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A revised way of thinking is essential for promoting harm reduction strategies and reducing the negative implications of injection drug use (IDU). Despite the growth of harm reduction approaches in the United States, there is limited guidance for designing and implementing multi-sector efforts that address the external determinants that promote and facilitate IDU. Current frameworks fail to acknowledge the individual's role and influence in multi-sector change. To address the multifaceted nature of IDU, we must address the complex relationship between people who inject drugs (PWID) and their external environment. As part of a community-academic partnership, a framework was developed to address the gaps in current theoretical models and community practice. Our Harm Reduction Collaboration Framework (HRCF) accepts PWID as key stakeholders and presents a practical framework in which PWID and community organizations partner in decision making to influence policy, systems, and environmental change. We provide examples of two organizations that have made substantive changes in implementing harm reduction strategies in their communities by utilizing the HRCF., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Machine learning techniques have been used to quantify the relationship between local structural features and variations in local dynamical activity in disordered glass-forming materials. To date these methods have been applied to an array of standard (Arrhenius and super-Arrhenius) glass formers, where work on "soft spots" indicates a connection between the linear vibrational response of a configuration and the energy barriers to non-linear deformations. Here we study the Voronoi model, which takes its inspiration from dense epithelial monolayers and which displays anomalous, sub-Arrhenius scaling of its dynamical relaxation time with decreasing temperature. Despite these differences, we find that the likelihood of rearrangements can nevertheless vary by several orders of magnitude within the model tissue and extract a local structural quantity, "softness," that accurately predicts the temperature dependence of the relaxation time. We use an information-theoretic measure to quantify the extent to which softness determines impending topological rearrangements; we find that softness captures nearly all of the information about rearrangements that is obtainable from structure, and that this information is large in the solid phase of the model and decreases rapidly as state variables are varied into the fluid phase.

We use molecular simulations to study jamming of a crumpled bead-spring model polymer in a finite container and compare to jamming of repulsive spheres. After proper constraint counting, the onset of rigidity is seen to occur isostatically as in the case of repulsive spheres. Despite this commonality, the presence of the curved container wall and polymer backbone bonds introduce new mechanical properties. Notably, these include additional bands in the vibrational density of states that reflect the material structure as well as oscillations in local contact number and density near the wall but with lower amplitude for polymers. Polymers have fewer boundary contacts, and this low-density surface layer strongly reduces the global bulk modulus. We further show that bulk-modulus dependence on backbone stiffness can be described by a model of stiffnesses in series and discuss potential experimental and biological applications.

Although cell shape can reflect the mechanical and biochemical properties of the cell and its environment, quantification of 3D cell shapes within 3D tissues remains difficult, typically requiring digital reconstruction from a stack of 2D images. We investigate a simple alternative technique to extract information about the 3D shapes of cells in a tissue; this technique connects the ensemble of 3D shapes in the tissue with the distribution of 2D shapes observed in independent 2D slices. Using cell vertex model geometries, we find that the distribution of 2D shapes allows clear determination of the mean value of a 3D shape index. We analyze the errors that may arise in practice in the estimation of the mean 3D shape index from 2D imagery and find that typically only a few dozen cells in 2D imagery are required to reduce uncertainty below 2%. Even though we developed the method for isotropic animal tissues, we demonstrate it on an anisotropic plant tissue. This framework could also be naturally extended to estimate additional 3D geometric features and quantify their uncertainty in other materials., Competing Interests: The authors have declared that no competing interests exist.

In polycrystalline materials, grain boundaries are sites of enhanced atomic motion, but the complexity of the atomic structures within a grain boundary network makes it difficult to link the structure and atomic dynamics. Here, we use a machine learning technique to establish a connection between local structure and dynamics of these materials. Following previous work on bulk glassy materials, we define a purely structural quantity (softness) that captures the propensity of an atom to rearrange. This approach correctly identifies crystalline regions, stacking faults, and twin boundaries as having low likelihood of atomic rearrangements while finding a large variability within high-energy grain boundaries. As has been found in glasses, the probability that atoms of a given softness will rearrange is nearly Arrhenius. This indicates a well-defined energy barrier as well as a well-defined prefactor for the Arrhenius form for atoms of a given softness. The decrease in the prefactor for low-softness atoms indicates that variations in entropy exhibit a dominant influence on the atomic dynamics in grain boundaries., Competing Interests: The authors declare no conflict of interest.

