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Biomedical subjects

G B Forbes

Publications and source records attributed to G B Forbes.

At least 19 recordsLinked to original sources
PubMed1992

Sequence of changes in body composition induced by testosterone and reversal of changes after drug is stopped.

OBJECTIVE: --To study the changes in body composition produced by large doses of testosterone and reversal of changes when the drug is discontinued. DESIGN: --Weekly injections of testosterone enanthate were given to young adult male volunteers for 12 weeks. Repeated assays of lean body mass (LBM) by potassium 40 counting were made during this period and at intervals during the ensuing 5 to 6 months. PARTICIPANTS AND SETTING: --Subjects who were living on their own, who were known to be free of significant disease, and who volunteered as controls for a study of patients with neuromuscular disease. Assays were done in the Clinical Research Center. MAIN OUTCOME MEASURES: --Changes in body weight, LBM, and (by subtraction) body fat. RESULTS: --Testosterone treatment produced a progressive increase in LBM and a progressive decrease in body fat. Body composition reverted slowly toward normal when the injections were stopped; thus, the effects of testosterone lingered for some time. The magnitude of the observed changes in LBM was in keeping with the change in urinary creatinine excretion reported for these same subjects. CONCLUSION: --Testosterone is a powerful anabolic agent that also serves to reduce body fat content.

Adipose Tissue↗
PubMed1992

Body size and composition of perimenarchal girls.

A number of measurements are reported on a cross-sectional sample of girls who were studied at times ranging from 54 months prior to menarche to 82 months after menarche. Included are anthropometric measurements, lean weight, body fat, abdomen-hip ratio, skeletal size, bone age, muscle strength, and urinary hydroxyproline excretion. The years preceding menarche are associated with an array of physiological and anatomical changes, making it difficult to assign a causative role to any one of them.

Adipose Tissue↗
PubMed1992

Energy expenditure under free-living conditions in normal-weight and overweight women.

Total energy expenditure under free-living conditions of 12 normal-weight and 26 overweight women was determined with the 2H2(18)O method. Overweight women tended to expend more energy (mean +/- SD, 11.20 +/- 1.79 MJ/d) than normal-weight women (9.46 +/- 0.87 MJ/d, P less than 0.005). Approximately half of this effect was explained by an increase in basal metabolic rate (BMR) in the overweight group compared with the normal-weight group (6.47 +/- 0.74 vs 5.68 +/- 0.39 MJ/d, respectively, P less than 0.005) and the other half by an increase in above-basal energy expenditure (4.73 +/- 1.49 vs 3.78 +/- 0.94 MJ/d, P less than 0.05). Total energy expenditure was approximately 1.7 times the BMR in both groups. After adjusting energy expenditure for weight or lean body mass by analysis of covariance, there was no significant difference between normal-weight and overweight groups. We conclude that most overweight subjects must consume more energy than lean subjects to maintain their excess weight, although some could maintain their obesity without eating more than lean subjects.

Adult↗
PubMed1992

Exercise and lean weight: the influence of body weight.

Exercise can produce a modest gain of lean body mass (LBM) and loss of fat in weight-stable individuals, but it is important to realize that if much weight is lost during exercise there is a risk of some erosion of the LBM. Data from both human and animal experiments show that exercise cannot conserve lean weight in the face of significant energy deficit, although moderate obesity affords a modicum of protection in this respect.

Adipose Tissue↗
PubMed1991

Science, Volume 133, 1961: Estimation of total body fat from potassium-40 content.

On the assumption that the potassium content of the lean body mass is constant, it should be possible to estimate fat content in living man from a measurement of potassium-40 activity in the whole-body scintillation counter. A series of such measurements on children and young adults shows good correlations with skin-fold thickness and weight/height ratio as indices of fatness.

Adipose Tissue↗
PubMed1991

Exercise and body composition.

We assessed changes in body composition in 41 young adults who engaged in various exercise and/or training programs on ad libitum diets. Most of those who gained weight sustained an increase in lean body mass (LBM), and most of those who lost weight lost LBM as well as fat. The change in LBM was directly related to the change in weight, with a regression slope of 0.500. An analysis of published data confirms these findings and, in concert with our data, provides the additional information that the magnitude of the change in body composition in exercising individuals is influenced by body fat content, just as it is for nonexercising individuals.

Adipose Tissue↗
PubMed1990

Do obese individuals gain weight more easily than nonobese individuals?

