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Biomedical subjects

J A Weststrate

Publications and source records attributed to J A Weststrate.

At least 19 recordsLinked to original sources
PubMed1992

Short-term effects of different amounts of protein, fats, and carbohydrates on satiety.

This study investigated the satiating efficiencies of proteins, fats, and carbohydrates (CHOs). Twenty-nine female, normal-weight subjects each received 10 liquid breakfasts, which varied in energy and macronutrient contents. Besides a zero condition [0.3 MJ (8 kcal)], there were three energy levels [0.42, 1.05, and 1.67 MJ (100, 250, and 400 kcal)] combined with three dominant sources of macronutrients (99% of energy from CHO, 92% of energy from fat, and 77% of energy from protein). After breakfast the subjects were not allowed to eat or drink (except water) for 3.5 h. They then recorded their voluntary food intake for the remainder of the day. Subjects also rated their subjective feelings concerning food intake on five different types of appetite. The results showed that neither energy content nor macronutrient composition of the liquid breakfasts had any effect on energy and macronutrient intake during lunch and the remainder of the day. Ratings of different types of appetite showed an increasing satiating effect with increasing energy content of the breakfasts. Proteins, fats, and CHOs had similar effects on appetite.

Adult↗
PubMed1992

Amylose-amylopectin ratio in a meal affects postprandial variables in male volunteers.

To study the postprandial effects of changing the amylose-to-amylopectin ratio (Am:Ap) in the starch fraction of a meal, male volunteers were given hot mixed lunches (13% of energy as protein, 24% as fat, 6% as mono- and disaccharides, and 57% as polysaccharides) in which Am:Ap was either 0:100 or 45:55. The increase in Am:Ap resulted in a change in the shape of the glucose and insulin responses in the blood with significantly lower initial responses but a small increase for glucose and a decrease for insulin if averaged over the 6 h of the study. The rises in the concentration of free glycerol and free fatty acid that occurred after an initial drop were stronger at low Am:Ap. High-Am:Ap meals induced more satiety up to 6 h postprandially. There was no effect of Am:Ap on postprandial triacylglycerol in the blood or on breath hydrogen except for a weak trend toward a higher concentration at 6 h after the high-Am:Ap meals.

Adult↗
PubMed1992

Visceral fat accumulation in obese subjects: relation to energy expenditure and response to weight loss.

Seventy-eight healthy obese subjects, 40 premenopausal women and 38 men aged 27-51 yr received a 4.2 MJ/day energy-deficit diet for 13 wk. Resting metabolic rate (RMR) and diet-induced thermogenesis (DIT) were measured by indirect calorimetry. Abdominal subcutaneous and visceral fat areas were calculated from magnetic resonance imaging scans before and after weight loss. Before weight loss, visceral fat accumulation was positively correlated with higher levels of RMR (P < 0.05) and DIT (P < 0.01) in women but not in men. The mean weight reduction was 12.2 +/- 3.5 (SD) kg. In men but not in women, an initially large visceral fat depot was associated with a reduced loss of weight and total fat mass (P < 0.05). Within each sex, an initial abundance of visceral fat was significantly related to a larger loss of visceral fat (P < 0.001) and in men to a smaller loss of subcutaneous fat (P < 0.05). These results suggest that there may be gender differences in the associations between visceral fat accumulation and components of energy expenditure (RMR and DIT) in obese subjects. Obese subjects with an initial abundance of visceral fat do not lose more body weight but more visceral fat than subjects with less visceral fat.

Adipose Tissue↗
PubMed1991

Body mass index as a measure of body fatness: age- and sex-specific prediction formulas.

