Differences in Fecal Gut Microbiota, Short-Chain Fatty Acids and Bile Acids Link Colorectal Cancer Risk to Dietary Changes Associated with Urbanization Among Zimbabweans.

The incidence of colorectal cancer (CRC) is gradually rising in sub-Saharan Africa. This may be due to dietary changes associated with urbanization, which may induce tumor-promoting gut microbiota composition and function. We compared fecal microbiota composition and activity in 10 rural and 10 urban Zimbabweans for evidence of a differential CRC risk. Dietary intake was assessed by a food frequency questionnaire. Fecal microbiota composition, metabolomic profile, functional microbial genes were analyzed, and bile acids and short chain fatty acids quantified. Animal protein intake was higher among urban volunteers, but carbohydrate and fiber intake were similar. Bacteria related to Blautia obeum, Streptococcus bovis, and Subdoligranulum variabile were higher in urban residents, whereas bacteria related to Oscillospira guillermondii and Sporobacter termitidis were higher in rural volunteers. Fecal levels of primary bile acids, cholic acid, and chenodeoxycholic acid (P < 0.05), and secondary bile acids, deoxycholic acid (P < 0.05) and ursodeoxycholic acid (P < 0.001) were higher in urban residents. Fecal levels of acetate and propionate, but not butyrate, were higher in urban residents. The gut microbiota composition and activity among rural and urban Zimbabweans retain significant homogeneity (possibly due to retention of dietary fiber), but urban residents have subtle changes, which may indicate a higher CRC risk.

Evaluating the contribution of differences in lean mass compartments for resting energy expenditure in African American and Caucasian American children.

BACKGROUND: Resting energy expenditure (REE), adjusted for total lean mass (LM), is lower in African American (AA) than Caucasian American (CA) children. Some adult studies suggest that AA-CA differences in lean mass compartments explain this REE difference. Similar data are limited in children. OBJECTIVE: To evaluate differences in compartment-specific lean mass between AA and CA children and examine the individual contributions of high-metabolic rate-at-rest trunk lean mass (TrLM) and low-metabolic-rate-at-rest appendicular lean mass (AppLM) for AA-CA differences in REE. METHODS: We studied a convenience sample of 594 AA (n = 281) and CA (n = 313) children. REE was measured by using indirect calorimetry; dual-energy X-ray absorptiometry was used to assess body composition. ANCOVAs were performed to examine AA-CA differences in TrLM, AppLM and REE. After accounting for age, sex, height, pubertal development, bone mass and adiposity, REE was evaluated adjusting for total LM (model A) and separately adjusting for TrLM and AppLM (model B). RESULTS: African American children had greater adjusted AppLM (17.8 ± 0.2 [SE] vs. 16.0 ± 0.2 kg, p < 0.001) and lower TrLM (17.2 ± 0.2 vs. 17.7 ± 0.2 kg, p = 0.022) than CA children. REE adjusted for total LM was 77 ± 16 kcal/d lower in AA than CA (p < 0.001). However, after accounting separately for AppLM and TrLM, the discrepancy in REE between the groups declined to 28 ± 19 kcal/d (p = 0.14). In the adjusted model, both TrLM (p < 0.001) and AppLM (p < 0.027) were independently associated with REE. CONCLUSION: In children, AA-CA differences in REE appear mostly attributable to differences in body composition. Lower REE in AA children is likely due to lower TrLM and greater AppLM.

African American women exhibit similar adherence to intervention but lose less weight due to lower energy requirements.

