditions.

Two experiments were conducted to determine changes in body composition and various physiologic variables in feeder pigs under simulated marketing conditions. In the first experiment, pigs were assigned to 1 of 4 treatment groups for 48 hours: (1) no water and feed; (2) water ad libitum, no feed; (3) no water, feed ad libitum; or (4) water and feed ad libitum. During a 48-hour recovery period, all pigs were allowed feed and water ad libitum. Plasma triiodothyronine decreased (P less than 0.01) within the first 24 hours in groups-1 and -2 pigs, but increased (P less than 0.01) within the first 6 hours of the recovery period. The circadian rhythm of plasma cortisol was disrupted in groups-1 and -3 pigs and during recovery in group-1 pigs. Packed cell volume increased (P less than 0.05) in groups-1 and -3 pigs and returned to initial values within the first 24 hours of the recovery period. In the second experiment, body composition was estimated by the 40K technique for fat-free body mass, percentage of nitrogen, and percentage of fat. Body composition was determined before and after pigs were allotted to 1 of 2 groups for 48 hours: group-1 pigs were given feed and water ad libitum and group-2 pigs were not given feed and water. Group-1 pigs gained 2.2 kg of body weight (P less than 0.01), 0.6% fat (P less than 0.01), 0.7 kg of fat-free body mass, and 0.02% nitrogen (P greater than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2000

Resting energy expenditure, growth hormone indices, body composition and adipose tissue distribution in premenopausal women.

OBJECTIVES: A significant growth hormone (GH) contribution to interindividual variance in energy expenditure (REE) in women can be hypothesized. The present study examines the independent association between physiological levels of GH function indices and REE. SETTING: All subjects were hospitalized in the Institute of Internal Medicine of the University of Verona. SUBJECTS: Twenty-four premenopausal overweight (BMI = 28-55 kg m-2) women aged 18-49 years. INTERVENTIONS: REE was estimated by indirect calorimetry and body composition and fat distribution by single slice computed tomography method. GH activity and GH status were determined by measuring serum levels of insulin-like growth factor I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3). RESULTS: GH indices did not show any significant correlation with REE. The relation between GH indices and REE was also examined by multiple regression analysis to account for possible confounders such as body composition, adipose tissue distribution and age. When body composition was considered, body fat and fat-free mass were the only significant predictors of REE (R2 = 0.699, P = 0.0001). The contributions of GH indices were not significant. CONCLUSIONS: Our findings do not support the hypothesis that GH in physiological conditions could be an independent determinant of REE in women with obesity.

Adipose Tissue↗

PubMedDate not supplied

Evaluation of leg-to-leg BIA in assessing body composition in high-school-aged males and females.

The current investigation was conducted to evaluate the accuracy of the Tanita 300WA leg-to-leg (LL) bioelectrical impedance analyzer (BIA) for measuring body composition in an American high-school-aged population. Body composition was determined in 77 students, comparing BIA measurements with the criterion, hydrostatic weighing (HW). Among the males, there were no significant differences found in percent body fat (%BF) between BIA (14.1 +/- 7.8%) and HW (14.9 +/- 9.1%); however, skinfolds (SK; 11.8 +/- 7.2%) were significantly different from HW. A significant correlation in fat-free mass (FFM) was found between BIA and HW (r = 0.96, p < 0.001), and the standard error of estimate (SEE) for FFM was 3.28 kg for males. In females, a significant difference (p < 0.001) in %BF was found for both BIA (26.4 +/- 5.7%) and SK (27.9 +/- 5.1%) when compared with HW (23.6 +/- 5.9%). The correlation in FFM between BIA and HW was lower (r = 0.78, p < 0.001) and the SEE for FFM was 2.93 kg for females. The Tanita 300WA LL-BIA system is appropriate for assessing body composition in male adolescents, but it warrants future research in female adolescents.

Adiposity↗

PubMed1995

Effects of aerobic exercise and dietary carbohydrate on energy expenditure and body composition during weight reduction in obese women.

