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J O Hill

Publications and source records attributed to J O Hill.

At least 19 recordsLinked to original sources
PubMed2006

Successful dieters have increased neural activity in cortical areas involved in the control of behavior.

OBJECTIVE: To investigate whether dietary restraint, a landmark of successful dieting, is associated with specific patterns of brain responses to the sensory experience of food and meal consumption. DESIGN AND SUBJECTS: Cross-sectional study of the brain's response to the sensory experience of food and meal consumption in nine successful dieters (age: 38+/-7 years, body fat (%): 28+/-3) and 20 non-dieters (age: 31+/-9 years, body fat (%): 33+/-9), all women. MEASUREMENTS: Changes in brain activity in response to the sensory experience of food and meal consumption were assessed by using positron emission tomography and (15)O water as a radiotracer. Body fatness was assessed by dual X-ray absorptiometry. Subjective ratings of hunger and fullness were measured by visual analogue scale. Dietary restraint, disinhibition and hunger were assessed by the Three Factor Eating Questionnaire. RESULTS: Successful dieters had a significantly higher level of dietary restraint compared to non-dieters. In response to meal consumption, successful dieters had a greater activation in the dorsal prefrontal cortex (DPFC), dorsal striatum and anterior cerebellar lobe as compared to non-dieters. In response to the same stimulation, the orbitofrontal cortex (OFC) was significantly more activated in non-dieters as compared to successful dieters. Dietary restraint was positively correlated with the response in the DPFC and negatively with the response in the OFC. The responses in the DPFC and OFC were negatively intercorrelated. CONCLUSION: Cortical areas involved in controlling inappropriate behavioral responses, such as the DPFC, are particularly activated in successful dieters in response to meal consumption. The association between the degree of dietary restraint and the coordinated neural changes in the DPFC and OFC raises the possibility that cognitive control of food intake is achieved by modulating neural circuits controlling food reward.

Adult↗
PubMed2006

Model for predicting and phenotyping at normal weight the long-term propensity for obesity in Sprague-Dawley rats.

Tests were conducted to determine whether weight gain or nutrient intake measures during the first week of exposure to a macronutrient diet can accurately predict an animal's long-term propensity towards obesity. In multiple groups of normal-weight Sprague-Dawley rats (n=35-70/group), daily weight gain during the first 5 days on a high-fat diet (45-60% fat) was found to be strongly, positively correlated (r=+0.71 to r=+0.82) with accumulated body fat in 4 dissected depots after 4-6 weeks on the diet. This measure consistently identified obesity-prone (OP) rats which, relative to the obesity-resistant (OR) rats, were only slightly heavier (+15 g, 4%) and hyperphagic (+9 kcal, 8%) after 5 days but markedly heavier (+70g) with up to 2-fold greater fat mass after several weeks on the diet. Other dietary conditions and measures revealed weaker relationships to ultimate body fat accrual. The OP rats identified by their 5-day weight-gain score exhibited at this early stage clear disturbances characteristic of markedly obese rats. These included elevated leptin, insulin, triglycerides and glucose, along with increased lipoprotein lipase activity (LPL) in adipose tissue and galanin expression in the paraventricular nucleus. Most notable were significant reductions in muscle of LPL activity and ratio of beta-hydroxyacyl-CoA dehydrogenase to citrate synthase activity, indicating a decline in lipid transport and capacity of muscle to metabolize lipids. By occurring early with initial weight gain, these hypothalamic and metabolic disturbances in OP rats, favoring fat storage in adipose tissue over fat oxidation in muscle, may have causal relationships to long-term accumulation of body fat.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2005

Different forms of obesity as a function of diet composition.