BACKGROUND: African American (AA) women have been shown to lose less weight than Caucasian women in response to behavioral interventions. Our objective was to examine adherence to intervention and metabolic factors that may explain this difference. DESIGN AND SUBJECTS: We examined longitudinal changes in body weight and energy expenditure (EE), and objective assessment of physical activity (PA) and energy intake (EI) during 6 months of a weight-loss intervention program, including prescribed calorie restriction and increased PA in 66 Caucasian and 39 AA severely obese women. Comparisons were also made in 25 Caucasian and 25 AA women matched for initial body weight. RESULTS: The AA women lost 3.6 kg less weight than Caucasian women. Total daily EE (TDEE) and resting metabolic rate (RMR) adjusted for fat free mass (FFM) were significantly lower in the AA women, whereas the decrease in RMR in response to weight loss was greater in Caucasian women. Adherence to the prescribed PA and change in PA in response to intervention were similar in AA and Caucasian women. Prescribed EI (1794±153 and 1806±153 kcal per day) and measured EI during intervention (2591±371 vs 2630±442 kcal per day) were nearly identical in matched AA and Caucasian women. However, the AA women lost significantly less body weight due to lower energy requirements (2924±279 vs 3116±340 kcal per day; P<0.04), resulting in a lower energy deficit (333±210 vs 485±264 kcal per day). CONCLUSION: Adherence to the behavioral intervention was similar in AA and Caucasian women. However, neglecting to account for the lower energy requirements in AA women when calculating the energy prescription resulted in a lower level of calorie restriction and, hence, less body weight loss. Therefore, to achieve similar weight loss in AA women, the prescribed caloric restriction cannot be based on weight alone, but must be lower than in Caucasians, to account for lower energy requirements.

Reduced skeletal muscle oxidative capacity and elevated ceramide but not diacylglycerol content in severe obesity.

OBJECTIVE: The link between a reduced capacity for skeletal muscle mitochondrial fatty acid oxidation (FAO) and lipotoxicity in human insulin resistance has been the subject of intense debate. The objective of this study was to investigate whether reduced FAO is associated with elevated acyl CoA, ceramide, and diacylglycerol (DAG) in severely obese insulin resistant subjects. METHODS: Muscle biopsies were conducted in lean (L, 22.6 ± 0.5 kg/m(2) , n = 8), Class I (CI, 32.1 ± 0.4 kg/m(2) , n = 7) and Class II&III obese (CII&III, 45.6 ± 1.1 kg/m(2) , n = 15) women for acyl CoA, sphingolipid and DAG profiling. Intramyocellular triglyceride (IMTG) content was determined by histology. FAO was assessed by incubating muscle homogenates with [1-C]palmitate and measuring CO2 production. Cardiolipin content was quantified as an index of mitochondrial content. Lipid metabolism proteins, DGAT1, PLIN5, and PNPLA2 were quantified in biopsy samples by western blot. RESULTS: CII&III were more insulin resistant (HOMA-IR: 4.5 ± 0.5 vs. 1.1 ± 0.1, P < 0.001), and had lower FAO (∼58%, P = 0.007) and cardiolipin content (∼31%, P = 0.013) compared to L. IMTG was elevated in CI (P = 0.04) and CII&III (P = 0.04) compared to L. Sphingolipid content was higher in CII&III compared to L (13.6 ± 1.1 vs. 10.3 ± 0.5 pmol/mg, P = 0.031) whereas DAG content was not different among groups. DGAT1 was elevated in CII&III, and PLIN5 was elevated in CI compared to L. CONCLUSIONS: Severe obesity is associated with reduced muscle oxidative capacity and occurs concomitantly with elevated IMTG, ceramide and insulin resistance.

High energy expenditure masks low physical activity in obesity.

OBJECTIVE: To investigate energy expenditure in lean and obese individuals, focusing particularly on physical activity and severely obese individuals. DESIGN: Total daily energy expenditure (TDEE) was assessed using doubly labeled water, resting metabolic rate (RMR) by indirect calorimetry, activity energy expenditure (AEE) by difference and time spent in physical activity by multisensor activity monitors. SUBJECTS: In all, 177 lean, Class I and severely obese individuals (age 31-56 years, body mass index 20-64 kg m(-2)) were analyzed. RESULTS: All components of energy expenditure were elevated in obese individuals. For example, TDEE was 2404±95 kcal per day in lean and 3244±48 kcal per day in Class III obese individuals. After appropriate adjustment, RMR was similar in all groups. Analysis of AEE by body weight and obesity class indicated a lower AEE in obese individuals. Confirming lower physical activity, obese individuals spent less time engaged in moderate-to-vigorous physical activity (2.7±1.3, 1.8±0.6, 2.0±1.4 and 1.2±1.0 h per day in lean, Class I, Class II and Class III individuals) and more time in sedentary behaviors. CONCLUSIONS: There was no indication of metabolic efficiency in even the severely obese, as adjusted RMR was similar across all groups. The higher AEE observed in the obese is consistent with a higher cost of activities due to higher body weight. However, the magnitude of the higher AEE (20-25% higher in obese individuals) is lower than expected (weight approximately 100% higher in Class III individuals). Confirming a lower volume of physical activity in the obese, the total time spent in moderate-to-vigorous physical activity and average daily metabolic equivalent of task level were lower with increasing obesity. These findings demonstrate that high body weight in obese individuals leads to a high TDEE and AEE, which masks the fact that they are less physically active, which can be influenced by duration or intensity of activity, than in lean individuals.

