PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “BASAL METABOLISM”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed1989

Intraspecific allometry of basal metabolic rate: relations with body size, temperature, composition, and circadian phase in the kestrel, Falco tinnunculus.

The relationship between body size and basal metabolic rate (BMR) in homeotherms has been treated in the literature primarily by comparison between species of mammals or birds. This paper focuses on the intraindividual changes in BMR when body mass (W) varies with different maintenance regimens. BMR varied in individual kestrels in proportion to W1.67, which is considerably steeper than the mass exponents for homomorphic change (0.667; Heusner, 1984) for interspecific comparison among all birds (0.677) or raptors (0.678), for interindividual comparison of kestrels on ad libitum maintenance regimens (0.786), and for mass proportionality (1.00). The circadian range of telemetered core temperature also varied more strongly with intraindividual than with interspecific (Aschoff, 1981a) variation in mass. This was due to reduced nocturnal core temperature at low-maintenance regimens, which was, however, insufficient to account for the excessive reduction in BMR. kidney lean mass at Carcass analysis of eight birds sacrificed revealed a disproportionate reduction in heart and kidney lean mass at low-maintenance regimens. We surmise that variation in BMR primarily reflects variation in these metabolically highly active tissues. This may account for positive correlations found between heart, kidney, and BMR residuals relative to interspecific allometric prediction, and between alpha and rho residuals, as expected on the basis of the constant excess of BMR during alpha above BMR during rho (Aschoff & Pohl, 1970a).

Animals↗
PubMed1998

The basal metabolic rate and energy cost of standardised walking of short and tall men.

OBJECTIVES: To assess the influence of stature on the basal metabolic rate (BMR) and on the energy cost of standardised walking. A second objective was assess the accuracy of the FAO/UNU/WHO (1985) equations to predict BMR. DESIGN/SUBJECTS: Forty-six young men were selected on the basis of their stature and assigned to the group of short, S (n = 25, mean stature = 1.65 +/- 0.03 m) or of tall, T (n = 21, mean stature = 1.87 +/- 0.04 m). SETTING: Rome, Italy. INTERVENTIONS: Body composition was assessed by underwater weighing. BMR and energy cost walking at 5 km/h was measured by the Douglas bag. RESULTS: Body fat % was similar in the two groups (15.2 +/- 4.3 for S; 17.4 +/- 5.3 for T; ns). The BMR of T was 20% higher than that of S, but 12% and 10% lower when standardised respectively for body weight (BW) and fat free mass (FFM). However these differences were removed when BMR was covaried for BW or FFM, or normalised by BW0.62 or FFM0.64. Measured BMR was 7% for T and 6% for S lower than that predicted by the FAO/WHO/UNU (1985) equation; the inclusion of stature did not reduce the overestimation. The energy cost of walking was 27% higher in T than in S, but 9% and 5% lower when standardised respectively for BW and FFM. The differences disappeared when expressing the energy cost of walking as net cost per kg FFM. CONCLUSIONS: Tall people have lower BMR per unit of BW or FFM than short people, and it is necessary to control for the diverse body mass by the appropriate method. However, qualitative differences in the composition of FFM are plausible, due to the diverse proportion of metabolically active internal organs in people of different height, which might be reflected in the higher BMR/kg FFM of the shorter subjects. The sex- and age-specific FAO/WHO/UNU (1985) equation significantly overestimates the BMR of both short and tall people, but there is no simple explanation of this observation. The energy cost of walking is not affected by stature when expressed as net cost per kg FFM.

Adipose Tissue↗
PubMed1988

Overnight and basal metabolic rates in men and women.

The FAO/WHO/UNU recommendations for energy requirements assume that the energy cost of sleep is equal to the basal metabolic rate (BMR). We have tested the validity of this assumption by analysing overnight and BMR measurements made by whole-body indirect calorimetry. Data from 80 healthy subjects measured on a total of 246 occasions have been used. In a subgroup of 40 normal lean subjects the mean ratio of overnight metabolic rate (Overnight MR): BMR was 0.95 (range 0.85 - 1.02, s.d. 0.04). The mean ratio of lowest sleeping metabolic rate (Lowest SMR): BMR was 0.88 (range 0.83 - 0.96, s.d. 0.04). Ratios of Overnight MR: BMR were not significantly affected by different levels of exercise on the preceding day. This ratio was significantly higher for subjects who were obese, late pregnant or attached to ECG electrodes. With the exception of the late pregnant subjects these groups had the same Lowest SMR:BMR ratios as the normal lean subjects, indicating that the higher Overnight MR was caused by disturbed sleep. The data suggest that the use of BMR to estimate overnight energy expenditure would introduce an average overestimate of approximately 5 per cent during the actual hours of sleep, but that when applied over 24 h the error becomes negligible.

Adult↗
PubMed1996

A longitudinal study of changes in body composition and basal metabolism in physically active elderly men.

