Search

Magnitude and variation of ratio of total body potassium to fat-free mass: a cellular level modeling study. Am J Physiol Endocrinol Metab 281: E1-E7, 2001.--Potassium is an essential element of living organisms that is found almost exclusively in the intracellular fluid compartment. The assumed constant ratio of total body potassium (TBK) to fat-free mass (FFM) is a cornerstone of the TBK method of estimating total body fat. Although the TBK-to-FFM (TBK/FFM) ratio has been assumed constant, a large range of individual and group values is recognized. The purpose of the present study was to undertake a comprehensive analysis of biological factors that cause variation in the TBK/FFM ratio. A theoretical TBK/FFM model was developed on the cellular body composition level. This physiological model includes six factors that combine to produce the observed TBK/FFM ratio. The ratio magnitude and range, as well as the differences in the TBK/FFM ratio between men and women and variation with growth, were examined with the proposed model. The ratio of extracellular water to intracellular water (E/I) is the major factor leading to between-individual variation in the TBK/FFM ratio. The present study provides a conceptual framework for examining the separate TBK/FFM determinants and suggests important limitations of the TBK/FFM method used in estimating total body fat in humans and other mammals. water distribution; body fat measurement; body composition

Increased variety in the food supply may contribute to the development and maintenance of obesity. Thirty-nine studies examining dietary variety, energy intake, and body composition are reviewed. Animal and human studies show that food consumption increases when there is more variety in a meal or diet and that greater dietary variety is associated with increased body weight and fat. A hypothesized mechanism for these findings is sensory-specific satiety, a phenomenon demonstrating greater reductions in hedonic ratings or intake of foods consumed compared with foods not consumed. Nineteen studies documenting change in preference, intake, and hedonic ratings of food after a food has been eaten to satiation in animals and humans are reviewed, and the theory of sensory-specific satiety is examined. The review concludes with the relevance of oral habituation theory as a unifying construct for the effects of variety and sensory-specific satiety, clinical implications of dietary variety and sensory-specific satiety on energy regulation, and suggestions for future research.

We evaluated the accuracy in using the Small Animal Composition Analyzer (EM-SCAN[R], Model SA-2) for estimating body composition of live meadow voles (Microtus pennsylvanicus). To investigate the necessity for a species-specific calibration equation, we compared the average error in estimates of lipid mass using meadow vole data in calibration equations derived for meadow voles in this study to equations derived for prairie voles (very similar in size and shape to meadow voles) and to those provided by the manufacturer. Analyses using a complete data set (n = 27 voles) and 2 subsets representing 'lean' voles (n = 16) and 'fat' voles (n = 11) were performed. The equation derived for meadow voles more accurately estimated lipid mass than the other equations with an average error of 1.55 g compared to 3.64 g using the prairie-vole equation and 4.73 g with the manufacturer equation, supporting the need for a species-specific equation even with species of very similar size and morphology. Key words: body composition, meadow vole, Microtus pennsylvanicus, total body electrical conductivity