The effects of prolonged darkness on temperate and tropical marine phytoplankton, and their implications for ballast water risk management.

Phytoplankton assemblages from tropical (Goa) and temperate (UK) locations were exposed to a 28 day dark period, followed by a period of re-exposure to light. During this time phytoplankton survival and changes in nutrient concentrations were mapped. The tropical plankton water samples showed high nutrient levels after the dark period which were utilised by cells during the re-exposure period. UK experiments looked at the effect of three different water types on population recovery after the 28 day dark period, and differences due to seasonal effects. The population growth observed during the re-exposure period in the tropical population was comparable to that of the temperate population. Water type affected recovery and of the three tested media fresh seawater promoted the highest levels of growth. Seasonality had a significant influence on species survival. Understanding the effects of all these factors can aid the development of effective risk assessments in ballast water management.

Validity of self-reported energy intake in lean and obese young women, using two nutrient databases, compared with total energy expenditure assessed by doubly labeled water.

OBJECTIVE: To compare self-reported total energy intake (TEI) estimated using two databases with total energy expenditure (TEE) measured by doubly labeled water in physically active lean and sedentary obese young women, and to compare reporting accuracy between the two subject groups. DESIGN: A cross-sectional study in which dietary intakes of women trained in diet-recording procedures were analyzed using the Minnesota Nutrition Data System (NDS; versions 2.4/6A/21, 2.6/6A/23 and 2.6/8.A/23) and Nutritionist III (N3; version 7.0) software. Reporting accuracy was determined by comparison of average TEI assessed by an 8 day estimated diet record with average TEE for the same period. RESULTS: Reported TEI differed from TEE for both groups irrespective of nutrient database (P<0.01). Measured TEE was 11.10+/-2.54 and 11.96+/-1.21 MJ for lean and obese subjects, respectively. Reported TEI, using either database, did not differ between groups. For lean women, TEI calculated by NDS was 7.66+/-1.73 MJ and by N3 was 8.44+/-1.59 MJ. Corresponding TEI for obese women were 7.46+/-2.17 MJ from NDS and 7.34+/-2.27 MJ from N3. Lean women under-reported by 23% (N3) and 30% (NDS), and obese women under-reported by 39% (N3) and 38% (NDS). Regardless of database, lean women reported higher carbohydrate intakes, and obese women reported higher total fat and individual fatty acid intakes. Higher energy intakes from mono- and polyunsaturated fatty acids were estimated by NDS than by N3 in both groups of women (P< or =0.05). CONCLUSIONS: Both physically active lean and sedentary obese women under-reported TEI regardless of database, although the magnitude of under-reporting may be influenced by the database for the lean women. SPONSORSHIP: USDA Hatch Project award (ARZT-136528-H-23-111) to LB Houtkooper and WH Howell.

Body composition of African American and white children: a 2-year follow-up of the BAROC study.