To test the benefits of aerobic exercise and dietary carbohydrate during reduced-energy feeding, 23 obese women (44 +/- 4% fat) were randomly assigned to either aerobic exercise (Ex) or no exercise (Nx), and to a low-fat (LF) or low-carbohydrate (LC) reducing diet (5.00 +/- 0.56 MJ/d) for 12 wk. Changes in body composition, postabsorptive resting metabolic rate (RMR), thermic effect of a meal (TEM), and total daily energy expenditure (TDEE) were measured by respiratory gas exchange and doubly labeled water. Significant effects of Ex included a greater loss of fat mass (Ex: -8.8 +/- 2.1 vs Nx: -6.1 +/- 2.3 kg, P = 0.008) and maintenance of TDEE (Ex: +0.07 +/- 1.23 vs Nx: -1.46 +/- 1.04 MJ/d, P = 0.004), due to a difference in physical activity (Ex: +0.75 +/- 1.06 vs Nx: -0.61 +/- 1.03 MJ/d, P = 0.006), which was not attributable solely to the Ex sessions. RMR in both groups decreased comparably (-0.54 MJ/d), and TEM (% of meal) did not change. Diet composition did not significantly influence body composition or energy expenditure changes, but a greater weight loss was observed after the LC than after the LF (-10.6 +/- 2.0 vs -8.1 +/- 3.0 kg, P = 0.037) diet. The addition of aerobic exercise to a low-energy diet was beneficial in the treatment of moderate obesity because of its favorable effects on body composition, physical activity, and TDEE.

Adult↗

PubMedDate not supplied

[Body composition in a group of young women studied by bioelectrical impedance analysis].

Bioelectrical impedance analysis (BIA), based upon electrical conductivity of fat free mass, seems to be a rapid and useful method to predict body composition. The purpose of this study was to estimate the body composition of 32 young women using BIA and to compare its results with anthropometry (skinfolds measurements). No significant differences between fat-free mass or fat mass obtained by the two different methods were found. A high correlation between both methods for fat free mass (r = 0.826), fat mass (r = 0.861) and percentage of fat (r = 0.697) were found. On the other hand, correlation between resistance (r = -0.661), impedance (r = -0.663), height2/resistance (r = 0.803), height2/impedance (r = 0.804) and height2/reactance (r = 0.533) and fat free mass obtained by skinfolds measurements have been observed. These results suggest that BIA may be an adequate method besides anthropometry to assess body composition in homogeneous population with a stable body weight.

Adult↗

PubMed1994

Post-mortem limitations of body composition analysis by computed tomography.

Few of the indirect methods for measuring body composition have every been validated against direct human cadaver evidence. Computed tomography (CT), like NMR, has proved to be an important diagnostic tool and they appear to be the techniques of the future for body composition studies. The purpose of the present study (Cadaver Analysis Study III), undertaken at the Vrije Universiteit Brussel in a joint venture with the University of Göteborg, Sweden, was to validate tomographic measurements of volumes and areas from different tissues using data from CT-scanning of unembalmed deep-frozen cadavers and data collected by dissection of the same cadavers. Six Belgian adults were extensively measured and dissected. The body was divided into several slices for comparison of the CT image with photography of the same slice and comparison of tissue-volumes per segment for the whole body. Due to post-mortem changes and the frozen state of the cadavers, the CT measurements were greatly affected by artefacts disturbing adipose tissue (AT) and muscle area determinations. Only the bone area measurements were similar between the two techniques. However, when the volumes (per segment) of the same tissues were considered, no apparent difference was found between CT and dissection data for the muscle volume.

Aged↗

PubMed1999

Body composition by dual-energy X-ray absorptiometry in black compared with white women.

