Biomedical subjects

Klaas R Westerterp

Publications and source records attributed to Klaas R Westerterp.

At least 19 recordsLinked to original sources

PubMed2006

Obesity and thermogenesis related to the consumption of caffeine, ephedrine, capsaicin, and green tea.

The global prevalence of obesity has increased considerably in the last decade. Tools for obesity management, including caffeine, ephedrine, capsaicin, and green tea have been proposed as strategies for weight loss and weight maintenance, since they may increase energy expenditure and have been proposed to counteract the decrease in metabolic rate that is present during weight loss. A combination of caffeine and ephedrine has shown to be effective in long-term weight management, likely due to different mechanisms that may operate synergistically, e.g., respectively inhibiting the phosphodiesterase-induced degradation of cAMP and enhancing the sympathetic release of catecholamines. However, adverse effects of ephedrine prevent the feasibility of this approach. Capsaicin has been shown to be effective, yet when it is used clinically it requires a strong compliance to a certain dosage, that has not been shown to be feasible yet. Also positive effects on body-weight management have been shown using green tea mixtures. Green tea, by containing both tea catechins and caffeine, may act through inhibition of catechol O-methyl-transferase, and inhibition of phosphodiesterase. Here, the mechanisms may also operate synergistically. In addition, tea catechins have antiangiogenic properties that may prevent development of overweight and obesity. Furthermore, the sympathetic nervous system is involved in the regulation of lipolysis, and the sympathetic innervation of white adipose tissue may play an important role in the regulation of total body fat in general.

Animals↗

PubMed2006

Energy expenditure during overfeeding.

The large inter-individual variation in weight gain during standardized overfeeding together with a weight gain that is often less than theoretically calculated from the energy excess suggest that there are differences between persons in the capacity to regulate energy expenditure and hence metabolic efficiency. Adaptive thermogenesis is defined as the regulated production of heat in response to environmental changes in temperature and diet, resulting in metabolic inefficiency. The question is whether adaptive thermogenesis can be identified in overfeeding experiments. From the numerous human overfeeding experiments we selected those studies that applied suitable protocols and measurement techniques. Five studies claimed to have found evidence for adaptive thermogenesis based on weight gains smaller than expected or unaccounted increases in thermogenesis above obligatory costs. Results from the other 11 studies suggest there is no adaptive thermogenesis as weight gains were proportional to the amount of overfeeding and the increased thermogenesis was associated with theoretical costs of an increased body size and a larger food intake. These results show that in humans, evidence for adaptive thermogenesis is still inconsistent. However, they do not rule out the existence, but emphasize that if present, adaptive changes in energy expenditure may be too small to measure considering measurement errors, errors in assumptions made and small (day-to-day) differences in physical activity. In addition, it is not clear in which component or components of total energy expenditure adaptive changes can occur and whether components can overlap due to measurement limitations.

Journal Article↗

PubMed2006

Perception, passive overfeeding and energy metabolism.

The palatability of a diet is an important determinant of energy intake. Due to a high palatability, a relatively high energy density, and a weak effect on satiation, the consumption of high-fat foods induces passive overfeeding. It is well known that a high-fat diet often leads to a loss of portion control of tasty foods. Here, studies are reviewed on the effect of overfeeding on substrate utilization and energy expenditure. It is often suggested that humans differ in the susceptibility to weight gain in response to overfeeding. Six years ago, non-exercise activity thermogenesis was presented as a new mechanism to explain differences in weight gain between subjects. Activation of non-exercise activity thermogenesis could dissipate excess energy to preserve leanness and only failure to activate non-exercise activity thermogenesis resulted in ready fat gain. However, there is still little evidence for this form of adaptive thermogenesis from additional studies. The conclusion is that the fat content has an effect on body fat as a function of the effect of dietary fat on energy intake.

Dietary Fats↗

PubMed2006

Heat production and body temperature during cooling and rewarming in overweight and lean men.

