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PubMed2000

Mechanisms of changes in basal metabolism during ageing.

A considerable number of physiological functions are known to show a gradual decline with increasing age. However, the effects of ageing differ widely between organ systems. It is believed that basal metabolic rate (BMR) falls dramatically with age. These observations, largely based on cross-sectional surveys, are discussed in light of our present understanding of the biology of ageing. This paper reviews both the longitudinal and cross-sectional studies of BMR and presents evidence that the fall in BMR with ageing may be less dramatic than previously perceived. Indeed, some subjects may show an increase in BMR with ageing. The mechanism of changes in BMR during ageing will be discussed. Organ weight changes appear to have a profound impact on BMR. The use of BMR to predict total energy expenditure in the 'old elderly' (>75 y) is unlikely to be of any practical use due to wide intra- and inter-individual variation in BMR. This wide intra- and inter-individual variation in BMR is due to illness, disease and other metabolic disorders seen in the elderly. Finally, the importance of measuring BMR in elderly populations for its use in clinical medicine will be discussed.

Aged↗
PubMed2007

Basal metabolic rate of birds is associated with habitat temperature and precipitation, not primary productivity.

A classic example of ecophysiological adaptation is the observation that animals from hot arid environments have lower basal metabolic rates (BMRs, ml O2min-1) than those from non-arid (luxuriant) ones. However, the term 'arid' conceals within it a multitude of characteristics including extreme ambient temperatures (Ta, degrees C) and low annual net primary productivities (NPPs, gCm-2), both of which have been shown to correlate with BMR. To assess the relationship between environmental characteristics and metabolic rate in birds, we collated BMR measurements for 92 populations representing 90 wild-caught species and examined the relationships between BMR and NPP, Ta, annual temperature range (Tr), precipitation and intra-annual coefficient of variation of precipitation (PCV). Using conventional non-phylogenetic and phylogenetic generalized least-squares approaches, we found no support for a relationship between BMR and NPP, despite including species captured throughout the world in environments spanning a 35-fold range in NPP. Instead, BMR was negatively associated with Ta and Tr, and positively associated with PCV.

Animals↗
PubMedDate not supplied

Total body capacity correlated with basal metabolic rate.

This study was conducted to establish the relationship between a new bioelectrical parameter, total body capacitance (TBpF), as an expression of body cell mass, measured using an impedance analyser and basal metabolic rate (BMR), by indirect calorimetry in 75 healthy subjects (38 females and 37 males, aged between 13 y and 43 y). A significant high correlation was found between TBpF and BMR (r = 0.992, SEE = 238 kcal) with the equation: BMR (kcal day-1) = Capacity (pF) x 2.29.

Adolescent↗
PubMed2006

Overweight and basal metabolic rate in boys with attention-deficit/hyperactivity disorder.

We investigated a possible association between attention-deficit/hyperactivity disorder (ADHD) and overweight by measuring weight status and energy expenditure (basal metabolic rate, BMR) in 39 ADHD-boys with hyperactivity (mixed hyperactive/impulsive and inattentive or predominantly hyperactive/impulsive) and 30 healthy boys. The age range for the total group was 8-14 years. Weight and height were measured by a calibrated scales and stadiometer. Body mass index standard deviation scores (BMI-SDS) were calculated. BMR was determined by indirect calorimetry. Significant differences were obtained between the ADHD- and the control-group, but not between ADHD-subgroups. Both BMI-SDS and BMR were higher in the group of ADHD-boys, whereby the differences were more marked when they were older. More overweight and obese subjects were found in the ADHD-sample. Impulsive behavior in ADHD-boys with hyperactivity may lead to an increased food intake, which is then likely to overcompensate the heightened energy expenditure.

Adolescent↗
PubMed1997

The validity of predicting the basal metabolic rate of young Australian men and women.