Early-weaned pigs (n = 64) averaging 5.3 [+ or -] 0.3 kg and distributed into two environments (dirty and clean) were used to evaluate effects of conjugated linoleic acid (CLA) on growth performance, immune competence, and empty body composition. A factorial (2 x 4) arrangement within a split-plot design, with four littermate pigs as the experimental unit for the environment, pig within litter as the experimental unit for dietary treatment, and d-0 body weight used as covariate, were used in data analysis. Diets were formulated to contain CLA at 0, 0.67, 1.33, or 2% and to exceed the NRC (1988) nutrient needs of pigs. Animals were given ad libitum access to feed for 7 wk in three phases (I, 1 to 2; II, 3 to 5; and III, 6 to 7 wk). Within phases, diets were isocaloric and isonitrogenous. In Phase I, as dietary CLA concentration increased, ADG and ADFI decreased linearly (P [is less than] 0.05 and P [is less than] 0.02, respectively). In Phase II, upon adaptation to dietary CLA supplementation, ADG increased quadratically (603, 623, 622, and 548 g/d; P [is less than] 0.01), ADFI decreased linearly (873, 840, 867, and 717 g/d; P [is less than] 0.02) and gain:feed ratio tended to increase linearly (691, 742, 715, and 763; P [is less than] 0.07). In Phase III, no differences in growth performance were attributed to either dietary or environmental treatments. The poor health status associated with the dirty environment induced a growth suppression; pigs in the clean room had a greater cumulative ADG (P [is less than] 0.01) and ADFI (P [is less than] 0.01) than pigs in the dirty room. In Phase I, lower plasma urea nitrogen levels observed in pigs found in the dirty room (P [is less than] 0.03) indicated a lower protein intake caused by a lower ADFI. The effects of dietary CLA on peripheral phenotypic profiles of lymphoytes did not appear until d 42. However, as indicated by the growth suppression of pigs in the dirty room, the negative effects of the environmental challenge on pig health and growth had already appeared during phase I. On d 42, CLA induced a linear increase in percentages of [CD8.sup.+] lymphocytes (21.7, 22.3, 28.0, and 32.7%; P [is less than] 0.001). These data suggest that a 42-d dietary CLA supplementation preceding a disease challenge could have prevented disease-associated growth suppression. Also, CLA-mediated amelioration of particular infectious diseases will depend on which [CD8.sup.+] T cell subset (i.e., CD8[Alpha][Alpha]-immu-noregulatory or CD8[Alpha][Beta]-cytotoxic) is most influenced by dietary CLA supplementation. Key Words: [CD8.sup.+] Lymphocytes, Cell-Mediated Immunity, Immunomodulators, Linoleic Acid, Pigs

For [is greater than] 20 y, weight gain has been a commonly reported side effect of adjuvant chemotherapy (CT) for breast cancer. To determine causes for this energy imbalance, we undertook a study that assessed body weight and composition (via dual energy X-ray absorptiometry [DXA]), resting metabolic rate (RMR; via indirect calorimetry), energy intake (via 2-d 24-h dietary recalls) and physical activity (Stanford 5-City Physical Activity Questionnaires) throughout the year after the diagnosis of Stage I or II breast cancer in premenopausal patients who received CT compared with patients who received localized treatment (LT; surgery with or without radiation). Body weight and RMRs were measured at baseline and at 2, 6 and 12 mo; DXA was performed at baseline and at 6 and 12 mo; energy intake was assessed semimonthly and physical activity was assessed weekly. Analyses to determine differences in linear trends over time were performed (two-tailed tests; [Alpha] = 0.05). Preliminary analyses on complete data from 53 participants (n = 36 in the CT group, n = 17 in the LT group) suggest that there are significant gains in body weight by patients who receive CT compared with patients who receive LT (2.7 [+ or -] 4.5 vs. 1.0 [+ or -] 1.4 kg/y; P = 0.04). Furthermore, percent body fat increased from 33.6% [+ or -] 8.6% at baseline to 35.8% [+ or -] 9.0% at 1 y in the CT group whereas no change was noted in the LT group (i.e., 28.6% [+ or -] 6.7% to 28.5% [+ or -] 7.0%) (age- and race-controlled P-value = 0.001). Significant differences between groups also were seen with regard to lean body mass (P = 0.002), especially in the leg region (P = 0.01), where the CT group experienced losses and the LT group experienced slight gains. Decreases in physical activity were observed from baseline to follow-up in the AC group (506 [+ or -] 101 vs. 458 [+ or -] 114 kcal/d; P = 0.017), however, were not seen in the LT group. No differences over time or between groups were noted with regard to RMR or energy intake. These data support the need for early interventions focused on increased physical activity in order to reduce gains in weight and percent body fat by young women with breast cancer.

