New equations to estimate basal metabolic rate in children aged 10-15 years.

OBJECTIVE: To develop new equations for the estimation of basal metabolic rate in children aged 10-15 years, and to evaluate the impact of including pubertal stage into the equations. DESIGN: Mixed longitudinal. SETTING: The children were recruited from schools in Oxford, and the measurements were made in the schools. SUBJECTS: 195 school children, aged 10-15 years, were recruited in three cohorts. The gender distribution of the subjects was 40% boys and 60% girls. METHODS: Basal metabolic rate (BMR) was measured, by indirect calorimetry, at 6-monthly intervals for 3 years. Anthropometric data, height, weight, body breadths and skinfold measurements (biceps, triceps, subscapular, suprailiac and medial calf) were collected on each occasion. Fat and fat-free mass was calculated from the skinfold measurements. Pubertal development was also assessed on annually by paediatricians. Pubic hair (PH) and gonad (G) development was assessed in boys and breast (B) development in girls. The girls were questioned about menarche. Stepwise multiple regression analysis was used to develop and assess new formulae for BMR that also incorporate pubertal development. RESULTS: The mean BMR measured was 5.754 (s.d. 0.933) MJ/day (138 (s.d. 22) kJ/kg body wt/day) in the boys (n = 351) and 5.476 (s.d. 0.725) MJ/day (121 (s.d. 20) kJ/kg body wt/day) in the girls (n = 554). Weight was the most important factor in developing the regression equations for the calculation of BMR in both sexes (R2 = 0.61 and 0.52 for boys and girls, respectively). Stepwise multiple regression analyses, with independent variables such as gender, weight, height, puberty stage and skinfolds, allowed several BMR regression equations to be developed. The inclusion of the menarche status in the regression equations significantly (P < 0.05) improved BMR estimation in the pre-menarche girls. Boys, pubertal stage as assessed by Pubic Hair (PH) and Gonadal Stage (G) did not contribute to a significant improvement in BMR estimation, except for 11-year-olds. CONCLUSIONS: The inclusion of pubertal stage afforded only minor improvements in the derivation of regression equations for the estimation of BMR of children aged between 10 and 15 years.

Influence of palm olein on protein utilisation in the growing rat.

In view of our preliminary findings that refined palm oil (RPOL) enhanced protein utilisation, and because of the growing importance of palm oil in human diets, two separate studies were conducted. The first study aimed to investigate the effect of the palm oil source and fraction on protein utilisation, as determined by net protein utilization (NPU) in growing rats. The second study aimed to investigate the influence of the dietary concentration of one particular palm oil fraction, refined palm olein (RPO) on net protein utilisation. The fat source of each of the semi-purified diets was as follows: crude palm oil (CPO), refined palm kernel oil (RKO), refined palm olein (RPO), refined palm stearin (RPS), and refined palm oil (RPOL). A sixth control group was offered an identical diet but with olive oil (OO, control) as the fat source. Both the oil source (P < 0.01) and the oil level (P < 0.05) influenced NPU in rats. NPU values were generally higher for rats given the RPO-containing diets, particularly at the 20% dietary level (P < 0.01) compared to the diets containing ground nut oil (GNO). The results of these two experiments indicate that RPO influences protein metabolism specifically at a concentration of at least 20% in the diet. This may suggest that RPO is superior to GNO as a source of fat for the rehabilitation of malnourished children. Human trials notably during the rehabilitation of malnourished children may therefore be the next step in this line of research.

Relationship between tissue mobilization and storage in the rat.

The amount of energy mobilized or stored as protein, expressed as a proportion of the total energy stored or mobilized (defined as the P ratio, Payne & Dugdale, 1977), was investigated in the young male (rapid growth) and adult female (slow growth) rat. Energy mobilization was induced by a 3 d fast and the changes in body content of fat and lean tissues were used to estimate the fasting P ratio (Pfast). Tissue storage was subsequently effected by 17 d of refeeding and the corresponding ratio (P(refed)) was calculated from the amounts of lean and fat tissue regained. The same experimental protocol was used for measuring Pfast and P(refed) in weanling (30 d) and adult (130 d) rats. Weight-matched individuals were assigned to three groups. All animals in group 1 were killed at the beginning of the experiment. Animals in group 2 were fasted for 3 d and then killed. Group 3 animals were first fasted for 3 d, then had free access to a stock diet for a further 17 d before being killed. During fasting, a close linear relationship was found between weight change and body energy changes (r 0.985, and r 0.92, P < 0.001 for weanlings and adult rats respectively) and between carcass N loss and urinary N loss (r 0.933, P < 0.001). These relationships were used to estimate the body energy and N content of each animal at the end of the initial fasting period. Hence, both Pfast and P(refed) values could be calculated for all individuals at both ages. When Pfast and P(refed) were calculated for adult rats, the mean values were similar (0.138 (SE 0.002) and 0.130 (SE 0.006) respectively). Individually, the Pfast and P(refed) values were correlated (r 0.54, P = 0.058). In weanling rats, the mean P(refed) value was about 2.5 times the Pfast (0.421 (SE 0.0113) v. 0.156 (SE 0.004)). Despite the differences in Pfast and p(refed), the individual values were again correlated (r 0.668, P < 0.05). These results support the suggestion made by Payne & Dugdale (1977), that particular P. ratio values are characteristic of individuals and describe the extent to which protein is mobilized or stored during fasting or refeeding. These observations are discussed in relations to the predictions made by the Payne-Dugdale model.

