Sleeping metabolic rate in relation to body composition and the menstrual cycle.

The relationship between sleeping metabolic rate (SMR) measured from 0300 to 0600 h in a respiration chamber and body composition was studied in 47 healthy adult subjects (23 men and 24 women). The effect of the menstrual cycle on SMR was examined in 16 of the 24 women. SMR increased in the postovulation phase of the menstrual cycle (estimated as days 18-29 after last menstruation) 7.7% on average (P less than 0.001). A stepwise regression showed that both fat-free mass (FFM), fat mass (FM), and the phase of the menstrual cycle contributed significantly to SMR. After adjustment for FFM and FM, no sex differences in SMR (men vs preovulation women) remained. The inclusion of FM in this model is an improvement that eliminates the sex difference in SMR/FFM that is usually found. A prediction equation is given that explains 85% of the variance in SMR among individuals.

Fecapentaene excretion and fecal mutagenicity in relation to nutrient intake and fecal parameters in humans on omnivorous and vegetarian diets.

Fecapentaenes are strong fecal mutagenic compounds presumably occurring in the majority of Western human individuals, and are possibly essential initiators of colon carcinogenesis. Dietary factors have been shown to influence colorectal cancer risk and to modulate both fecal mutagenicity and fecapentaene concentrations. Therefore, in this study, excretion of fecapentaenes is determined in humans consuming either vegetarian or omnivorous diets. The results show that the most predominant fecapentaene forms are excreted in higher concentrations by vegetarians. Consumption of cereal fiber, calcium and carotene as well as fecal concentrations of iso-lithocholic acid were found to correlate positively with excreted concentrations of one or more fecapentaene analogues. On average, 22% of excreted fecapentaene concentrations was found to be related to nutrient intake in stepwise regression models. Dietary calcium intake was found to be the most significant factor positively correlating with excreted fecapentaene concentrations. Intake of mono-unsaturated fatty acids or fiber from vegetables and fruit could be shown to correlate with fecapentaene excretion to a lesser degree. Despite high fecapentaene concentrations in fecal dichloromethane extracts, only 1 out of 20 samples revealed significant mutagenic activity in Salmonella typhimurium TA 100. Further, aqueous extracts of feces from omnivores appeared to be equally mutagenic as feces from vegetarians and contained non-detectable concentrations of fecapentaenes. It is concluded that dietary factors do affect excreted fecapentaene levels, but only to a relatively minor extent. Since vegetarians at low risk for colorectal cancer excrete higher concentrations of fecapentaenes, it could be hypothesized that relatively increased fecapentaene excretion in combination with antimutagenic compounds in feces represents colon cancer prevention.

Nitrate contamination of drinking water: evaluation of genotoxic risk in human populations.

Nitrate contamination of drinking water implies a genotoxic risk to man due to the endogenous formation of carcinogenic N-nitroso compounds from nitrate-derived nitrite. Thus far, epidemiological studies have presented conflicting results on the relation of drinking water nitrate levels with gastric cancer incidence. This uncertainty becomes of relevance in view of the steadily increasing nitrate levels in regular drinking water supplies. In an attempt to apply genetic biomarker analysis to improve the basis for risk assessment with respect to drinking water nitrate contamination, this study evaluates peripheral lymphocyte chromosomal damage in human populations exposed to low, medium, and high drinking water nitrate levels, the latter being present in private water wells. It is shown that nitrate contamination of drinking water causes dose-dependent increases in nitrate body load as monitored by 24-hr urinary nitrate excretion in female volunteers, but this appears not to be associated with peripheral lymphocyte sister chromatid exchange frequencies.

Substrate utilization in man: effects of dietary fat and carbohydrate.