OBJECTIVE: To characterize the phenotype of obesity on a high-carbohydrate diet (HCD) as compared to a high-fat diet (HFD) or moderate-fat diet (MFD). METHODS AND PROCEDURES: In four experiments, adult Sprague-Dawley rats (275-300 g) were maintained for several weeks on a: (1) HFD with 50% fat; (2) balanced MFD with 25% fat; or (3) HCD with 10% fat/65% carbohydrate. Then, based on the amount of body fat accumulated in four dissected fat pads, the animals were subgrouped as lean (lowest tertile) or obese (highest tertile) and characterized with multiple measures. RESULTS: The obese rats of these diet groups, with 70-80% greater body fat than the lean animals, exhibited elevated levels of leptin and insulin and increased activity of lipoprotein lipase in adipose tissue (aLPL), with no change in muscle LPL. Characteristics common to the obese rats on the HFD or MFD, but not seen on the HCD, were hyperphagia, elevated circulating levels of triglycerides (TG), nonesterified fatty acids (NEFA) and glucose, and a significant increase in beta-hydroxyacyl-CoA dehydrogenase (HADH) activity in muscle, reflecting its greater capacity to metabolize fat. This was accompanied by a significant increase in expression of the peptide, galanin (GAL), in the paraventricular nucleus (PVN), as measured by in situ hybridization and real-time quantitative PCR, and also in GAL peptide immunoreactivity. These measures of GAL were consistently, positively correlated with circulating TG levels and also with HADH activity in muscle. In contrast to these fat-associated changes, rats that became obese on an HCD maintained normal caloric intake and levels of TG, NEFA, and glucose. They also showed no change in PVN GAL mRNA or peptide. Instead, they exhibited a significant reduction in HADH activity compared to the lean animals, along with increased activity of phosphofructokinase in muscle, a key enzyme in glycolysis. CONCLUSION: Specific characteristics of obesity, including expression of hypothalamic peptides, are dependent upon diet composition. Whereas obesity on an HFD is associated with hyperphagia and elevated lipids, fat metabolism in muscle, and fat-stimulated peptides such as GAL, obesity on an HCD with a similar increase in body fat shows none of these characteristics and instead exhibits a metabolic pattern in muscle that favors carbohydrate over fat oxidation. These results suggest the existence of multiple forms of obesity with different underlying mechanisms that are diet dependent.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed2004

Commercially available pedometers: considerations for accurate step counting.

BACKGROUND: Many commercially available pedometers undercount, especially at slower speeds. We examined the effects of age, obesity, and self-selected walking speed on pedometer accuracy. We also compared the accuracy of piezoelectric and spring-levered pedometers at slow walking speeds. METHODS: Study 1: 259 subjects walked on a motorized treadmill at two self-selected walking speeds. Steps were counted using a spring-levered pedometer. Study 2: 32 subjects walked on a motorized treadmill at slow walking (1.0-2.6 MPH) speeds. Steps were counted using spring-levered and piezoelectric pedometers. RESULTS: Study 1: self-selected walking speed and pedometer accuracy decreased with increasing age, weight, and body mass index (BMI). Accuracy was 71% below 2.0 MPH, 74-91% between 2.0 and 3.0 MPH, and 96% above 3.0 MPH. Decreased accuracy was best predicted by increasing age. Study 2: between 1.8 and 2.0 MPH, the accuracy of the piezoelectric pedometer (>97%) exceeded that of the spring-levered pedometers (52-95%). Even at 1.0 MPH, accuracy of the piezoelectric pedometer (56.4 +/- 33.8%) was superior to the spring-levered pedometers (7-20%). CONCLUSION: Accuracy of all pedometers tested exceeded 96% at speeds 3.0 MPH, but decreased at slower walking speeds. In individuals that naturally ambulate at slower walking speeds (e.g., elderly), we recommend the use of more sensitive (e.g., piezoelectric) pedometers.

Adult↗
PubMed2004

Promoting long-term weight control: does dieting consistency matter?