Influence of palm oil and palm oil fractions on protein utilisation.

The influence of dietary palm-oil fractions on protein utilisation has been investigated in the growing rat. At 30 days of age, 4-6 groups of four animals were offered one of six semi-purified diets that differed only in the palm-oil fraction. Diets contained 200g casein, 550 g carbohydrate, and 200g fat/kg. The different palm-oil fractions were: crude palm oil (CPO), refined palm-kernel oil (PKO), refined palm olein (RPO), refined palm stearin (RPS), refined palm oil (RPOL). The control groups were given Olive oil (OO) as the dietary fat source. The conversion efficiency of dietary protein was assessed as Net Protein Utilisation (NPU), using a 10-day comparative carcass technique. Weight gain and food intake were not altered by the various palm-oil fractions. However, the NPU of rats given RPO was significantly higher (p<0.05) than that of rats given all other palm-oil fractions or the OO control. It is concluded that the RPO has the potential to significantly improve NPU in the rat, compared to four other palm-oil fractions as well as olive oil.

Basal metabolic rate of women on the contraceptive pill.

OBJECTIVE: To investigate the variability in basal metabolic rate (BMR) of women taking the contraceptive pill, through sequential measurement over the course of one menstrual cycle. DESIGN: Randomised. SETTING: Metabolic room, School of Biological and Molecular Sciences, Oxford Brookes University. SUBJECTS AND MEASUREMENTS: BMR of five weight-stable women taking the contraceptive pill, was measured three to four times each week for a period of five consecutive weeks, BMR was measured using a Douglas bag. RESULTS: The pattern of variation in BMR was random for individual subjects throughout the period of measurement. The level of intraindividual variation indicated by the coefficient of variation (CV) ranged from 2.4 to 4.87%. CONCLUSIONS: Women taking the contraceptive pill did not exhibit the cyclicity or variation in BMR observed in some normally ovulating subjects. BMR in women taking the contraceptive pill could therefore be considered a 'biological constant'.

PIP: The aim of this study was to investigate the variability in basal metabolic rate (BMR) of women taking the contraceptive pill through sequential measurement over the course of one menstrual cycle. A randomized study design was used, and the setting was the metabolic room at the School of Biological and Molecular Sciences, Oxford Brookes University, in the UK. BMR of 5 weight-stable women taking the contraceptive pill was measured 3-4 times each week for a period of 5 consecutive weeks. BMR was measured using a Douglas bag. The pattern of variation in BMR was random for individual subjects throughout the period of measurement. The level of intraindividual variation indicated by the coefficient of variation (CV) ranged from 2.4% to 4.87%. Women taking the contraceptive pill did not exhibit the cyclicity or variation in BMR observed in some normally ovulating subjects. BMR in women taking the contraceptive pill could therefore be considered a 'biological constant'.

Protein utilization, growth and survival in essential-fatty-acid-deficient rats.

The relationship between essential fatty acids (EFA) deficiency and the utilization of dietary protein, growth rate and survival of offspring was investigated in rats during development and reproduction. EFA deficiency was induced by feeding a 200 g casein/kg-based diet containing 70 g hydrogenated coconut oil (HCO)/kg as the only source of fat. The conversion efficiency of dietary protein was assessed as net protein utilization (NPU), using a 10 d comparative carcass technique. Consumption of the deficient diet during the 10 d assay period induced biochemical changes characteristic of mild EFA deficiency in humans (triene:tetraene 0.27 (SD 0.04) compared with 0.026 (SD 0.004) for non-deficient controls), but there were no significant changes in growth rate or protein utilization. These variables were also unchanged when the deficient diet was fed for an additional 7 d before the assay, although triene:tetraene increased to 0.8 (SD 0.02). Feeding the deficient diet for 63 d before assay produced severe EFA deficiency (triene:tetraene 1.4 (SD 0.3) v. 0.036 (SD 0.005) for controls), a fall in growth rate (25% during assay period), and NPU (31.5 (SD 0.63) v. 39.0 (SD 0.93) for controls). These severely-EFA-deficient animals had a 30% higher fasting-resting rate of energy metabolism than that of age-matched controls. However, there was no change in the rate of endogenous N loss. Voluntary energy consumption was increased in animals fed on deficient diets, either with 200 g protein/kg, or protein free. The reduced efficiency of protein utilization could be entirely accounted for by the restricted amount of energy available for growth and protein deposition. Consumption of an EFA-deficient diet during pregnancy and lactation resulted in high mortality (11% survival rate at weaning compared with 79% for controls) and retarded growth in the preweaning offspring. It is concluded that animals are particularly sensitive to EFA deficiency during reproduction and pre- and post-natal stages of development. However, after weaning only severe EFA deficiency retarded growth, primarily through changes in energy balance.