The aim of the present study was to see whether combining eicosapentaenoic acid (EPA) with a nutritional supplement might lead to net weight gain in patients with advanced pancreatic cancer. Twenty patients were asked to consume 2 cans daily of a nutritional supplement fortified with fish oil in addition to their normal food intake. Each can contained 310 kcal, 16 g protein and 1.09 g EPA. Weight, body composition, dietary intake, resting energy expenditure (REE) and performance status were measured at baseline and after 3 wk. No intervention-related adverse events were observed apart from steatorrhea, which responded to pancreatic enzyme replacement. Patients consumed a median 1.9 cans/d. All patients were losing weight at baseline at a median rate of 2.9 kg/mo (interquartile range 3.9-2.1 kg/mo). After administration of the supplement, patients had significant weight gain at 3 (median 1 kg, range 0-2 kg, P = 0.024) and 7 wk (median 2.5 kg, range 0.1-4.6 kg, P = 0.028). There was no change in percentage of total body water, suggesting that weight gain was not due to the accumulation of water. Analysis of body composition revealed a significant gain in lean body mass and no change in fat mass after 3 and 7 wk. Dietary intake increased significantly by [is greater than] 370 kcal/d (P = 0.0016). Although overall REE remained unchanged (P = 0.18), REE per kg body weight and per kg lean body mass fell significantly (P [is less than] 0.03). Performance status was significantly improved at 3 and 7 wk (P [is less than] 0.05). In contrast to previous studies of conventional oral nutritional supplements in weight-losing cancer patients that have shown no benefit, this study suggests that a nutritional supplement fortified with fish oil may reverse cachexia in advanced pancreatic cancer.

The introduction of high fructose corn syrup as a substitute sweetener for sucrose in the mid-1970s has contributed to a general increase in fructose consumption in the U.S. diet. Although several previous investigations suggested that dietary fructose increases serum triglyceride concentration and body fat, these studies have, in general, evaluated this effect in young rats fed the experimental diets for a relatively short period of the life span of the animals. Moreover, these investigations did not control for the possible effects that increased adiposity due to fructose feeding may have on serum triglyceride concentration. The purpose of the current investigation was to describe the long-term effects of specific dietary carbohydrates on serum lipid concentrations and body composition. To this end, we measured serum triglyceride, total cholesterol and HDL cholesterol concentrations and body composition of rats aged 9, 18 and 26 mo that had free access to or were restricted to 60% of free access intake of one of five diets that varied in carbohydrate source (cornstarch, sucrose, glucose, fructose or equimolar fructose plus glucose) starting at 3 mo of age. Dietary fructose significantly increased serum triglyceride concentration across the life span in rats that had free access to food or were calorie restricted. The source of dietary carbohydrate did not have a significant effect on body composition, total cholesterol or the distribution of the cholesterol fractions. These data suggest that dietary fructose per se and not the interaction between fructose and the energy content of the diet increases serum triglyceride concentration in rats. J. Nutr. 130: 3077-3084, 2000. KEY WORDS: * aging * body composition * calorie restriction * cholesterol * fructose * triglyceride * rats

We evaluated the effects of dietary fat type on fat metabolism and deposition in broiler chickens. Birds were fed diets containing either 8 g dietary saturated (beef tallow) or polyunsaturated fat (sunflower oil)/100 g for 32 d. The abdominal fat deposition of chickens fed the sunflower oil-enriched diet was significantly lower than that of chickens fed the tallow-enriched diet (2.63 [+ or -] 0.47 versus 3.03 [+ or -] 0.44 g/100 g live wt.; P = 0.033). The specific activities of heart carnitine palmitoyltransferase I and L-3-hydroxyacyl-CoA dehydrogenase were higher (P [is less than or equal to] 0.03) in chickens fed the sunflower oil-enriched diets, indicating a greater rate of [Beta]-oxidation. Liver fatty acid synthetase activity was lower (P = 0.01) in chickens fed the sunflower oil-enriched diet, suggesting reduced hepatic lipogenesis in this group. Postprandial plasma triglyceride levels were significantly lower (P [is less than] 0.05) in birds fed the sunflower oil-enriched diet, indicating a higher rate of dietary lipid clearance from the bloodstream to tissues. In conclusion, the lower fat deposition observed in broilers fed sunflower oil-enriched diets appears to be the net result of an increased rate of lipid catabolism and lower rate of fatty acid synthesis despite higher dietary fat absorption. J. Nutr. 130: 3034-3037, 2000. KEY WORDS: * dietary fat type * lipogenesis * lipolysis * fat deposition * broiler chickens

