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Biomedical subjects

J S Garrow

Publications and source records attributed to J S Garrow.

At least 73 records · Page 4Linked to original sources
PubMed1985

The energy cost of aerobic exercise in fed and fasted normal subjects.

It has been claimed that there is a prolonged thermogenic effect of aerobic exercise although the evidence is by no means conclusive. We have therefore studied the thermogenic effect of moderate aerobic exercise in the fasted and fed state in four lean subjects during weight maintenance. Exercise was performed at a constant rate on a bicycle ergometer during the initial 20 min for four successive hours. The first two exercise periods were in the fasted state while the last two followed an 800 kcal (3.4 MJ) mixed meal. Oxygen uptake increased 22% over the 165 min after the meal on rest days (p less than 0.001). There was a significant but similar elevation of mean O2 uptake during 40 min postexercise by 13.6% in both the fasted (p less than 0.001) and fed state (p less than 0.001). Sixty minutes after ceasing exercise mean O2 uptake was not different from preexercise levels (p greater than 0.05). We conclude that there is no prolonged thermogenic effect of moderate repeated aerobic exercise in weight-maintaining lean subjects. In addition there was no interaction between exercise and dietary induced thermogenesis.

Adult↗
PubMed1985

The contribution of protein synthesis to thermogenesis in man.

There is ample evidence in man that there is some process which results in an increase or decrease in resting metabolic rate with over- or under-feeding. The change occurs within a few days of altering the plane of nutrition, and cannot be accounted for by changes in body composition. There is also agreement that metabolic rate increases after a meal, and more so after a meal of protein. The reasons for these changes are not well understood, but a suggestion made some time ago that they reflect changes in the rate of protein synthesis is still plausible. However, all thermogenesis cannot be accounted for by increased protein synthesis: after a glucose load metabolic rate increases but the rate of protein synthesis decreases. Within the last five years there have been amazing improvements in technology for measurement of protein turnover in man using stable isotopes. In the next five years the careful application of these techniques should enable us to measure exactly the contribution of protein synthesis to thermogenesis in man.

Animals↗
PubMed1985

Creatinine excretion over 24 hours as a measure of body composition or of completeness of urine collection.

Continuous collections of urine for up to 3 weeks from obese patients on a meat-free low-energy diet showed fluctuations in creatinine excretion so that the coefficient of variation was 8.7-34.4 per cent. Urine creatinine excretion was poorly correlated with measures of lean body mass such as density, body water or body potassium. Under the conditions of our study creatinine excretion is not a reliable indicator of either lean body mass nor the completeness of urine collection. We also conclude that the increased lean body mass in obese women contains a relatively small proportion of muscle.

Body Composition↗
PubMed1985

Quetelet's index (W/H2) as a measure of fatness.

A weight-height index of adiposity should indicate the relative fatness of subjects of differing height unless obesity is itself correlated with height. The average body fat among adult women attending a hospital outpatient clinic for obesity was 40.5 percent of body weight. The height of an unselected series of 286 of these outpatients was found to be similar to that of the general population of women of similar age, which indicates that obesity in adult women is not significantly related to height. Body composition was measured by body density, body water and body potassium in a series of 104 female and 24 male subjects aged 14-60 years. In both sexes density, water and potassium gave progressively higher estimates of body fat (kg), and there was a significant difference between the values by different methods. The average of the estimates by these three methods was taken to be the 'true' value for each individual (F kg). Regression of F/H2 on W/H2 (Quetelet's index) gave a correlation coefficient of 0.955 for women and 0.943 for men. The deviation of the body fat estimated from Quetelet's formula from the 'true' value was not much greater than that when density, water or potassium were used as a basis for estimating body fat. It is concluded that Quetelet's formula is both a convenient and reliable indicator of obesity.

Adipose Tissue↗
PubMed1984

Increased energy expenditure in poorly controlled Type 1 (insulin-dependent) diabetic patients.

The basal energy expenditure of 10 Type 1 (insulin-dependent) C-peptide-negative diabetic patients (2042 +/- 62 kcal/24 h) was found to be significantly higher than the 1774 +/- 52 kcal/24 h predicted from their age, sex and body surface area (p less than 0.01). Intravenous insulin treatment significantly reduced energy expenditure to 1728 +/- 19 kcal/24h (p less than 0.01), which matched predicted values. The observed increase in metabolic rate in uncontrolled diabetic patients is associated with increased protein turnover, increased plasma glucagon, but no significant increase in cortisol, growth hormone or triiodothyronine concentrations in plasma. It may be accounted for by the energy cost of protein synthesis, or gluconeogenesis, or possibly increased sympathetic activity. This increased energy expenditure will contribute to the weight loss seen in Type 1 diabetic patients.

Adult↗
PubMed1984

The composition of excess weight in obese women estimated by body density, total body water and total body potassium.

