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Biomedical subjects

L Garby

Publications and source records attributed to L Garby.

At least 37 records · Page 2Linked to original sources
PubMed1990

The effect of long-term dexfenfluramine treatment on 24-hour energy expenditure in man. A double-blind placebo controlled study.

In order to investigate the effect of long-term treatment with dexfenfluramine (dF) on 24-hour energy expenditure (EE), 10 obese females were studied in a double-blind design. Shortly before and 4 weeks after cessation of a 13 months treatment period with either dF (30 mg/day) or placebo (PL) the 24-hour EE was measured. The measurements were performed using a 24 m3 direct heat sink calorimeter with continuous real time measurements of evaporative and sensible heat losses. The patients performed a standardized program of exercise, rest and meals. The measurements were performed at 24 degrees C and at a humidity between 3 and 11 g/m3. Discontinuation of dF treatment did not change energy expenditure significantly from placebo, neither when expressed in kJ/kg lean body mass nor in kJ/kg body weight. After cessation of treatment total 24-hour EE decreased likewise nonsignificantly by 2.9 percent in the dF group and by 4.0 percent in the PL group. EE measured over 24 hours was subdivided into day and night periods and into resting energy expenditure as well as a measurement of the heat losses over a period of 3 hours after a meal. This subdivision of the EE showed similar nonsignificant differences. The conclusion is therefore that dF possesses no significant thermogenic effect during long-term administration in human obese subjects.

Adult↗
PubMed1990

Comparison of estimates of fat-free mass in normal and obese women from measurements of body potassium, body water and body density.

The relation between the estimates of fat-free mass (FFM) obtained from measurements of density, total body potassium and water was investigated in 104 women with Quetelet's Index between 19.9 and 49.7 kg/m2, body weight between 42.3 and 133.5 kg. The mean difference between the estimates based on water and potassium, previously reported as 2.2 kg or 4.4 per cent, was found to be independent of Quetelet's Index. The mean difference (s.e.m.) between the estimates of FFM based on density, compared with the average values from water and potassium, was found to be +7.0 (1.0), +6.3 (0.7) and +7.4 (1.1) kg in the ranges of Quetelet's Index 19.9-30.0, 30.1-40.0, and 40.1-49.7, respectively. The relative independence on Quetelet's Index of the difference between the estimates based on density compared with (water + potassium) is consistent with the idea that tissues of a higher density (ie, skin and bone) make up a larger proportion of the fat-free body weight in thin subjects than in fat ones.

Adult↗
PubMed1990

Changes in energy expenditure of light physical activity during a 10 day period at 34 degrees C environmental temperature.

The energy expenditure of a 2 h programme of light activity was observed daily in 8 young men after a change in habitual environmental indoor temperature of 20-24 degrees C to 34 degrees C and an absolute humidity of 6-10 g/m3 during a 10 day period. No changes were observed with respect to the daily energy intake, body weight, rectal temperature and average skin temperature, but the energy expenditure showed a decrease of between 3 and 8 per cent. The observations support results of previous studies on acclimatization with respect to energy expenditure, and indicate that differences in energy expenditure due to habitual differences in environmental temperature are small, presumably less than 5 per cent.

Adolescent↗
PubMed1990

Negligible effects of previous moderate physical activity and changes in environmental temperature on whole body electrical impedance.

Several studies have shown that the predictive power of various linear combinations of anthropometric data (body weight, height, sex, age, etc.) to estimate fat free mass is improved after inclusion of measurements of electrical impedance (see eg Khaled et al., 1988). Published algorithms are based on measurements performed under fairly standardized conditions with the subjects at stationary conditions of rest, of environmental temperature and of body fluids. Use of the method under less standardized conditions raises the question of possible effects of deviations from these standard conditions. Hydration and dehydration by 1-2 l of fluid increased or decreased, respectively, the electrical resistance by about 14 per cent and the effects persisted for more than 1 h (Khaled et al., 1988). A change in environmental temperature by 21 degrees C from 35 degrees C to 14 degrees C (with almost constant relative humidity) during 90 min caused an increase in the resistance of about 9 per cent (Caton et al., 1988). The perturbations used in the studies quoted above are fairly drastic and not likely to occur under reasonably controlled field conditions. Therefore, we report here results of measurements of whole body electrical impedance before, during and after a period of 10 degrees C increased environmental temperature and before and after a 5-min period of light to moderate physical exercise.

Electric Conductivity↗
PubMed1989

[Bioimpedance analysis in determining body composition. Testing of a new simple apparatus].

In the assessment of human body composition, only expensive and time consuming methods have hitherto been available. Recently, the new bioimpedance method has been introduced. It offers an easy, quick, inexpensive and noninvasive measurement with an accuracy comparable to that of the classical methods. A new inexpensive Danish apparatus was tested against the most used and validated equipment. Fifteen normal subjects underwent measurements with both apparatuses. The two methods gave identical results with a coefficient of correlation of 0.99 and a coefficient of variation of 5.6%. The apparatus can be recommended for clinical and scientific purposes.