OBJECTIVE: The present study examined whether long-term weight loss maintenance is enhanced by maintaining the same diet regimen across the week and year or by dieting more strictly on weekdays and nonholiday periods than at other times. METHOD: National Weight Control Registry participants (N=1429) indicated on an eight-point scale whether they dieted more strictly on weekends than weekdays, adhered to the same diet regimen throughout the week, or dieted more strictly on weekdays. Participants responded to a similar question about holiday and vacation eating. Participants were then followed prospectively to determine whether scores on these questions were related to self-reported weight regain over the subsequent 12 months. RESULTS: There was a linear relationship between scores on the dieting consistency questions and weight change over the 1-y period (P's <0.01), with smaller weight gains in those who reported more consistency. Participants who reported a consistent diet across the week were 1.5 times more likely to maintain their weight within 5 pounds over the subsequent year (OR=1.58, 95% CI: 1.2-2.2) than participants who dieted more strictly on weekdays. A similar relationship emerged between dieting consistency across the year and subsequent weight regain. CONCLUSION: Dieting consistency appears to be a behavioral strategy that predicts subsequent long-term weight loss maintenance.

Adult↗
PubMed2004

Persistence of abnormal neural responses to a meal in postobese individuals.

OBJECTIVE: To determine whether abnormal obese-like neural responses to a meal persist in postobese individuals, who achieved and maintained a normal body weight despite a past history of severe obesity. DESIGN AND SUBJECTS: Cross-sectional study of the brain's response to tasting and consuming a satiating meal in 11 postobese (age: 40+/-6 y, body mass index (BMI): 23.6+/-1.9 kg/m(2)), 23 obese (age: 29+/-6 y, BMI: 39.6+/-3.8 kg/m(2)) and 21 lean (age: 33+/-9 y, BMI: 22.8+/-2.1 kg/m(2)) subjects. MEASUREMENTS: Regional cerebral blood flow (rCBF, a marker of neural activity) at baseline (after a 36-h fast), after tasting and after consuming a satiating liquid meal was assessed using positron emission tomography and state-dependent changes (taste-baseline; satiation-baseline), and compared across groups. Subjective ratings of hunger and fullness were measured by a visual analogue scale and body fatness by dual-energy X-ray absorptiometry. RESULTS: In response to tasting the liquid meal, changes in rCBF were different in the obese as compared to the lean individuals (P<0.05, corrected for multiple comparisons) in the middle insula (peak voxel, x=-41, y=1, z=8; Montreal Neurological Institute coordinates) and posterior cingulate cortex (peak voxel, x=17, y=-47, z=40). The middle insular cortex exhibited a similar increase of neural activity in the obese and postobese subjects, whereas in the lean subjects the regional activity did not change. In the posterior cingulate cortex, the changes in rCBF in the postobese subjects were not different from those in the other groups. In response to a satiating amount of the same liquid meal, changes in rCBF were different in the obese as compared to the lean individuals (P<0.05, corrected for multiple comparisons) in the posterior hippocampus (peak voxel, x=21, y=-45, x=4), posterior cingulate cortex (peak voxel, x=17, y=-47, z=40), and amygdala (peak voxel, x=27, y=1, z=-24). The posterior hippocampus exhibited a similar decrease of neural activity in the obese and postobese subjects, whereas in the lean subjects the regional activity increased. In the posterior cingulate cortex and amygdala, the changes in rCBF were not different between the postobese and lean individuals. None of the changes in neural activity were correlated with the age of the individuals, the subjective ratings of hunger and fullness, or the meal induced-changes in plasma glucose, insulin, or serum free fatty acids. CONCLUSION: Persistence of abnormal neural responses to a meal in the postobese individuals, a group at high risk for relapse, indicates that a predisposition to obesity may involve areas of the brain that control complex aspects of eating behavior including anticipation and reward, chemosensory perception, and autonomic control of digestion (insular cortex), as well as enteroception and learning/memory (hippocampus).

Adult↗
PubMed2004

Validation of the BodyGem hand-held calorimeter.