Measurements of body composition were made on 104 women aged 14-60 years whose fat content varied from 6 per cent to 60 per cent of body weight. Estimates of fat content were systematically lower when based on a measurement of body density than when based on body water, and were higher still when based on total body potassium. When body weight and body fat were corrected for stature by dividing by height squared there was a coefficient of correlation between these two variables of 0.936, 0.921 and 0.938 for estimates of fat based on density, water and potassium respectively. When the mean of all three estimates of fat was used the correlation was 0.955. Neither the slope of the regression line nor the strength of the correlation was affected if gross body weight was correlated with total body fat without correction for stature. It is concluded that differences in weight between women of similar height is attributable to tissue which is 70-78 per cent fat and 22-30 per cent lean, and that in the treatment of obese patients it is desirable that no more than 22 per cent of the weight loss should be lean tissue.

Adipose Tissue↗
PubMed1983

Effect of poor diabetic control and obesity on whole body protein metabolism in man.

We have investigated whole body protein turnover in the fasted state in five normal men, five male Type 1 diabetic patients off insulin therapy, and five obese women, using IV 13C-leucine as a tracer. In diabetic patients, there was, as expected, a greater net loss of protein in the fasted state than in normal subjects. However, contrary to animal and studies in vitro, our diabetic patients in the fasted state showed a greater rate of protein synthesis than normal subjects (p less than 0.01). The increased net loss of protein in diabetic patients compared with normal subjects arose because, in the diabetic patients, protein breakdown was increased even more than protein synthesis under the conditions of this study. Plasma leucine concentration was higher in diabetic and in insulin-insensitive obese patients than in normal subjects (p less than 0.01), and higher in diabetic than in obese patients (p less than 0.05). The rate of protein synthesis per kg lean body mass was also higher in diabetic patients than in obese or normal subjects (p less than 0.01), and higher in obese than normal subjects (p less than 0.05). We conclude that, in human subjects, whole body leucine and protein metabolism are very sensitive to the action of insulin.

Adult↗
PubMed1983

Thermic response to isoenergetic protein, carbohydrate or fat meals in lean and obese subjects.

The thermic response of five lean and five obese subjects was measured by indirect calorimetry before, and for 157.5 min after a meal of protein, carbohydrate or fat, each of which provided 1.25 MJ. The change in plasma glucose, insulin and (in the case of the carbohydrate meal) the rate of exogenous glucose oxidation was also measured. There was no significant difference between the lean and obese groups in the magnitude of the thermic response to any of the three meals. In both weight groups the response was largest and most prolonged after the protein meal (P less than 0.01). The obese group showed a higher concentration of fasting plasma insulin (P less than 0.01) and a larger increase in plasma glucose (P less than 0.05) after the carbohydrate meal, but there was no significant difference in the oxidation of exogenous glucose when compared with the lean group. Previous studies on dietary-induced thermogenesis in lean and obese subjects have given conflicting results. In general reports of decreased thermogenesis in obese subjects are characterized by either (a) high pre-meal metabolic rates in the obese group, especially in diabetic subjects, or (b) a group classified as 'normal' who have been selected for their high thermogenic capacity.

Adult↗
PubMed1983

A study of 'starch blockers' in man using 13C-enriched starch as a tracer.

It is claimed that commercial preparations of an alpha-amylase inhibitor, taken in tablet form 10 min before a meal, will inhibit the digestion of up to 100 g starch in the following meal. This was tested by giving five obese women three meals each containing cornflour enriched with 13C after a tablet of 'Starchex' or 'Calorex' or a placebo, in randomized sequence. The response to the meal in the rate of evolution of 13CO2, the increase in plasma insulin and the increase in blood sugar did not differ with the type of tablet which preceded the meal. We conclude that these starch-blocker tablets do not affect starch digestion or absorption in vivo.

Adult↗
PubMed1982

Is there a body protein reserve?

Evidence from experimentally protein-depleted dogs and adult human volunteers shows that about 20-25% of total body protein can be lost without fatality. Muscle protein is used to protect visceral proteins. In obese adults 15% of body protein (together with a large amount of fat) can be lost without ill effects. Experience with malnourished children shows that rapid repletion of protein is not practicable or therapeutically helpful. Protein stores in the body undoubtedly exist, and are mobilized whenever the capacity for protein synthesis is inadequate to cover the rate of protein catabolism. It is not necessarily helpful, in such situations, to give more amino acids intravenously.

Adult↗
PubMed1982

Effect of exercise on spontaneous calorie intake in obesity.

The effect of increased physical activity on energy intake and balance was investigated in six obese women (mean 167% above ideal body weight) voluntarily hospitalized for metabolic balance studies. Three 19-day treatments-one sedentary and two with treadmill exercise which increased daily expenditure to 110% (mild) and 125% (moderate) of sedentary expenditure-were imposed on each subject. Individual daily expenditure and ad libitum intake were determined by activity diaries and covert monitoring, respectively. Subjects selected and did not not change an intake level which allowed for energy balance during the sedentary period only. Therefore, the difference between intake and expenditure between treatments was significantly different (sedentary 11, mild -114, and moderate -369 kcal/day). The negative balance observed with mild and moderate exercise was obtained because while expenditure was raised with exercise, no compensatory increase in intake occurred. Moderate, realistic levels of activity did not regulate intake.

Adult↗