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Biomedical subjects

G R Goldberg

Publications and source records attributed to G R Goldberg.

At least 19 recordsLinked to original sources
PubMed2006

Variability of appetite control mechanisms in response to 9 weeks of progressive overfeeding in humans.

BACKGROUND: The current epidemic of obesity demonstrates that mechanisms for maintaining human energy balance are readily subverted by adverse environmental conditions. The critical elements of this dysregulation are poorly understood. Most previous research into what regulates the intake side of the energy balance equation has been handicapped by the use of short-term within-day experimental tests. OBJECTIVE: We enrolled six non-obese men to a 17-week protocol involving three 21 days periods of progressive overfeeding (+20, +40 and +60%) separated by free diet periods to test for compensatory satiety. RESULTS: Responses to overfeeding differed markedly with evidence of 'compensators' and 'non-compensators', but on average, subsequent food intake was stimulated rather than suppressed after overfeeding in spite of markedly elevated body fat (+13%) and fasting leptin (+116%). DISCUSSION: The inefficient response of in-built appetite control mechanisms emphasizes the need to adopt intentional cognitive restraint in the modern environment when food is plentiful.

Adipose Tissue↗
PubMed2003

Leptin does not respond to 48 h fat deposition or mobilization in women.

OBJECTIVE: To test the hypothesis that acute responses of plasma leptin concentration to energy balance manipulation are mediated by fat flux. DESIGN: Ten healthy women aged 31-63 y, mass 48-113.5 kg, fat mass 8.5-62.5 kg, were studied for 3 days in a whole-body calorimeter on two occasions. After a control day (D1) during which energy balance was maintained, diet was manipulated to induce fat deposition (FD) or mobilization (FM) of 50 g/day for 2 days (D2 & D3). A difference totalling of 194+/-18.6 g fat was achieved between manipulations without significant effects on carbohydrate or protein balance. Fasting plasma leptin was measured on D2 and D4. RESULTS: After the control day plasma leptin concentration averaged 19.01+/-9.8 ng/ml, and was found to be linearly related to body fat mass. After 2 days manipulation of fat balance, leptin concentrations were 21.4+/-10.3 ng/ml (FD) and 21.2+/-11.3 ng/ml (FM). There was no significant difference between treatments in either control day or postmanipulation leptin concentrations, nor did the treatments induce any differences in glucose or insulin concentration responses. CONCLUSION: Although in states of energy balance leptin concentration is linearly related to fat mass, acute modulation of leptin concentration during energy imbalance is not mediated by fat flux.

Adipose Tissue↗
PubMed2001

Dose-response relationship between fat ingestion and oxidation: quantitative estimation using whole-body calorimetry and 13C isotope ratio mass spectrometry.

OBJECTIVE: To determine dose-dependent relationship between ingested fat and its oxidation in the immediate post-prandial period in humans. DESIGN: Subjects were randomly selected for the study at the Dunn Clinical Nutrition Centre, Cambridge, UK. Subjects ingested naturally enriched 13C corn-oil doses (range 20-140g) in a whole-body indirect calorimeter, and were studied for 8 h. Ingested fat oxidation was estimated from the subject's breath 13C enrichment and total carbon dioxide production. Total fat and carbohydrate oxidation were estimated from non-protein oxygen and carbon dioxide exchanges. Endogenous fat oxidation was estimated as the difference between total fat and ingested fat oxidation. RESULTS: The amount of fat dose oxidized was nonlinearly related to the amount ingested. On average, 25.6+/-2.7% of the mean fat dose was oxidized. A significant (r = - 0.72, P < 0.001) inverse correlation was found between the amount of fat dose and the proportion oxidized. Endogenous carbohydrate oxidation was negatively and significantly correlated to fat dose oxidized (r= -0.61, P < 0.01), but it was not correlated to endogenous fat oxidation. CONCLUSIONS: There was a nonlinear relationship between amount of fat dose and its quantity that was oxidized in the immediate post-prandial period. The inverse relationship between the size of the fat load and the proportion that was oxidized post-prandially implies increased dietary fat storage beyond about 50 g in a normal resting adult. This has important implications for 13CO2-based studies.

Adolescent↗
PubMed2000

Energy adaptations in human pregnancy: limits and long-term consequences.

