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J A Weststrate

Publications and source records attributed to J A Weststrate.

69 records · Page 4Linked to original sources
PubMed1990

The effects of short-term carbohydrate overfeeding and prior exercise on resting metabolic rate and diet-induced thermogenesis.

In 10 young, normal-weight subjects, the effects were investigated of carbohydrate overfeeding and prior glycogen-depleting exercise on resting metabolic rate (RMR) and diet-induced thermogenesis (DIT). Subjects were kept on controlled diets in a crossover design for two periods of 8 days, with a 1-week interval in between. During the last 4 days of each period, additional carbohydrates were added to the subjects' diet. The carbohydrate overfeeding started at 15% in excess of the energy requirements on day 1 and increased to 60% on day 4. At the beginning and the end of the carbohydrate overfeeding periods, RMR and DIT were measured, respectively, for 1 and 3.5 hours using a ventilated hood system. In one of the 8-day periods, on evenings before the energy exchange measurements, subjects performed a maximum work capacity test on a cycle ergometer, and then cycled for a total of approximately 80 minutes at fixed percentages of their maximum work capacity. Carbohydrate overfeeding did not affect RMR, but increased DIT significantly, on average by 39%. Glycogen-depleting exercise the day before increased RMR significantly by, on average, 9% and increased DIT (P = .08), on average, by 23%. The impact of exercise on RMR was less when carbohydrate overfeeding was administered, but there was no significant interaction effect of carbohydrate overfeeding and exercise on RMR or DIT. It is concluded that both prior glycogen-depleting exercise and an antecedent diet high in carbohydrates may influence RMR or DIT.

Adult↗
PubMed1990

Does variation in palatability affect the postprandial response in energy expenditure?

The impact of variation in palatability on diet- and sucrose-induced thermogenesis was studied in two experiments with 24 healthy young normal-weight subjects, 12 men and 12 women. In the first study, subjects received at random in duplicate either a normal liquid test meal (2,000 kJ, 12% protein, 33% fat, 55% carbohydrate), or an iso-energetic test meal made highly unpalatable with kinin. The difference in palatability did not have a significant impact on postprandial metabolism. In the second study subjects received at random either a palatable sucrose solution (900 kJ), an iso-energetic standard sucrose solution, or an iso-energetic unpalatable sucrose solution. Kinin and a citrus flavour were used to vary palatability. Postprandial energy expenditure over a period of 150 min was not significantly affected by differences in palatability. A separate control experiment to assess the effect of kinin on energy expenditure was carried out in eight subjects. Kinin had no significant effect on energy expenditure over a period of 120 min after ingestion.

Adult↗
PubMed1990

Alcohol and its acute effects on resting metabolic rate and diet-induced thermogenesis.

The impact of alcohol (ethanol) on resting energy expenditure of male non-obese volunteers was determined in two studies. In the first study the thermic effect of alcohol on resting metabolic rate (RMR) was assessed in ten male non-obese volunteers. In the second study the impact of alcohol on diet-induced thermogenesis (DIT) was determined in twelve male non-obese volunteers. Energy expenditure was measured with a ventilated-hood system. RMR was measured for 60 min with the subjects in a fasting state. In the first study subjects received in random order 20 g alcohol in concentrations of 75, 180 and 300 ml/l water respectively. After measurement of the RMR the thermic effect of alcohol was measured for 90 min. In the second study volunteers received in random order and in duplicate either a meal of food (2 MJ) plus an alcoholic aperitif (20 g alcohol in a 180 ml/l solution) or an isoenergetic meal of food alone (2.55 MJ) plus a placebo aperitif containing no alcohol. DIT was measured for 240 min. Alcohol induced a significant thermic effect, which varied between 0.22 and 0.30 kJ/min. No systematic difference in DIT was observed among the different concentrations. DIT was not significantly affected by the ingestion of alcohol. Total DIT was 219 (SE 14) kJ for the alcohol treatment and 185 (SE 20) kJ for the control treatment. The results do not support the suggestion that alcohol is less efficiently used as an energy source in comparison with, for example, fats and carbohydrates.