Context: Insulin resistance (IR) and type 2 diabetes are increasing, particularly in Hispanic (H) vs non-Hispanic White (NHW) populations. Adiponectin has a known role in IR, and therefore, understanding ethnic and sex-specific behavior of adiponectin across the lifespan is of clinical significance., Objective: To compare ethnic and sex differences in adiponectin, independent of body mass index, across the lifespan and relationship to IR., Design: Cross-sectional., Setting: Primary care, referral center., Patients: A total of 187 NHW and 117 H participants (8-57 y) without diabetes. Life stage: pre-/early puberty (Tanner 1/2), midpubertal (Tanner 3/4), late pubertal (Tanner 5, <21 years), and adult (Tanner 5, ≥21)., Interventions: None., Main Outcome Measure(s): Fasting adiponectin, insulin, glucose, and revised homeostatic model assessment of insulin resistance., Results: Adiponectin was significantly inversely correlated with revised homeostatic model assessment of insulin resistance. Regarding puberty, adiponectin trended downward in late puberty, but only males were significantly lower in adulthood. By sex, adiponectin was lower in adult males vs females of both ethnicities. Regarding ethnicity, H adults of both sexes had lower adiponectin than NHW adults. Of note, in NHW females, adiponectin trended highest in adulthood, whereas in H females, adiponectin fell in late puberty and remained lower in adulthood., Conclusions: Adiponectin inversely correlated with IR, trended down in late puberty, and was lowest in adult males. H adults of both sexes had lower adiponectin than NHW adults, and H females followed a more "male pattern," lacking the rebound in adiponectin seen in NHW females after puberty. These data suggest that adiponectin, independent of body mass index, may relate to the greater cardiometabolic risk seen in H populations and in particular H females.

Gay men may not be physically active at recommended levels to achieve health benefits. Thus, a need exists to identify general (i.e., common across populations) and population-specific barriers that hinder or stop gay men from participating in physical activity (PA). Salient barriers may be identified through the extent each barrier limits PA (i.e., barrier limitation) and the level of one's confidence to overcome barriers and engage in PA (i.e., self-regulatory efficacy). The purposes of this study were to (1) provide a description of general and population-specific barriers to PA among sufficiently and insufficiently active gay men, (2) identify barrier limitation and self-regulatory efficacy for the reported barriers, and (3) examine the associations between meeting the current PA recommendation, barrier limitation, and self-regulatory efficacy. Participants were 108 self-identified gay males aged 21 to 64 years who completed a web-based survey. A total of 35 general barriers and no population-specific barriers were identified by the sufficiently and insufficiently active groups. The sufficiently active group reported higher self-regulatory efficacy and lower barrier limitation for nearly all reported barriers. A binary logistic regression used to examine the associations between PA, barrier limitation, and self-regulatory efficacy was statistically significant, χ(2)(2, N = 108) = 19.26, p < .0001, R(2) = .16. Only barrier limitation significantly contributed to the model. Future research should continue to examine barriers to PA among gay men to determine whether an intervention needs to be designed specifically for gay men or whether a one-size-fits-all intervention would be effective in helping all men overcome common barriers to engaging in PA., (© The Author(s) 2015.)