The very slow rate of human fetal growth generates a lower incremental energy stress than in any other mammalian species. This creates a situation in which adaptive changes in metabolic rate and in the amount of additional maternal fat stored during gestation can make a profound difference to the overall energy needs of pregnancy. Comparisons of women in affluent and poor countries have recorded mean population energy needs ranging from as high as 520 MJ to as low as -30 MJ per pregnancy. These energy costs are closely correlated with maternal energy status when analyzed both between and within populations, suggesting that they represent functional adaptations that have been selected for their role in protecting fetal growth. Although this metabolic plasticity represents a powerful mechanism for sustaining pregnancy under very marginal nutritional conditions, it must not be construed as a perfect mechanism that obviates the need for optimal nutritional care of pregnant women. The fact that fetal weight represents up to 60% of total pregnancy weight gain in many pregnancies in poor societies (compared with a well-nourished norm of 25%) indicates that the fetus is developing under suboptimal nutritional and physiologic conditions. It has long been recognized that this has immediate consequences for the offspring in terms of increased perinatal mortality. The more recent appreciation that impaired fetal growth may also precipitate longer-term defects in terms of adult susceptibility to noncommunicable and infectious diseases reinforces the view that pregnancy may be the most sensitive period of the life cycle in which nutritional intervention may reap the greatest benefits.

Adaptation, Physiological↗
PubMed1999

Effects of inactivity and diet composition on human energy balance.

OBJECTIVES: To investigate the influences of inactivity and dietary macronutrient composition on energy and fat balance and to look for interactions between them. DESIGN: Two-day measurements of energy expenditure and substrate oxidation on five occasions; ad libitum food intake from diets of 35% and 60% energy as fat, with and without imposed activity, and a fixed overfeeding at 35% fat with free activity. SUBJECTS: Eight normal-weight male volunteers. MEASUREMENTS: Energy expenditure and substrate oxidation by indirect whole-body calorimetry, and macronutrient intakes from food consumption on ad libitum regimens. RESULTS: Subjects consumed the same energy, mean 11.6 MJ/d, regardless of activity level, on the 35% diet. Subjects consumed more energy on the 60% than the 35% diet, mean 14 vs. 11.6 MJ/d. Inactivity induced a strong positive energy balance: 5.1 (60% diet), and 2.6 MJ/d (35% diet). Energy balance with activity was not significantly different between diets, nor significantly different from zero: 1.1 MJ/d (60% diet), and -0.2 MJ/d (35% diet). When intentionally overfed, subjects failed to compensate by raising voluntary activity. CONCLUSION: Energy intake was not regulated over a 2-day period in response to either imposition of inactivity or a high-fat diet. Activity proved essential to the avoidance of significant positive energy balance.

Adult↗
PubMed1998

Dietary compensation in response to covert imposition of negative energy balance by removal of fat or carbohydrate.

Compensatory changes in energy intake (EI) and macronutrient metabolism in response to modest covert underfeeding were tested by whole-body calorimetry in eight lean men. Each was studied on three occasions comprising a controlled stabilization day followed by manipulation and outcome days in a whole-body calorimeter. On the manipulation day EI was fixed, and calculated to maintain energy balance (CONTROL) or to provide 85% of CONTROL BY removing energy as carbohydrate (CHOred) or as fat (FATred). On the outcome day, ad libitum EI was allowed at fixed mealtimes. CHOred and FATred manipulations generated significantly different energy balances (-1.10 (SE 0.13) MJ, P = 0.000; -1.10 (SE 0.12) MJ, P = 0.000) and fat balances (-0.61 (SE 0.23) MJ, P = 0.03; -1.09 (SE 0.20) MJ, P = 0.000), but not carbohydrate balances (-0.39 (SE 0.22) MJ, NS; 0.11 (SE 0.23) MJ, NS) by the end of the manipulation day compared with CONTROL. On the outcome day, EI was significantly higher than CONTROL after CHOred (+1.58 (SE 0.33) MJ, P = 0.004) and FATred (+1.21 (SE 0.49) MJ, P = 0.022) with no differences between treatments. Overall 48 h energy balances averaged close to zero at -0.14, +0.34, +0.04 MJ on CONTROL, CHOred and FATred respectively. Total 48 h energy intakes on CHOred and FATred averaged 101 (SE 1.7)% and 99 (SE 2.5)% of CONTROL, thus demonstrating accurate detection of a mild energy deficit and efficient next-day compensation. Despite significant differences in macronutrient oxidation rates, the energy homeostatic mechanism appeared to be independent of specific macronutrient deficits.

Adult↗
PubMed1996

Alcohol and the regulation of energy balance: overnight effects on diet-induced thermogenesis and fuel storage.