Adolescent↗
PubMed1989

Enthalpy changes and heat production induced by a meal.

In 1974 Pittet and coworkers measured the thermic effect of glucose and amino acids by both direct and indirect calorimetry. Their results have been re-analysed in this paper. Only about 20 per cent of the substrate ingested was combusted during the period of observation (2 1/2 h). The change in enthalpy due to combustion, as measured by indirect calorimetry, can be divided into two parts. Direct calorimetry shows that about 40 per cent represents heat lost from or stored in the body; the form in which the remainder is stored cannot be evaluated from the data, but it is likely that it is in chemical form, resulting from reactions that increase the enthalpy content of the substrate that was not combusted within 2 1/2 h.

Calorimetry↗
PubMed1988

Measurement of exchange of trace metals between the body and its surroundings with the use of tracer methodology. A critique of current applications.

Application of general tracer theory to the problem of estimating fluxes of tracee between the gastrointestinal tract and the body proper, from observations of the movement of tracer, shows that a number of assumptions must be fulfilled. Two specific sets of assumptions are discussed and, in both cases, measurement of tracer fluxes yields information on the integrated absorption of the tracee.

Digestive System↗
PubMed1988

Effect of 12 weeks' light-moderate underfeeding on 24-hour energy expenditure in normal male and female subjects.

The effect of 12 weeks' light-moderate underfeeding on the 24-h energy expenditure of a fixed physical activity programme was studied in six male and six female subjects. During a control period of 2 weeks, measurements were made of 24-h energy expenditure by direct calorimetry, the lean and fat body masses and the subjects' habitual energy intakes. The average body weight was 107 per cent of ideal, and did not change significantly during the control period. The subjects were asked to continue to record their daily food intake while reducing it by 25 per cent and to continue their daily activity habits during a period of 12 weeks. The mean change in body weight was -2.9 kg with an average change in body energy content of -66 MJ. The 24-h energy expenditure was measured three times during the period, ie, after 4, 8 and 12 weeks from the start of the decreased energy intake, and found to be practically the same as the control value, ie, with average differences (s.d.) of -0.2(3.9), -0.8(5.7) and +0.6(4.2) per cent from the control value. In the six subjects who had the largest loss of body weight, this was found to be 5.0 kg, and the mean differences (s.d.) in energy expenditure were found to be -1.0(3.4), 0.0(5.6) and -0.6(3.9) per cent, respectively, from the control value. A significant part of the between-subjects variation in the differences from the control value is due to random measurement error and it is concluded that a loss of body energy content of the magnitude reported here, and due mainly to a reduced food intake, does not result in a significant increase in the efficiency of energy conversion, ie, in metabolic adaptation.

Adult↗
PubMed1988

Relation between energy expenditure and body composition in man: specific energy expenditure in vivo of fat and fat-free tissue.

The relationship between energy expenditure and body composition, in terms of fat and fat-free masses, has previously been described by a variety of predictive regression equations with parameters devoid of physiological content. We present here results obtained by calculating the specific energy expenditure, ie, the energy expenditure per unit of mass, of fat and fat-free tissue on the basis of measurements of the total energy expenditure (EE), the masses of fat (FM), and fat-free (FFM) tissue using the following simple model: EE = k1.FM + k2.FFM where k1 and k2 are the specific energy expenditures of fat and fat-free tissue, respectively. The results of observations on 104 women at rest yielded values for k1 and k2 of 0.31 and 1.35 watts/kg of fat and fat-free mass, respectively, with standard errors of estimate of 0.074 and 0.052 watts/kg, respectively. Analysis of several series of measurements, from other sources and on smaller samples of subjects, yielded similar values at rest but with larger standard errors of estimate. Data from subjects performing varying amounts of work in 24-h measurements showed, as expected, larger values for both tissues. The results explain to a very large extent the well-established relation between resting metabolic rate and body weight, ie, a linear relation with a non-zero intercept. The results also offer a clear-cut explanation for the well known difference in energy expenditure between men and women with the same body weight.

Adipose Tissue↗
PubMed1987

Effect of the preceding day's energy intake on the energy costs of rest, arm and leg exercise.

