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Biomedical subjects

D A Schoeller

Publications and source records attributed to D A Schoeller.

At least 19 recordsLinked to original sources
PubMed2006

The role of conjugated linoleic acid in reducing body fat and preventing holiday weight gain.

OBJECTIVE: The incidence of obesity and overweight in the US has increased considerably during the past two decades and currently affects 65% of the adult population. Research has indicated that small, yet irreversible, gains during the holiday season contribute to increases in weight during adulthood. Conjugated linoleic acid (CLA), a naturally occurring dietary fatty acid, has been found to reduce weight gain and dramatically decrease fat mass in animals. Although research in humans has shown inconsistent results, most studies have been of insufficient duration or have utilized body composition methods that are less accurate than the currently accepted criterion. DESIGN: Randomized, double-blind, placebo-controlled study of 3.2 g/day CLA for 6 months. SUBJECTS: Forty healthy, overweight subjects (age: 18-44 years; body mass index: 25-30 kg/m(2)). MEASUREMENTS: Body composition by the four-compartment model, resting metabolic rate (RMR) by indirect calorimetry, self-reported physical activity and dietary intake, and blood chemistries were determined at baseline and after 6 months. Body weight was measured monthly during the pre-holiday season (August-October), holiday season (November-December) and post-holiday season (January-March). Adverse events were assessed monthly. RESULTS: Compared to CLA, the placebo group showed a greater rate of weight gain during the holiday season (P=0.01). Within the placebo group, holiday weight change was significantly greater compared to the pre-holiday period (August-October) (P=0.03). Six-month change in body composition was improved with CLA compared to placebo (P=0.02), and body fat was significantly reduced within the CLA group (-1.0+/-2.2 kg, P=0.05). CLA had no effect on RMR, physical activity or dietary intake. The rate of reported negative emotions decreased significantly with CLA, although there was no difference in any other category of adverse event. In comparison to the placebo, CLA did not affect insulin resistance, blood lipids and markers of liver function or markers of inflammation, with the exception of a significant decrease in a biomarker of endothelial dysfunction. CONCLUSION: CLA supplementation among overweight adults significantly reduced body fat over 6 months and prevented weight gain during the holiday season. Although no adverse effects were seen, additional studies should evaluate the effect of prolonged use of CLA.

Adipose Tissue↗
PubMed2005

Sustained increase in dietary oleic acid oxidation following morning exercise.

OBJECTIVE: We have previously reported that prior exercise increases the oxidation of dietary monounsaturated fat in comparison to rest when the fat is given in a mixed meal 30 min following the completion of exercise. In this study, we determined whether the increase in dietary fat oxidation after exercise persisted when the time between exercise and fatty acid administration was lengthened. DESIGN: Six female subjects (age=24+/-0.1 y, BMI=21+/-1 kg/m2) were recruited for a total of six visits each. During three visits, a stationary cycle exercise session (1250 kJ) was performed at 65% VO2 peak in a whole-body calorimeter; while during three other visits, exercise was replaced with rest. Subjects received [1-13C]oleate and [d31]palmitate with a different meal at each visit: breakfast, lunch, and dinner. RESULTS: Dietary oleate oxidation following prior rest did not differ between dose times and was 36+/-3, 42+/-5, and 42+/-3% for the 13 h following breakfast, lunch, and dinner. Prior exercise resulted in greater oleate oxidation following all dose times than prior rest (P<0.01) being 52+/-4, 64+/-3, and 53+/-3% for the breakfast, lunch, and dinner dose. The oxidation was significantly greater following lunch than the other dose times (P<0.05). Prior exercise (1250 kJ) did not result in greater oxidation of palmitate; however, oxidation following prior exercise increased with later dose times (13+/-2, 23+/-2, and 23+/-3% for breakfast, lunch, and dinner; P<0.05) and following rest (18+/-2, 22+/-2, and 27+/-2% for breakfast, lunch, and dinner; P<0.005). CONCLUSIONS: The increase in oleate oxidation when administered after early morning exercise was found to persist for all three meals of the day, with the greatest effect occurring for the lunch meal. Palmitate oxidation, while apparently resistant to the effects of 1250 kJ of prior exercise, increases when administered later in the day, suggesting a diurnal variation in the oxidation of dietary fatty acids. These results demonstrate that prior exercise selectively alters the partitioning of dietary fatty acids. Furthermore, these findings demonstrate additional benefits of substituting monounsaturated for saturated fatty acids in the diet.

Adult↗
PubMed2003

Precision of the doubly labeled water method in a large-scale application: evaluation of a streamlined-dosing protocol in the Observing Protein and Energy Nutrition (OPEN) study.