Dual-energy X-ray absorptiometry (DXA) has recently been applied to the measurement of body composition using a three-compartment model consisting of fat, lean and bone mineral. The mass of skeletal muscle may be approximated by measurement of the lean tissue mass of the extremities. In addition, body fat distribution can be estimated by determining the ratio of fat in the trunk to the fat in the extremities. In the current study, DXA was used to compare body composition and fat distribution between black (n = 162) and white women (n = 203). Black women had a higher mineral mass and a higher skeletal muscle mass. The ratio of mineral to muscle mass was higher in black women, even when the data were adjusted for age, height and weight. Both total body bone mineral and muscle mass declined with age in both races, with evidence for an accelerated loss of bone mineral after menopause. Body size (height and weight) was generally a significant variable in developing regressions of each compartment against age. Their higher musculoskeletal mass may lead to misclassification of 12% of black women as obese if body mass index is used as an index of obesity. Body fat distribution (trunk/leg) did not differ between races in the raw data. However, for women of the same age, height and weight, white women have a significantly higher trunk/leg fat ratio. Body composition values for fat, lean and bone mineral obtained from DXA should be adjusted not only for gender but also for age, height, weight and ethnicity.

Absorptiometry, Photon↗

PubMed2006

Growth and body composition of dairy calves fed milk replacers containing different amounts of protein at two feeding rates.

Previous research has demonstrated that increasing the CP concentration from 16 to 26% in milk replacers fed to male preruminant dairy calves at 1.5% of BW (DM basis) daily resulted in increased ADG, G:F, and deposition of lean tissue. However, the effects of dietary CP would be expected to vary depending on ME intake. Here, male Holstein calves < 1 wk old were used to determine the effects of feeding rate and CP concentration of isocaloric, whey protein-based milk replacers on growth and body composition. After a 2-wk standardization period, calves were assigned randomly to an initial baseline group or to treatments in a 2 x 4 factorial arrangement of feeding rate (1.25 or 1.75% of BW daily, DM basis) and milk replacer CP concentration (14, 18, 22, or 26% of DM). No starter was offered, but calves had free access to water. After a 5-wk feeding period, calves were slaughtered and body composition was determined. Increasing the feeding rate increased (P < 0.05) ADG, G:F, empty-body gains of chemical components and energy, the percentage of fat in empty BW gain and in the final empty body, and concentrations of IGF-I and insulin in plasma. Increasing the feeding rate decreased (P < 0.01) percentages of water and protein in the empty body and decreased urea N in plasma. Increasing dietary CP concentration linearly increased (P < 0.05) ADG, body length, heart girth, and gains of water and protein but linearly decreased (P < 0.05) fat gain. As dietary CP increased, fat content in empty body gain decreased, and water and protein increased. Increasing CP concentration increased (quadratic, P < 0.02) G:F, with greatest efficiencies for calves fed 22% CP. Gross energetic efficiency (retained energy:intake energy) was greater (P < 0.05) for calves fed at 1.75% of BW daily. Efficiency of dietary protein use for protein gain was greater for calves fed at 1.75% of BW daily but was not affected by dietary CP. The ratio of protein gain to apparently digestible protein intake above maintenance decreased as dietary CP increased. Interactions (P < 0.05) of feeding rate and CP concentration for gains of water and protein indicated that when dietary CP was 26% the ME supply limited protein use by calves fed at 1.25% of BW daily. Body composition of preruminant calves can be markedly altered by manipulating the protein to energy ratio in milk replacers. These dietary effects on body composition and growth are not predicted by current NRC standards.

Animal Feed↗

PubMed1996

Body composition in normal black women: the four-compartment model.

The four-compartment model of body composition was studied in 112 healthy black women to develop normative data to be used to assess deviations in illness. Each compartment was measured by an independent method: tritiated water dilution, prompt-gamma neutron activation analysis (for nitrogen), inelastic neutron scattering (for carbon) and dual energy x-ray absorptiometry (for calcium). The mean age of the population was 43.2 years. Race was self-declared. The mean values for the four compartments were [kg SE] protein: 9.6 (0.07); mineral 3.0 (0.03); fat 24.2 (0.70); and water 33.1 (0.29). Each of the compartments changed significantly with age (P < .0001). There were declines in total body water, mineral, and protein, whereas fat increased linearly with age. Linear regressions performed on pre- and postmenopausal women showed a significant difference only for the mineral compartment. Various models were fit to the data to adjust for body size and age. The equation y = age + height + weight fits the data as well as the other models. Equations and graphs were developed to assess each compartment using this linear model and may be used to assess the body composition status of healthy and ill black women. Although black women tended to be heavier than white women, after controlling for differences in body weight (and age) black women had a greater mass of protein, mineral, and water and a similar fat store. These differences, while statistically significant, were not of great magnitude. This was a cross-sectional study and suspected trends with aging must be confirmed by a longitudinal study.