OBJECTIVES: To assess the accuracy of the Schofield, Schofield & James (1985) equations and those of Hayter & Henry (1994) for the prediction of the basal metabolic rate (BMR), of young Australians. DESIGN: BMR was measured by indirect calorimetry, while fat free mass (FFM) and fat mass (FM) were measured by bioelectric impendence analysis (BIA) in 128 volunteers (39 men and 89 women), aged between 18 and 30 y. SETTING: Deakin Institute of Human Nutrition, Deakin University, Melbourne, Australia. RESULTS: The measured BMR of Australian men and women were significantly lower (P < or = 0.001) than the predicted BMR using the Schofield et al (1985) equation, with a mean (s.d.) bias (bias = measured - predicted BMR) of -406(513) kj/d in men and -124(348) kj/d in women. The measured BMR of Australian men and women were similar to the predicted BMR using the equations of Hayter & Henry (1994) and bias was unrelated to body weight. BMR adjusted for FFM and FM was significantly higher by three percent in women on oral contraceptive agents (OCA) as compared to those not on OCA. CONCLUSIONS: The Schofield et al (1985) equations are not valid for the prediction of BMR of young Australian men and women. The equations of Hayter & Henry (1994) for North Europeans and Americans, provide an accurate estimate of the BMR of Australian men and women at the group level. However, in young women not using OCA a correction factor of 0.97 applied to the predicted BMR provides a better estimate.

Adipose Tissue↗
PubMed1995

Do highly physically active females have a lowered basal metabolic rate?

In several studies estimated energy intake has been found to be low compared with estimated energy expenditure in female athletes. It has therefore been suggested that female athletes may have a depressed basal energy expenditure (BMR). The main purpose of the present study was to explore this possibility by measuring BMR in physically extremely active females. Eight female dancers and 7 controls with low physical activity, all musicians, were studied; the variables measured included body weight, height, skinfold thickness and total body potassium. BMR was measured by indirect calorimetry. In conclusion, the present study lends no support to the idea of a lowered basal metabolic rate in female athletes as an explanation of the general finding of a lower estimated energy intake than energy expenditure in this type of subjects.

Adult↗
PubMed1983

Adaptation to underfeeding in growing rats. Effect of energy restriction at two dietary protein levels on growth, feed efficiency, basal metabolism and body composition.

Adaptation to a 50% restriction in energy at two levels of protein intake was studied in growing male and female rats. Growth was proportional to diet intake. The basal metabolic rate (BMR) (VO2/kilogram 0.75) was unaltered, whereas the percent fat deposited was reduced in diet-restricted rats at both 10% and 20% levels of protein. The percent of the total energy intake for tissue deposition was reduced in food-restricted groups to such an extent that the amount of energy available over what is required for tissue deposition was the same in all groups. The relationship between energy available for maintenance and that for BMR was low in diet-restricted groups. These observations suggest that growing rats adapt to low energy intake by reducing tissue deposition and by better utilization of energy for maintenance without reducing BMR. By lowering protein level in the diet feed efficiency is reduced in both diet-restricted groups and groups fed ad libitum.

Adaptation, Physiological↗
PubMed1978

Closer correlation between serum triiodothyronine and basal metabolic rate during antithyroid drug treatment in patients with Graves' disease.

The correlations between serum triidothyronine (T3), thyroxine (T4), 131I-triiodothyronine resin sponge uptake (RT3U) or free thyroxine index (T7) and the basal metabolic rate (BMR) during antithyroid drug treatment in 86 patients with Graves' disease were investigated. Although serum T3, T4, RT3U and T7 during therapy with MMI showed significant positive correlations with BMR, the coefficient of correlation (r = 0.6088, P less than 0.001) between T3 and BMR was the highest of all. While the normal range of BMR in control subjects was between -1.9 and +14.9 (the range of mean +/- SD), the corresponding values of T3, T4, RT3U and T7 calculated from the regression lines, ranged from 94.2 to 184.0 ng/dl, from 5.32 to 8.75 microgram/dl, from 26.5 to 28.9% and from 1.57 to 2.47 respectively. On the other hand, when the corresponding values of BMR to normal values of T3 (100-170 ng/dl), T4 (7.6-12.2 microgram/dl), RT3U (26.7-36.5% and T7 (2.29-3.49) in control subjects were calculated from the regression lines, the range of value obtained from the regression line of T3 coincided better with normal value of BMR in control subjects that those calculated from other regression lines (T4, RT3U and T7). These results suggest that serum T3 level would be a better index of evaluation of the thyroid function that T4 or RT3U in patients with Graves' disease under antithyroid drug treatment.