We evaluated the effects of conjugated linoleic acid (CLA) on growth performance, tissue fatty acid composition and ex vivo lipogenic enzyme activity in piglets (n = 40) reared on sows fed diets supplemented with CLA or linoleic acid (LA). Weaned offspring of both sow groups were offered either a CLA- or LA-enriched starter diet for 35 d. The starter diets were formulated to contain 2 g CLA (containing 58.9 g CLA/100 g total fatty acids) or LA per 100 g feed. All piglets were slaughtered at 70 d of age and tissue samples of the back fat, omental fat and longissimus dorsi were collected. Irrespective of the dietary fat supplied in the starter period, piglets reared on the CLA sows had greater final body and warm carcass weights (P [is less than] 0.01), and greater feed intake (P = 0.02) than piglets reared on the LA sows. The dietary effect on the fatty acid composition was similar for the adipose and muscle tissues. Compared with the LA-enriched diets, CLA increased the level of total saturated fatty acids (P [is less than] 0.05), whereas that of monounsaturated fatty acids was decreased (P [is less than] 0.05). Dietary CLA increased glucose6-phosphate dehydrogenase (P [is less than] 0.01) and malic enzyme activities (P [is less than] 0.06) in the fat tissues, but did not affect fatty acid synthase activity. The shift toward a higher deposition of saturated fatty acids and a lower deposition of monounsaturated fatty acids is the result of down-regulation of [Delta]9-desaturase activity that was induced by CLA rather than an altered rate of de novo synthesis. J. Nutr. 130: 2981-2989, 2000. KEY WORDS: * piglets * conjugated linoleic acids * adipose tissue * lipogenesis

Lange, Kai Henrik Wiborg, Fredrik Isaksson, Anders Juul, Michael Hojby Rasmussen, Jens Bulow, and Michael Kjaer. Growth hormone enhances effects of endurance training on oxidative muscle metabolism in elderly women. Am J Physiol Endocrinol Metab 279: E989-E996, 2000.--The present study investigated whether recombinant human (rh) growth hormone (GH) combined with endurance training would have a larger effect on oxidative capacity metabolism, and body fat than endurance training alone. Sixteen healthy, elderly women, aged 75 yr, performed closely monitored endurance training on a cycle ergometer over 12 wk. rhGH was given in a randomized, double-blinded, placebo-controlled design in addition to the training program. GH administration resulted in a doubling of serum insulin-like growth factor I levels. With endurance training, peak oxygen uptake increased by -18% in both groups, whereas the marked increase in muscle citrate synthase activity was 50% larger in the GH group compared with the placebo group. In addition, only the GH group revealed an increase in muscle L-3-hydroxyacyl-CoA dehydrogenase activity. Body weight remained unchanged in both groups, but the GH group showed significant changes in body composition with a decrease in fat mass and an increase in lean body mass. Twenty-four-hour indirect calorimetry performed in four subjects showed a marked increase in energy expenditure with increased relative and absolute fat combustion in the two subjects receiving rhGH. In conclusion, rhGH adds to the effects of endurance training on muscle oxidative enzymes and causes a reduction in body fat in elderly women. insulin-like growth factor I; enzymes; exercise; calorimetry; body composition

Three experiments were conducted to test the hypothesis that different starter feeding programs (High, high quality; Low, low quality) will affect growth performance and body composition of pigs from weaning to market weight and that this effect may be influenced by gender (barrows or gilts) and breed (F, Yorkshire-Duroc x Hampshire; P, PIC Camborough 15 x PIC line 405). In Exp. 1, 21 [+ or -] 4-d-weaned F pigs (n = 90) were used in a 2 (High or Low) x 2 (barrows or gilts) factorial design. In Exp. 2, 21 [+ or -] 3-d-weaned pigs (n = 184) were used in a 2 (F or P) x 2 (High or Low) x 2 (barrows or gilts) factorial design. In Exp. 3, 21 F pigs from each gender and feeding program treatment were killed at d 0, 3, 7, 14, 42, 82, or 152 postweaning for evaluating body composition. Two starter feeding programs (High or Low) were applied to pigs for 6 wk postweaning. Pigs from both High and Low treatments were provided the same corn-soybean meal-based diets for the growing and finishing periods. Although the ADG of all pigs receiving the High treatment during the early starter period were higher (P [is less than] .01) than those of tho Low, tho terminal BW of F barrows were similar between High and Low (Exp. 1 and 2) and those of gilts were similar between High and Low (Exp. 2) (P [is greater than] .80). However, the BW of P pigs receiving the High treatment, regardless of gender, tended to be heavier than those receiving the Low (Exp. 2) and F barrows receiving the High treatment tended to be heavier than those receiving the Low (Exp. 1). For the first 7 d postweaning, the High-fed pigs gained more protein (P [is less than] .05) and lost less fat (P [is less than] .05) than Low-fed pigs. During the growing-finishing period, the Low-fed pigs exhibited compensatory protein gain and achieved a body protein content similar (P [is less than] .60) to High-fed pigs by termination. Protein gains from weaning to termination between High- and Low-fed pigs were not different in Exp. 2 and 3. The protein gain of gilts was higher (P [is less than] .05) than that of barrows. Similarly, fat gain within genders was not affected by starter feeding program. Fat gain of gilts, however, was lower (P [is less than] .08) than that of barrows in Exp. 3. In conclusion, the nutritional quality of the starter feeding program affected growth performance immediately after weaning but did not affect protein gain over the entire production period. Key Words: Body Composition, Body Protein, Feed Rations, Growth Rate, Pigs