In man there is evidence that the ability to adjust fat oxidation to fat intake is less effective than the ability to adjust carbohydrate and protein oxidation to carbohydrate and protein intake. The short-term (3-day) effects of a low-fat (LF), mixed (M), and high-fat (HF) diet on human substrate balances were studied using a respiration chamber. Subjects were 14 young female students classified by means of their scores on psychometric questionnaires as "restrained" or "unrestrained" eaters. Subjects were in energy balance, ie, the mean difference between energy intake (EI) and energy expenditure (EE) was 86 +/- 85 kJ/d. The fat content of the food significantly influence the 24-hour respiratory quotient (RQ) and nonprotein respiratory quotient (NPRQ). For both the LF and M diets, the 24-hour RQ was significantly lower than the food quotient (FQ), whereas the RQ on the HF diet was not different from the FQ. Oxidation of fat and carbohydrate significantly increased with, respectively, an increasing fat and carbohydrate content of the diet for both restrained- and unrestrained-eating subjects. Restrained-eating subjects showed a decreased fat oxidation compared with unrestrained eaters in response to a HF diet, resulting in a positive fat balance for restrained-eating subjects. On a LF diet, fat balance was negative for both groups of subjects, indicating net endogenous fat oxidation. In conclusion, restrained-eating subjects have more difficulty in the handling of a HF diet, possibly explaining their higher susceptibility to becoming obese.

Comparison of doubly labeled water with respirometry at low- and high-activity levels.

In previous studies the doubly labeled water method for measuring energy expenditure in free-living humans has been validated against respirometry under sedentary conditions. In the present investigation, energy expenditure is measured simultaneously with doubly labeled water and respirometry at low- and high-activity levels. Over 6 days, five subjects were measured doing mainly sedentary activities like desk work; their average daily metabolic rate was 1.40 +/- 0.09 (SD) times sleeping metabolic rate. Four subjects were measured twice over 3.5 days, including 2 days with heavy bicycle ergometer work, resulting in an average daily metabolic rate of 2.61 +/- 0.25 (SD) times sleeping metabolic rate. At the low-activity level, energy expenditures from the doubly labeled water method were on the average 1.4 +/- 3.9% (SD) larger than those from respirometry. At the high-activity level, the doubly labeled water method yielded values that were 1.0 +/- 7.0% (SD) lower than those from respirometry. Results demonstrate the utility of the doubly labeled water method for the determination of energy expenditure in the range of activity levels in daily life.

Use of the doubly labeled water technique in humans during heavy sustained exercise.

We measured energy expenditure with the doubly labeled water technique during heavy sustained exercise in the Tour de France, a bicycle race lasting more than 3 wk. Four subjects were observed for consecutive intervals of 7, 8, and 7 days. Each interval started with an oral isotope dose to reach an excess isotope level of 200 ppm 18O and 130 ppm 2H. The biological half-lives of the isotopes were between 2.25 and 3.80 days. Energy expenditure was compared with simultaneous measurements of energy intake, and body mass and body composition did not change significantly. The doubly labeled water technique gave higher values for energy expenditure than the food record technique. The discrepancy showed a systematic increment from the first to the third interval, being 12.9 +/- 7.9, 21.4 +/- 9.8, and 35.3 +/- 4.4% of the energy expenditure calculated from dietary intake, respectively. Possible explanations for the discrepancy are discussed. The subjects reached an average daily metabolic rate of 3.4-3.9 or 4.3-5.3 times basal metabolic rate based on the food record technique and the doubly labeled water technique, respectively. Thus, when measured with the same technique, the energetic ceiling for performance in humans is comparable with that of animals like birds.

A dual-respiration chamber system with automated calibration.

This study characterizes respiration chambers with fully automated calibration. The system consists of two 14-m3 pull-type chambers. Care was taken to provide a friendly environment for the subjects, with the possibility of social contact during the experiment. Gas analysis was automated to correct for analyzer drift and barometric pressure variations and to provide ease of use. Methods used for checking the system's performance are described. The gas-analysis repeatability was within 0.002%. Results of alcohol combustion (50-350 ml/min CO2) show an accuracy of 0.5 +/- 2.0 (SD) % for O2 consumption and -0.3 +/- 1.6% for CO2 production for 2- to 24-h experiments. It is concluded that response time is not the main factor with respect to the smallest practical measurement interval (duration); volume, mixing, gas-analysis accuracy, and levels of O2 consumption and CO2 production are at least equally important. The smallest practical interval was 15-25 min, as also found with most chamber systems described in the literature. We chose to standardize 0.5 h as the minimum measurement interval.