Adolescent↗
PubMed2000

Basal metabolic rate and energy costs at rest and during exercise in rural- and urban-dwelling Papua New Guinea highlanders.

OBJECTIVE: (1) To evaluate inter-individual variations, regional and sex differences in the basal metabolic rate (BMR) and related variables; (2) to compare measured BMR with estimated BMR using predictive equations; and (3) to examine the net mechanical efficiency (NME) in step tests. DESIGN: BMR and energy costs at rest and during step tests were measured by the Douglas bag technique of indirect calorimetry. NME was calculated from BMR and energy costs of step tests. SETTING: Rural villages under subsistence agriculture and urban settlements under cash economy. SUBJECTS: Adult males and females (n=33) including 16 rural villagers and 17 urban migrants. INTERVENTIONS: Step exercise test. RESULTS: There were significant regional differences in BMR (per body weight) in both sexes. The BMR predicted by Schofield equation correlated with the measured BMR (-1 to+3%), while the BMR predicted by Henry and Rees equations under-estimated the measured BMR by 6-11%. NME was higher in urban subjects with larger body size than in rural subjects for both sexes, albeit insignificantly. NME tended to be higher with increased stepping level in both sexes. CONCLUSIONS: Urban migrants had lower BMR than rural dwellers, and the BMR predicted by Schofield equation correlated with the measured BMR in both sub-groups.

Adolescent↗
PubMed1998

Adaptive reduction in basal metabolic rate in response to food deprivation in humans: a role for feedback signals from fat stores.

We assessed the importance of lean and fat tissue depletion as determinants of the adaptive reduction in basal metabolic rate (BMR) in response to food deprivation by reanalyzing the data on BMR and body composition for the 32 men participating in the classic Minnesota experiment of semi-starvation and refeeding. We used individual data on BMR, body fat, and fat-free mass (FFM) assessed during the control (prestarvation) period, at weeks 12 and 24 of semistarvation (S12 and S24), and week 12 of restricted refeeding (R 12) to calculate an index of the reduction in thermogenesis at S12, S24, and R12, defined as the change in BMR adjusted for changes in FFM and fat mass, and an index of the state of depletion of the fat mass and FFM compartments at these times, defined as the deviation in fat mass or FFM relative to control values. The results indicated a positive relation between the reduction in thermogenesis and the degree of fat mass depletion (but not FFM depletion) during weight loss as well as during weight recovery (r = 0.5, P < 0.01). Furthermore, the residual variance was predicted by the initial (prestarvation) percentage fat and the cormic index (sitting height/height). Taken together, these results in normal-weight men responding to severe food deprivation reveal anthropometric predictors for human interindividual variability in the capacity for energy conservation and suggest that the adaptive reduction in BMR is partly determined by an autoregulatory feedback control system linking the state of depletion of fat stores to compensatory mechanisms that suppress thermogenesis.

Adipose Tissue↗
PubMed2005

[Longitudinal changes in body composition and basal metabolic rate in institutionalized or domiciled obese adolescents].