Vol 20, Spring 2000 * Practical application of bioelectrical impedance analysis (BIA) for body composition evaluation. C. Fields-Gardner. [...]

Otsuka Long Evans Tokushima Fatty (OLETF) rats were developed as a model of noninsulin-dependent diabetes mellitus (NIDDM) with mild obesity. Changes in carcass composition and in the daily profile of energy expenditure were examined before and after manifestation of diabetes (8 and 24 wk, respectively), and compared with the normal control Long Evans Tokushima (LETO) rats and streptozotocin (STZ)-induced diabetic LETO rats. OLETF rats had greater body weights than LETO rats and significantly greater absolute and relative fat weights. A diurnal rhythm of energy expenditure associated with two peaks was observed in LETO rats, but the two peaks were not apparent in OLETF rats at 24 wk of age. A diurnal rhythm associated with one peak was observed in STZ-induced diabetic LETO rats. Energy derived from fat constituted this peak; the pattern of the daily energy expenditure was significantly different from that of either nontreated LETO or OLETF rats at 24 wk of age. NIDDM in OLETF rats at 24 wk of age has only a small role in modification of the diurnal rhythm of energy expenditure, whereas STZ-induced diabetes significantly affected the rhythm. J. Nutr. 130: 2562-2567, 2000. KEY WORDS: * energy expenditure * insulin resistance * diurnal rhythm * insulin-dependent diabetes mellitus * obesity * rats

The study objectives were to assess the relationships among human immunodeficiency virus (HIV) replication, energy balance, body composition and growth in children with HIV-associated growth failure (GF). Energy intake and expenditure, body composition and level of HIV RNA were measured in 16 HIV-infected children growth failure (HIV+/GF+), defined as a 12-mo height velocity [is less than or equal to] 5th percentile for age, and 26 HIV-infected children with normal rates of growth (HIV+/GF-). Energy intake was measured by repeated 24-h dietary recall, resting energy expenditure (REE) by indirect calorimetry and total energy expenditure (TEE) by the doubly labeled water method. Fat-free mass (FFM) was determined by dual X-ray energy absorptiometry and plasma HIV RNA by the polymerase chain reaction method. The mean plasma HIV RNA content among the HIV+/GF+ group was nearly 1.5 log higher than that of the HIV+/GF- group (4.89 [+ or -] 1.08 vs. 3.43 [+ or -] 1.64 x [10.sup.2] copies/L, P = 0.009). The mean daily energy intake, and age-adjusted REE and TEE were lower in HIV+/GF+ children (P = 0.003, 0.06 and 0.16, respectively). HIV+/GF+ children had a mean daily energy deficit of 674 [+ or -] 732 kJ/d compared with HIV+/GF- children who had a mean energy surplus of 1448 [+ or -] 515 kJ/d (P = 0.030). There were no differences in REE after adjustment for differences in FFM and age using multiple regression analysis (P = 0.88). There was a significant inverse relationship between FFM and plasma HIV RNA [[R.sup.2] = 0.64, standard error of the estimate (SEE) = 3.23] and between viral load and 12-mo growth velocity ([R.sup.2] = 0.61, SE = 1.51). Viral load and energy intake were also inversely related ([R.sup.2] = 0.17, SEE = 573.2, P = 0.0125). In HIV-infected children, rate of growth, quantity of FFM and energy intake are closely related to the level of HIV replication. The energy intake of children with HIV-associated GF may not be adequate for supporting normal development of FFM and growth, despite possible decreases in total energy expenditure. J. Nutr. 130: 2498-2502, 2000. KEY WORDS: * HIV-associated growth failure * children * energy balance * viral load * fat-free mass

