Biomedical subjects

M J Toth

Publications and source records attributed to M J Toth.

72 records · Page 4Linked to original sources

PubMed1995

Sympathetic nervous system activity, body fatness, and body fat distribution in younger and older males.

It was hypothesized that an increase in total and central body fatness is related to higher sympathetic nervous system activity (SNSA) in older men. Resting SNSA was measured from norepinephrine (NE) kinetics in 69 younger (18-36 yr) and 69 healthy older men (55-80 yr). Body fat distribution was estimated from the waist circumference, body composition from underwater weighing, peak oxygen consumption from a treadmill test to exhaustion, and dietary intake from food diaries. Plasma NE concentrations were 41% higher (P < 0.001) in older men due to a 27% increase (P < 0.001) in NE appearance rate and a tendency for a lower NE clearance rate (P = 0.08). NE appearance rate was higher in individuals of both age groups who exhibited a greater waist circumference and body fatness (range of r values 0.49-0.69; P < 0.01). The waist circumference, and not age, was the strongest predictor of the increase in NE appearance rate in older men. Statistically controlling for the waist circumference or body fatness diminished age-related differences in NE concentrations and in NE appearance rate. These findings suggest that an accumulation of total and central body fat is associated with higher levels of SNSA in older males.

Adipose Tissue↗

PubMed1995

Exercise, substrate utilization and energy requirements in the elderly.

We consider the impact of endurance and resistance exercise on energy expenditure and substrate utilization in the elderly. We present data to show that endurance exercise increases resting metabolic rate in elderly men and women and these changes appear to be sympathetically mediated. Preliminary data also shows that vigorous endurance exercise causes a compensatory decline in energy expenditure during the non-exercising portion of the day, suggesting that this type of exercise prescription may actually be counter-productive to promoting fat loss. Several studies using resistance training interventions in older individuals suggests that this exercise mode also increases resting metabolic rate and basal sympathetic nervous system activity. The impact of age and endurance exercise on fat mobilization and oxidation are briefly considered. The major findings are that whole body fat oxidation decreased with advancing age and this decrease was primarily related to the age-associated decrease in fat-free mass. Furthermore, endurance training altered basal utilization patterns in the elderly by shifting disposal of fatty acids from nonoxidative to oxidative pathways and that increases in fat oxidation were related to the increase in norepinephrine appearance rate. Exercise interventions that preserve fat-free mass and/or enhance aerobic capacity may increase or maintain fat oxidation and possibly blunt the tendency towards increasing adiposity in older individuals.

Aged↗

PubMed1995

Resting metabolic rate and cardiovascular disease risk in resistance- and aerobic-trained middle-aged women.

OBJECTIVE: To examine differences in resting metabolic rate (RMR) and cardiovascular disease risk in middle-aged women differing in training status. DESIGN: Cross-sectional. SUBJECTS: Fifty-four healthy middle-aged women characterized as resistance-trained (RT; n = 8; 43 +/- 3 yrs), aerobic-trained (AT; n = 12; 42 +/- 5 yrs) or untrained (UT; n = 34; 44 +/- 4 yrs) according to habitual exercise practices. MEASUREMENTS: RMR, substrate oxidation, body composition, body fat distribution, supine blood pressure, peak oxygen consumption (peak VO2), dietary intake and fasting levels of plasma lipids and hormones. RESULTS: RMR was higher (P < 0.01) in AT and RT women compared to UT women, independent of differences in fat-free mass. No differences in RMR were noted between RT and AT groups. No differences in estimated rates of carbohydrate or fat oxidation were noted among groups. RT women displayed lower plasma cholesterol (P < 0.01), LDL-C (P < 0.01) and supine diastolic blood pressure (P < 0.05) compared to UT and AT women. No differences, however, were noted among groups for triglycerides, HDL-C, supine systolic blood pressure or the insulin to glucose ratio. Stepwise regression analysis revealed that fat mass accounted for the greatest portion of the variation in plasma cholesterol and LDL-C. Statistical control for fat mass diminished differences in these variables among the groups. CONCLUSION: (1) Resting energy requirements are higher in AT and RT middle-aged women compared to UT women, and (2) the lower fasting cholesterol and LDL-C in RT middle-aged women were primarily related to their lower amount of body fat.

Adult↗

PubMed1995

Body fatness and waist circumference are independent predictors of the age-associated increase in fasting insulin levels in healthy men and women.

OBJECTIVE: Elevated levels of fasting insulin increase the risk for coronary artery disease. In this study, we considered the independent contributions of age, total body fatness, abdominal fat distribution, peak aerobic capacity, leisure time physical activity, dietary intake, and fasting glucose levels to the age-associated increase in fasting insulin levels in healthy men and women. DESIGN: A cross-sectional analysis. SUBJECTS: A total of 427 healthy men and 293 healthy women age 18 to 90 years. MEASUREMENTS: Plasma glucose and insulin levels were measured in the fasted state and subjects were characterized for body fatness from underwater weighting, abdominal fat distribution from the waist circumference, peak VO2 from a treadmill test to exhaustion, leisure time physical activity from a structured interview and dietary intake from a 3-day food diary. The independent predictors of fasting insulin levels were determined by stepwise multiple regression analysis. RESULTS: Fasting insulin concentrations increased with age in both men (0.09 +/- 0.02 pmol/yr, unadjusted slope +/- SEE) and women (0.14 +/- 0.03 pmol/yr). In men, the major independent predictors of fasting insulin levels were percent body fat (r2 = 28%, P < 0.001) and waist circumference (r2 = 3% P < 0.001). Age, glucose concentration, and peak VO2 were small (1% each), but independent contributors to the variance in insulin levels. In women, the waist circumference (r2 = 18%, P < 0.001) and the fasting glucose concentration (r2 = 7%, P < 0.001) were the independent correlates of fasting insulin concentrations. CONCLUSIONS: Our data suggest that total adiposity and central body fat distribution are significant determinants of the increase in fasting insulin levels, whereas age, dietary intake, and levels of aerobic fitness and physical activity appear to be less important contributors to the variation in fasting insulin concentrations in healthy men and women.

