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Biomedical subjects

A Astrup

Publications and source records attributed to A Astrup.

At least 181 records · Page 10Linked to original sources
PubMed1992

Three months aerobic training fails to affect 24-hour energy expenditure in weight-stable, post-obese women.

Sedentary 24 h energy expenditure (EE) in seven reduced-obese pre-menopausal women was measured in a respiration chamber before and after a three month aerobic training period. Six of the seven women showed a higher VO2max after the training period, while resting heart rate and blood pressure decreased significantly. No significant effects of training were seen in daytime, sleeping or total 24 h EE. However, change in daytime EE was positively correlated to the change in VO2max. Sleeping and 24 h respiratory quotients were slightly increased after the training period. A negative correlation was found between the change in VO2max and the change in fasting FFA. Change in postprandial glucose concentration was also negatively correlated to change in VO2max. Satiety measured 135 min after lunch was decreased after the training period. It is concluded that the moderate physical training programme was not sufficient to obtain a substantial elevation of sedentary 24 h EE.

Adult↗
PubMed1992

Obesity: an inherited metabolic deficiency in the control of macronutrient balance?

It has generally been assumed that the body is 'energy blind' and calories from all three macronutrients contribute with the same value to energy balance. There is, however, accumulating evidence to suggest that during ad-libitum conditions energy balance is achieved by a separate regulation of carbohydrate, fat and protein balances. Regulation of carbohydrate balance has the highest priority in the hierarchy, which is appropriate because the limited glycogen stores are only capable of covering the carbohydrate oxidation for a few days. Due to the higher satiating power of carbohydrate and protein compared with fat, a reduction in the dietary fat/carbohydrate ratio produces a negative fat balance in normal subjects consuming the diet ad libitum, while an increase in dietary fat/carbohydrate ratio results in a positive fat balance and weight gain. Subjects with a genetically determined predisposition to obesity become obese when they are exposed to a particular range of environmental conditions. The available knowledge suggests that the genetic propensity to weight gain is caused by a susceptibility to dietary fat due to an impaired capacity to increase their lipid/carbohydrate oxidation when fed a high-fat/low-carbohydrate diet. This in turn promotes lipid storage, depletion of carbohydrate stores and increases appetite. By enlarging the fat stores, the accompanying insulin resistance and higher levels of circulating non-esterified fatty acids increase lipid oxidation until it is commensurate with the dietary fat intake. The development of obesity may therefore be viewed as a regulatory mechanism by which the impaired lipid oxidation rate is raised to match a high fat intake. However, by decreasing the dietary ratio of fat to carbohydrate, macronutrient balance may be achieved with a high energy expenditure and a normal body composition. The results support current dietary recommendations, but with less emphasis on carbohydrate source, and they are also applicable for the prevention and treatment of obesity.

Dietary Fats↗
PubMed1991

[The "Lundberg cure"--an ineffective weight loss regimen. Study of the increase in metabolic rate supposedly induced by the "Lundberg cure"].

A recently marketed training principle, the "Lundberg" cure was postulated to cause an extraordinary weight loss when practised for only seven minutes per day. One hour of intensive training should lead to an additional energy expenditure of approx. 500 kcal. If the "Lundberg" cure was intensive, the treatment would mean a weight loss of approx. 240 g/mo. By testing the principle using respiratory chambers, it was shown that the metabolism was unchanged after the training period and that the additional energy expenditure during training averaged 0.94 kJ/kg lean body mass (SEM 0.07) corresponding to 63 g fat tissue/month or half a slice of white bread a day. It is concluded that the "Lundberg" cure, if practised as described in the press, will not lead to any weight loss, apart from that expected from the physical activity.

Adult↗
PubMed1991

Thermogenic synergism between ephedrine and caffeine in healthy volunteers: a double-blind, placebo-controlled study.

Animal and human studies have suggested a thermogenic synergism between ephedrine (E), a beta-agonist, and caffeine (C), an adenosine antagonist, which may be suitable for the treatment of obesity. To study this phenomenon, the thermogenic effect of single doses of oral placebo, E 10 mg, E 20 mg, C 100 mg, and C 200 mg were compared with the effects of three different combinations of E + C, 10 mg/200 mg, 20 mg/100 mg, and 20 mg/200 mg, measured by indirect calorimetry in six healthy, lean subjects. The thermogenic effect after E + C 20 mg/200 mg was larger than that of any of the other combinations. In this dose ratio, ephedrine and caffeine exerted a supra-additive synergism, whereas the thermogenic effects of the other two combinations were only additive. The 3-hour postintake increase in systolic blood pressure after all three combinations averaged 5 to 7 mm Hg more than placebo (P less than .01), which exceeded the predicted additive effect fivefold to sevenfold. Diastolic blood pressure was not increased by E + C 20 mg/200 mg, whereas the other two combinations increased it by approximately 4 mm Hg more than placebo. E + C 20 mg/100 mg and 20 mg/200 mg increased heart rate more than placebo, while E + C 10 mg/200 mg had no effect on heart rate. As expected, all combinations increased plasma glucose, insulin, and C-peptide from their ephedrine content. No significant effects of the combinations were found on plasma lactate, glycerol, nonesterified fatty acids (NEFA), triglyceride, potassium, or sodium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Noradrenaline release in skeletal muscle and in adipose tissue studied by microdialysis.