Objective: Exercise has been suggested to have cardioprotective benefits due to a lowering of postprandial triglycerides (PPTG). We hypothesized that a morning exercise bout would significantly lower PPTG measured over a full day, in response to moderate fat meals (35% energy) in men more so than women, and in metabolic syndrome (MetS) relative to normal weight (NW) individuals., Materials/methods: Participants completed two randomized study days; one control and one exercise day (60 min of morning exercise, 60% VO(2peak)). Meals were consumed at breakfast, lunch and dinner with the energy expended during exercise replaced on the active day. The areas (AUC) and incremental areas (IAUC) under the curve were calculated for total triglycerides, total cholesterol and other metabolites., Results: Exercise did not significantly change the PPTG AUC & IAUC overall, or within, or between, each sex or group (NW and MetS). Exercise induced a 30% decrease in total cholesterol IAUC (p=0.003) in NW subjects. Overall, women had a lower IAUC for PPTG compared to men (p=0.037), with the greatest difference between MetS women and MetS men, due to a sustained drop in TG after lunch in the women. This suggests that PP, rather than fasting, lipid analyses may be particularly important when evaluating sex differences in metabolic risk., Conclusions: With energy replacement, moderate morning exercise did not result in a significant decrease in PPTG excursions. Exercise did elicit a significant decrease in PP cholesterol levels in NW subjects, suggesting a potential mechanism for the cardioprotective effects of exercise., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Despite living in an environment that promotes weight gain in many individuals, some individuals maintain a thin phenotype while self-reporting expending little or no effort to control their weight. When compared with obesity prone (OP) individuals, we wondered if obesity resistant (OR) individuals would have higher levels of spontaneous physical activity (SPA) or respond to short-term overfeeding by increasing their level of SPA in a manner that could potentially limit future weight gain. SPA was measured in 55 subjects (23 OP and 32 OR) using a novel physical activity monitoring system (PAMS) that measured body position and movement while subjects were awake for 6 days, either in a controlled eucaloric condition or during 3 days of overfeeding (1.4 × basal energy) and for the subsequent 3 days (ad libitum recovery period). Pedometers were also used before and during use of the PAMS to provide an independent measure of SPA. SPA was quantified by the PAMS as fraction of recording time spent lying, sitting, or in an upright posture. Accelerometry, measured while subjects were in an upright posture, was used to categorize time spent in different levels of movement (standing, walking slowly, quickly, etc.). There were no differences in SPA between groups when examined across all study periods (P > 0.05). However, 3 days following overfeeding, OP subjects significantly decreased the amount of time they spent walking (-2.0% of time, P = 0.03), whereas OR subjects maintained their walking (+0.2%, P > 0.05). The principle findings of this study are that increased levels of SPA either during eucaloric feeding or following short term overfeeding likely do not significantly contribute to obesity resistance although a decrease in SPA following overfeeding may contribute to future weight gain in individuals prone to obesity.

The goals of the study were to determine if moderate weight loss in severely obese adults resulted in (i) reduction in apnea/hypopnea index (AHI), (ii) improved pharyngeal patency, (iii) reduced total body oxygen consumption (VO(2)) and carbon dioxide production (VCO(2)) during sleep, and (iv) improved sleep quality. The main outcome was the change in AHI from before to after weight loss. Fourteen severely obese (BMI > 40 kg/m(2)) patients (3 males, 11 females) completed a highly controlled weight reduction program which included 3 months of weight loss and 3 months of weight maintenance. At baseline and postweight loss, patients underwent pulmonary function testing, polysomnography, and magnetic resonance imaging (MRI) to assess neck morphology. Weight decreased from 134 +/-6.6 kg to 118 +/- 6.1 kg (mean +/- s.e.m.; F = 113.763, P < 0.0001). There was a significant reduction in the AHI between baseline and postweight loss (subject, F = 11.11, P = 0.007). Moreover, patients with worse sleep-disordered breathing (SDB) at baseline had the greatest improvements in AHI (group, F = 9.00, P = 0.005). Reductions in VO(2) (285 +/- 12 to 234 +/-16 ml/min; F = 24.85, P < 0.0001) and VCO(2) (231 +/- 9 to 186 +/- 12 ml/min; F = 27.74, P < 0.0001) were also observed, and pulmonary function testing showed improvements in spirometry parameters. Sleep studies revealed improved minimum oxygen saturation (minSaO(2)) (83.4 +/- 61.9% to 89.1 +/- 1.2%; F = 7.59, P = 0.016), and mean SaO(2) (90.4 +/- 1.1% to 93.8 +/- 1.0%; F = 6.89, P = 0.022), and a significant increase in the number of arousals (8.1 +/- 1.4 at baseline, to 17.1 +/- 3.0 after weight loss; F = 18.13, P = 0.001). In severely obese patients, even moderate weight loss (approximately 10%) boasts substantial benefit in terms of the severity of SDB and sleep dynamics.