OBJECTIVE: To evaluate the 2-year changes in body composition of white and African American boys and girls. RESEARCH METHODS AND PROCEDURES: A total of 114 boys and girls ages 12 to 14 years with equal sex and ethnic distribution between African American and white races participated in measurements of body composition using DXA, underwater weighing (densitometry), skinfold thickness, corporal diameters, circumferences, isotope dilution (H(2)(18)O), and bioelectric impedance. RESULTS: Sixty-eight of the 114 children advanced from Tanner Stages 1 and 2 to Tanner Stages 3 to 5 over a 2-year period. More than 50% of the children were in the top 15th percentile according to normative data for body mass index but not for triceps skinfold. All measures except for percentage of fat, density, and four of the six skinfolds increased significantly during the 2 years, with no differences between races, genders, or fat group. The boys who advanced in Tanner Stage reduced their percentage of fat and a number of skinfolds and increased their lean body mass, but the girls did not. The percentage of water was significantly higher in the fatter children and declined significantly over 2 years. Most children remained in the same quartile of body fat, lean body mass, and bone mineral content over 2 years. DISCUSSION: The data are consistent with the hypothesis that over 2 years, growth is the major determinant of changing body composition, with body-fat group and sexual maturation being additional variables.

Bender transducer design and operation.

An empirical study covering a wide range of bender transducer sizes and operating frequencies is reported. A spherical device model is shown to give good account of bender performance, including interaction effects. A set of empirical rules for scaling equivalent circuit parameters according to the device geometry is identified. An effective spherical radius, approximately half the diaphragm radius, is identified for the typical bender. The effects of pressure and drive voltage on performance are described for particular devices. Sensitivity factors for the equivalent circuit parameters to the operating conditions are determined. These are related to sensitivity factors for the coupling coefficient (Kc) and electromechanical transformer turns ratio (N). Both these parameters are shown to have similar sensitivity responses, decreasing with pressure (planar stress), and increasing with voltage (electric field). The results of high drive tests carried out at Seneca Lake are reported. Values of conventional figures of merit (FOM(V) and FOM(M)), close to the highest claimed for any underwater transducer, are tabled. When allowance for the operating efficiency is included in the figure of merit definitions, the bender appears to be superior to other device types.

Evaluation of body fat in fatter and leaner 10-y-old African American and white children: the Baton Rouge Children's Study.

BACKGROUND: Only a few published studies in children used several methods to compare body fat in large groups of fatter and leaner multiethnic children. We hypothesized that the preferred methods of determining body fat may differ in children with larger compared with smaller amounts of body fat, in boys compared with girls, and in African Americans compared with whites. OBJECTIVE: Our objective was to evaluate several methods of predicting body fat in 10-12-y-old white and African American boys and girls. DESIGN: The body fat of 129 African American and white boys and girls aged 10-12 y, distributed equally by sex and race, was measured with use of dual-energy X-ray absorptiometry (DXA), underwater weighing (densitometry), isotope dilution (H(2)18O), bioelectrical impedance, skinfold thicknesses, corporal diameters, and circumferences. RESULTS: With use of DXA as the criterion variable, body fat was bimodally distributed in the boys and skewed to higher values in the girls. Biceps skinfold thickness had the highest predictive value of any single skinfold thickness compared with DXA fat. All formulas for estimating body fat from skinfold thicknesses, body density, or impedance performed better in the children in the upper one-half of the fat distribution (the fatter children) than in those in the lower one-half (the leaner children). Body mass index was highly correlated with body fat (R2 = 0.77); there was a good correlation for the fatter children (R2 = 0.66) and no correlation for the leaner children (R2 = 0.09). The hydration of the fat-free mass was significantly higher in the fatter children than in the leaner ones (79.2% compared with 76.7%). CONCLUSIONS: These data are consistent with the hypothesis that all methods of estimating body fat work better in children with larger amounts of body fat. The best formulas use skinfold thicknesses, bioelectrical impedance, and a 4-compartment model.

Relationship of dietary fat and serum cholesterol ester and phospholipid fatty acids to markers of insulin resistance in men and women with a range of glucose tolerance.