1. In adipose tissue and in skeletal muscle the extracellular noradrenaline levels were studied by microdialysis in the conscious dog and compared with the noradrenaline concentration in arterial plasma. 2. The experiments were performed with and without tyramine added to the perfusion medium, and noradrenaline was measured by a sensitive radioenzymic assay. 3. In the absence of tyramine, the interstitial noradrenaline levels in adipose tissue and skeletal muscles were similar to arterial blood concentrations, provided that the former were corrected for recovery. The recovery estimated from experiments in vitro averaged 16% at room temperature. 4. With tyramine added to the perfusates, noradrenaline levels increased 10-fold. Arterial noradrenaline concentrations did not change, indicating that noradrenaline was released only locally in the tissue. 5. Our results indicate that the microdialysis technique combined with a sensitive assay for measuring noradrenaline may be applicable to the assessment of local noradrenaline release in adipose tissue and in skeletal muscle. This may be of interest, especially in adipose tissue during physiological stimulation in which sympathetic activity is difficult to evaluate by other techniques.

Adipose Tissue↗
PubMed1991

Cardiac contractility, central haemodynamics and blood pressure regulation during semistarvation.

Eight obese patients were studied before and after 2 weeks of treatment by a very-low-calorie diet (VLCD). Cardiac output and central blood volume (pulmonary blood volume and left atrial volume) were determined by indicator dilution (125I-albumin) and radionuclide angiocardiography (first pass and equilibrium technique by [99Tcm]red blood cells). Cardiac output decreased concomitantly with the reduction in oxygen uptake as the calculated systemic arteriovenous difference of oxygen was unaltered. There were no significant decreases in left ventricular contractility indices, i.e. the ejection fraction, the peak ejection rate and changes in end-systolic volume. Also the diastolic function evaluated by the peak filling rate remained normal. Furthermore, no sign of backward failure could be demonstrated since the central blood volume was not significantly increased. Both systolic and diastolic blood pressure (BP) declined. The fall in BP was caused by the reduction in cardiac output as the total peripheral resistance was unchanged. Finally, the decline in total blood volume was not significant. These findings together with a reduction in heart rate indicated that a reduced sympathetic tone via increased capacitance of the venous bed was the main operator of a reduced venous return. Thus, the haemodynamic alterations in obese patients during short-term semistarvation may be caused by the fall in oxygen uptake and produced mainly by changes in the sympathetic tone.

Adult↗
PubMed1990

[Dietary fiber added to a very-low caloric diet reduces hunger and alleviates constipation].

To investigate whether supplement dietary fibre improves compliance to very low calorie diets (VLCD), a nutritional powder providing 388 kcal/day was compared with a similar preparation containing 30 plant fibre per day. Twenty-two obese patients participated in the study. After three days on their habitual diet they were allocated at random according to a single blind design to VLCD either with or without dietary fibre for two weeks. Thereafter, they were crossed over to the other form of diet for two further weeks. All of the patients completed the study. Both of the groups had considerable weight losses which were similar (about 10 kg/4 weeks) and dietary fibre did not improve the result further. During the period with VLCD with fibre, hunger ratings were significantly lower than on diets with VLCD without fibre (fibre effect p less than 0.01). Bowel movements decreased from 1.9 per day on the habitual diet to 0.7 per day on VLCD without fibre but increased to 1.0 per day with the fibre supplement (fibre effect p less than 0.01). No differences were found between the effects of the two types of diet on satiety, consistency of the faeces and flatulence. The supplement of dietary fibre did not influence plasma concentrations of divalent cations such as calcium, iron or magnesium nor did it contribute to the lowering effect of VLCD on plasma glucose, cholesterol or triglyceride. It is concluded that supplementation of VLCD with dietary fibre may improve compliance by normalising hunger and increasing the number of bowel movements without impairing the absorption of divalent cations.

Adolescent↗
PubMed1990

Impaired glucose-induced thermogenesis and arterial norepinephrine response persist after weight reduction in obese humans.

A reduced thermic response and an impaired activation of the sympathetic nervous system (SNS) has been reported after oral glucose in human obesity. It is, however, not known whether the reduced SNS activity returns to normal along with weight reduction. The thermic effect of glucose was lower in eight obese patients than in matched control subjects (1.7% vs 9.2%, p less than 0.002). The increase in arterial norepinephrine after glucose was also blunted in the obese patients. After a 30-kg weight loss their glucose and lipid profiles were markedly improved but the thermic effect of glucose was still lower than that of the control subjects (4.2%, p less than 0.001). The glucose-induced arterial norepinephrine response remained diminished in the reduced obese patients whereas the changes in plasma epinephrine were similar in all three groups. The results suggest that a defective SNS may be a cause in the development of obesity.