OBJECTIVE: To compare overweight and lean subjects with respect to thermogenesis and physiological insulation in response to mild cold and rewarming. RESEARCH METHODS AND PROCEDURES: Ten overweight men (mean BMI, 29.2 +/- 2.8 kg/m(2)) and 10 lean men (mean BMI, 21.1 +/- 2.0 kg/m(2)) were exposed to cold air for 1 hour, followed by 1 hour of rewarming. Body composition was determined by hydrodensitometry and deuterium dilution. Heat production and body temperatures were measured continuously by indirect calorimetry and thermistors, respectively. Muscle activity was recorded using electromyography. RESULTS: In both groups, heat production increased significantly during cooling (lean, p = 0.004; overweight, p = 0.006). The increase was larger in the lean group compared with the overweight group (p = 0.04). During rewarming, heat production returned to baseline in the overweight group and stayed higher compared with baseline in the lean group (p = 0.003). The difference in heat production between rewarming and baseline was larger in the lean (p = 0.01) than in the overweight subjects. Weighted body temperature of both groups decreased during cold exposure (lean, p = 0.002; overweight, p < 0.001) and did not return to baseline during rewarming. DISCUSSION: Overweight subjects showed a blunted mild cold-induced thermogenesis. The insulative cold response was not different among the groups. The energy-efficient response of the overweight subjects can have consequences for energy balance in the long term. The results support the concept of a dynamic heat regulation model instead of temperature regulation around a fixed set point.

Adult↗

PubMed2006

Evidence of negative energy balance using doubly labelled water in elite Kenyan endurance runners prior to competition.

Previous studies have found Kenyan endurance runners to be in negative energy balance during training and prior to competition. The aim of the present study was to assess energy balance in nine elite Kenyan endurance runners during heavy training. Energy intake and expenditure were determined over 7 d using weighed dietary intake and doubly labelled water, respectively. Athletes were on average in negative energy balance (mean energy intake 13 241 (SD 1330) kJ/d v. mean energy expenditure 14 611 (SD 1043) kJ/d; P=0.046), although there was no loss in body mass (mean 56.0 (SD 3.4) kg v. 55.7 (SD 3.6) kg; P=0.285). The calculation of underreporting was 13 % (range -24 to +9 %) and almost entirely accounted for by undereating (9 % (range -55 to +39 %)) as opposed to a lack of significant underrecording (i.e. total water intake was no different from water loss (mean 4.2 (SD 0.6) l/d v. 4.5 (SD 0.8) l/d; P=0.496)). Fluid intake was modest and consisted mainly of water (0.9 (SD 0.5) l/d) and milky tea (0.9 (SD 0.3) l/d). The diet was high in carbohydrate (67.3 (SD 7.8) %) and sufficient in protein (15.3 (SD 4.0) %) and fat (17.4 (SD 3.9) %). These results confirm previous observations that Kenyan runners are in negative energy balance during periods of intense training. A negative energy balance would result in a reduction in body mass, which, when combined with a high carbohydrate diet, would have the potential in the short term to enhance endurance running performance by reducing the energy cost of running.

Adult↗

PubMed2006

Basal metabolic rate as a proxy for overnight energy expenditure: the effect of age.

Recommendations for daily energy requirements use factorial calculations based on BMR. Expressing total energy requirements as a multiple of BMR is based on the assumption that BMR is equal to overnight metabolic rate (OMR). The objective of the present study was to determine if BMR is an appropriate proxy for OMR in children, young adults and elderly. Data are presented of thirty children (11 (SD 2) years), thirty young adults (25 (SD 5) years) and fifty-nine elderly (61 (SD 5) years). OMR was measured in a respiration chamber while sleep was not hindered and BMR was measured directly afterwards with a ventilated hood system under strictly controlled conditions. The mean ratio of OMR:BMR was 0.92 (SD 0.09) for children, which was significantly different from 1.00 (P<0.001), 1.00 (SD 0.07) for young adults and 1.06 (SD 0.09) for elderly which was also different from 1.00 (P<0.001). For adults, BMR is an appropriate measure of OMR. In children, the use of BMR to estimate OMR would introduce an overestimate and for elderly an underestimate.

Adult↗

PubMed2006

Ghrelin and glucagon-like peptide 1 concentrations, 24-h satiety, and energy and substrate metabolism during a high-protein diet and measured in a respiration chamber.