Background: The prevention and treatment of obesity is a public health challenge., Objective: We investigated the effects of dietary composition, insulin sensitivity (S(I)), and energy balance on predicted changes in body composition., Design: In a randomized crossover design study, 39 normal-weight (n = 23), overweight (n = 8), and obese (n = 8) men and women (aged 25-36 y) each followed a 15-d isocaloric high-fat (HF; 50% fat) and high-carbohydrate [HC; 55% carbohydrate (CHO)] diet with a 4-6-wk washout period during the first year. During each treatment, energy balance was measured while the subjects were inactive by using indirect calorimetry on day 15, and S(I) was measured by using a euglycemic clamp study (40 mU . m(-2) . min(-1)) on day 16. Weight and body composition were then measured annually for 4 y. The outcomes for fat mass, percentage body fat, and weight were measured by using a linear 2-stage mixed model., Results: CHO balance (day 15) and S(I) (day 16) on the HC diet were highly and significantly correlated (r = 0.55, P < 0.001). On the HC diet, the subjects who had a higher positive CHO balance (day 15) gained less fat mass (P < 0.001), percentage body fat (P = 0.006), and weight (P = 0.024) over time. When adjusted for S(I), CHO balance remained a significant predictor of changes in fat mass (P = 0.021) and percentage body fat (P = 0.025)., Conclusions: On a HC diet, the subjects who had a higher positive CHO balance on day 15 while they were inactive gained less fat mass during 4 y, a predictive effect independent of S(I). As suggested in rodents, the capacity to expand the glycogen pool might reduce energy intake and protect against fat and weight gain.

The role of ingested fat in the etiology of obesity is controversial. The aims of this study were to determine the contributions of ingested fat oxidation to: 1) 24-h total energy expenditure (TEE), and 2) substrate oxidation during acute stationary cycle exercises in adult humans. Healthy, moderately obese (n = 18; BMI = 31 +/- 1 kg/m2) subjects (8 men; 10 women) were each studied in a whole-room calorimeter for 24 h. They were fed mixed meals (55, 30, and 15% as energy from carbohydrate, fat and protein, respectively) to maintain energy balance. Each subject performed 1255-kJ cycle exercises at 50% VO2max in the calorimeter. Study test meal fat was labeled with carbon-13 (13C). Ingested fat oxidation was estimated from breath 13CO2 excretion and the subject's chamber CO2 production. Total fat and carbohydrate oxidations were estimated from nonprotein respiratory quotient (NP-RQ) values. Endogenous fat oxidation was estimated as the difference between total fat and ingested fat oxidations. TEE was estimated from gas exchanges; 28 +/- 3% of ingested fat was oxidized and it provided 8 +/- 1% of 24-h TEE. During cycle exercises, ingested fat provided 50% of total fat oxidized and 13.0 +/- 2% of energy expended. Endogenous fat oxidation contributed 10.4 +/- 3% of energy expenditure during cycle exercises. This study extended to 24-h observations of previous studies that lasted 6-9 h on ingested fat oxidation in humans. Understanding the factors that promote ingested fat oxidation could lead to more effective obesity intervention programs.

Seven nonobese adult females (40 +/- 8 years) were studied in a room calorimeter on a day that resistance exercise (REX) was performed (4 sets of 10 exercises) and on a nonexercise control day (CON). Twenty-four-hour energy expenditure (EE) on the REX day (mean +/- SD, 2,328 +/- 327 kcal.d(-1)) was greater than CON (2,001 +/- 369 kcal.d(-1), p < 0.001). The net increase in EE during and immediately after (30 minutes) exercise represented 76 +/- 12% of the total increase in 24-hour EE. Twenty four-hour RQ on the REX day (0.86 +/- 0.06) did not differ from CON (0.87 +/- 0.02). Twenty four-hour carbohydrate oxidation was elevated on the REX day, but 24-hour fat and protein oxidation were not different. Thus, in women, the increase in EE due to resistance exercise is largely seen during and immediately after the exercise. The increased energy demand is met by increased carbohydrate oxidation, with no increase in 24-hour fat oxidation.

Background: Hispanics are disproportionately affected by the obesity epidemic in the United States. Obesity is a primary risk factor for the development of cardiovascular disease (CVD) and Type 2 diabetes, which are problematic in Hispanic adults. There are limited data relating obesity status in Hispanic adolescents to diabetes and CVD risk., Methods: We studied 115 lean and obese adolescents (89 Hispanic, 26 Caucasian), ranging in body mass index (BMI) from 15 to 52 kg/m(2). We assessed the relationships between four anthropometric indices of obesity and risk factors for Type 2 diabetes (insulin (INS), glucose (GLU)), and CVD (total cholesterol, triglycerides, HDL, and systolic (SBP) and diastolic (DBP) blood pressure)., Results: All anthropometric indices were positively correlated with total cholesterol, triglycerides, log(INS), GLU, SBP, and DBP, and negatively correlated with HDL. Correlations and multiple regression analyses indicated that weight and waist circumference (WC) were generally the best single predictors of disease risk. Using more than one anthropometric measure in multiple regression did not improve predictions of risk over using a single predictor., Conclusions: These results indicate that overweight adolescents (particularly Hispanics) are at risk for developing Type 2 diabetes and CVD, and that WC and weight are useful for identifying those at particular risk.