Adult↗
PubMed1990

Caffeine: a double-blind, placebo-controlled study of its thermogenic, metabolic, and cardiovascular effects in healthy volunteers.

In humans caffeine stimulates thermogenesis by unknown mechanisms and its effect on body weight has not been studies. The effect of placebo and 100, 200, and 400 mg oral caffeine on energy expenditure, plasma concentrations of substrates and hormones, blood pressure, and heart rate was investigated in a double-blind study in healthy subjects who had a moderate habitual caffeine consumption. Caffeine increased energy expenditure dose dependently and the thermogenic response was positively correlated with the response in plasma caffeine (r = 0.52; p less than 0.018), plasma lactate (r = 0.79; p less than 0.000001), and plasma triglyceride (r = 0.53; p less than 0.02). Stepwise regression analysis with the thermogenic response as the dependent variable excluded plasma caffeine and yielded the following equation: thermic effect (kcal/3 h) = -0.00459 X heart rate + 0.30315 X (triglyceride) + 0.53114 X (lactate) + 15.34 (r = 0.86; p = 0.0001). The results suggest that lactate and triglyceride production and increased vascular smooth muscle tone may be responsible for the major part of the thermogenic effect of caffeine.

Adult↗
PubMed1990

Prediction of 24-h energy expenditure and its components from physical characteristics and body composition in normal-weight humans.

The applicability of body composition as estimated by the bioimpedance method to predict energy expenditure (EE) was studied. Ten healthy subjects underwent measurement of body composition and 24-h energy expenditure (24-h EE) twice in a respiration chamber on a fixed program. The 24-h EE and its components, sleeping EE (SEE), basal EE (BEE), and daytime EE, for an individual were very reproducible (coefficient of variation 2.3%, 1.4%, 5.0%, & 3.1%, respectively). The variability of 24-h EE among subjects was 11.4% but only 4.1% when adjusted for differences in lean body mass (LBM). LBM was the best determinant of 24-h EE, BEE, and SEE and accounted for 91-93% of the interindividual variance of EE. The prediction equations were 24EE (kcal/d) = 390 + 33.3 LBM (r2 = 0.93, P = 0.000001), SEE (kcal/h) = 9.8 + 1.1 LBM (r2 = 0.92, P = 0.000001), and BEE (kcal/h) = -3.1 + 1.35 LBM (r2 = 0.91, P = 0.000002). In conclusion, 24EE, BEE, and SEE can be predicted with a high degree of precision from LBM as estimated by bioimpedance in normal-weight subjects.

Adult↗
PubMed1990

Diet-induced changes in subcutaneous adipose tissue blood flow in man: effect of beta-adrenoceptor inhibition.

The effect of a carbohydrate-rich meal on subcutaneous adipose tissue blood flow was studied with and without continuous i.v. infusion of propranolol in healthy volunteers. The subcutaneous adipose tissue blood flow was measured with the 133Xe washout method in three different locations: the forearm, the thigh and the abdomen. The subjects were given a meal consisting of white bread, jam, honey and apple juice (about 2300 kJ). The meal induced a twofold increase in blood flow in the examined tissues. Propranolol abolished the flow increase in the thigh and the abdomen and reduced it in the forearm. This indicates that the mechanism for the flow increase is elicited by a stimulation of vascular beta-adrenoceptors in the subcutaneous adipose tissue, since the beta-adrenoceptor inhibition did not affect the overall metabolic and hormonal responses to the meal.

Adipose Tissue↗
PubMed1990

Dietary fibre added to very low calorie diet reduces hunger and alleviates constipation.

To examine whether supplement of dietary fibre may improve compliance to a very low calorie diet (VLCD) a nutrition powder providing 388 kcal/day (men: 466 kcal/day) was compared with a similar version containing plant fibre 30 g/day. Twenty-two obese patients entered the study. After a baseline habitual diet, they were randomized to two weeks of treatment in a single blind design to either VLCD with or without dietary fibre. Subsequently, they were crossed over for further 2 weeks of treatment. All patients completed the study. The two groups had similar weight losses (about 10 kg/4 weeks), and dietary fibre did not improve this result. During VLCD with fibre hunger ratings were significantly lower than during VLCD without fibre (fibre effect, ANOVA; P less than 0.01). Bowel movements decreased from 1.9/day on habitual diet to 0.7/day on VLCD without fibre, but increased to 1.0/day by fibre supplement (fibre effect, P less than 0.01). No effect of fibre supplementation to VLCD was found on satiety, consistency of faeces and flatulence. The supplement of dietary fibre did not influence plasma concentrations of divalent cations as calcium, iron or magnesium, nor did it add any lowering effect on plasma glucose, cholesterol or triglyceride to that of VLCD. In conclusion, the supplement of dietary fibre to VLCD may improve compliance by reducing hunger and increasing the number of bowel movements, without impairment of absorption of divalent cations.

Adolescent↗
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

[Fat and sugar].

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Adipose Tissue↗