OBJECTIVE: To assess the validity and reliability of a hand-held indirect calorimeter. DESIGN: Resting metabolic rate (RMR) was measured on two separate mornings. SUBJECTS: A heterogeneous sample of 41 healthy adults. MEASUREMENTS: RMR using both a metabolic cart (Sensormedics 2900, SM-2900) and a hand-held indirect calorimeter (BodyGem, BG). RESULTS: There were no trial-to-trial differences in RMR measured by the BG (6756+/-163 vs 6697+/-163 kJ/day) or the SM-2900 (6400+/-163 vs 6396+/-167 kJ/day). RMR measured by the BG was significantly higher than that measured by the SM-2900 during both trials. In a sample of 10 subjects, the energy cost of holding the BG in position was determined to be (0.17+/-0.04 kJ/min, or 255+/-84 kJ/day). After applying this adjustment, the differences between systems were no longer significant during trial 1 (mean difference=101+/-67 kJ/day) or trial 2 (46+/-75 kJ/day). In overweight and obese individuals, RMR measured by the BodyGem was more accurate than that estimated by the Harris-Benedict equations. CONCLUSION: The BodyGem provides valid and reliable measurements of RMR. The BodyGem produces significantly higher values than the Sensor Medics 2900 indirect calorimeter, with the increase largely due to an increased energy demand required to hold the BG in position.

Adult↗
PubMed2003

Tracmor system for measuring walking energy expenditure.

OBJECTIVE: Walking is an important mode of exercise and is likely to represent a major component of nonexercise activity thermogenesis. The question arises, how best to quantify walking-energy expenditure (EE) in free-living individuals. The triaxial accelerometer for movement registration (Tracmor) is a valid measure of body displacement and so we wanted to evaluate this tool for quantifying walking-EE. HYPOTHESIS: In this study, we test the hypothesis that walking-EE, measured in a Room Calorimeter, can be predicted from Tracmor output using a regression equation derived from a brief Tracmor/treadmill/Metabolic Cart protocol. DESIGN: First, 11 healthy subjects completed a 40-min procedure whereby they wore a Tracmor unit and walked on a treadmill at 0, 1, 2 and 3 mph while EE was measured using a Metabolic Cart. This allowed a regression equation to be defined for each subject to convert Tracmor output to EE. Each subject then entered a Room Calorimeter wearing the Tracmor Unit and walked at two self-selected velocities ('slow', 'fast') while EE was measured. 'Tracmor/regression equation' predictions of walking-EE were compared with Room Calorimeter measurements of walking-EE for the two velocities. RESULTS: The 'Tracmor/regression equation' prediction of EE for walking slowly was 6.36+/-1.67 kJ/min, and for walking fast it was 11.0+/-2.60 kJ/min. Room Calorimeter measurements were 6.43+/-1.85 and 10.9+/-3.03 kJ/min, respectively. The intraclass correlation coefficient for slow-paced walking was 0.93 (P<0.001), and for fast-paced walking it was 0.82 (P<0.005). CONCLUSIONS: When combined with laboratory measures of EE, the Tracmor accelerometer provides useful data on walking-EE and is applicable to free-living individuals.

Acceleration↗
PubMed2003

Time course for changes in aerobic capacity and body composition in overweight men and women in response to long-term exercise: the Midwest Exercise Trial (MET).