Objective: To evaluate and compare methods for achieving 24-hour energy balance in a whole-room indirect calorimeter., Research Methods and Procedures: Twenty-four-hour energy expenditure (EE) for 34 healthy adults (16 women, 18 men) was measured in a calorimeter during a prestudy day and on a subsequent nonconsecutive assessment day (AD). Several methods for estimating EE on the AD using activity factors or regression equations with data available before the AD [anthropometrics, body composition, resting metabolic rate (RMR), sleeping metabolic rate (SMR) on prestudy day, 24-hour EE on prestudy day] were compared for predictive accuracy., Results: Use of a 24-hour calorimeter stay gave the smallest mean absolute error (119 +/- 16 kcal/d) and smallest single maximum error (361 kcal/d). However, several other methods were only slightly, and not significantly, less accurate (e.g., mean absolute error = 131 +/- 17, 140 +/- 20, and 141 +/- 22 kcal/d and greatest error = 384, 370, and 593 kcal/d for anthropometric, RMR, and SMR regression equations, respectively). Fat-free mass alone and SMR with a simple activity factor were seen to be less accurate., Discussion: Our results indicate that there may be some improvement in achieving 24-hour energy balance in a metabolic chamber by using a preceding 24-hour calorimeter stay; that only slightly less accurate predictions can be obtained using a combination of anthropometric, body composition, and/or RMR measurements; and that there is little or no advantage in using SMR from a previous overnight calorimeter stay.

To determine whether total energy expenditure (TEE) is increased in the human immunodeficiency virus (HIV) lipodystrophy syndrome, we compared energy expenditure (EE) and substrate oxidation rates in 12 HIV-infected men with lipodystrophy, 7 HIV-infected men without lipodystrophy, and 14 healthy controls. TEE and nutrient oxidation rates were assessed by whole-room indirect calorimetry. Resting energy expenditure (REE) was measured by indirect calorimetry using the open-circuit technique. Body composition was assessed by dual-energy x-ray absorptiometry (DEXA). Insulin sensitivity was measured using the insulin-modified frequently sampled intravenous glucose tolerance test. TEE adjusted for lean body mass (LBM) was significantly higher in the HIV-infected group with lipodystrophy compared to HIV-infected patients without lipodystrophy (2,873.3 +/- 69 v 2,573.9 +/- 92 kcal/d, P =.02) and compared to healthy controls (2,873.3 +/- 69 v 2,404.0 +/- 64 kcal/d, P <.001). REE and sleeping metabolic rate (SMR) adjusted for LBM were also significantly higher in the HIV-infected group with lipodystrophy compared to both HIV-infected and healthy controls. Carbohydrate oxidation rates adjusted for LBM were higher in men with HIV lipodystrophy as compared to healthy controls (362.5 +/- 23 v 250.0 +/- 22 g/d, P = <.01) and tended to be higher as compared to HIV-infected controls (362.5 +/- 23.6 v 297.3 +/- 31 g/d, P =.1). In conclusion, TEE and carbohydrate oxidation are increased in the HIV lipodystrophy syndrome. The increase in TEE appears to be due to increases in REE. The pathogenesis of elevated EE in HIV lipodystrophy and other forms of lipodystrophy remains to be determined., (Copyright 2003 Elsevier Inc. All rights reserved.)