High-fat diets are associated with insulin resistance, however, this effect may vary depending on the type of fat consumed. The purpose of this study was to determine the relationship between intakes of specific dietary fatty acids (assessed by 3-day diet records and fatty acid composition of serum cholesterol esters [CEs] and phospholipids [PLs]) and glucose and insulin concentrations during an oral glucose tolerance test (OGTT). Nineteen men and 19 women completed the study. Nine subjects had type 2 diabetes or impaired glucose tolerance. Fasting insulin correlated with reported intakes of total fat (r = .50, P < .01), monounsaturated fat (r = .44, P < .01), and saturated fat (r = .49, P < .01), but not with trans fatty acid intake (r = .11, not significant [NS]). Fasting glucose also correlated with total (r = .39, P < .05) and monounsaturated fat intakes (r = .37, P < .05). In multivariate analysis, both total and saturated fat intake were strong single predictors of fasting insulin (R2 approximately .25), and a model combining dietary and anthropometric measures accounted for 47% of the variance in fasting insulin. Significant relationships were observed between fasting insulin and the serum CE enrichments of myristic (C14:0), palmitoleic (C16:1), and dihomo-gamma-linolenic (C20:3n-6) acids. In multivariate analysis, a model containing CE 14:0 and percent body fat explained 45% of the variance in fasting insulin, and C14:0 and age explained 30% of the variance in fasting glucose. PL C20:3n-6 explained 30% of the variance in fasting insulin, and a model including PL C18:1n-11 cis, C20:3n-6, age and body fat had an R2 of .58. In conclusion, self-reported intake of saturated and monounsaturated fats, but not trans fatty acids, are associated with markers of insulin resistance. Furthermore, enhancement of dihomo-gamma-linolenic and myristic acids in serum CE and PL, presumably markers for dietary intake, predicted insulin resistance.

Conjugated linoleic acid persistently increases total energy expenditure in AKR/J mice without increasing uncoupling protein gene expression.

AKR/J mice fed a high fat diet were treated with a 1% (1 g/100 g) admixture of conjugated linoleic acids (CLA) for 5 wk and compared with control mice. Body weights, energy intakes and energy expenditure (EE) determined by indirect calorimetry were measured weekly. CLA treatment reduced adipose depot weights by approximately 50% but had no significant effects on either body weight or energy intake. CLA increased EE persistently by an average of 7.7% throughout the 5-wk experiment. This greater EE, despite no difference in energy intake, was sufficient to account for the lower body fat stores in the CLA-treated mice. De novo fatty acid biosynthesis in adipose tissue, measured by incorporation of deuterium-labeled water, was not decreased by CLA treatment and therefore did not explain the lower adipose lipid in these mice. Expression of uncoupling protein (UCP) in skeletal muscle, white adipose tissue and kidney was not affected by CLA treatment. In brown adipose tissue, UCP1 expression was not affected by CLA treatment. However, UCP2 expression, although quite low, was significantly greater in CLA-fed mice. We conclude that CLA acts to reduce body fat stores by chronically increasing metabolic rate. This effect on metabolic rate is likely not due to increased UCP gene expression. Furthermore, the reduced body fat is not due to decreased de novo fatty acid synthesis in white adipose tissue.

Differential oxidation of individual dietary fatty acids in humans.

BACKGROUND: Dietary fatty acids that are more prone to oxidation than to storage may be less likely to lead to obesity. OBJECTIVE: The aim of this study was to determine the effect of chain length, degree of unsaturation, and stereoisomeric effects of unsaturation on the oxidation of individual fatty acids in normal-weight men. DESIGN: Fatty acid oxidation was examined in men consuming a weight-maintenance diet containing 40% of energy as fat. After consuming the diet for 1 wk, subjects were fed fatty acids labeled with (13)C in the methyl or carboxyl position (10 mg/kg body wt). The fatty acids fed in random order were laurate, palmitate, stearate, oleate, elaidate (the trans isomer of oleate), linoleate, and linolenate blended in a hot liquid meal. Breath samples were collected for the next 9 h and the oxidation of each fatty acid was assessed by examining liberated (13)CO(2) in breath. RESULTS: Cumulative oxidation over the 9-h test ranged from a high of 41% of the dose for laurate to a low of 13% of the dose for stearate. Of the 18-carbon fatty acids, linolenate was the most highly oxidized and linoleate appeared to be somewhat conserved. (13)C recovery in breath from the methyl-labeled fatty acids was approximately 30% less than that from the carboxyl-labeled fatty acids. CONCLUSIONS: In summary, lauric acid is highly oxidized, whereas the polyunsaturated and monounsaturated fatty acids are fairly well oxidized. Oxidation of the long-chain, saturated fatty acids decreases with increasing carbon number.