Adult↗
PubMed1990

Lack of a systematic sustained effect of prolonged exercise bouts on resting metabolic rate in fasting subjects.

Resting metabolic rate (RMR) and respiratory quotient (RQ) were measured in nine young men of normal weight after an overnight fast on three occasions, twice with and once without exercise on the previous evening. Exercise was cycling for 90 min at 100 W or 175 W. A Latin-square experimental design was used to balance the order of treatment with the type of treatment. Energy expenditure was measured by indirect calorimetry using a ventilated hood system. No significant after-effect of exercise on RMR was found: on the 100 W treatment the RMR had decreased by 0.04 +/- 0.06 kJ/min from the control value (4.68 +/- 0.13 kJ/min), and after the 175 W treatment it had increased by 0.11 +/- 0.08 kJ/min. On the 175 W exercise treatment RQs decreased significantly from 0.85 +/- 0.01 (control) to 0.82 +/- 0.01 (P less than 0.05). This indicates that single bouts of prolonged exercise can have a persisting effect on the type of substrate oxidized in the fasting state.

Adult↗
PubMed1990

The effect of psychological stress on diet-induced thermogenesis and resting metabolic rate.

The effect of psychological stress on resting metabolic rate (RMR) and diet-induced thermogenesis (DIT) was assessed in 12 healthy young non-obese men of body weight 70.2 +/- 1.2 kg (mean +/- s.e.m.) and age 25 +/- 0.6 years. Two types of commercially available motion pictures (video films) were shown to the subjects during the measurements, ie stress-inducing horror films and as a control, romantic family films. The study was conducted according to a cross-over design. RMR and respiratory quotients were not significantly influenced by the type of film shown to the subjects. DIT, assessed over 4 h, was significantly increased by the stress-inducing treatment, 0.95 +/- 0.05 kJ/min (mean +/- s.e.m.) versus 0.76 +/- 0.06 kJ/min (control). No significant effect was observed of psychological stress on postprandial substrate oxidation rates, nutrient balances, and urinary catecholamine excretion.

Adult↗
PubMed1989

Changes in fat-free mass during weight loss measured by bioelectrical impedance and by densitometry.

A group of 13 apparently healthy, premenopausal obese women (134-196% ideal weight) volunteered in a weight reduction study for 8 wk on a 4200 kJ (1000 kcal) diet. Before and after the weight reduction period body composition was measured by densitometry and by the bioelectrical impedance method. Changes in fat mass and fat-free mass were calculated. Mean weight loss was 10.0 +/- 2.8 kg and loss of fat-free mass was measured to be 2.3 +/- 1.7 kg (23%) by densitometry and 0.6 +/- 1.9 kg (6%) by impedance measurements. The underestimation of the change in fat-free mass measured by the impedance method could be due to losses of water bound to glycogen after the weight-reduction period. For this reason the impedance method may be not applicable in studies in which changes in glycogen stores can be expected.

Adult↗
PubMed1989

Body composition changes assessed by bioelectrical impedance measurements.

Twelve healthy volunteers consumed a very-low-calorie diet for 2 d to achieve a body-weight loss mainly from a loss of fat-free mass, ie, of glycogen plus water. Body weight, body density, and bioelectrical impedance were measured before and after weight loss. Body-weight loss was 1.3 +/- 0.5 kg. Loss of fat-free mass as measured by densitometry was 1.2 +/- 0.8 kg. Changes in body weight and fat-free mass measured by densitometry did not differ significantly and were significantly different from zero. Reduction of fat-free mass as determined by bioelectrical impedance was 0.5 +/- 0.8 kg, which was significantly different from body-weight loss and loss of fat-free mass as measured by densitometry but not significantly different from zero. The results show that after weight loss the bioelectrical impedance method overestimates the fat-free mass by approximately 1 kg.