OBJECTIVE: To evaluate whether the doubly labeled water (DLW) method is precise under conditions required for a large-scale evaluation of dietary intake instruments. DESIGN: Energy expenditure was measured in 484 subjects (main study). Subjects received one of five different weight DLW dose bottles prepared in advance of the study. A repeat energy expenditure measure was obtained in a subset of 24 subjects (substudy). DLW measures of energy expenditure were performed over a 2-week interval with urine collection at the beginning and end. SETTING: Free-living environment with three clinic visits in the Maryland suburban area of Washington, DC. SUBJECTS: A total of 484 subjects (261 men and 223 women) aged 40-69 y, 24 of whom (13 men and 11 women) participated in a substudy in which DLW was administered a second time. RESULTS: The coefficient of variation of the DLW energy expenditure measurement was 5.1%. This included a 2.9% analytical and a 4.2% physiologic variation. Based on observed initial isotopic enrichment, the preweighed dosages were optimal in 70% of the main study subjects, and 9% received a dose that was less than optimal. Only six subjects (1%) were excluded because the final isotopic enrichment was too low to conduct precise measurement. CONCLUSIONS: Use of preweighed DLW dosages did not compromise the precision of the DLW method. The DLW method is a reliable measure of energy expenditure for large-scale evaluations of dietary intake instruments.

Adult↗
PubMed2002

Determinants of the energy costs of light activities: inferences for interpreting doubly labeled water data.

OBJECTIVE: To investigate the controversy regarding the means of adjusting the energy cost of physical activity measured by doubly labeled water for differences in body size. DESIGN: We performed a cross-sectional study of the energy costs of carefully reproduced light activities with careful control for fidgeting and other unnecessary movement. SUBJECTS: :The study was performed in 23 healthy, young to middle aged adults with body masses between 39 and 118 kg. MEASUREMENTS: Energy expenditure was measured by respiratory gas exchange while subjects performed controlled light activities representative of activities of daily life. Body composition was measured by bioelectrical impedance analysis. RESULTS: The energy costs of individual controlled light activities were proportional to body weight except for mock vacuum cleaning. When the energy costs of all five activities were taken together, allometric regression analysis indicated that the energy cost of these light activities was proportional to body weight (slope=0.88+/-0.07), but not to fat-free mass (1.24+/-0.10), fat mass (0.27+/-0.03) or resting metabolic rate (1.43+/-0.12). CONCLUSION: Normalization of energy expenditure of physical activity by division by body weight is an appropriate means for comparing the volume (intensity x time) of physical activity between individuals of different body size.

Activities of Daily Living↗
PubMed2002

Pattern and cost of weight gain in previously obese women.

Weight gain is common among postobese individuals, providing an opportunity to address the cost of weight regain on energy expenditure. We investigated the energy cost of weight regain over 1 yr in 28 women [age 39.5 +/- 1.3 (SE) yr; body mass index 24.2 +/- 0.5 kg/m(2)] with recent weight loss (>12 kg). Body composition, total energy expenditure (TEE) using doubly labeled water, resting metabolic rate (RMR), and thermic effect of a meal (TEM) were assessed at 0 and 12 mo. Metabolizable energy intake (MEI) was calculated from TEE and change in body composition. Fourteen women had a weight gain of 13.2 +/- 2.1 kg. Twelve-month cumulative excess MEI, calculated as the intake in excess of TEE at month 0, was 749 +/- 149 MJ. Of this, 462 +/- 83 MJ (62%) were stored as accrued tissue, and 287 +/- 72 MJ (38%) was increased TEE. Expressed per kilogram of body weight gain, the energy cost of weight gain was calculated to be 54.8 +/- 4.6 MJ/kg. Interestingly, weight regain time courses fell into three distinct patterns, possibly requiring varying countermeasures.

Adult↗
PubMed2001

Validation of deuterium labeled fatty acids for the measurement of dietary fat oxidation: a method for measuring fat-oxidation in free-living subjects.