Changes in body composition with conjugated linoleic acid.

Conjugated linoleic acid has been shown to reduce body fat accumulation in several animal models. We have conducted several studies in AKR/J mice showing that CLA reduces body fat accumulation whether animals are fed a high-fat or low-fat diet, with no effect on food intake. One mechanism by which CLA reduces body fat is by increased energy expenditure, which is observed within one week of CLA feeding and is sustained for at least six weeks. The increased energy expenditure is sufficient to account for the decreased fat accumulation. Increased uncoupling protein gene expression does not appear to be involved in the increased energy expenditure. We have observed increased fat oxidation but no decrease in de novo fat biosynthesis with CLA feeding. We have also observed increased liver weights and plasma insulin levels with higher doses of CLA. In all of the studies we have conducted to date we have used a CLA preparation that contains several isomers, primarily c9,t11 and t10,c12. It was assumed that the active form was c9,t11, as CLA was identified as an anticarcinogenic compound from cooked beef, of which the c9,t11 form accounts for 60% to 80% of the CLA. Most of the studies conducted so far must be repeated using the purified isomers in order to determine which isomers are responsible for each of the identified actions of CLA.

The effect of an herbal dietary supplement containing ephedrine and caffeine on oxygen consumption in humans.

OBJECTIVE: To determine if an herbal dietary supplement for weight loss increases metabolism. DESIGN: Measurement of peak oxygen consumption in response to the supplement followed by a double-blind placebo-controlled crossover measurement of oxygen consumption in response to the supplement. SETTING: The study was conducted in an academic research clinic. SUBJECTS: Ten obese females (aged 41 +/- 4 years [body mass index (BMI)] 33.3 +/- 2.6 kg/m2) participated in the peak oxygen consumption test; six of these females participated in the crossover trial. INTERVENTIONS AND OUTCOME MEASURES: Peak oxygen consumption was measured for 45 minutes after taking two herbal dietary supplement capsules orally, each containing the equivalent of 10 mg of caffeine and 5 mg of ephedrine. The crossover trial measured oxygen consumption for 45 minutes after taking two herbal dietary supplement capsules or two placebo capsules orally. RESULTS: The herbal dietary supplement increased peak oxygen consumption 0.178 +/- 0.03 (SEM) kcal/min (8.01 +/- 1.35 kcal/min expressed over 45 minutes) above baseline (p < 0.0001), and 2.0 +/- 0.56 kcal/min over 45 minutes compared to placebo (p < 0.006). CONCLUSIONS: The herbal dietary supplement increased oxygen consumption when taken according to the package directions. The significance of this rise for weight loss requires further research.

Implementation of a system for reagent selection and library enumeration, profiling, and design.

We describe an integrated suite of computational tools which are used to assist in the selection of compounds for biological assays and the design of combinatorial libraries. These functions are delivered in a platform-independent manner via a corporate intranet and are used by computational experts and nonexperts alike. While the system was primarily designed to be used prior to synthesis, it can also be used to provide structural information for library registration and for decoding beads in tagged libraries. We describe a simple statistical method for monomer selection and compare it to computationally more demanding approaches.

Eradication of Helicobacter pylori infection with proton pump-based triple therapy in patients in whom bismuth-based triple therapy failed.

To study the effects of treatment of Helicobacter pylori infection in a hyperendemic population, 143 infected patients from the region of Nariño, Colombia, were treated for 2 weeks with clarithromycin (500 mg twice a day), amoxicillin (1 g twice a day), and either lansoprazole (30 mg twice a day) or omeprazole (30 mg twice a day). All patients belong to a low socioeconomic strata, had multifocal atrophic gastritis documented by gastric biopsies, and had been treated previously and unsuccessfully for 2 weeks with bismuth subsalicylate (262 mg four times a day), amoxicillin (500 mg three times a day), and metronidazole (400 mg three times a day). 13C-urea breath tests were performed 6, 12, 24, and 60 weeks after completing therapy. The 13C-urea breath test was negative in 79.7% of patients 1 month after finishing therapy, and in 69.2% of patients 1 year after finishing treatment. There were no differences in eradication rates between patients treated with omeprazole versus lansoprazole. Dyspepsia symptoms decreased from 74% in patients at baseline to 19% at the time of finishing treatment. In low-socioeconomic status populations with hyperendemic infection, triple therapy using omeprazole or lansoprazole plus clarithromycin and amoxicillin is an effective alternative when previous standard bismuth-based triple therapy has failed.