Intraindividual variation in the basal metabolic rate of women: Effect of the menstrual cycle.

The validity of using the basal metabolic rate (BMR) to calculate an individual's energy requirements is based upon the assumption that the intraindividual variation in BMR is small. Early studies (pre-1940) on BMR in women had shown that the menstrual cycle may have a profound effect, contributing to high levels of intraindividual variation. To investigate this issue further, and to explore whether BMR is indeed a biological constant in women, sequential measurements of BMR were made in women over one menstrual cycle. Two independent studies were undertaken in which the BMR of 12 weight-stable women (not taking the contraceptive pill) was measured every day (excluding weekends) for a period of 5 weeks. The six women participating in the first study were measured using a Douglas bag, while the six subjects in the second study were measured with a Deltatrac (Datex, Helsinki). Nine of the 12 subjects demonstrated a peak in BMR during the late luteal phase of the menstrual cycle, while 8 of the 12 subjects exhibited a fall in BMR after the onset of menstruation. Group analysis of the results indicated that the BMR during the early follicular phase was significantly lower than the BMR during the late luteal phase (Wilcoxon's signed rank test: P < 0.01). The level of intraindividual variation was assessed by calculating the coefficient of variation (CV) for the measurement period. The CV in six of the women exhibited a level of variation comparable to men (2-4%). However, intraindividual variation in the BMR of the other six women was considerably higher (up to 12%). In these six women, therefore, BMR may not be considered a biological constant. All available data on sequential measurements of BMR in fertile women were collated from the literature for the first time, and statistically analyzed. BMR during the early follicular phase was found to be significantly lower (P < 0.05) than during the late luteal phase. Further work on the biological constancy of BMR in women and the impact of the menstrual cycle on BMR is required. This area is of particular importance given the fact that the energy requirements of both individuals and populations are now calculated using the BMR. © 1996 Wiley-Liss, Inc.

Effect of carbohydrate source on lipid metabolism in lactating mice and on pup development.

The effect of long-term sucrose intake on lipid metabolism and milk composition was examined in lactating mice and correlated with the development of their pups. Female mice were weaned onto semi-purified diets containing 685 g starch or sucrose/kg diet. Food intake was similar on the two diets. At mid-lactation, milk was collected and analysed. Milk from sucrose-fed dams had a lower percentage of linoleic acid (18:2n-6) and a higher percentage of oleic acid (18:1n-9), although milk fat content was similar. Hepatic fatty acid synthesis (as measured by 3H2O incorporation into fatty acid) was three times faster in sucrose-fed than in starch-fed dams. Dietary carbohydrate had no effect on fatty acid synthesis or functional lipoprotein lipase (EC 3.1.1.34) activity in mammary gland, nor on plasma triacylglycerol concentration. Pups from first litters were killed at 11-12 d and body composition analysed. Pups born to sucrose-fed dams were significantly heavier with increased body fat and higher levels of plasma glucose and triacylglycerol. Litters of sucrose- and starch-fed dams were cross-fostered at birth and killed at 10-12 d. Analysis of variance indicated that maternal sucrose intake, both during pregnancy and lactation, increased body fat of offspring. The increases in body weight and plasma triacylglycerol of preweaning offspring were caused primarily by maternal sucrose intake during lactation.

The local and systemic effects of minor injury on muscle protein synthesis in the rat.

Massive physical trauma has marked effects on metabolism of body tissues. At present, however, there is little data available on the effect of minor injury on protein metabolism. In this study we examined the effects of a minor muscle injury on the rate of protein synthesis in injured muscle as well as its contralateral control. Rats were injured by removing a small piece of tissue from the interior of one gastrocnemius muscle. Muscle protein synthesis was measured in vivo by a flooding dose technique. The injury had no significant effect on food intake, body weight, muscle protein content or plasma insulin concentration at any time during the following 48 hr. However the rate of protein synthesis in the injured muscle increased 48 hr after injury (mean value in injured muscle 16.1 +/- 1.8 (SEM, n = 18) % per day, uninjured muscle in the same animals 13.1 +/- 1.3% per day, P < 0.05 by paired t-test). These results indicate that even a minor injury causes a local increase in the rate of protein synthesis 48 hr later. This may be an obligatory part of the process of repair and regrowth of muscle tissue.

Effect of surgical trauma on muscle protein synthesis in the rat.

The rate of protein synthesis in skeletal muscle was measured in vivo in rats at various times during the first 2 days after abdominal surgery. Protein synthesis in abdominal muscle at the site of the wound was slightly reduced 2 h after operation, had returned to normal by 24 h and was massively increased by 48 h after surgery. In contrast, there was no change at any time in the rate of protein synthesis in either the gastrocnemius muscle or abdominal muscle distant from the wound site. Surgery had no effect on the weight or protein content of the gastrocnemius muscle, although urinary nitrogen excretion was increased relative to food intake, indicating the presence of a net catabolic response. Changes in whole-body protein turnover in response to uncomplicated abdominal surgery are thus likely to reflect the anabolic processes of wound healing and repair as well as any catabolic response in uninjured tissues.