BACKGROUND: Fatty acid oxidation has frequently been measured using (13)C or (14)C labeled fatty acids. While providing valuable data, the breath test method is hindered by the need for a controlled environment to measure VCO(2) and collect frequent breath samples. Additionally, the CO(2) breath tests require the use of (13)C- or (14)C-acetate to correct for isotope exchange in the TCA cycle. We validated d(31)-palmitic acid for measuring dietary fat oxidation. When oxidized, the deuterium appears as water and mixes with the body water pool providing a cumulative record of fat oxidation. METHODS: The recovery of deuterium from d(31)-palmitic acid at 10 h post-dose was compared to that of (13)CO(2) from [1-(13)C]-palmitic acid in nine subjects (body mass index (BMI)=23.6+/-2.8; percentage body fat (%BF)=22.6+/-5.3; mean+/-s.d.). Subjects were studied at rest. [1-(13)C]-acetate (2 mg/kg) was dosed in a liquid breakfast. On a second day, [1-(13)C]-palmitic acid (10 mg/kg) and d(31)-palmitic acid (15 mg/kg) were dosed with the same liquid breakfast. RESULTS: Recovery of (13)CO(2) from [1-(13)C]-acetate at 10 h post-dose was 53.7+/-10.4%. Recovery of d(31)-palmitic acid was 13.2+/-7.7% (mean+/-s.d.) and [1-(13)C]-palmitic acid recovery was 6.4+/-3.6%. When the (13)C data was corrected for [1-(13)C]-acetate (Na salt) recovery, the mean difference in percentage recovery between the two tracers was 0.5+/-2.8% and cumulative recoveries through 10 h post-dose were highly correlated (y=1.045x - 0.47; r(2)=0.88, P<0.0002). Our data shows both labels to be equivalent in their ability to measure dietary fat oxidation in resting subjects. CONCLUSIONS: The use of deuterium labeled palmitic acid eliminates the need for rigid control over the subjects' environment. Frequent sampling and measurement of VCO(2) are not needed for accurate calculation of percentage recovery of the deuterium label. In addition, the deuterium label has a decreased potential for isotopic exchange compared to (13)C or (14)C, so a recovery correction factor is probably not required.

Adult↗
PubMed2001

The importance of clinical research: the role of thermogenesis in human obesity.

The hypothesis that human obesity is caused by deficient thermogenesis has been proposed by many investigators throughout the 20th century. Supporting evidence was obtained from epidemiologic studies of dietary intake, animal models with aberrant brown adipose tissue (BAT) function, and genetic studies of human polymorphisms of genes involved in BAT function. Supporting evidence was also obtained from clinical studies of the thermogenic effect of meals, but these measures capture only a short portion of the day and may miss some of the thermogenic effect. To capture the effects throughout the day and to move the studies out of the metabolic ward, investigators have used the doubly labeled water (DLW) method to measure total daily energy expenditure. DLW studies have not supported the above hypothesis. Increases in total energy expenditure (TEE) during overfeeding have been small (0.9 +/- 0.8 MJ/d) and account for an average of only 18 +/- 18% of the excess energy intake. Most of this increase is in the resting metabolic rate. Moreover, these studies showed little variation in the changes in resting metabolic rate or in thermogenesis from meals during overfeeding. Instead, the component that is most variable and that accounts for the variability in weight gain during overfeeding is the energy expended in physical activity. This component of TEE deserves greater attention in future studies. These studies of thermogenesis have shown the importance of clinical research as part of a comprehensive approach to understanding the etiology of human obesity.

Adipose Tissue, Brown↗
PubMed2001

Natural abundance deuterium and 18-oxygen effects on the precision of the doubly labeled water method.

The doubly labeled water method for measuring total energy expenditure is subject to error from natural variations in the background 2H and 18O in body water. There is disagreement as to whether the variations in background abundances of the two stable isotopes covary and what relative doses of 2H and 18O minimize the impact of variation on the precision of the method. We have performed two studies to investigate the amount and covariance of the background variations. These were a study of urine collected weekly from eight subjects who remained in the Madison, WI locale for 6 wk and frequent urine samples from 14 subjects during round-trip travel to a locale > or = 500 miles from Madison, WI. Background variation in excess of analytical error was detected in six of the eight nontravelers, and covariance was demonstrated in four subjects. Background variation was detected in all 14 travelers, and covariance was demonstrated in 11 subjects. The median slopes of the regression lines of delta2H vs. delta18O were 6 and 7, respectively. Modeling indicated that 2H and 18O doses yielding a 6:1 ratio of final enrichments should minimize this error introduced to the doubly labeled water method.

Adolescent↗
PubMed2001

Evaluation of dietary assessment instruments against doubly labeled water, a biomarker of habitual energy intake.

Epidemiological studies of diet and disease rely on the accurate determination of dietary intake and subsequent estimates of nutrient exposure. Although methodically developed and tested, the instruments most often used to collect self-reported intake data are subject to error. It had been assumed that this error was only random in nature; however, an increasing body of literature suggests that systematic error in the reporting of true dietary intake exists as well. Here, we review studies in which dietary intake by self report was determined while energy expenditure was simultaneously measured using the doubly labeled water (DLW) method. In seeking to establish the relative accuracy of each instrument to capture true habitual energy intake, we conclude that none of the self-reported intake instruments demonstrates greater accuracy against DLW. Instead, it is evident that the physical and psychological characteristics of study participants play a significant role in the underreporting bias observed in these studies. Further research is needed to identify underreporters and to determine how to account for this bias in studies of diet and health.