The predictive values of anthropometric measurements, race, gender, gestational and postnatal ages, and season at birth and at study for the total body dual energy X-ray absorptiometry (DXA)-derived lean mass (LM), fat mass (FM) and fat mass as a percentage of body weight (%FM) were determined in 214 singleton appropriate birth weight for gestational age infants [101 Caucasian (60 boys, 41 girls) and 113 African American (55 boys, 58 girls)]. Gestational ages were 27-42 wk and the infants were studied between birth and 391 d, weighing between 851 and 13446 g. In addition, predictive value of body weight, LM and FM for DXA bone measurements was also determined. Scan acquisition used Hologic QDR 1000/W densitometer and infant platform and scans without significant movement artifacts were analyzed using software 5.64p. Body weight, length, gender and postnatal age were significant predictors of LM (adjusted [R.sup.2] [is greater than] 0.94) and FM (adjusted [R.sup.2] = [is greater than] 0.85). Physiologic variables had little predictive value for %FM except in the newborns (adjusted [R.sup.2] 0.69). Body weight was the dominant predictor of LM and FM, although length had similar predictive value for LM with increasing postnatal age. Female infants had less LM and more FM throughout infancy (P [is less than] 0.01). LM or FM offered no advantage over body weight in the prediction of bone mass measurements. DXA is a useful means with which to determine body composition, and our data are important in the design and assessment of nutritional intervention studies. J. Nutr. 130: 2188-2194, 2000. KEY WORDS: * race * gender * bone * fat * lean tissue * humans

Resting energy expenditure-fat-free mass relationship: new insights provided by body composition modeling. Am J Physiol Endocrinol Metab 279: E539-E545, 2000.--The relationship between resting energy expenditure (REE) and metabolically active fat-free mass (FFM) is a cornerstone in the study of physiological aspects of body weight regulation and human energy requirements. Important questions, however, remain unanswered regarding the observed linear REE-FFM association in adult humans. This led us to develop a series of REE-body composition models that provide insights into the widely used simple linear REE-FFM prediction model derived experimentally in adult humans. The new models suggest that the REE-FFM relationship in mammals as a whole is curvilinear, that a segment of this function within a FFM range characteristic of adult humans can be fit with a linear equation almost identical to that observed from a composite review of earlier human studies, and that mammals as a whole exhibit a decrease in the proportion of FFM as high metabolic rate organs with greater FFM. The present study thus provides a new approach for examining REE-FFM relationships, advances in a quantitative manner previously observed albeit incompletely formulated REE-body composition associations, and identifies areas in need of additional research. energy metabolism; body composition

Growing pigs (n = 25; 17.8 [+ or -] 0.1 kg) were used to study the effects of L-carnitine and protein intake on nitrogen (N) balance and body composition. Fat-supplemented (40 g soy oil/kg diet), corn-soybean meal basal diets containing low or high protein (136 or 180 g/diet) were formulated so that protein accretion would be limited by metabolizable energy (ME). Each basal diet was supplemented with 0 or 500 mg/kg L-carnitine and fed to pigs for 10 d in a nutrient balance trial. Final body composition was compared with weight and age-matched pigs measured on d 0 to calculate nutrient accretion rates. High protein feeding increased (P [is less than] 0.01) average daily gain (ADG) by 34%, as well as nitrogen digestibility (4.4%), retention (5.2%), urinary excretion (29%) and crude protein (CP) accretion (33%). Total-body carnitine accretion rate was 4.5 fold greater and total body carnitine concentration was almost 100% greater than in unsupplemented controls (P [is less than] 0.01). Irrespective of protein level, carnitine increased ADG (by 7.3%, P [is less than] 0.10) and CP accretion rate (9%, P [is less than] 0.10). Congruently, carnitine supplementation improved the efficiency of nitrogen retention (P [is less than] 0.05) and reduced urinary nitrogen excretion (14%, P [is less than] 0.10). Carcass fat content also was reduced in carnitine-supplemented pigs (P [is less than] 0.10). Collectively, these data support the hypothesis that carnitine can improve the efficiency of nitrogen utilization in 20-kg pigs fed energy-limited, fat-containing diets. We conclude that endogenous carnitine biosynthesis may be adequate to maintain sufficient tissue levels during growth, but that supplemental dietary carnitine (at 500 mg/kg) may be retained sufficiently so as to alter nutrient partitioning and thus body composition of 20-kg pigs. J. Nutr. 130: 1809-1814, 2000. KEY WORDS: * pigs * carnitine * biosynthesis * nitrogen balance * body composition