Adult↗
PubMed1989

Body composition in children: proposal for a method for calculating body fat percentage from total body density or skinfold-thickness measurements.

A method is presented for assessing childhood obesity in a more objective way than most other routine methods used for diagnosing childhood obesity. The sum of bicipital, tricipital, subscapular, and suprailiacal skinfold thicknesses is related to total body density by use of theoretically defined prediction equations. Total body density is used to estimate total body fat percentage by use of age- and sex-dependent equations on the relation between body fat percentage and body density. These equations are constructed on the basis of published data on changes in the density of fat-free mass with age in children. With the proposed method childhood obesity can be assessed routinely in a more consistent way than with most other routine methods used to diagnose obesity in children. A preliminary validation study indicated that in children aged 7-10 y predicted body density differed on average less than 1% from measured body density. In addition, predicted body density was highly correlated (r greater than 0.7) with measured body density.

Adipose Tissue↗
PubMed1989

Diurnal variation in postabsorptive resting metabolic rate and diet-induced thermogenesis.

Postabsorptive resting metabolic rate (RMR) and diet-induced thermogenesis (DIT) were repeatedly assessed on different days in 10 young men of normal weight on mornings and afternoons. No significant diurnal variation was found in RMR, DIT, total postprandial substrate oxidation, and overall postprandial nutrient balances. The pattern of postprandial substrate oxidation indicated an increased glucose oxidation in the first hour after ingestion of a meal on morning tests compared with afternoon tests. This was probably related to differences in the degree of the postabsorptive state, ie, 12-14 h on morning tests and 6-7 h on afternoon tests.

Adult↗
PubMed1989

Is an adaptation of Siri's formula for the calculation of body fat percentage from body density in the elderly necessary?

Using data from the literature on changes in the mineral content, muscle mass and the amount of water in the body during aging, the age-related changes in the chemical composition of the fat-free mass have been calculated. In men the decrease in minerals (bone loss) during aging equals the decrease in protein and water (muscle) in the fat-free mass. As a consequence the chemical composition of the fat-free mass is hardly affected by aging in men. In women, however, the loss of minerals during aging is considerably higher than the decrease in protein and water in the fat-free mass. As a consequence the change in the chemical composition of the fat-free mass in females is remarkable, and therefore in females, the density (kg/l) of the fat-free mass decreases with age. Consequently the body fat percentage calculated from body density with Siri's equation overestimates the real body fat percentage by 2-3 per cent, depending on age. Based on the calculated chemical composition of the fat-free mass at several ages, and its calculated theoretical density, Siri's equation has been adapted. In females but not in men the adapted formulas give a more valid estimate of the body fat percentage calculated from body density compared to Siri's formula.

Adipose Tissue↗
PubMed1989

Indices of body fat distribution and adiposity in Dutch children from birth to 18 years of age.

Skinfold thicknesses, Quetelet index and waist-to-hip circumference ratio (WHR) were measured in 2285 Dutch children aged 0-17 years. Skinfold thicknesses, Quetelet index and WHR were significantly influenced by age. No significant differences were found between the sexes in Quetelet index. Skinfolds were generally higher in older girls compared to older boys. WHR and the trunk-to-total skinfolds percentage were used as possible indicators of body fat distribution. On average, boys had higher WHR and trunk-to-total skinfolds percentage than girls, especially in the older age groups. The WHR decreased from about 1.1 in the youngest children to about 0.8 in pubertal children. The trunk-to-total skinfolds percentage increased from about 42 per cent in both sexes at younger ages to about 60 per cent in pubertal boys and to about 52 per cent in pubertal girls. Several correlations were calculated controlled for age. Low but significant correlations were found between WHR and skinfold thicknesses or the Quetelet index. WHR was strongly inversely related to body height. In girls 58 per cent of the variation in skinfold thicknesses was associated with the Quetelet index, in boys this was 42 per cent. The prevalence of obesity in the studied population varied between 0.5 and 10 per cent according to the reference standard chosen to assess obesity. It is concluded that more research is necessary to assess whether the WHR in children is a valid indicator of body fat distribution, especially in prepubertal children. It is also concluded that more research is needed to develop a method for assessing childhood obesity in an objective way.