Body Mass Index↗
PubMed2000

Use of an automated chromium reduction system for hydrogen isotope ratio analysis of physiological fluids applied to doubly labeled water analysis.

The doubly labeled water method is commonly used to measure total energy expenditure in free-living subjects. The method, however, requires accurate and precise deuterium abundance determinations, which can be laborious. The aim of this study was to evaluate a fully automated, high-throughput, chromium reduction technique for the measurement of deuterium abundances in physiological fluids. The chromium technique was compared with an off-line zinc bomb reduction technique and also subjected to test-retest analysis. Analysis of international water standards demonstrated that the chromium technique was accurate and had a within-day precision of <1 per thousand. Addition of organic matter to water samples demonstrated that the technique was sensitive to interference at levels between 2 and 5 g l(-1). Physiological samples could be analyzed without this interference, plasma by 10000 Da exclusion filtration, saliva by sedimentation and urine by decolorizing with carbon black. Chromium reduction of urine specimens from doubly labeled water studies indicated no bias relative to zinc reduction with a mean difference in calculated energy expenditure of -0.2 +/- 3.9%. Blinded reanalysis of urine specimens from a second doubly labeled water study demonstrated a test-retest coefficient of variation of 4%. The chromium reduction method was found to be a rapid, accurate and precise method for the analysis of urine specimens from doubly labeled water.

Chromium↗
PubMed2000

The role of exercise in the treatment of obesity.

The prevalence of obesity in the USA has increased dramatically in the past decade. This foreshadows an increase in the rates of morbidity and mortality from obesity-related diseases and increases in the number of individuals undergoing weight-loss therapy. Although exercise has long been recommended for inclusion in such therapy, the present review has found that it has had little or no effect on weight loss per se when the exercise is limited to the typically prescribed 3-5 h/wk of moderate or vigorous activity. However, further review has shown that exercise helps to preserve and at times even increase fat-free mass during weight loss. At the same time, fat loss is generally increased. Neither type nor amount of exercise appears to have much effect during treatment, with the possible exception of resistance training, which is associated with the best outcome for fat-free mass. The most important role of exercise, however, is in the maintenance of the weight loss. In this respect, the volume of exercise seems to be important because several lines of evidence have indicated that exercise must expend roughly 2500 kcal/wk to maintain weight loss. Studies of weight maintenance, however, have generally not included randomized controls; thus, further research is required to solidify these conclusions.

Body Composition↗
PubMed2000

De novo lipogenesis in adipose tissue of lean and obese women: application of deuterated water and isotope ratio mass spectrometry.

OBJECTIVE: To evaluate the feasibility of using deuterated water and isotope ratio mass spectrometry to measure de novo fatty acid synthesis in adipose tissue, and to compare this parameter in obese and lean women. SUBJECTS: Six lean and six obese premenopausal Caucasian women in the main study and three obese Pima Indians in a pilot study. MEASUREMENTS: Deuterated water was administered orally twice daily for 14 days to create stable deuterium enrichment in body water, during which series of blood samples were collected to measure body water deuterium enrichment and deuterium incorporation into plasma total Triacylglycerol (TG) fatty acids and total cholesterol. Subcutaneous fat at different sites were sampled at the beginning and the end of deuterium administration to measure deuterium incorporation into TG fatty acids. RESULTS: Fractional de novo synthesis rate of TG fatty acids in adipose tissue was 0. 014+/-0.005 and 0.014+/-0.007% in lean and obese Caucasian women, corresponding to 2+/-0.7 and 5.6+/-3.2 g (P=0.3) of fatty acids synthesized daily, respectively. Plasma TG fatty acids and cholesterol synthesis rates were comparable to those reported previously. A pilot study showed that de novo lipid synthesis in adipose tissue of obese Pima Indians was also quantitatively minor. CONCLUSION: Human adipose tissue, like the liver, does not make a major contribution to whole body lipogenesis under eucaloric conditions. A combination of deuterated water and isotope ratio mass spectrometry is a useful research tool for studying accumulation of de novo synthesized lipids in human adipose tissue.

Adipocytes↗
PubMed2000

Bioelectrical impedance analysis. What does it measure?