Adipose Tissue↗

PubMed2003

Studies on human body composition during the first 4 months of life using magnetic resonance imaging and isotope dilution.

Assessing body composition during infancy requires data for the so-called reference infant. Currently available data for this purpose need to be updated and extended using methods based on principles different from those used previously to define the reference infant. Thus, magnetic resonance imaging was applied to full-term healthy boys (n = 25) and girls (n = 21), 4-131 d old, to estimate adipose tissue volume (ATV) and the amounts of s.c. and non-s.c. adipose tissue (AT). Total body water was estimated using isotope dilution. Total body fat (TBF), fat free weight (FFW) and the degree of hydration in FFW were calculated. Increases in weight, TBF, and FFW with age agreed with current reference data, although when compared with the reference, a slightly more rapid increase in % TBF was observed for boys. The degree of hydration in FFW was 78.9 +/- 4.5% (n = 45). Both sexes showed significant increases with age in s.c. ATV (14.7 and 13.0 mL/d for boys and girls, respectively) and in non-s.c. ATV (1.58 and 1.26 mL/d, respectively). Subcutaneous ATV was 90.5 +/- 1.8% (boys) and 91.1 +/- 1.9% (girls) of total ATV. In conclusion, a pronounced increase with age in the amount of AT was demonstrated involving a considerable gain in s.c. fat during early life. Except for % TBF in boys, changes in body composition with age agreed with current reference data.

Adipose Tissue↗

PubMed1998

Influences of low intensity exercise on body composition, food intake and aerobic power of sedentary young females.

The present study was designed to investigate the influences of aerobic training on the body composition, aerobic power and food intake of sedentary young females in relation to the initial levels of these variables. Thirty one untrained college females (age = 19.8 +/- 0.2 yr, stature = 154.4 +/- 0.8 cm, body mass = 53.3 +/- 1.2 kg, mean +/- SEM) participated in an exercise regimen consisting of 40% of maximum oxygen uptake (VO2max) for 30 minutes per day on a bicycle ergometer 5 times a week in a training period of 12 weeks. Food consumption was ad libitum but the content of daily food intake was recorded accurately throughout the whole training period and analyzed weekly. The average body mass index (BMI) and fat mass relative to body mass (% FM), estimated from the data of skinfold thickness, decreased significantly after the 12 wk training. There were significant negative correlations between the relative changes (% delta s) and initial levels of both body mass (r = -0.447, p < 0.05) and fat mass (r = -0.638, p < 0.05), but the corresponding correlation for lean body mass (LBM) was not significant (r = 0.186, p > 0.05). While the energy intake during the training period did not differ significantly from that during the control period on the average, the % delta value in energy intake between the two periods was negatively correlated to the energy intake during the control period (r = -0.604, p < 0.05). In addition, there were low but significant negative correlations between both the initial levels of BMI and %FM and % delta in energy intake; r = -0.413 (p < 0.05) for BMI and r = -0.393 (p < 0.05) for %FM. However, no significant correlations were found between % delta in energy intake and those in body composition variables (r = 0.116 to 0.237, p > 0.05). On the average VO2max relative to body mass (VO2max/BM) increased significantly, but VO2max relative to LBM (VO2max/LBM) did not. However, not only VO2max/BM but also VO2max/LBM was negatively correlated to the initial level; r = -0.671 (p < 0.05) for VO2max/BM and r = -0.625 for VO2max/LBM. Thus, the present results indicate that whether the body composition, food intake and aerobic power of sedentary young females can be modified by the exercise regimen eliciting 40% of VO2max depends on their initial levels.