Clustering of dietary variables and other lifestyle factors (Dutch Nutritional Surveillance System).

STUDY OBJECTIVE: The aim was to investigate whether dietary factors cluster in a favourable or unfavourable way and to characterise the groups identified by lifestyle and sociodemographic variables. DESIGN AND SETTING: This cross sectional study was based on data of the 1987-1988 Dutch national food consumption survey (DNFCS), obtained from a panel by a stratified probability sample of the non-institutionalised Dutch population. PARTICIPANTS: 3781 adults (1802 males and 1979 females) of the DNFCS, aged 19 to 85 years, were studied. MEASUREMENTS AND MAIN RESULTS: To estimate dietary intake two day food records were used. Lifestyle factors were collected by structured questionnaire and sociodemographic variables were available from panel information. Cluster analysis was used to classify subjects into groups based on similarities in dietary variables. Subsequently, these groups were characterised by sociodemographic and lifestyle factors as well as by the consumption of food groups. Eight clusters were found. In comparison with the guidelines, the dietary quality in four clusters was poor. The cluster with the poorest dietary intake (high intake of fat, cholesterol, and alcohol; low intake of dietary fibre) showed on average a high consumption of animal products (except milk), fats and oils, snacks, and alcoholic beverages, and a low consumption of fruit, potatoes, vegetables, and sugar rich products. Smoking, body mass index, dietary regimen on own initiative, hours of sleep, gender, age, socioeconomic status, and day of the week were found to discriminate among the clusters. CONCLUSIONS: Cluster analysis resulted in substantial differences in mean nutrient intake and seems useful for dietary risk group identification. Undesirable lifestyle habits were interrelated in some clusters, but an exclusive lifestyle for health risk has not been found.

Cardiovascular effects of dietary linoleic acid.

A survey is given of the effects of a linoleic-acid-rich diet on arterial thrombosis, blood platelet function and blood pressure in rats and man, and on coronary flow rate and heart muscle function of isolated rat hearts. Dietary linoleic acid decreases arterial thrombosis tendency in a dose-dependent manner in rats, as measured by the aorta loop technique. In a group of patients, a linoleic-acid-rich diet improved blood platelet aggregation measured with the filtragometer as compared with a similar group which was given a linoleic-acid-poor diet. The patients who received a high linoleic acid diet showed a lower cardiovascular death rate than the low linoleic acid group. Salt-induced hypertension in rats can be prevented and cured by a high linoleic acid diet. In man, the results of a few experiments show a decreasing tendency of blood pressure during a diet enriched with linoleic acid. In the isolated hearts of rats fed a diet high in linoleic acid, coronary flow and heart muscle function both increase as compared to control groups fed lard or hardened coconut oil. The observed effects are discussed against the background of recent findings in the field of prostaglandin research.

Influences of dietary fats on coronary flow rate and left ventricular work of the isolated rat heart: sunflower seed oil versus lard.

The influences of dietary sunflower seed oil and lard on coronary flow rate and external left ventricular work were studied in the isolated Langendorff-perfused and working rat heart. For 1, 4 or 6 weeks, rats were fed diets containing 25--50% of the total digestible energy as fat, 23% as casein an 52--27% as starch. The coronary flow rate and the maximum left ventricular work of hearts of rats fed sunflower seed oil were higher than those of hearts of rats fed lard (about 15 and 10%, respectively). The maximum left ventricular work was achieved at a left ventricular filling pressure of 10--12 mm Hg: this value was not affected by the type of dietary fat. The effect of dietary fat on coronary flow rare is already seen after 1 week of feeding, and on left ventricular work after 4 weeks of feeding. Analysis of variance shows a positive relationship between the maximum left ventricular work and the amount of sunflower seed oil. It is concluded that dietary fats affect coronary flow rate and left ventricular work in the isolated rat heart. The increase in left ventricular work may be caused by an increase in contractility.

Effects of dietary fats on the coronary flow rate and the left ventricular function of the isolated rat heart.