BACKGROUND: The mechanism of protein-induced satiety remains unclear. OBJECTIVE: The objective was to investigate 24-h satiety and related hormones and energy and substrate metabolism during a high-protein (HP) diet in a respiration chamber. DESIGN: Twelve healthy women aged 18-40 y were fed in energy balance an adequate-protein (AP: 10%, 60%, and 30% of energy from protein, carbohydrate, and fat, respectively) or an HP (30%, 40%, and 30% of energy from protein, carbohydrate, and fat, respectively) diet in a randomized crossover design. Substrate oxidation, 24-h energy expenditure (EE), appetite profile, and ghrelin and glucagon-like peptide 1 (GLP-1) concentrations were measured. RESULTS: Sleeping metabolic rate (6.40 +/- 0.47 compared with 6.12 +/- 0.40 MJ/d; P < 0.05), diet-induced thermogenesis (0.91 +/- 0.25 compared with 0.69 +/- 0.24 MJ/d; P < 0.05), and satiety were significantly higher, and activity-induced EE (1.68 +/- 0.32 compared with 1.86 +/- 0.41; P < 0.05), respiratory quotient (0.84 +/- 0.02 compared with 0.88 +/- 0.03; P < 0.0005), and hunger were significantly lower during the HP diet. There was a tendency for a greater 24-h EE during the HP diet (P = 0.05). Although energy intake was not significantly different between the diet groups, the subjects were in energy balance during the HP diet and in positive energy balance during the AP diet. Satiety was related to 24-h protein intake (r2 = 0.49, P < 0.05) only during the HP diet. Ghrelin concentrations were not significantly different between diets. GLP-1 concentrations after dinner were higher during the HP than during the AP diet (P < 0.05). CONCLUSION: An HP diet, compared with an AP diet, fed at energy balance for 4 d increased 24-h satiety, thermogenesis, sleeping metabolic rate, protein balance, and fat oxidation. Satiety was related to protein intake, and incidentally to ghrelin and GLP-1 concentrations, only during the HP diet.

Adolescent↗

PubMed2006

Body mass regulation at altitude.

Altitude exposure decreases energy intake and thus induces an energy deficit resulting in the loss of body mass. The energy deficit is worsened when energy expenditure is increased by exercise because the increase is not matched by an increased energy intake. The indicated fuel for the optimal use of the rarefied oxygen at altitude is carbohydrate. For optimal taste and maximizing energy intake, fat is the best. Protein should rather be limited because of its high thermic effect. Intestinal malabsorption probably does not play a role in the energy deficit. Even though the sensation of exertion during climbing at high altitude is intense, the actual energy expenditure is not high.

Altitude↗

PubMed2006

The effects of 6 months of increased water intake on blood sodium, glomerular filtration rate, blood pressure, and quality of life in elderly (aged 55-75) men.

OBJECTIVES: To study whether there are any negative or positive effects of 6 months of increased fluid intake in reasonably healthy elderly men. DESIGN: Randomized trial. SETTING: Community-based. PARTICIPANTS: One hundred forty-one healthy participants aged 55 to 75. INTERVENTION: One group was given the advice to increase their daily fluid intake by 1.5 L of water; the other group was given placebo medication (8 mL inactive syrup per day). MEASUREMENTS: At 6 months blood sodium, glomerular filtration rate (GFR), blood pressure, and quality of life (QOL) were measured. The changes in water turnover were measured using deuterium. RESULTS: Most subjects did not manage to increase their fluid intake by 1.5 L. The average increase in the intervention group was approximately 1 L. Twenty-four-hour water turnover in the water group was 359 mL (95% confidence interval=171-548) higher than that of the control group at 6-month follow-up. Blood pressure, sodium level, GFR, and QOL did not change significantly in either group during the intervention period. In addition, the cases reporting a worsening on the effect measures were equally distributed over the two study groups. CONCLUSION: The advice to increase fluid intake by 1.5 L had no negative effects in reasonably healthy men aged 55 to 75.

Aged↗

PubMed2006

Accelerometry and heart rate as a measure of physical fitness: cross-validation.