The effect of alcohol on overnight energy expenditure and substrate disposal was studied in eleven subjects (five men, six women) using whole-body indirect calorimetry for 15.5 h after test meals. Three test meals were studied in random order with at least 48 h between treatments: control, 50% of maintenance energy needs provided as 14, 40 and 46% energy from protein, fat and carbohydrate respectively; alcohol addition, control plus 23% energy as alcohol; alcohol substitution, control with alcohol replacing 23% of carbohydrate energy. ANOVA revealed no significant sex effects. Alcohol-induced thermogenesis dissipated only 15 (SD 14)% of the alcohol energy. Alcohol addition had no significant effect on protein or carbohydrate oxidation but fat oxidation was suppressed (P < 0.0005) to an extent equivalent to storing 74 (SD 51)% of the alcohol energy as fat. Alcohol substitution reduced carbohydrate oxidation (P < 0.009) to an equivalent of 42 (SD 41)% and also spared fat (P < 0.005) to an equivalent of 59 (SD 37)% of the alcohol energy. It is concluded that alcohol has no special thermogenic capacity, and that its energy can be accounted for in a similar way to carbohydrate.

Adult↗
PubMed1996

Changes in macronutrient balance during over- and underfeeding assessed by 12-d continuous whole-body calorimetry.

Alterations in energy balance must be accommodated by adjustments in the net storage of the major energy-yielding macronutrients: carbohydrate, protein, and fat. This study used continuous whole-body calorimetry to measure changes in energy expenditure and substrate oxidation during a 12-d imposed energy imbalance in six lean men on mixed diets (overfeeding: 16.5 MJ/d, +33%, n = 3; underfeeding: 3.5 MJ/d, -67%, n = 3). Changes in total energy expenditure (TEE) and its components were modest; TEE changed by +6.2% (overfeeding) and -10.5% (underfeeding). In consequence, body weight changed by +2.90 and -3.18 kg. Marked changes in metabolic fuel selection occurred over the course of the study. Carbohydrate intake (540 and 83 g/d for overfeeding and underfeeding, respectively) exerted direct autoregulatory feedback on carbohydrate oxidation (551 and 106 g/d at day 12 for overfeeding and underfeeding, respectively). Subjects were close to balance by day 5. Changes in protein oxidation were small and not sufficient to prevent the oxidation of body protein mass, or its accretion, in response to energy deficit or surplus. Fat oxidation (59 and 177 g/d for overfeeding and underfeeding, respectively) was not sensitive to dietary fat intake (150 and 20 g/d, for overfeeding and underfeeding, respectively), rather, its oxidation was inversely related to the oxidation of other substrates. Changes in fat balance accounted for 74.1% and 84.0% of the energy imbalance during overfeeding and underfeeding, respectively. This study shows a clear oxidative hierarchy for the macronutrients. Metabolic fuel selection is dominated by the need to maintain carbohydrate balance. This induces inappropriate counterregulatory alterations in fat oxidation during energy surplus.

Adult↗
PubMed1996

Interactions between 2H and 18O natural abundance variations and DLW measurements of energy expenditure.

Appropriate corrections for 2H and 18O natural abundance are necessary in energy expenditure measurements with the doubly labeled water (DLW) method. The contribution of natural abundance variations to errors in the method is generally ignored if an appropriate dose level is given. Calculation of the appropriate dose level assumes that 2H and 18O natural abundance values are covariant and have a fixed slope. This study has investigated the between- and within-subject natural abundance variations, the latter over periods of time similar to those used in DLW experiment. Although 2H and 18O natural abundance values are covariant between subjects, the slope of their relationship is different from that of the Meteoric Water Line. Within subjects there is no such demonstrable covariance. It is concluded that: 1) the determinants of 2H and 18O natural abundance are different within and between subjects; 2) the concept of an optimal ratio of doses is not valid, and a safer strategy is probably to use a ratio > 10; 3) natural abundance variations may contribute significantly to the magnitude of error in the DLW measurements of energy expenditure.

Deuterium↗
PubMed1996

Metabolic fuel utilisation in obese women before and after weight loss.