Adult↗

PubMed1993

Impact of regional and total body composition and hormones on resting energy expenditure in overweight postmenopausal women.

The independent impact of regional and total body composition and sex and thyroid hormone levels on resting energy expenditure (REE) was assessed in 121 healthy, overweight (body mass index [BMI], 25 to 42 kg/m2), postmenopausal women (aged 49 to 58 years). REE was measured by indirect calorimetry with a ventilated hood, and the total, trunk, and peripheral body composition by dual-energy x-ray absorptiometry (DXA). Sex and thyroid hormone levels were also measured. REE correlated significantly (P < .05) better with trunk lean tissue mass ([LTM] r = .61) than with total-body (r = .53) or peripheral LTM (r = .30). Trunk LTM (R2 = .37), total-body fat tissue mass ([FTM] R2 = .04), androstenedione (R2 = .03), and total triiodothyronine ([T3] R2 = .02) were all significantly independently associated with REE. Together they explained 46% (model R2) of the interindividual variation in REE, with a standard error of estimate (SEE) of 549 kJ/d. We conclude that the interindividual variation in REE is explained mainly by differences in the visceral component of LTM, with additional minor information from the total-body FTM, androstenedione, and T3.

Absorptiometry, Photon↗

PubMed2001

Genomic scan for genes affecting body composition before and after training in Caucasians from HERITAGE.

An autosomal genomewide search for genes related to body composition and its changes after a 20-wk endurance-exercise training program has been completed in the HERITAGE Family Study. Phenotypes included body mass index (BMI), sum of eight skinfold thicknesses, fat mass (FM), fat-free mass, percent body fat (%Fat), and plasma leptin levels. A maximum of 364 sib-pairs from 99 Caucasian families was studied with the use of 344 markers with single-point and multipoint linkage analyses. Evidence of significant linkage was observed for changes in fat-free mass with the S100A and the insulin-like growth factor I genes (P = 0.0001). Suggestive evidence (2.0 < or = Lod < 3.0; 0.0001 < P < or = 0.001) was also observed for the changes in FM and %Fat at 1q31 and 18q21-q23, in %Fat with the uncoupling protein 2 and 3 genes, and in BMI at 5q14-q21. At baseline, suggestive evidence was observed for BMI at 8q23-q24, 10p15, and 14q11; for FM at 14q11; and for plasma leptin levels with the low-density lipoprotein receptor gene. This is the first genomic scan on genes involved in exercise-training-induced changes in body composition that could provide information on the determinants of weight loss.

Adipose Tissue↗

PubMed1982

Differences in body compositions, growth and food intakes between mice which have been selected for a small or large body size.

1. Q-strain mice selected for high-line (QLF) or low-line (QSC) body-weights at 6 weeks of age were culled to litters of two or eight (QLF-2, QLF-8, QSC-2, QSC-8) at birth and were suckled in these groups until 19 d of age. 2. Body-weights were measured daily for all groups and body compositions compared at birth and 19 and 42 d of age. Food intakes and urinary and faecal nitrogen were measured during metabolism trials between 19 and 42 d. 3. QLF-2 and QSC-2 mice grew faster than the corresponding groups of eight until 19 d of age. They also deposited more fat as a percentage of total gain. 4. In the period 19-42 d the influence of genetic selection reappeared and was manifest in a slowing of growth rates of QLF-2 and QSC-2 animals so that by 42 d of age there were no differences in body-weight between the groups within a line. 5. During the period 19-42 d the total food intakes of each group within a line did not differ although, on the basis of food intake per unit metabolic body-weight (g/kg body-weight 0.75 per d) QLF-2 and QSC-2 ate less food than QLF-8 and QSC-8 respectively. 6. The differences in body-weight at 19 d between groups were largely overcome by the increased contribution of protein and water to the weight gain of the groups of eight during the post-weaning period.

Aging↗