PURPOSE: We recently reported on a new method to assess physical fitness, based on the combined use of accelerometry and heart rate (HR) registration. This study tested the validity of the prediction formula in a group of healthy young adults. METHODS: Twenty-six healthy subjects performed a maximal incremental test on a bicycle ergometer to determine VO2max. A triaxial accelerometer and a HR monitor were worn for 7 d under free-living conditions. The prediction formula developed in a previous experimental group (EXP) was applied on the cross-validation group (CV). RESULTS: No difference was found in subjects' characteristics between the EXP and CV groups except for accelerometer output (activity counts). Although measured VO2max could be predicted for 80% (P < 0.0001), a paired t-test showed a significant difference between measured and predicted VO2max (178 mL.min(-1); P = 0.015). Because of the difference in activity between the EXP and the CV groups, all data were combined and sorted according to activity counts, then two new groups were formed. As a result, EXP and CV groups were created that did not significantly differ in activity or any other parameters. The formula developed in the new experimental group (R2 = 0.74; P < 0.0001) explained 72% (P < 0.0001) of the variation in VO2max in the cross-validation group, a paired t-test showed no difference between measured and predicted VO2max, and Bland-Altman plotting showed no systematic bias. CONCLUSION: Although a good correlation was seen between measured and predicted VO2max in the cross-validation group, care should be taken in applying the prediction formula on groups that differ in physical activity from the current study population.

Activities of Daily Living↗

PubMed2005

Metabolic efficiency and energy expenditure during short-term overfeeding.

OBJECTIVE: To investigate whether efficiency of weight gain during a short period of overfeeding is related to adaptive differences in basal metabolic rate (BMR) and physical activity. SUBJECTS: Fourteen healthy females (age 25+/-4 years, BMI 22.1+/-2.3 kg/m2). DESIGN AND MEASUREMENTS: Subjects were overfed with a diet supplying 50% more energy than baseline energy requirements for 14 days. Overfeeding diets provided 7% of energy from protein, 40% from fat and 53% from carbohydrates. Body composition was determined using hydrodensitometry and isotope dilution, total energy expenditure (TEE) with doubly labeled water and basal metabolic rate (BMR) with indirect calorimetry. Physical activity (PA) was recorded with a tri-axial accelerometer. RESULTS: Body weight increased by 1.45+/-0.86 kg (mean+/-S.D.) (P<0.0001), fat mass increased by 1.05+/-0.75 kg. Energy storage was 57.0+/-17.9 MJ, which is the difference between energy intake (207.2 MJ) and energy expenditure (150.2 MJ) during overfeeding. There was no difference between metabolically efficient and metabolically inefficient subjects in changes in BMR and PA. CONCLUSION: These results indicate that the metabolic efficiency of weight gain was not related to adaptive changes in energy expenditure.

Adaptation, Physiological↗

PubMed2005

Measuring free-living energy expenditure and physical activity with triaxial accelerometry.

OBJECTIVE: To investigate the ability of a newly developed triaxial accelerometer to predict total energy expenditure (EE) (TEE) and activity-related EE (AEE) in free-living conditions. RESEARCH METHODS AND PROCEDURES: Subjects were 29 healthy subjects between the ages of 18 and 40. The Triaxial Accelerometer for Movement Registration (Tracmor) was worn for 15 consecutive days. Tracmor output was defined as activity counts per day (ACD) for the sum of all three axes or each axis separately (ACD-X, ACD-Y, ACD-Z). TEE was measured with the doubly labeled water technique. Sleeping metabolic rate (SMR) was measured during an overnight stay in a respiration chamber. The physical activity level was calculated as TEE x SMR(-1), and AEE was calculated as [(0.9 x TEE) - SMR]. Body composition was calculated from body weight, body volume, and total body water using Siri's three-compartment model. RESULTS: Age, height, body mass, and ACD explained 83% of the variation in TEE [standard error of estimate (SEE) = 1.00 MJ/d] and 81% of the variation in AEE (SEE = 0.70 MJ/d). The partial correlations for ACD were 0.73 (p < 0.001) and 0.79 (p < 0.001) with TEE and AEE, respectively. When data on SMR or body composition were used with ACD, the explained variation in TEE was 90% (SEE = 0.74 and 0.77 MJ/d, respectively). The increase in the explained variation using three axes instead of one axis (vertical) was 5% (p < 0.05). DISCUSSION: The correlations between Tracmor output and EE measures are the highest reported so far. To measure daily life activities, the use of triaxial accelerometry seems beneficial to uniaxial.