A review of studies done on human subjects who were overfed under controlled conditions for periods ranging from 2 to 12 wk shows that the energy cost of induced weight gain is a function of initial body weight and of lean body mass, body fat, and percent body fat. Therefore, bigger and fatter people need to eat more to gain a given amount of weight than do those who are thin. A likely explanation is that obese individuals tend to put on a large proportion of fat, a high-energy tissue, whereas thin people tend to gain more lean, which is a low-energy tissue.

Adipose Tissue↗
PubMed1990

The abdomen: hip ratio normative data and observations on selected patients.

Normative data for abdominal circumference:hip circumference ratio, of current interest as a possible health risk, are presented for a large number of healthy subjects aged 6-71 years. The ratio declines during childhood, and during adolescence, in females, while that for males remains about the same. In the adult years there is a rise in the ratios for both sexes, that for males preceding the rise for females. For most of the age span, the sex difference and the age trends are such that age and sex must be taken into consideration in evaluating data on patients with various disorders. Patients with diabetes mellitus and those with obesity tend to have elevated abdomen:hip ratios at all ages. Those with cystic fibrosis also tend to have higher ratios, but here the difference is due to a smaller hip circumference rather than a larger abdominal circumference, and the same is true for the younger diabetics. The ratios for athletes are in the normal range but exhibit much less variability; those for patients with anorexia nervosa are normally distributed.

Abdomen↗
PubMed1989

Deuterium oxide as a tracer for measurement of compliance in pediatric clinical drug trials.

We tested the hypothesis that a deuterium oxide (D2O) tracer could discriminate among patterns of clinically significant, imperfect compliance during drug trials. A model was developed to predict deuterium concentration during multiple dose regimens. After developing a regression equation to predict one of the model parameters for children, we selected healthy children (N = 20) at random to receive one of five 10-day D2O regimens. Five urine samples were obtained from each child during 15 days and analyzed for deuterium level by mass spectrometry. Each child's height, weight, age, and the first four urinary deuterium levels were used to estimate the amount and timing of deuterium administration. These estimates were compared with the five regimens to determine the closest match between estimate and regimen. The closest matching regimen was the regimen actually administered to 19 (95%) of the 20 children. Two of these children had D2O administration estimates that could be confused with another regimen. The correlation between the model's predicted levels and the measured levels of all urine samples was 0.96. We conclude that a D2O tracer shows excellent promise as a quantitative method of assessing compliance with liquid medications under specified conditions.

Child↗
PubMed1989

Hormonal response to overfeeding.

We assessed the hormonal status of adult female volunteers before and during a 3-wk period of weight gain induced by mixed diet overfeeding. Forty-six percent of the 4.3-kg average weight gain experienced by these subjects consisted of lean body mass (LBM) and it is of interest that there were also increases in plasma Somatomedin-C/Insulin-like Growth Factor (SM-C/IGF-1) and testosterone concentrations as well as insulin. We suggest that it was the combined anabolic effect of these three hormones that facilitated the increase in LBM. Of the other assays done, increases were recorded for urinary 17-ketosteroids, 17-hydroxysteroids, epinephrine, and creatinine, whereas there were no changes in serum cortisol or triiodothyronine (T3), or urine norepinephrine; serum thyroxine (T4) fell slightly. Thus it appears that energy surfeit as well as energy deficit (reported by others) has an effect on blood hormone concentrations.

Adolescent↗
PubMed1989

Bromide space determination using anion-exchange chromatography for measurement of bromide.

A high-pressure liquid chromatographic method for bromide measurement is used to determine extracellular water volume in humans. The method uses 5 microL serum ultrafiltrate and has a sensitivity of 7.5 pmol. Because of the extreme sensitivity of this method, relatively small quantities of Br can be administered and small amounts of blood are needed for the analysis. By this method, the mean corrected Br space in 82 healthy adults representing a wide range of body weights was 0.218 +/- .034 L/kg (mean +/- 1 SD) with a range of 0.153-0.295 L/kg, which is consistent with reported values. There was a significant, inverse relationship between corrected Br space per kilogram and obesity as measured by body mass index. The corrected Br space in six children aged 3-36 mo was 0.335-0.394 L/kg, which is also consistent with reported values in children of this age. This method for Br measurement can easily and readily be applied for the determination of extracellular water volume.

Adult↗