Two groups of rats were fed diets containing large amounts (45-50% of the total digestible energy) of sunflower seed oil or hydrogenated coconut oil for 4-5 days. The left ventricular working capacity, the coronary flow rate, the oxygen consumption, the glucose uptake and the lactate release were determined in the isolated perfused heart. The fatty acid composition of the heart phospholipids was also determined. The left ventricular working capacity and the coronary flow rate of hearts of rats fed sunflower seed oil are higher (10-20%) than those of rats fed hydrogenated coconut oil. Feeding the two fats for 3-4 weeks instead of 4-5 days does not alter the results. There are no or only minor differences between the two dietary groups as to the other quantities mentioned. It is concluded that dietary fats affect the properties of the heart already after a short feeding time.

Deceleration in cumulative food intake curves, changes in body temperature and diet-induced thermogenesis.

In order to assess the relationship between the shape of the cumulative food intake curve and a reflection of internal processes, eating behaviour, postprandial thermogenesis, and skin and core temperature of normal weight restrained and unrestrained eating women and of obese restrained eating women were recorded during four-course solid food lunches, eaten in a laboratory setting (respiration chamber) at a constant ambient temperature of 22 degrees C. The skin temperature (upper arm, upper leg, liver proximity) and core temperature were measured constantly from one hour prior to until two hours after the lunch. Normal weight unrestrained eaters displayed decelerated cumulative food intake curves and an increase in the liver temperature data of 0.8-1.5 degrees C, from the beginning of the meal onwards, remaining high until 60-90 minutes after the meal was consumed. The postprandial thermogenesis of normal weight unrestrained eaters was on average 8.1 +/- 1.3%, calculated over two and a half hours from the beginning of the meal. Overweight and normal weight restrained eaters displayed linear cumulative food intake curves, almost no changes in skin and core temperatures and a postprandial thermogenesis of 4.2 +/- 0.3% and 4.8 +/- 0.7%, calculated over two and a half hours from the beginning of the meal onwards. In conclusion, deceleration in cumulative food intake curves is positively correlated with a temperature increase in the skin in the proximity of the liver, and with postprandial thermogenesis.

Diet-induced thermogenesis and cumulative food intake curves as a function of familiarity with food and dietary restraint in humans.

Cumulative food intake curves and diet-induced thermogenesis were recorded in women during four-course solid-food lunches, consisting of familiar and unfamiliar food, offered in ad lib or restricted portions, in order to assess a possible relation between eating behaviour on the one hand and a reflection of internal processes and subject characteristics on the other. The subjects were characterized as normal weight restrained, normal weight unrestrained, and overweight restrained. A negative relation was found between degree of restraint and deceleration of the cumulative food intake curve during the ad lib courses of any menu, and between degree of restraint and diet-induced thermogenesis (p less than 0.001). Consequently, a positive relation was found between deceleration of the cumulative food intake curves during the ad lib courses of any menu and diet-induced thermogenesis (p less than 0.001). Diet-induced thermogenesis during the first serving of a meal consisting of unfamiliar food was significantly higher in all groups than during the other two times, when meals consisting of more familiar food were served (+0.98%; 0.71%, p less than 0.05).

Effect of replacement of fat by nonabsorbable fat (sucrose polyester) in meals or snacks as a function of dietary restraint.

The effect of replacement of fat by nonabsorbable fat on energy intake and on feelings of hunger and satiety was assessed, in normal-weight dietary-restrained (n = 11), dietary-unrestrained (n = 13) and in postobese dietary-restrained women (n = 12), using 2 experimental designs. First, during breakfast and lunch on 2 sequential weekdays, 23 g of dietary fat was replaced by 23 g of a nonabsorbable fat. Second, dietary fat was replaced by a nonabsorbable fat in snacks consumed ad lib during a different week. Fat replacement in meals or in snacks did not result in changes in hunger and satiety ratings throughout the day. Replacement in meals yielded an energy intake reduction of 0.5 MJ/day (not significant) in dietary-unrestrained and in postobese dietary-restrained subjects; this reduction included 44% energy intake compensation. In normal-weight dietary-restrained subjects, energy intake reduction of 0.7 (p < 0.05) MJ/day was observed; this reduction included 22% energy intake compensation. Moreover, fat replacement in meals showed a shift in macronutrient composition from 35-40% energy from fat to 31-32% energy from fat. Replacement in snacks yielded an energy intake reduction of 0.4-0.5 MJ/day (not significant) in normal-weight dietary-restrained subjects and a reduction of 0.6-0.7 (p < 0.05) MJ/day in dietary-unrestrained and in postobese dietary-restrained subjects. In this situation, energy intake from snacks consisted of 48-78% energy from reduced-fat reduced-energy snacks, which implied a replacement of 10-15 g fat by 10-15 g SPE (sucrose polyester) and a shift in macronutrient composition from 35-40 percentage energy from fat to 33-36 percentage energy from fat. These results suggest short-term beneficial effects of fat replacement on energy and fat intake.