Acceleration↗

PubMed2005

Water loss as a function of energy intake, physical activity and season.

Although water is an important nutrient, there are no recommended intake values. Here, water intake, energy intake, physical activity and water loss was measured over 1 week in summer and in winter. Subjects were healthy volunteers, forty-two women and ten men, mean age of 29 (SD 7) years and mean BMI 21.8 (SD 2.2) kg/m2. Water intake was measured with a 7 d food and water record. Physical activity level (PAL) was observed as the ratio of total energy expenditure, as measured with doubly labelled water, to resting energy expenditure as measured in a respiration chamber. Water loss was measured with the deuterium elimination method. Water loss was highly reproducible and ranged from 0.20 to 0.35 l/MJ, independent of season and activity level, with higher values in women. Water loss was related to water and energy intake in summer (r 0.96, P<0.0001 and r 0.68, P<0.001, respectively) as well as in winter (r 0.98, P<0.0001 and r 0.63, P<0.01, respectively). Water loss was, for men, higher in subjects with a higher physical activity in summer (r 0.94, P<0.0001) and in winter (r 0.70, P<0.05). Normalizing water loss for differences in energy expenditure by expressing water loss in litres per MJ resulted in the same value for men in summer and winter. For women, physical activity-adjusted values of water loss were higher, especially in summer. In men, water turnover was determined by energy intake and physical activity, while seasonal effects appeared through energy expenditure. Women showed a higher water turnover that was unrelated to physical activity.

Adult↗

PubMed2005

Cold-induced heat production preceding shivering.

Individual changes in heat production and body temperature were studied in response to cold exposure, prior to shivering. The subjects ten women (seven men) were of normal weight, had a mean age of 23 (SD 3) years and average BMI 22.2 (SD 1.6) Kg/m2. They were lying supine under thermoneutral conditions for 30 min and were subsequently exposed to air of 15 degrees C until shivering occurred. Heat production was measured with a ventilated hood. Body composition was measured with underwater weighing and 2H dilution. Body temperatures were measured with thermistors. Heat production during cold exposure prior to shivering increased and reached a plateau. Skin temperature decreased and did not reach a plateau during the test period. The non-shivering interval (NSI) ranged from 20 to 148 min, was not related to body composition and was not significantly different between women (81 (sd 15) min) and men (84 (sd 34) min). NSI was negatively related to skin temperature (r2 0.44, P=0.004), and skin temperature was related to heat production (r2 0.39, P=0.007). In conclusion, subjects with a relatively large heat production during cold exposure maintained a relatively high skin temperature but showed a short NSI, independent of differences in body composition.

Adult↗

PubMed2005

Genetic analysis of physical activity in twins.

BACKGROUND: The reduced contribution of physical activity (PA) to daily energy expenditure contributes to the increased prevalence of obesity. A genetic control of activity-induced energy expenditure (AEE) may contribute to a genetic susceptibility to obesity. OBJECTIVE: Our aim was to investigate the relative contribution of genetic and environmental factors to the variation and covariation in AEE and PA. DESIGN: Twelve monozygotic and 8 same-sex dizygotic (including 2 same-sex sibling pairs; age differences: 2 and 2.5 y) twin pairs aged between 18 and 39 y participated. AEE was measured in a respiration chamber for 24 h and with doubly labeled water in daily life for 2 wk. PA was recorded simultaneously with a triaxial accelerometer. Structural equation modeling was used to separate and quantify the observed variance into sex-adjusted additive genetic and common and unique environmental contributions. RESULTS: In the respiration chamber, common and unique environmental factors explained the variance in AEE and PA, and no genetic contribution was found. In daily life, genetic factors explained 72% of the variance in AEE and 78% of the variance in PA. Unique environmental factors explained the remaining variance. The same additive genetic factors explained 67% of the covariance in AEE and PA in daily life. CONCLUSIONS: In the present exploratory study that used gold standard measurements for AEE and PA but a limited sample size, genetic influence explained a large part of the variation in AEE and PA in daily life, whereas both AEE and PA were influenced by environment only within the confined area of the respiration chamber.

Acceleration↗

PubMed2005

Accelerometry and heart rate as a measure of physical fitness: proof of concept.