Bioelectrical impedance analysis (BIA) has been proposed for measuring fat-free mass, total body water, percent fat, body cell mass, intracellular water, and extracellular water: a veritable laboratory in a box. Although it is unlikely that BIA is quite this versatile, correlations have been demonstrated between BIA and all of these body compartments. At the same time, it is known that all of the compartments are correlated among themselves. Because of this, it is difficult to determine whether BIA is specific for any or all of these compartments. To investigate this question, we induced acute changes in total body water and its compartments over a 3-h period. Using this approach, we demonstrated that multifrequency BIA, using the Cole-Cole model to calculate the zero frequency and infinite frequency resistance, measures extracellular and intracellular water.

Adipose Tissue↗
PubMed2000

Twenty-four-hour leptin levels respond to cumulative short-term energy imbalance and predict subsequent intake.

Leptin plays a vital role in the regulation of energy balance in rodent models of obesity. However, less information is available about its homeostatic role in humans. The aim of this study was to determine whether leptin serves as an indicator of short-term energy balance by measuring acute effects of small manipulations in energy intake on leptin levels in normal individuals. The 12-day study was composed of four consecutive dietary-treatment periods of 3 days each. Baseline (BASE) [100% total energy expenditure (TEE)] feeding, followed by random crossover periods of overfeeding (130% TEE) or underfeeding (70% TEE) separated by a eucaloric (100% TEE) washout (WASH) period. The study participants were six healthy, nonobese subjects. Leptin levels serially measured throughout the study period allowed a daily profile for each treatment period to be constructed and a 24-h average to be calculated; ad libitum intake during breakfast "buffet" following each treatment period was also measured. Average changes in mesor leptin levels during WASH, which were sensitive to energy balance effected during the prior period, were observed. After underfeeding, leptin levels during WASH were 88 +/- 16% of those during BASE compared with 135 +/- 22% following overfeeding (P = 0.03). Leptin levels did not return to BASE during WASH when intake returned to 100% TEE, but instead were restored (104 +/- 21% and 106 +/- 16%; not significant) only after subjects crossed-over to complementary dietary treatment that restored cumulative energy balance. Changes in ad libitum intake from BASE correlated with changes in leptin levels (r2 = 0.40; P = 0.01). Leptin levels are acutely responsive to modest changes in energy balance. Because leptin levels returned to BASE only after completion of a complementary feeding period and restoration of cumulative energy balance, leptin levels reflect short-term cumulative energy balance. Leptin seems to maintain cumulative energy balance by modulating energy intake.

Adult↗
PubMed1999

Energy intake, not energy output, is a determinant of body size in infants.

BACKGROUND: It has been proposed that the primary determinants of body weight at 1 y of age are genetic background, as represented by parental obesity, and low total energy expenditure. OBJECTIVE: The objective was to determine the relative contributions of genetic background and energy intake and expenditure as determinants of body weight at 1 y of age. DESIGN: Forty infants of obese and 38 infants of lean mothers, half boys and half girls, were assessed at 3 mo of age for 10 risk factors for obesity: sex, risk group (obese or nonobese mothers), maternal and paternal body mass index, body weight, feeding mode (breast, bottle, or both), 3-d energy intake, nutritive sucking behavior during a test meal, total energy expenditure, sleeping energy expenditure, and interactions among them. RESULTS: The only difference between risk groups at baseline was that the high-risk group sucked more vigorously during the test meal. Four measures accounted for 62% of the variability in weight at 12 mo: 3-mo weight (41%, P = 0.0001), nutritive sucking behavior (9%, P = 0.0002), 3-d food intake (8%, P = 0.0002), and male sex (3%, P = 0.05). Food intake and sucking behavior at 3 mo accounted for similar amounts of variability in weight-for-length, body fat, fat-free mass, and skinfold thickness at 12 mo. Contrary to expectations, neither total nor sleeping energy expenditure at 3 mo nor maternal obesity contributed to measures of body size at 12 mo. CONCLUSIONS: Energy intake contributes significantly to measures of body weight and composition at 1 y of age; parental obesity and energy expenditure do not.

Adult↗
PubMed1999

Recent advances from application of doubly labeled water to measurement of human energy expenditure.

The doubly labeled water (DLW) method was developed 50 years ago, but nearly 40 years passed before it became a major tool for human nutrition research. Its use has grown dramatically, however, since the first human applications. The DLW method is now the preferred method for determining energy requirements of healthy and clinical populations. The method has been applied extensively to the study of the growing problem of obesity in order to determine the role of energy expenditure and physical activity in weight control. Finally, DLW has provided a new means of validating methods for assessing dietary intake. The accuracy and noninvasive nature of the DLW method makes it ideal for the study of human energy metabolism.

Adolescent↗