The shape of the cumulative food intake curve in humans, during basic and manipulated meals.

The shape of the cumulative food intake curve of normal weight and obese women was studied during solid food lunches, artificially prolonged meals, and energetically enriched meals eaten in a laboratory setting. Subjects (86 normal weight, 50 obese) displayed consistent eating behaviour over 3-6 repeated meals, with marked differences between individuals. Aspects of eating behaviour were reflected in decelerated and nondecelerated (or linear) cumulative intake curves depending on changes or no changes in eating rate during the course of a meal, respectively. A change in eating rate was generally related to decrease in bite size, with bite rate remaining constant, from the third temporal quarter of the meal onwards, resulting in a decelerated cumulative intake curve. The nondecelerated (linear) cumulative intake curve does not show this change in eating rate: in the first three temporal quarters bite size and bite rate were constant, whereas in the fourth temporal quarter bite size decreased slightly, compensated by a small increase in bite rate. Intraindividual ranges for meal parameters such as chewing time per bite, bite interval and initial eating rate indicated consistency of individual eating behaviour. In manipulation experiments with a subset of 21 subjects in which meals were artificially prolonged by an interval of 8 min, the cumulative intake curves did not differ significantly from the original cumulative intake curves in 10 nondecelerated (linear) eaters, but showed a change towards nondecelerated curves in 8 out of 11 decelerated eaters.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of energy expenditure by recording heart rate and body acceleration.

The feasibility of a portable accelerometer equipped with a three-directional sensor for the assessment of physical activity and the consequences for energy expenditure was examined under laboratory conditions and during normal daily life. Heart rate monitoring was also conducted to allow comparison of both techniques. In the laboratory study 16 healthy subjects performed a number of specified exercises within a range of activity levels that may be expected in normal life. Accelerometer output was compared with energy expenditure measured by continuous respirometry. A linear relationship was found between accelerometer output and energy expenditure for the pooled data. The standard error of estimate is 79.1 J.min-1.kg-1. In the field study four subjects were observed during a week under free living conditions. Energy expenditure was calculated from food intake registered over the whole period. Energy expenditure calculated from accelerometer output and heart rate exceeded the energy intake figures by 30% and 33%, respectively. Possible explanations for this discrepancy are discussed. Despite this discrepancy, accelerometer output appeared to correlate highly with energy intake (r = 0.99, P less than 0.025), which suggests accurate performance of the accelerometer under free living conditions. The heart rate method gave much poorer results in estimating individual energy expenditure.

The work of walking: a calorimetric study.

Experiments were designed to test the traditional assumption that during level walking all of the energy from oxidation of fuel appears as heat and no work is done. Work is force expressed through distance, or energy transferred from a man to the environment, but not as heat. While wearing a suit calorimeter in a respiration chamber, five women and five men walked for 70 to 90 min on a level treadmill at 2.5, 4.6, and 6.7 km.h-1 and pedalled a cycle ergometer for 70 to 90 min against 53 and 92 W loads. They also walked with a weighted backpack and against a horizontal load. During cycling, energy from fuel matched heat loss plus the power measured by the ergometer. During walking, however, energy from fuel exceeded that which appeared as heat, meaning that work was done. The power increased with walking speed; values were 14, 29, and 63 W, which represented 11, 12, and 13% of the incremental cost of fuel above the resting level. Vertical and horizontal loads increased the fuel cost and heat loss of walking but did not alter the power output. This work energy did not re-appear as thermal energy during 18 h of recovery. The most likely explanation of the work done is in the inter-action between the foot and the ground, such as compressing the heel of the shoe and bending the sole. We conclude that work is done in level walking.