PURPOSE: This study focused on developing a new method to assess VO2max outside laboratory conditions and without the need for maximal exertion. We hypothesized that the combined use of accelerometry and HR monitoring, under daily life conditions, could provide a good estimate of physical fitness. METHODS: Twenty-six healthy subjects (15 women, 11 men), aged 28 +/- 7 yr, performed a maximal incremental test on a bicycle ergometer to determine VO2max. Body composition was measured with underwater weighing and deuterium dilution using a three-compartment model. A triaxial accelerometer (Tracmor) and an HR monitor were worn for seven consecutive days under free-living conditions. The ratio of HR to activity counts per minute (ACM) was used as a fitness index (HR.ACM(-1)). RESULTS: As hypothesized, HR.ACM(-1) was significantly correlated with VO2max. Using fat-free mass (FFM) (P < 0.0001), age (P = 0.025), and HR.ACM(-1) (P = 0.021) as the independent variables, the explained variation in VO2max was 76% (P < 0.0001, SEE = 363 mL x min(-1)). In order to generate a prediction formula that is applicable in the field when no data on body composition are available, the same analysis was done with body mass and gender in the model instead of FFM. HR.ACM(-1) was significantly (P = 0.023) correlated with VO2max. The total explained variation of the model was 71%, with a SEE of 409 mL x min(-1), or 13.7% of the average VO2max. CONCLUSION: After correction for body composition, VO2max was significantly related to HR.ACM(-1). It is, to our knowledge, the first tool that yields a measure of VO2max by monitoring people in their daily life activities without the need for a specific protocol or for maximal exertion, and therefore is applicable to a large variety of subjects.

Activities of Daily Living↗

PubMed2004

Diet induced thermogenesis.

OBJECTIVE: Daily energy expenditure consists of three components: basal metabolic rate, diet-induced thermogenesis and the energy cost of physical activity. Here, data on diet-induced thermogenesis are reviewed in relation to measuring conditions and characteristics of the diet. METHODS: Measuring conditions include nutritional status of the subject, physical activity and duration of the observation. Diet characteristics are energy content and macronutrient composition. RESULTS: Most studies measure diet-induced thermogenesis as the increase in energy expenditure above basal metabolic rate. Generally, the hierarchy in macronutrient oxidation in the postprandial state is reflected similarly in diet-induced thermogenesis, with the sequence alcohol, protein, carbohydrate, and fat. A mixed diet consumed at energy balance results in a diet induced energy expenditure of 5 to 15 % of daily energy expenditure. Values are higher at a relatively high protein and alcohol consumption and lower at a high fat consumption. Protein induced thermogenesis has an important effect on satiety.In conclusion, the main determinants of diet-induced thermogenesis are the energy content and the protein- and alcohol fraction of the diet. Protein plays a key role in body weight regulation through satiety related to diet-induced thermogenesis.

Journal Article↗

PubMed2004

Reproducibility, validity, and responsiveness to change of a short questionnaire for measuring fruit and vegetable intake.

The reproducibility, relative validity, and responsiveness to change of an eight-item food frequency questionnaire designed to measure fruit and vegetable consumption was assessed among 157 women (mean age = 41 years) in the Netherlands from spring 2001 to spring 2002. Plasma concentrations of vitamin C and total and specific carotenoids served as biomarkers against which validity was assessed. The questionnaire was completed and biomarker concentrations were determined three times: immediately preceding and following a controlled intervention of 1 month aimed at increasing fruit and vegetable consumption and 1 year after the start of the intervention. The 1-month and 1-year reproducibility of total fruit and vegetable consumption assessed in the control group was 0.80 and 0.79 (Spearman's r ). Correlations between consumption and plasma carotenoids and vitamin C at baseline were 0.39 and 0.37, respectively, for fruits and 0.24 and 0.26, respectively, for vegetables. Correlations between changes in consumption and plasma carotenoids and vitamin C were 0.32 and 0.33, respectively, for fruits and 0.28 and 0.30, respectively, for vegetables. On the basis of similar correlations reported in the literature, the authors conclude that the questionnaire appears to be suitable for ranking individuals according to their consumption of fruits and vegetables and according to changes in their consumption. However, the validity of the questionnaire remains to be established in males, other age groups, and populations of lower educational levels.

Adult↗