Ageing in the elderly is usually characterised by loss of fat-free mass (FFM) and reduction in basal metabolic rate (BMR). These age-related changes probably vary in rate, timing and extent between subjects in response to differences in leisure or occupational physical activity, disease and several other factors. Information on rates of change in BMR and FFM is limited by study design (most published work is cross-sectional rather than longitudinal), and possibly by methodology (use of imprecise and/or biased methods for assessment of changes in body composition). In the present study BMR and body composition were first measured in 22 physically active elderly men (mean age 62) in good health and measurements were repeated 6.5 years later. Changes in BMR, FFM and percentage body fat were small and not statistically significant over the time period (paired t, P > 0.05). The study suggests that physically active elderly men in good health in this age range can show very small age-related declines in BMR and FFM.

Aged↗
PubMed1987

Contribution of whole-body protein synthesis to basal metabolism in layer and broiler chickens.

The effect of starvation on whole-body protein synthesis and on the contribution of protein synthesis to basal metabolic rate was investigated in young chickens (Expt 1). Strain differences between layer and broiler chickens in whole-body protein synthesis and degradation rates were examined when the birds were starved (Expt 2). In Expt 1, 15-d-old White Leghorn male chickens were used, while in Expt 2 Hubbard (broiler) and White Leghorn (layer) male chickens at 14 d of age were used. They were starved for 4 d, and heat production was determined by carcass analysis after 2 and 4 d of starvation. Whole-body protein synthesis rates were measured on 0, 2 and 4 d of starvation (Expt 1), and on 0 and 4 d of starvation (Expt 2). The results showed that starving reduced whole-body protein synthesis in terms of fractional synthesis rate and the amount synthesized. Whole-body protein degradation was increased by starvation both in terms of fractional synthesis rate and the amount degraded on a per kg body-weight basis. Reduced fractional synthesis rate of protein in the whole body was accounted for by reductions in both protein synthesis per unit RNA and RNA:protein ratio. In the fed state, whole-body protein synthesis and degradation rates, whether expressed as fractional rates or amounts per unit body-weight, tended to be higher in layer than in broiler chickens. In the starved state, the difference in the rate of protein synthesis between the two strains virtually disappeared, while the degradation rates were higher in layer than in broiler birds.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Nutritional Physiological Phenomena↗
PubMed2000

Flexibility in basal metabolic rate and evaporative water loss among hoopoe larks exposed to different environmental temperatures.

The 'energy demand' hypothesis for short-term adjustments in basal metabolic rate (BMR) posits that birds adjust the size of their internal organs relative to food intake, a correlate of energy demand. We tested this hypothesis on hoopoe larks (Alaemon alaudipes), inhabitants of the Arabian desert, by acclimating birds for 3 weeks at 15 degrees C and at 36 degrees C, then measuring their BMR and total evaporative water loss (TEWL). Thereafter, we determined the dry masses of their brain, heart, liver, kidney, stomach, intestine and muscles of the pectoral region. Although mean body mass did not differ initially between the two groups, after 3 weeks, birds in the 15 degrees C group had gained mass (44.1+/-6.5 g), whereas larks in the 36 degrees C group had maintained a constant mass (36.6+/-3.6 g; means +/- s.d., N=6). Birds in the 15 degrees C group had a mean BMR of 46.8+/-6.9 kJ day(-1), whereas birds in the 36 degrees C group had a BMR of 32.9+/-6.3 kJ day(-1), values that were significantly different when we controlled for differences in body mass. When measured at 35 degrees C, larks in the cold-exposure group had a TEWL of 3.55+/-0.60 g H(2)O day(-)(1), whereas TEWL for birds in the 36 degrees C group averaged 2.23+/-0.28 g H(2)O day(-1), a difference of 59.2%. Mass-independent TEWL differed significantly between groups. Larks in the 15 degrees C group had a significantly larger liver, kidney and intestine than larks in the 36 degrees C group. The total increase in organ mass contributed 14.3% towards the total mass increment in the cold exposure group. Increased food intake among larks in the cold group apparently resulted in enlargement of some of the internal organs, and the increase in mass of these organs required a higher rate of oxygen uptake to support them. As oxygen demands increased, larks apparently lost more evaporative water, but the relationship between increases in BMR and TEWL remains unresolved.

Acclimatization↗
PubMed2005

Basal metabolic rate and thyroid hormones of late-middle-aged and older human subjects: the ZENITH study.