Effects of dehydration on gastric emptying and gastrointestinal distress while running.

Gastrointestinal distress is commonly reported by athletes after ingestion of a beverage. We speculate that ingestion may be occurring after dehydration has taken place. The high prevalence of GI disorders in marathon runners who have lost greater than or equal to 4% body weight supports this theory. To test this theory, the effects of dehydration, and dehydration in combination with endurance running, on gastric emptying (GE) and frequency of gastrointestinal (GI) complaints were tested in this experiment. A complete cross-over study was designed. Sixteen subjects ingested 8 ml.kg BW-1 of a 7% carbohydrate (296 mOsm.kg-1), solution after a euhydration or dehydration regime. Dehydration (4% BW loss) was produced by 60% maximal speed running at 30 degrees C or by intermittent sauna exposure at 100 degrees C. Euhydration experiments were conducted with a 2 h rest period with water administered at 20 and 40 min. Gastric drink volumes were measured every 10 min for 40 min. Emptying curves were compared using semi-log transformation of the percentage emptying data and simple linear regression. The slope of each line was used as a measure of average GE rate. Dehydration-exercise resulted in slower GE than in all other treatments (P less than 0.05). ANOVA revealed significant effects of dehydration (P less than 0.05) and exercise (P less than 0.05), these two effects being additive in delaying GE. GI complaints were reported by 37.5% of the subjects during dehydration-exercise experiments. No GI disturbance was reported in other tests.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of electrolytes in carbohydrate beverages on gastric emptying and secretion.

Two experiments were done at rest to examine gastric residue and secretion volume and electrolyte composition after ingestion of beverages of varying composition. In the first experiment the effects of two different sport drinks, one isotonic (7% carbohydrate, primarily sucrose) (I) and one hypertonic (18% carbohydrate, primarily maltodextrin) (H), and a control beverage (0.08 g.l-1 aspartame in water) (C) on titratable acid, pH, osmolality, gastric emptying and secretion volume, and Na+, K+, and Cl- content were measured. In a second experiment five solutions were tested all containing 150 g.l-1 maltodextrin, with 28 meq.l-1 Na+ (low Na), 140 meq.l-1 Na+(high Na), 28 meq.l-1 K+(K), or 140 meq.l-1 Na+ and 28 meq.l-1 K+(high NaK). Beverages H and C, and distilled water (W) were also tested. Samples were taken via a nasogastric tube. A dye dilution technique for serial sampling was employed to determine beverage and secretion volumes. After receiving a bolus of 8 ml.kg-1 body weight, samples of gastric residue were taken at 0, 10, 20, 30, 40, 60, and 80 min. Gastric secretion of Na+, K+, and Cl- was fairly constant despite large differences in beverage composition. Changes in gastric residue pH, titratable acid, osmolality, and electrolyte composition reflected the increasing proportion of the residue that was from gastric secretions. The effects of varying concentrations of Na+ and K+ (in a 150 g.l-1 maltodextrin solution) on gastric emptying were not significant. The high carbohydrate concentration and/or the large volume ingested may have overridden any effect of sodium or potassium. No differences were observed between W and C. Secretion was decreased in these two solutions versus all the others. Although nonsignificant, there was a trend for greater secretion in H versus the other carbohydrate containing solutions in experiment 2. This may be a result of the higher pH maintained after ingestion of this beverage.

Daily variation in gastric emptying when using the double sampling technique.

The purpose of this study was to establish the intra-individual variation in the rate of gastric emptying (GE) by using the double sampling technique of George. Eight healthy male volunteers, all familiar with gastric intubation and testing, participated in four GE tests, using an isotonic fluid as a test meal. Conditions were kept constant during all four tests, and each test was separated by at least 48 h. The within-subjects coefficient of variation proved to be 29%. The findings demonstrate that, given standard conditions, GE is reproducible from day to day.