A serial slaughter study was conducted to determine the effects of true ileally digestible lysine (IDLys) intake and metabolizable energy intake (MEI) on whole-body protein deposition (PD) and dietary lysine utilization in pigs between 45 and 75 kg live weight (LW). Conventional N balances were determined at the start and end of the serial slaughter study. Semisynthetic diets based on casein and cornstarch provided protein-bound lysine to support protein depositions of approximately 70% (Lys70%, IDLys 11.1 g/d) or 90% (Lys90%, IDLys 13.2 g/d) of a determined maximum PD. During the serial slaughter study and at Lys70%, pigs were fed one of six levels of MEI ranging from 14.1 to 23.5 MJ/d; at Lys90%, pigs were fed one of seven levels of MEI ranging from 15.6 to 26.4 MJ/d. The serial slaughter study and N balances indicated that MEI and IDLys had independent effects on PD and lysine utilization. Lysine utilization (calculated as the fraction of absorbed available lysine, over and above maintenance lysine requirements, that was retained in body protein) and PD increased with increasing MEI until plateau values were reached. At the plateaus, PD was determined by lysine intake. When lysine intake determined PD, lysine utilization did not decline (P [is greater than] 0.10) with increasing lysine intake. Based on the N balance study, there was no effect (P [is greater than] 0.1) of LW on lysine utilization. The marginal efficiency of using absorbed available lysine for PD was 0.75 and was not affected by LW, MEI, or IDLys. Key Words: Growing Pig, Lysine Utilization, Metabolizable Energy, Protein Deposition

Illner, Kirsten, Gisbert Brinkmann, Martin Heller, Anja Bosy-Westphal, and Manfred J. Muller. Metabolically active components of fat free mass and resting energy expenditure in nonobese adults. Am. J. Physiol. Endocrinol. Metab. 278: E308--E315, 2000.--Resting energy expenditure (REE) and components of fat-free mass (FFM) were assessed in 26 healthy nonobese adults (13 males, 13 females). Detailed body composition analyses were performed by the combined use of dual-energy X-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), bioelectrical impedance analysis (BIA), and anthropometrics. We found close correlations between REE and [FFM.sub.BIA] (r = 0.92), muscle [mass.sub.DEXA] (r = 0.89), and sum of internal [organs.sub.MRI] (r = 0.90). In a multiple stepwise regression analysis, [FFM.sub.BIA] alone explained 85% of the variance in REE (standard error of the estimate 423 kJ/day). Including the sum of internal [organs.sub.MRI] into the model increased the [r.sup.2] to 0.89 with a standard error of 381 kJ/day. With respect to individual organs, only skeletal [muscle.sub.DEXA] and liver [mass.sub.MRI] significantly contributed to REE. Prediction of REE based on 1) individual organ masses and 2) a constant metabolic rate per kilogram organ mass was very close to the measured REE, with a mean prediction error of 96 kJ/day. The very close agreement between measured and predicted REE argues against significant variations in specific REEs of individual organs. In conclusion, the mass of internal organs contributes significantly to the variance in REE. body composition; muscle mass; organ mass; dual-energy X-ray absorptiometry; magnetic resonance imaging; bioelectrical impedance analysis; anthropometrics