UNLABELLED: The prevalence of obesity in children has increased dramatically during the past decades, and requires efficient care. OBJECTIVES: To determine changes in anthropometric parameters and basal metabolic rate (BMR) in obese adolescents during and after 2 types of weight-reduction programs. SUBJECTS AND METHODS: Twenty-six adolescents (group I, Z-score of BMI = 4.72) followed a 9-month-weight reduction program including a moderate energy restriction and regular physical activities in a specialized institution. In addition, 39 adolescents (group E, Z-score of BMI = 2.83) followed at home a 9-month-weight reduction program including medical and dietetic advices. Body composition (by impedancemetry) and BMR (by indirect calorimetry) were assessed before the beginning (M0), 4 months after (M4) and at the end (M9) of the programs, then 4 months (M13) and 16 month (M25) after the end of the weight-reduction programs. RESULTS: Twenty-two adolescents in group I and 20 adolescents in group E completed the study. At M0, age, body weight (BW), fat-free mass (FFM) and BMR of subjects of group I were higher (1.0 year, 36 %, 30 % and 23 %, respectively, P < 0.001), than those of group E. Pubertal stage and percentage of fat mass (FM) were not significantly different between the 2 groups. At M9, adolescents of group I showed significant reductions in BW and FM (-19 and -37 %, respectively, P < 0.001), but not significant differences in FFM. In addition, BMR decreased significantly between M0 and M4, both in absolute value (-6.7%, P < 0.001) and after adjustment for FFM (-5.8%, P < 0.001), and the difference was maintained until M9. Between M9 and M13, BW and Z-score of BMI were maintained in 12 adolescents, but increased (+9.7% and 14.8%, respectively, P < 0.001) in 10 adolescents. However, BMR did not change significantly in all adolescents. Between M13 and M25, BW, FM, FFM and BMR increased significantly (+13%, +34%, +6% et +5%, respectively, P < 0.001). During the 25 month period, adolescents of group E showed significant increases in BW, FFM and BMR (+8%, +14% and +10%, respectively, P < 0.001), and maintained their Z-score and FM. CONCLUSION: The reduction in BMR during the weight-reduction program at the institution could contribute to body weight regain in the post-obese adolescents if they do not maintain the lifestyle habits taught during the weight-reduction period. In other respects, Z-score was stabilized in 51% of domiciled obese adolescents.

Adipose Tissue↗
PubMedDate not supplied

A study of basal metabolic rate in adult Kashmiris.

Sixty two adults, including forty one males (16-36 yrs.) and twenty one females (16-25 yrs.), were studied by closed circuit method as regards their B.M.R. Males showed a greater lowering of metabolism than the females when compared to MF and AD standards. The females actually showed a higher B.M.R. than the RR standards. Both the sexes had a higher basal metabolism than the value reported from other parts of the country. The difference, however, was significant only in the case of females. Winter metabolism was not sigificantly higher than the summer value in either sex, though females showed some what greater variation.

Adolescent↗
PubMedDate not supplied

Locomotor mode, maximum running speed, and basal metabolic rate in placental mammals.

The locomotor performance (absolute maximum running speed [MRS]) of 120 mammals was analyzed for four different locomotor modes (plantigrade, digitigrade, unguligrade, and lagomorph-like) in terms of body size and basal metabolic rate (BMR). Analyses of conventional species data showed that the MRS of plantigrade and digitigrade mammals and lagomorphs increases with body mass, whereas that of unguligrade mammals decreases with body mass. These trends were confirmed in plantigrade mammals and lagomorphs using phylogenetically independent contrasts. Multiple regression analyses of MRS contrasts (dependent variable) as a function of body mass and BMR contrasts (predictor variables) revealed that BMR was a significant predictor of MRS in the complete data set, as well as in plantigrade and nonplantigrade mammals. However, there was severe multicollinearity in the nonplantigrade model that may influence the interpretation of these models. Although these data show mass-independent correlation between BMR and MRS, they are not necessarily indicative of a cause-effect relationship. However, the analyses do identify a negligible role of body size associated with MRS once phylogenetic and BMR effects are controlled, suggesting that the body size increase in large mammals over time (i.e., Cope's rule) can probably rule out MRS as a driving variable.

Animals↗