Objective: To determine if total calcium (Ca(2+)) intake and intake of Ca(2+) from dairy sources are related to whole-body fat oxidation., Design: : Cross-sectional study., Subjects: A total of 35 (21 m, 14 f) non-obese, healthy adults (mean+/-s.d., age: 31+/-6 y; weight: 71.2+/-12.3 kg; BMI: 23.7+/-2.9 kg m(-2); body fat: 21.4+/-5.4%)., Measurements: Daily (24 h) energy expenditure (EE) and macronutrient oxidation using whole-room indirect calorimetry; habitual Ca(2+) intake estimated from analysis of 4-day food records; acute Ca(2+) intake estimated from measured food intake during a 24-h stay in a room calorimeter., Results: Acute Ca(2+) intake (mg. kcal(-1)) was positively correlated with fat oxidation over 24 h (r=0.38, P=0.03), during sleep (r=0.36, P=0.04), and during light physical activity (r=0.32, P=0.07). Acute Ca(2+) intake was inversely correlated with 24-h respiratory quotient (RQ) (r=-0.36, P=0.04) and RQ during sleep (r=-0.31, P=0.07). After adjustment for fat mass, fat-free mass, energy balance, acute fat intake, and habitual fat intake, acute Ca(2+) intake explained approximately 10% of the variance in 24-h fat oxidation. Habitual Ca(2+) intake was not significantly correlated to fat oxidation or RQ. Total Ca(2+) intake and Ca(2+) intake from dairy sources were similarly correlated with fat oxidation. In backwards stepwise models, total Ca(2+) intake was a stronger predictor of 24 h fat oxidation than dairy Ca(2+) intake., Conclusion: Higher acute Ca(2+) intake is associated with higher rates of whole-body fat oxidation. These effects were apparent over 24 h, during sleep and, to a lesser extent, during light physical activity. Calcium intake from dairy sources was not a more important predictor of fat oxidation than total Ca(2+) intake.

Objective: A reported lower resting metabolic rate (RMR) in African-American women than in white women could explain the higher prevalence of obesity in the former group. Little information is available on RMR in African-American men., Research Methods and Procedures: We assessed RMR by indirect calorimetry and body composition by DXA in 395 adults ages 28 to 40 years (100 African-American men, 95 white men, 94 African-American women, and 106 white women), recruited from participants in the Coronary Artery Risk Development in Young Adults (CARDIA), Birmingham, Alabama, and Oakland, California, field centers., Results: Using linear models, fat-free mass, fat mass, visceral fat, and age were significantly related to RMR, but the usual level of physical activity was not. After adjustment for these variables, mean RMR was significantly higher in whites (1665.07 +/- 10.78 kcal/d) than in African Americans (1585.05 +/- 11.02 kcal/d) by 80 +/- 16 kcal/d (p < 0.0001). The ethnic x gender interaction was not significant (p = 0.9512), indicating that the difference in RMR between African-American and white subjects was similar for men and women., Discussion: RMR is approximately 5% higher in white than in African-American participants in CARDIA. The difference was the same for men and women and for lean and obese individuals. The prevalence of obesity is not higher in African-American men than in white men. Because of these reasons, we believe that RMR differences are unlikely to be a primary explanation for why African-American women are more prone to obesity than white women.

The aim of this study was to determine the effects of exercise at different intensities on 24-h energy expenditure (EE) and substrate oxidation. Sixteen adults (8 men and 8 women) were studied on three occasions [sedentary day (Con), a low-intensity exercise day (LI; 400 kcal at 40% of maximal oxygen consumption) and a high-intensity exercise day (HI; 400 kcal at 70% of maximal oxygen consumption)] by using whole room indirect calorimetry. Both 24-h EE and carbohydrate oxidation were significantly elevated on the exercise days (Con < LI = HI), but 24-h fat oxidation was not different across conditions. Muscle enzymatic profile was not consistently related to 24-h fat or carbohydrate oxidation. With further analysis, it was found that, compared with men, women sustained slightly higher rates of 24-h fat oxidation (mg x kg FFM(-1) x min(-1)) and had a muscle enzymatic profile favoring fat oxidation. It is concluded that exercise intensity has no effect on 24-h EE or nutrient oxidation. Additionally, it appears that women may sustain slightly greater 24-h fat oxidation rates during waking and active periods of the day.

Background: A better understanding of the environmental factors that contribute to obesity is imperative if any therapeutic effect on the increasing prevalence of overweight and obesity in the United States is to be achieved., Objective: This study examined the effect of the interaction of diet composition and physical inactivity on energy and fat balances., Design: Thirty-five normal-weight and obese subjects were randomly assigned to either a 15-d isoenergetic high-carbohydrate (HC) or high-fat (HF) diet according to a crossover design. During the first 14 d, body weight and physical activity were maintained. On day 15, subjects spent 23 h in a whole-room indirect calorimeter and were fed a diet similar to that consumed during the previous 7 d while remaining physically inactive., Results: Energy intakes required to maintain body weight stability during the first 14 d were similar between diets. Normal-weight and obese subjects consuming both diets had a positive energy balance on the sedentary day (day 15), suggesting that subjects were less active in the calorimeter. There was no significant effect of diet composition on total energy balance and total protein-energy balance on day 15; however, carbohydrate balance was more positive with the HC (2497.8 +/- 301.2 kJ) than with the HF (1159 +/- 301.2 kJ) diet (P = 0.0032). Most importantly, fat balance was more positive with the HF (1790.8 +/- 510.4 kJ) than with the HC (-62.8 +/- 510.4 kJ) diet (P = 0.0011)., Conclusion: Chronic consumption of a high-carbohydrate diet could provide some protection against body fat accumulation in persons with a pattern of physical activity that includes frequent sedentary days.