OBJECTIVE: To determine the time course for changes in aerobic capacity, body weight (BW), and composition in overweight adults in response to a supervised exercise trial with a targeted energy expenditure of 2000 kcal week(-1). DESIGN: The Midwest Exercise Trial (MET) was a randomized, controlled, 16-month verified, supervised exercise trial. Aerobic exercise progressed to 45 min day(-1), 5 days week(-1) over 6-months and was then maintained for 10 months. Controls maintained their normal physical activity and all participants maintained ad libitum diets. SUBJECTS: A total of 131 participants were randomized to exercise or control groups and 74 completed the intervention and all laboratory testing. MEASUREMENTS: At baseline and months 4, 9, 12, and 16, aerobic capacity (VO(2max) ) was measured by indirect calorimetry, BW by digital scale, and fat weight and fat-free weight by hydrostatic weighing. RESULTS: Aerobic capacity (ml kg(-1) min(-1)) increased (P<0.05) from baseline (39.2+/-5.2, mean+/-s.d.) to 9 months (48.8+/-4.3) in exercising men as well as women (32.8+/-4.2-39.6+/-5.5) with no significant changes occurring at 12 or 16 months. From baseline to 9 months BW (94.0+/-12.6-88.7+/-9.7 kg) and fat weight (26.8+/-6.8-21.8+/-4.5 kg) significantly decreased in exercising men with no changes occurring at 12 or 16 months. There were no changes in fat-free weight across the 16 months for exercising men or for BW or composition in exercising women. Further, there were no significant changes for the control men for aerobic capacity, BW, or body composition across 16 months. Women in the control group showed significant increases in weight of 2.9+/-5.5 kg and fat weight of 2.1+/-4.8 kg at 16 months only. CONCLUSIONS: We recommend that investigations that use exercise without diet as the stimulus for weight loss have at least a 9-month duration to provide sufficient time for the full effects to be realized, should such effects be present.

Adipose Tissue↗
PubMed2003

Relation between calcium intake and fat oxidation in adult humans.

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.

Adult↗
PubMed2002

From instinct to intellect: the challenge of maintaining healthy weight in the modern world.

The global obesity epidemic is being driven in large part by a mismatch between our environment and our metabolism. Human physiology developed to function within an environment where high levels of physical activity were needed in daily life and food was inconsistently available. For most of mankind's history, physical activity has 'pulled' appetite so that the primary challenge to the physiological system for body weight control was to obtain sufficient energy intake to prevent negative energy balance and body energy loss. The current environment is characterized by a situation whereby minimal physical activity is required for daily life and food is abundant, inexpensive, high in energy density and widely available. Within this environment, food intake 'pushes' the system, and the challenge to the control system becomes to increase physical activity sufficiently to prevent positive energy balance. There does not appear to be a strong drive to increase physical activity in response to excess energy intake and there appears to be only a weak adaptive increase in resting energy expenditure in response to excess energy intake. In the modern world, the prevailing environment constitutes a constant background pressure that promotes weight gain. We propose that the modern environment has taken body weight control from an instinctual (unconscious) process to one that requires substantial cognitive effort. In the current environment, people who are not devoting substantial conscious effort to managing body weight are probably gaining weight. It is unlikely that we would be able to build the political will to undo our modern lifestyle, to change the environment back to one in which body weight control again becomes instinctual. In order to combat the growing epidemic we should focus our efforts on providing the knowledge, cognitive skills and incentives for controlling body weight and at the same time begin creating a supportive environment to allow better management of body weight.

Biological Evolution↗
PubMed2002

Metabolic and anthropometric factors related to skeletal muscle UCP3 gene expression in healthy human adults.

This cross-sectional investigation sought to determine the relationship between selected metabolic, endocrine, and anthropometric factors and skeletal muscle UCP3 mRNA in healthy adult humans. Twenty-four healthy adults (13 male and 11 female) across a range of aerobic capacity, age, and body composition were studied. Muscle biopsies were obtained from the vastus lateralis, from which UCP3 mRNA was quantified by Northern blot, and fiber type was determined by use of the myosin ATPase staining procedure. In addition, resting energy expenditure and maximum rate of oxygen consumption were determined by indirect calorimetry, body composition was determined by dual-energy X-ray absorptiometry, and fasting plasma leptin and insulin were determined by ELISA. UCP3 mRNA was correlated positively with the percent type I fibers (r = 0.842, P < 0.001), plasma leptin (r = 0.454, P = 0.026), and plasma insulin (r = 0.615, P < 0.001) and inversely to age (r = -0.411, P = 0.046). Stepwise multiple regression analysis determined that percent type I muscle fibers was the best predictor of vastus lateralis UCP3 mRNA, and no other variable entered the equation (model r(2) = 0.66). This study suggests that of the variables measured, UCP3 mRNA is primarily related to skeletal muscle fiber type in healthy adults. The factors that contribute to fiber-specific differences in UCP3 mRNA expression will need to be examined in future studies.