OBJECTIVE: This paper describes baseline data on basal metabolic rate (BMR), thyroid hormone levels and body composition of middle-aged and older people participating in the ZENITH project and the correlation of thyroid hormone levels with zinc status. DESIGN: A multicentre prospective intervention study employing a randomised double blind design. SETTING: Clermont-Ferrand, Theix (France), Coleraine (Northern Ireland), Grenoble (France), Rome (Italy). INTERVENTIONS: BMR has been measured on a subsample of 70 middle-aged volunteers (35 men and 35 women recruited in Clermont-Ferrand, France, aged 55-70 y) and 108 older volunteers (56 men and 52 women recruited in Rome, Italy, aged 70-85 y). Thyroid hormone levels were evaluated in the entire group of ZENITH volunteers (n = 387). BMR was measured by indirect calorimetry. Fat-free mass (FFM) was derived by four skinfold thicknesses using Durnin and Womersley's equations. Concentrations of thyroid hormones (total T3 and T4) were measured using a competitive immunoassay with an enhanced chemiluminescence end point. RESULTS: Italian older volunteers had a significantly lower FFM than middle-aged French volunteers (-7% P < 0.01). A negative correlation between BMR and age (men, r = -0.64; women, r = -0.62; both P < 0.0001) was observed: BMR was significantly (P < 0.000001) lower in Italian elderly volunteers (4.03+/-0.46 kJ/min and 3.29+/-0.42 kJ/min for men and women, respectively) than in middle-aged French volunteers (4.84+/-0.45 kJ/min and 3.87+/-0.38 kJ/min for men and women, respectively), even after adjustment for FFM (-12%). No correlation has been observed between BMR and thyroid hormones both in French and Italian subjects. Total T4 (TT4) concentrations were lowest in middle-aged population (-10%, P < 0.0001). A moderate negative correlation has been found with TT4 and red blood cell zinc (r = -0.12, P < 0.02, slope -0.026). CONCLUSIONS: The results confirm an age-related decline in BMR not entirely explained by body composition or thyroid hormones differences.

Age Factors↗
PubMed1992

Energy supplementation reverses changes in the basal metabolic rates of chronically undernourished individuals.

The objective of the present study was to examine the influence of energy supplementation and its cessation thereafter on the basal metabolic rates (BMR) of chronically undernourished individuals. Seven apparently healthy males were supplemented daily with 3.35 MJ (15 g protein, 35 g fat, 105 g carbohydrate) for 12 weeks. The average gain in body-weight was 1.9 kg (body fat, 58%; fat-free mass (FFM), 42%). The rise in BMR exceeded that accounted for by the increases in FFM during the 12 weeks of supplementation and was attributed to increases in the amount and activity of the visceral tissue as well as to an added cost of lipogenesis. At 12 weeks after cessation of the supplement, body-weights and FFM had decreased to presupplementation levels. BMR at this stage were significantly lower than at the 12th week of supplementation, when expressed per kg FFM or when adjusted for FFM using an analysis of covariance. These results suggest an increase in the metabolic efficiency during this negative energy balance period. The study demonstrates that, in the chronically undernourished, the changes in BMR are reversible and, hence, physiologically important to the process of adaptation to low-energy intakes.

Adaptation, Physiological↗
PubMed2001

The prediction of basal metabolic rate in female patients with anorexia nervosa.

OBJECTIVE: To evaluate in female patients with anorexia nervosa the accuracy of a specific predictive formula for basal metabolic rate (BMR) already proposed in the literature and to derive a new disease-specific equation with the same purpose. DESIGN: Cross-sectional study. SUBJECTS: One-hundred and twenty adolescent girls (<18 y) and young-adult women (18-30 y) with anorexia nervosa. MEASUREMENTS: BMR was determined by indirect calorimetry or predicted according to the Schebendach formula, which was specifically derived for anorexia nervosa. RESULTS: On average the Schebendach formula performed well in the adolescent group but not in the young-adult group. The range including 95% of the predicted-measured differences was in both cases wider than 2000 kJ/day. In the young-adult patients the accuracy of the prediction was also related to age and body mass index. Weight and age (but not height or body mass index) emerged as predictors of BMR in the sample as a whole, and only weight when the two age groups were considered separately, thus leading to three different equations. The intercepts of these regression lines were very close and not significantly different from zero while their standard error of estimate was 500-550 kJ/day. CONCLUSION: The Schebendach formula is not very accurate in estimating the BMR of female anorectic patients. Moreover, in this group the relationship between BMR and weight was altered. The predictive formulas proposed by the present study have a reasonable prediction power.

Adolescent↗
PubMed1993

Basal metabolic rate in human subjects migrating between tropical and temperate regions: a longitudinal study and review of previous work.

A review of the studies of basal metabolic rate (BMR) in human subjects migrating between tropical and temperate countries is presented. Such an analysis showed conflicting results of BMR in tropical migrants when expressed as BMR/kg/d. Much of this confusion may be attributable to experimental design and poor selection of subjects. A longitudinal study of BMR in 18-30-year-old males migrating for the first time from a tropical to a temperate country (the UK) was undertaken to address disparities seen in the earlier reviewed work. BMR was measured in tropical migrants and their temperate resident peers serially from 2 to 3 weeks post-migration to up to 6 months later, making advances on previous studies which did not measure BMR so promptly post-migration, or conduct serial measurements. The tropical migrants recruited in this investigation were of high socioeconomic status and well nourished. BMR/kg/d was similar in tropical migrants and temperate residents, there being no time trend in either group through the course of the study. The BMR of both groups was similar to that of populations born and resident in temperate regions, in contrast to the lower BMRs of born and resident tropical peoples reported in the literature. It is suggested that these lower BMRs are the result of a different relationship of BMR with body weight in individuals who are undernourished and/or of low socio-economic status, the corollary of which is a lower body weight, stature and body mass index.

Adolescent↗