Adipose Tissue↗
PubMed1988

Resting metabolic rate and diet-induced thermogenesis in abdominal and gluteal-femoral obese women before and after weight reduction.

Fifteen premenopausal obese women, seven abdominal obese (AO) and eight gluteal-femoral obese (GFO), followed an energy-reduced diet of 1000 kcal/d (4.2 MJ/d) over 8 wk. Body-fat distribution was assessed using a cutoff point of 0.80 for the waist-to-hips girth ratio. Before and after the dietary treatment resting metabolic rate (RMR) and diet-induced thermogenesis (DIT) (after a normal breakfast) were measured by indirect calorimetry. Body-weight reduction and energy intake during the diet period did not differ significantly between both groups. Before weight loss the AO group had slightly greater RMR than the GFO group. After weight loss mean RMR decreased about 10% in the AO group and about 2.5% in the GFO group. Before weight loss DIT was slightly but not significantly higher in the AO group than in the GFO group. After weight loss DIT increased significantly in the GFO group. Weight loss was generally associated with decreased blood glucose, serum triglycerides, and total serum cholesterol levels in the AO women but not in the GFO women.

Abdomen↗
PubMed1988

Factors affecting bioelectrical impedance measurements in humans.

In several groups of young healthy subjects the effect of the ingestion of a meal, of drinking normal tea or beef tea, of exercise and of the menstrual cycle on body impedance was assessed. The day-to-day reproducibility of the method was also investigated under standardized conditions. Two to four hours after ingestion of a meal, body impedance had decreased by about 13-17 Ohms in comparison with body impedance in the fasting state. Drinking 200 ml of normal tea did not result in a change of body impedance, but drinking 200 ml beef tea lowered the body impedance significantly by 4 +/- 4 Ohms. Moderate exercise on a bicycle ergometer (90 min, 100 W) did not influence body impedance, but strenuous exercise (90 min, 175 W) resulted in a decrease of 9 +/- 11 Ohms in body impedance. In general, changes in body impedance during the menstrual cycle were small, and only the difference between measurements of body impedance 1 week before the onset of the menstruation and again 1 week after menstruation (8 +/- 9 Ohms) was statistically significant. Under standardized conditions (in the morning, in the fasting state after emptying the bladder) the within-person between-day variation was found to be 2.8 per cent (13 Ohms).

Adipose Tissue↗
PubMed1986

Changes in skinfold thicknesses and body mass index in 171 children, initially 1 to 5 years of age: a 5 1/2-year follow-up study.

Changes in skinfold thicknesses and BMI were investigated in 171 children aged 1-5 years in 1978 and 5 1/2 years later aged 6-10 years in 1984. Tracking in skinfold thicknesses or body fatness and BMI was determined using the correlation coefficients between these variables in 1978 and 1984. Body fatness tracking was higher in girls than in boys. There were no marked differences between skinfold correlations from sites of the trunk and those from the extremities. Generally, about 50 percent of the variation in skinfold thicknesses in girls aged 6-10 years was associated with skinfold thicknesses 5 1/2 years before. In boys, only about 5 percent of the variation of skinfold thicknesses at ages 6-10 years could be explained by values 5 1/2 years before. There was no marked sex difference in BMI tracking. Initially fatter girls showed higher skinfold thickness tracking than initially leaner girls. Parental fatness level and social class were both related to changes in skinfold thicknesses. Children who became relatively fatter in 5 1/2 years had fatter mothers than children who became relatively leaner. Relatively more children of the lower social class became fatter than children of the higher social class. However, parental fatness level and social class were not in a simple additive way related to changes in skinfold thicknesses.

Age Factors↗