Adult↗
PubMed2001

Intakes of most nutrients remain at acceptable levels during a weight management program using the food exchange system.

OBJECTIVE: The purpose of this study was to determine if the food exchange system allows subjects' nutrient intake to remain at recommended levels during a weight-loss program. DESIGN: Subjects in an intervention were prescribed an energy-restriction diet and exercise program lasting 32 weeks, and nutrient intake was measured prestudy and after 12, 16, and 32 weeks. SUBJECTS/SETTING: Healthy but overweight and obese premenopausal women (n = 219) were recruited at 6 university sites into community-based weight loss programs. One hundred fifteen women completed all aspects of the study. INTERVENTION: Energy intake was set at 0.8 x resting metabolic rate (RMR) for weeks 1 through 12, 1.0 x RMR for weeks 13 through 20, and 1.2 x RMR for weeks 21 through 32. Energy intake was based on food exchange tables, with the number of food exchanges adjusted to encourage a distribution of 55% carbohydrate, 30% fat, and 15% protein. Subjects increased their daily walking distance to 3.2 km above prestudy levels. MAIN OUTCOME MEASURES: Nutrient intake was measured from four 3-day food records. STATISTICAL ANALYSES PERFORMED: Repeated measures analysis of variance, with specific time point changes assessed from paired t tests adjusted for multiple comparisons. RESULTS: Body mass decreased by a mean +/- SD of 6.7 +/- 3.2 kg at week 12 and 7.8 +/- 6.2 kg by week 32. Walking distance increased by an average of 17.2 +/- 10.0 km/week during the first 12 weeks, and 12.4 +/- 12.4 km/week during the last 20 weeks. Despite a 23% to 36% reduction in energy intake during the study, intake of most nutrients was maintained. Intake of vitamin E, calcium, iron, and zinc decreased significantly from prestudy levels during the first 16 weeks of the intervention, but not at week 32. APPLICATIONS/CONCLUSIONS: Intake of most nutrients can remain at recommended levels when overweight and obese women follow the American Diabetes Association/American Dietetic Association food exchange system during a community-based weight-loss program.

Adult↗
PubMed2001

Regulation of macronutrient balance in healthy young and older men.

OBJECTIVE: To determine the influence of age on the ability to adjust macronutrient oxidation to changes in diet composition. Our hypothesis was that the ability to adjust macronutrient oxidation to changes in diet composition would be impaired with age. DESIGN: Cross-sectional, randomized to three different isocaloric diets containing a constant percentage protein but varying in percentage fat and percentage carbohydrate: mixed diet (M; 15/30/55); high-fat diet (HF; 15/60/25), and high-carbohydrate (HC; 15/15/70). SUBJECTS: Six young (YM; age=25+/-1 y) and five middle-aged and older men (OM; age=63+/-3 y). MEASUREMENTS: Each subject underwent 24 h whole-room calorimetry on day 4 of each diet to determine 24 h macronutrient oxidation rates. Macronutrient balance was calculated from the individual macronutrient oxidation rates and the corresponding macronutrient intake. RESULTS: Body mass, percentage fat, and fat-free mass were similar in the two groups. Twenty-four-hour energy expenditure (EE) and energy balance did not differ across diets or between groups; 24 h EE was approximately 7% lower (NS) in the OM. Macronutrient oxidation rates were not significantly different in YM vs OM during M. Protein oxidation was similar across diets, but higher (P<0.05) in OM. Fat oxidation contributed 28.8+/-7.0% vs 37.8+/-4.7% to 24 h EE on M (NS) in the OM vs YM, respectively. This increased to 58.4+/-6.7 vs 51.9+/-5.3% of 24 h EE (NS) in the OM vs YM, respectively, during HF and decreased to 25.4+/-9.7 vs 20.2+/-14.3% (NS) during HC (diet effect, both P<0.05). Carbohydrate oxidation contributed 54.3+/-10.5% vs 56.6+/-2.4% of 24 h EE (NS) on M in the OM vs YM, respectively. This decreased to 19.5+/-10.6 vs 29.9+/-12.6% (NS) during HF and increased to 53.6+/-12.3 vs 64.7+/-14.3% (NS) in the OM vs YM, respectively during HC (diet effect, P<0.05). CONCLUSION: Taken together, these results suggest that the ability to adjust macronutrient oxidation to changes in diet composition is maintained in OM and, thus, is unlikely to contribute to the increased susceptibility to weight gain and obesity development that accompanies aging.