Burguera, Bartolome, David Proctor, Niki Dietz, ZengKui Guo, Michael Joyner, and Michael D. Jensen. Leg free fatty acid kinetics during exercise in men and women. Am. J. Physiol. Endocrinol. Metab. 278: E113-E117, 2000.--We previously reported that epinephrine stimulates leg free fatty acid (FFA) release in men but not in women. The present studies were conducted to determine whether the same is true during exercise. Six men and six women bicycled for 90 min at 45% of peak [O.sub.2] consumption, during which time systemic and leg FFA kinetics ([9,10-[sup.3]H]palmitate) were measured. The catecholamine and hormonal responses to exercise were not different in men and women. The baseline systemic and leg palmitate release was 94 [+ or -] 15 vs. 114 [+ or -] 5 [micro]mol/min and 16 [+ or -] 2 and 20 [+ or -] 3 [micro]mol/min, respectively, in men and women [P = nonsignificant (NS)]. Systemic and leg palmitate release increased (both P [is less than] 0.001) to 251 [+ or -] 18 vs. 212 [+ or -] 16 [micro]mol/min and 73 [+ or -] 19 vs. 80 [+ or -] 12 [micro]mol/min in men and women, respectively, during the last 30 min of exercise (P = NS, men vs. women). We conclude that the systemic and leg adipose tissue lipolytic response to exercise is not different in nonobese men and women. lipolysis; body composition; indirect calorimetry

Zhou, Jun, Xiaolang Yan, Donna H. Ryan, and Ruth B. S. Harris. Sustained effects of repeated restraint stress on muscle and adipocyte metabolism in high-fat-fed rats. Am. J. Physiol. 277 (Regulatory Integrative Comp. Physiol. 46): R757-R766, 1999.--Repeated restraint stress 3 h/day for 3 days in rats causes a temporary hypophagia but a sustained weight loss. We investigated whether poststress changes in peripheral tissue metabolism contributed to these responses. One day after the last restraint, insulin sensitivity, measured by oral glucose tolerance test, was improved in restrained rats. Restraint and pair-fed rats weighed less than controls, but body fat content was the same in all groups. Muscle glucose uptake, measured in vitro, was not changed by treatment, whereas in vitro adipocyte glucose uptake was substantially inhibited only in restrained rats. Adipocytes from restrained rats had elevated rates of fatty acid oxidation but not fatty acid esterification, indicating a shift in energy supply from glucose to fatty acids. Five days after the last restraint, the reduced weight of restrained and pair-fed rats resulted from loss of both lean and fat tissue. These results demonstrate that restraint caused sustained, tissue-specific changes in metabolism that may contribute to changes in body composition and body weight of the rats. glucose tolerance; glucose transport; fatty acid oxidation; body composition

In quadrupedal trotting, contralateral fore and hind limbs are set down in unison and exert forces on the ground simultaneously. Ground reaction forces on individual limbs of trotting dogs were measured separately, using a series of four force platforms. Vertical and horizontal impulses were determined from force-time records of each limb. When average fore-aft acceleration of the body is zero (steady state) in a given trotting step, the fraction of total vertical impulse on the forelimb is equal to the fraction of body weight supported by the forelimbs during standing. When an animal speeds up (average forward acceleration) or slows down (average rearward acceleration) in a given trotting step, vertical impulse is redistributed to the hind limb or forelimb, respectively. These redistributions of vertical impulse are a direct result of pitching torques due to non-zero average fore-aft accelerations of the body. Vertical forces on the fore and hind limb prevent forward or rearward tipping of body, just as the legs of a table prevent tipping when it is unevenly loaded. Quadrupeds take advantage of the stability provided by the simultaneous support of a forelimb and hind limb in order to maintain a level posture during fore-aft accelerations.

This study was conducted to model the growth of carcass, viscera, and empty body components and component composition of pigs. Quantitative tissue and chemical composition of 319 swine, representative of barrows and gilts from five commercial genetic populations, was determined at eight stages of growth between 25 and 152 kg. After whole body grinding and carcass dissection, proximate analyses were performed to calculate concentrations of protein, lipid, moisture, and ash of carcass, viscera, empty body, carcass lean, and carcass fat. Linear and nonlinear equations were developed to investigate the growth patterns of each component. Nonlinear growth functions accounted for the greatest amount of variation in empty body protein, lipid, moisture, and ash mass. Differences (P < .05) existed between barrows and gilts for nearly all components investigated. Carcass lean and fat tissues significantly increased in lipid percentage and decreased in moisture percentage as live weight increased. There were significant changes in the ratio and composition of the tissues of barrows and gilts during growth. Nonlinear models fitted the data better than allometric equations for nearly all of the components investigated. Key Words: Pigs, Growth, Models, Composition