In 1229 subjects, 521 males and 708 females, with a wide range in body mass index (BMI; 13.9-40.9 kg/m2), and an age range of 7-83 years, body composition was determined by densitometry and anthropometry. The relationship between densitometrically-determined body fat percentage (BF%) and BMI, taking age and sex (males = 1, females = 0) into account, was analysed. For children aged 15 years and younger, the relationship differed from that in adults, due to the height-related increase in BMI in children. In children the BF% could be predicted by the formula BF% = 1.51 x BMI-0.70 x age - 3.6 x sex + 1.4 (R2 0.38, SE of estimate (SEE) 4.4% BF%). In adults the prediction formula was: BF% = 1.20 x BMI + 0.23 x age - 10.8 x sex - 5.4 (R2 0.79, SEE = 4.1% BF%). Internal and external cross-validation of the prediction formulas showed that they gave valid estimates of body fat in males and females at all ages. In obese subjects however, the prediction formulas slightly overestimated the BF%. The prediction error is comparable to the prediction error obtained with other methods of estimating BF%, such as skinfold thickness measurements or bioelectrical impedance.

Adipose Tissue↗
PubMed1991

Sex and age specific prediction formulas for estimating body composition from bioelectrical impedance: a cross-validation study.

In 827 male and female subjects, with a large variation in body composition and an age range of 7-83 years, body composition was measured by densitometry, anthropometry and bioelectrical impedance. The relationship between densitometrically determined fat free mass (FFM) with body impedance (R), body weight (W) and body height (H) was analysed, taking age and sex into account. The intercept of the regression equation FFM = a x H2/R + b was found to be age, and (at older ages) sex dependent, increasing from age 7 to age 15, and slowly decreasing after age 16. Therefore the population was subdivided into two age categories, the one 15 years and younger, and the other 16 years and older. Each age category was randomly divided into two groups, A and B. In each age category the developed prediction formula for group A was cross-validated in group B, and vice versa. No statistically and biologically meaningful differences between predicted and measured FFM were observed in either group. Therefore the data of group A and B in each age category were combined. The best fitted prediction formula at ages less than or equal to 15 was: FFM = 0.406 x 10(4) x H2/R + 0.360 W + 5.58 H + 0.56 Sex - 6.48: n = 166, R2 = 0.97, SEE = 1.68 kg (cv% = 4.9 percent); and at ages greater than or equal to 16: FFM = 0.340 x 10(4) x H2/R + 15.34 H + 0.273 W - 0.127 age + 4.56 sex - 12.44: n = 661, R2 = 0.93, SEE = 2.63 kg (cv% = 5.0 percent).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Resting energy expenditure in women: impact of obesity and body-fat distribution.

Postabsorptive resting metabolic rate (RMR) and diet-induced thermogenesis (DIT) were repeatedly assessed with an indirect calorimetric ventilated hood system in a group of 32 healthy premenopausal obese women, body fat percentage 46.4 +/- 0.9 (mean +/- SEM), age 38.5 +/- 0.9 years. RMR and DIT were also measured in a group of 10 healthy premenopausal non-obese women, body fat percentage 31.3 +/- 1.7, age 37.7 +/- 2.4 years. The obese women were subdivided according to the waist-to-hips girth ratio (WHR) into three groups with a different type of body fat distribution: A gluteal-femoral obese group (n = 10), WHR less than 0.79; an intermediate obese group (n = 10), 0.79 less than WHR less than 0.85; and an abdominal obese group (n = 12), WHR greater than 0.85. No significant differences were observed among the obese groups in age, body weight, body fat mass, and fat-free body mass. Body fat distribution was not associated with differences in DIT, pre- and postprandial respiratory quotients and substrate oxidation rates, but the abdominal obese women had significantly higher RMRs adjusted for age, fat mass, and fat-free body mass (6,075 +/- 200 kJ/d) in comparison with the gluteal-femoral obese women (5,502 +/- 205 kJ/d) and in comparison with obese women with an intermediate body fat distribution (5,517 +/- 193 kJ/d), but not in comparison with a non-obese control group, 6,790 +/- 261 kJ/d. It is concluded that within the total group of obese women, the non-abdominal obese can be characterized by relatively reduced resting metabolic rates in comparison with either the abdominal obese or with non-obese women.

Adipose Tissue↗
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↗