Conjugated linoleic acid rapidly reduces body fat content in mice without affecting energy intake.

Recent reports have demonstrated that conjugated linoleic acid (CLA) has effects on body fat accumulation. In our previous work, CLA reduced body fat accumulation in mice fed either a high-fat or low-fat diet. Although CLA feeding reduced energy intake, the results suggested that some of the metabolic effects were not a consequence of the reduced food intake. We therefore undertook a study to determine a dose of CLA that would have effects on body composition without affecting energy intake. Five doses of CLA (0.0, 0.25, 0.50, 0.75, and 1.0% by weight) were studied in AKR/J male mice (n = 12/group; age, 39 days) maintained on a high-fat diet (%fat 45 kcal). Energy intake was not suppressed by any CLA dose. Body fat was significantly lower in the 0.50, 0.75, and 1.0% CLA groups compared with controls. The retroperitoneal depot was most sensitive to the effects of CLA, whereas the epididymal depot was relatively resistant. Higher doses of CLA also significantly increased carcass protein content. A time-course study of the effects of 1% CLA on body composition showed reductions in fat pad weights within 2 wk and continued throughout 12 wk of CLA feeding. In conclusion, CLA feeding produces a rapid, marked decrease in fat accumulation, and an increase in protein accumulation, at relatively low doses without any major effects on food intake.

Long-term calorie restriction reduces energy expenditure in aging monkeys.

Calorie restriction to produce stable long-term adult body weight for approximately 10 years prevents obesity and diabetes in middle-aged rhesus monkeys. To determine whether this dietary regimen also alters energy metabolism, the doubly labeled water method was used to measure total daily energy expenditure. Six adult male rhesus monkeys, which had been calorie-restricted for more than 10 years, were compared to 8 control adult monkeys, which had been fed ad libitum for their entire lives. The calorie-restricted monkeys weighed less than the ad-libitum fed monkeys and had a lower lean body mass and lower fat mass. Total daily energy expenditure was lower in the calorie-restricted than in the ad-libitum fed monkeys, even when corrected for differences in body size using body weight (563 +/- 64 vs 780 +/- 53 kcal/d; p < .04), surface area (547 +/- 67 vs 793 +/- 56 kcal/d; p < .05), or lean body mass (535 +/- 66 vs 801 +/- 54 kcal/d; p < .02) as covariates. Thyroxine (T4) was reduced and the free thyroxine index was suggestively lower in the calorie-restricted monkeys whereas triiodothyronine (T3) was not significantly different. Activity in calorie-restricted monkeys was similar to that of a weight-matched younger adult comparison group. We conclude that the process of preventing obesity by long-term caloric restriction causes a significant and sustained long-term reduction in energy expenditure, even when corrected for lean body mass.

Role of energy expenditure in the development of pediatric obesity.

The role that energy expenditure plays in pediatric obesity was somewhat confused by early research purporting to show that, as a group, obese children have lower energy intakes than do lean children. On the basis of this intake data, the conclusion was drawn that obese persons are somehow energy efficient, leading to weight gain. More recent research examining energy expenditure has shown clearly that, as a group, obese children have higher energy expenditures than do their lean counterparts. With the advent of the doubly labeled water method for determining free-living energy expenditure, it has been shown that obese children underreport intake significantly more than do lean children. When measurements are properly adjusted for differences in body size, there are generally no major differences in energy expenditure between lean and obese groups. However, in some cross-sectional studies, a low level of physical activity has been shown to be related to current body fatness. In addition, longitudinal studies have shown that a low level of energy expenditure, particularly energy expended in physical activity, is associated with both body fatness and weight gain.