Adult↗
PubMed2001

Quantifying and separating the effects of macronutrient composition and non-macronutrients on energy density.

The purpose of the present study was to estimate and compare the effects of macronutrient composition (relative portions of macronutrients) and of non-macronutrient components (e.g. water and fibre) on energy density (energy per unit weight) of the diets of human subjects. We used standard macronutrient energy content values to develop a simple conceptual model and equation for energy density in terms of % energy from dietary fat and % non-macronutrients by weight. To study these effects in self-selected diets of free-living subjects, we used four consecutive days of self-weighed and recorded food records for thirty-two male and thirteen female free-living adult subjects. In the range of typical human diets, the effect of % non-macronutrients by weight was several times greater than that of % energy from dietary fat, both in absolute terms and relative to daily variation in subjects' diets. Both effects were large enough to be physiologically important. Non-macronutrients (% by weight) alone explained much more of the variation in self-selected dietary energy density either between subjects (R2 95 %) or day-to-day (R2 95 %) than did % energy from dietary fat (R2 5 % and 6 % respectively). Omitting beverages gave similar results. The smaller effect of macronutrient composition on energy density of diets is mainly because alterations in macronutrient composition affect only the portion of typical dietary intake that is macronutrients (one-quarter to one-third of weight). Mathematical methods are also useful in analysing observational data and for separating effects of macronutrient composition and non-macronutrients in intervention studies. These results illustrate the importance of considering non-macronutrients in the design and analysis of experimental or observational dietary data.

Adult↗
PubMed2001

Assessment of body composition change in a community-based weight management program.

OBJECTIVE: The purpose of this study was to validate the use of the leg-to-leg bioelectrical impedance analysis (BIA) system in assessing change in body composition over 32 weeks in overweight and obese women participating in a community weight management program. DESIGN: Intervention, with subjects prescribed an energy-restriction diet and exercise program for 32 weeks and body composition measured pre-study and after 12 and 32 weeks. SUBJECTS AND SETTING: Overweight and obese premenopausal women (n=201) with no overt disease were recruited at six sites into community-based weight loss programs. One hundred and twenty-four women completed all aspects of the study. INTERVENTION: Energy intake was set at 0.8 x resting metabolic rate (RMR) for weeks 1 through 12, 1.0 x RMR for weeks 13 through 20 and 1.2 x RMR for weeks 21 through 32. Energy intake was based on a food exchange table, with the number of food exchanges adjusted to encourage a percent distribution of 55% carbohydrate, 30% fat and 15% protein. Subjects increased their daily walking distance by 3.2 km above pre-study levels. MEASURES OF OUTCOME: Underwater weighing, seven skinfolds, and leg-to-leg BIA tests were used to assess body composition. RESULTS: A 3 x 3 repeated measures ANOVA revealed no significant difference in detecting change in FFM at 12 and 32 weeks among underwater weighing, BIA and skinfold, (F(4,492)=1.73, p=0.141) (decrease in FFM of 1.0+/-3.3 kg, 1.7+/-2.2 kg, and 1.4+/-3.3 kg respectively, 32 weeks). CONCLUSIONS: The leg-to-leg BIA system provides a valid measure of body composition change in overweight premenopausal women during a 32-week community-based weight loss program.

Adipose Tissue↗