Relatively little is known about the response of the human body to perturbations in the energy intake. In particular, results of the effect of a perturbation of the preceding day's energy intake on the energy expenditure on the following day are conflicting, ranging from no effect at all to an increase in the resting metabolic rate of 12 per cent following an increase in the preceding day's energy intake of 5 MJ. In the present study, the fasting energy expenditure of rest, light arm work and light leg work was determined on days following an intake of 4, 10 and 16 MJ in seven healthy men. In each subject, the difference in energy expenditure between days following intakes on the preceding day of 10-10 (control), 10-4 and 10-16 MJ was calculated for each of the three tasks. The mean percentage differences between the days following an intake of 10-10, 10-4 and 10-16 MJ were (s.d. in parenthesis) 0.0 (4.0), +1.3 (4.0) and +0.6 (3.2) for the resting metabolic rate, -1.7 (4.0), -2.2 (3.2) and -1.7 (3.7) for arm work and +0.3 (2.0), -1.2 (2.9) and -0.3 (3.2) for leg work. When the differences for the three tasks were averaged, the results were -0.5 (1.4), -0.7 (2.4) and -0.5 (1.3) for the three combinations respectively. None of these differences were found to be statistically different from zero. Changes in plasma adrenaline and noradrenaline concentrations were also measured but found not to be related to the changes in energy expenditure or to the energy intakes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Energy expenditure during sleep in men and women: evaporative and sensible heat losses.

Evaporative and sensible heat losses were measured during sleep in 38 male and 21 female subjects in a direct whole-body calorimeter (24 m3). The subjects were all apparently healthy, had a mean body weight of 66 kg and had spent the preceding day in the calorimeter performing different fixed physical activity programmes. Heat losses were measured continuously between 11.30 p.m. and 6.30 a.m. The average (+/- s.e.m.) rate of total heat loss during the 7h of sleep was 90.6 +/- 1.21 and 74.4 +/- 1.22 watts for men and women respectively. The total heat loss during basal resting conditions immediately following sleep was 83.8 +/- 1.5 and 69.2 +/- 1.6 watts, respectively. Heat production during basal resting conditions, as measured by indirect calorimetry about 1 h after awakening on the morning of the preceding day, was found to be 85.6 +/- 1.3 and 71.2 +/- 1.1 watts, respectively. The increase in heat loss during sleep above that of basal resting conditions could largely be attributed to an increase in the evaporative heat loss. The heat loss fell during the night by about 14 per cent in women and about 30 per cent in men, approaching basal resting values in the last hour of sleep. Heat production during sleep was calculated for the male subjects by correcting the heat loss data for the published decreases in rectal temperature during the night and was found to be on average 9 per cent lower than the heat loss. The present data, as well as previously reported data, suggest that the energy expenditure of sleep is 0.95 X BMR rather than 1.0 X BMR as reported in the recent FAO/WHO/UNU Expert consultation (1985).

Adolescent↗
PubMed1986

An improved algorithm and a computer program for the analysis of capillary gas exchange.

In most models of capillary gas exchange, the binding curves for O2 and CO2 are represented by simple analytical expressions, and the interactions among the haemoglobin ligands are either neglected or are assigned fixed values independent of PO2, PCO2, pH and red cell DPG. We here present algorithms and a computer program in which the binding curves are described in a near-rigorous manner. This enables solution of a set of typical equations for a unit of blood which undergoes gaseous and proton exchange. We have applied the algorithms to the problem of calculating pulmonary blood flow from the gaseous exchange in the lung by the single-breath method of Kim et al. (1966), where the CO2 binding curves of arterial and mixed venous blood are approximated by straight lines. The application of the algorithms shows that this approximation introduces significant errors in the calculated pulmonary blood flow.

2,3-Diphosphoglycerate↗
PubMed1986

24-h evaporative and sensible heat losses in relation to ambient humidity at 24 degrees C in clothed human subjects.

The effect of ambient humidity on the energy expenditure of clothed subjects was investigated. Fifty-six healthy men and women, weighing about 65 kg, spent 24 h in a large human calorimeter at 24 degrees C and performed either of two fixed activity programmes. The ambient humidity varied between experiments from 3 to 11 g m-3. The sensible heat output did not vary significantly with humidity but the evaporative heat loss decreased by about 1.5 W for each g m-3 increase in humidity.

Adolescent↗
PubMed1986

Energy expenditure over 24 hours on low physical activity programmes in human subjects.

The Fifth World Food Survey (FAO, 1986) has defined energy malnutrition as an intake below maintenance requirement and has suggested that maintenance requirement is equal to 1.4 times the resting metabolic rate (RMR), or, alternatively, 1.4 X RMR minus twice the standard deviation of the variation between normal subjects. In order to give substance to these numbers, we have measured the 24-h energy expenditure on two different physical activity programmes. The measurements were made on 38 men and 18 women, all apparently healthy and weighing about 65 kg. The measurements were performed at 24 degrees C and ambient humidity and the subjects wore clothes such as to be within the thermal comfort range. Measurements of the RMR were also performed. In one of the programmes, the average value of the 24-h energy expenditure divided by the RMR was found to be identical in men and women and equal to 1.38 X RMR. In another programme, with more intense physical activity, the corresponding number was 1.53 X RMR. In all three series of measurements, the coefficient of variation between subjects was found to be the same, ie between 6 and 8 per cent.

Adolescent↗