OBJECTIVE: To test the hypothesis that weight rebound following slimming diets may be caused by an adaptive alteration in fuel utilisation involving a suppression of fat oxidation thus favouring fat storage in adipose tissue. DESIGN: Repeat measurements before and after two 14 d cycles of controlled weight loss using a very low energy diet (1.9MJ/d). SUBJECTS: Eight moderately obese women (body weight: 85.6 +/- 10.1 kg, BMI: 31 +/- 2 kg/m2, age: 42.6 +/- 10.1 years). MEASUREMENTS: Energy expenditure and substrate balances using 24-h whole-body indirect calorimetry and naturally labelled 13C-glucose. RESULTS: Aggregate weight loss was 5.1 +/- 0.8 kg. Twenty-four hour energy expenditure declined by 12% (8359 +/- 282 to 7366 +/- 191 kJ/d, p < 0.001). Net fat utilisation was not significantly depressed (4009 +/- 366) to 3613 +/- 191 kJ/d, NS), and the proportion of energy derived from fat was unchanged at 48.0% before weight loss and 49.0% after weight loss. CONCLUSION: The well-recognised phenomenon of reduced energy expenditure is unlikely to be a major cause of weight regain. The results do not support the theory that altered fuel selection in post-obese subjects may be the cause of difficulty in maintaining weight loss.

Adaptation, Physiological↗
PubMed1996

Physical activity and obesity: problems in correcting expenditure for body size.

OBJECTIVE: To explore the best method of adjusting energy expended on physical activity (AEE) for differences in body size. Many publications have expressed AEE per kg body weight (i.e. using weight 1.0 as denominator). This makes the unjustified assumption that all activities are weight-dependent. DESIGN: Retrospective analysis of data from ninety-two 24-h whole-body calorimetry measurements in women, and 574 doubly-labelled water measurements in men and women to calculate the optimal exponents of body weight for adjusting AEE. RESULTS: The analysis proved that weight 1.0 over-corrects for size differences and yields invalid conclusions about relationships between physical activity and obesity. An exponent close to 0.5 is more appropriate for sedentary lifestyles. However the correct exponent is itself dependent on the relative mix of weight-dependent and non-weight-dependent activities undertaken. CONCLUSION: We conclude that it is impossible to recommend a generalizable coefficient for adjusting AEE, and that great caution must be exercised when interpreting AEE data from individuals of markedly different body sizes.

Body Constitution↗
PubMed1995

Dual-energy X-ray absorptiometry measurements of body composition: effects of depth and tissue thickness, including comparisons with direct analysis.

1. There are few data regarding the accuracy of Hologic QDR-1000W dual-energy X-ray absorptiometry for the measurement of body composition. In two studies, one in an in vitro experimental system using oil and water mixtures and the other in samples of pork meat, the effect of depth and tissue thickness on the measured composition was assessed. In the latter study the measured fat mass was compared with that measured by direct analysis. 2. All data indicated a trend in the measured fat mass with depth, such that more fat was measured at extremes of depth (< 10 cm and > 25 cm) than at intermediate depths. 3. In samples of meat weighing approximately 55 kg, dual X-ray absorptiometry significantly under-estimated the absolute fat mass compared with direct analysis (mean 20.4 +/- 1.65%) by 5-8% or 1-4 kg of fat. 4. These findings are of direct relevance to both clinical and research work using this technique to measure body composition, in particular in circumstances in which changes in body composition and/or tissue thickness are anticipated.

Absorptiometry, Photon↗
PubMed1995

Effects on metabolic rate and fuel selection of a selective beta-3 agonist (ICI D7114) in healthy lean men.

METHOD: ICI D7114 is a selective beta-3 agonist which in some animals increases metabolic rate, promotes weight loss and improves glucose tolerance. To investigate its potential usefulness in humans, 16 healthy young men (mean age 28.9 +/- 8.0 years; body mass index 22.5 +/- 1.6 kg/m2) were given ICI D7114 (150 mg/day, 2.08 +/- 0.24 mg/kg body weight) or placebo for 14 days in a double-blind randomised parallel group trial. Energy expenditure (EE) and substrate oxidation were assessed by continuous whole-body indirect calorimetry on Day 0 (before dosing), on day 1 (acute effect) and on Day 14 (chronic effect). RESULTS: Analysis of covariance indicated no significant effects on EE 4 h post-dose (Day 1, +2.4%, NS; Day 14, +1.0%, NS). There was no chronic effect on either the lowest 1 h of sleeping EE (+2.2%, NS) or 24 h EE (+0.7%, NS). There was a marginally significant chronic stimulation of basal metabolic rate (+3.6%, P = 0.042). ICI D7114 had no significant influence on protein, fat or carbohydrate oxidation. Tolerability and safety data showed that there were no increases in resting heart rate or blood pressure; no change in plasma potassium or reports of tremor; no haematological or biochemical abnormalities and no adverse events. CONCLUSION: We conclude that over 14 days ICI D7114 at a dose level of 150 mg/day has no biologically significant effect on EE in healthy, lean men.

Adolescent↗