Reports of low energy intakes in trained female athletes imply they have an increased energetic efficiency. To address this question, we determined how energy balance was achieved in endurance-trained females cyclists and lean controls (n = 5 in each group). Daily energy expenditure was measured by using standardized physical activity protocols in a whole room calorimeter on two separate occasions: a cycling day and a noncycling day. Energy intake for weight maintenance was determined by a period of controlled feeding 5 days before and the day of each energy expenditure measurement. Energy balance was achieved in the cyclists on the cycling day while they consumed 2,900-3,000 kcal (their usual condition) and in controls on the noncycling day while they consumed 2,100-2,200 kcal (their usual condition). Total daily energy expenditure was not significantly different between the cyclists and controls on the noncycling day with both groups performing similar levels of activity. On the cycling day, daily energy expenditure was significantly greater in the cyclists vs. controls (P < 0.03) as a result of their greater amount of cycling activity. Components of daily energy expenditure, i.e., resting metabolic rate and thermic effect of food and activity (noncycling), were not significantly different between groups. Overall, we found no significant increase in the energetic efficiency of endurance-trained female cyclists compared with controls.

The relationship between exercise and energy expenditure is unclear, with some suggestions that exercise leads to increased energy expenditure over and beyond the increase due to the exercise itself. In this cross-sectional study, we examined the relationships among aerobic fitness level, body composition, and total daily energy expenditure in 78 subjects. Daily energy expenditure (determined in a whole room calorimeter) was significantly correlated with both fat-free mass (FFM) and aerobic fitness (estimated from maximum aerobic capacity or VO2max). However, multiple-regression analysis demonstrated that, after accounting for FFM, VO2max did not explain a significant amount of the remaining variation in energy expenditure. In addition, the relationship between resting metabolic rate and both FFM and VO2max was evaluated using data from 214 weight-stable subjects analyzed retrospectively. The results were identical with the results obtained from the 78 subjects in that VO2max did not have effects independent of FFM on energy expenditure. We conclude that aerobic fitness does not have a direct effect on energy expenditure. However, it may have effects that are mediated through body composition, since in both populations studied here, VO2max was positively correlated with FFM and negatively correlated with adiposity.

The use of monoclonal anti-T-cell antibodies has been proposed as a means of eliminating T cells from bone marrow inocula, and thereby avoiding graft-versus-host reactions following transplantation. Since the mixed lymphocyte reaction (MLR) provides a measurement of alloreactive mature T cells, we have attempted to apply this assay to bone marrow populations before and after treatment with anti-T-cell antibodies and complement. However, initial studies showed MLR to be very difficult to measure using bone marrow as a responder cell population, and a systematic analysis of the reasons for this difficulty was therefore carried out. The first major problem in performance of standard one-way MLRs using bone marrow responder cells was found to be due to the presence of numerous non-T marrow cells that maintained high levels of background proliferation. Proliferation of these populations was found to be variable during MLR culture, leading to aberrant results. This problem was overcome by removing the rapidly proliferating population of marrow cells either by density centrifugation or by susceptibility to cryopreservation and thawing. A second problem causing variability even after removal of these proliferating cells was found to be due to additional non-T cells in the marrow that responded to soluble mediators produced by peripheral blood lymphocyte stimulator cells during an MLR. Such non-T-cell stimulation was not eliminated by removal of bone marrow T cells, obscuring the results of T cell depletion of the marrow. This problem was overcome by the use of HLA-defined B cell lines as stimulators. A mixture of such lines provided a reliable stimulator source that did not produce soluble mediators capable of stimulating additional marrow cells. These refinements of MLR conditions permit a reproducible and reliable assay of bone marrow MLR, and provide a means for assessment of elimination of such alloreactive cells by monoclonal antibodies and complement.