Adolescent↗

PubMed1994

The pharmacophore of the human C5a anaphylatoxin.

We have determined which amino acids contribute to the pharmacophore of human C5a, a potent inflammatory mediator. A systematic mutational analysis of this 74-amino acid protein was performed and the effects on the potency of receptor binding and of C5a-induced intracellular calcium ion mobilization were measured. This analysis included the construction of hybrids between C5a and the homologous but unreactive C3a protein and site-directed mutagenesis. Ten noncontiguous amino acids from the structurally well-defined 4-helix core domain (amino acids 1-63) and the C-terminal arginine-containing tripeptide were found to contribute to the pharmacophore of human C5a. The 10 mostly charged amino acids from the core domain generally made small incremental contributions toward binding affinity, some of which were independent. Substitutions of the C-terminal amino acid Arg 74 produced the largest single effect. We also found the connection between these 2 important regions to be unconstrained.

Alanine↗

PubMed1994

Sympathetic nervous system activity and resting metabolic rate in vegetarians.

We examined the resting metabolic rate (RMR) and sympathetic nervous system activity of young male vegetarians (n = 17) and nonvegetarians (n = 40). Subjects were characterized for RMR by indirect calorimetry, norepinephrine kinetics from infusions of tritiated norepinephrine, energy and macronutrient intake from a 3-day food diary, and body composition by underwater weighing. Vegetarians reported a greater relative intake of carbohydrates (62% +/- 5% v 51% +/- 6%, P < .01) and a lower relative intake of fat (25% +/- 5% v 33% +/- 6%, P < .01) than nonvegetarians, whereas no differences were observed in daily energy intake, body composition, or maximal aerobic capacity (VO2max) between groups. Vegetarians exhibited an 11% higher absolute RMR (1.29 +/- 0.15 v 1.16 +/- 0.13 kcal/min, P < .01), a higher plasma concentration of norepinephrine (216 +/- 33 v 165 +/- 18 pg/mL, P < .01), and a greater norepinephrine appearance rate (0.50 +/- 0.08 v 0.36 +/- 0.09 micrograms/min, P < .01) than nonvegetarians. After statistically controlling for differences in relative amounts of carbohydrate and fat in the diet and for norepinephrine concentrations, no significant differences in adjusted RMR between vegetarians and nonvegetarians were noted. These results suggest that the higher RMR observed in young male vegetarians is partially mediated by differences in dietary macronutrient composition and increased sympathetic nervous system activity.

Adolescent↗

PubMed1994

Contribution of body composition and physical activity to age-related decline in peak VO2 in men and women.

We examined the contribution of variations in body composition and leisure time physical activity to the age-related decline in peak oxygen consumption (VO2) in men and women. Healthy males 17-80 yr old (n = 378) and females 18-81 yr old (n = 224) were characterized for peak VO2 from a treadmill test to exhaustion, fat-free mass and fat mass by underwater weighing, and leisure time physical activity. Peak VO2 showed a greater absolute decline (P < 0.05) with age in males (r = -0.70, slope = -0.034 l.min-1.yr-1; P < 0.01) than in females (r = -0.78, slope = -0.028 l.min-1.yr-1; P < 0.01). After statistically controlling for differences in fat-free mass and fat mass, the decline in peak VO2 was diminished in both sexes, although a greater rate of decline persisted in males (r = -0.47, slope = -0.016 l.min-1.yr-1; P < 0.01) than in females (r = -0.39, slope = -0.009 l.min-1.yr-1; P < 0.01). We found that the addition of leisure time physical activity (independent of body composition) to the regression model further attenuated the rate of decline in males (r = -0.40, slope = -0.013 l.min-1.yr-1; P < 0.01) but did not alter the age-related decline in peak VO2 in females (r = -0.39, slope = -0.009 l.min-1.yr-1; P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗

PubMed1993

Determinants of decline in resting metabolic rate in aging females.

We considered the association of several metabolic and lifestyle variables as modulators of the decline in resting metabolic rate (RMR) and fat-free weight (FFW) in 183 healthy females (18-81 yr). RMR showed a curvilinear decline with age, which was significant in women aged 51-81 yr but not in women aged 18-50 yr. FFW showed a curvilinear decline with age, which was significant (P < 0.01) in women 48-81 yr but not in women 18-47 yr. The decline in RMR was primarily associated with the loss of FFW (r2 = 72%), whereas the decline in FFW was explained primarily by differences in maximal O2 consumption (VO2max), age, leisure time physical activity, and dietary protein intake (total r2 = 46%). We conclude that RMR and FFW showed a curvilinear decline with age which was accelerated beyond the middle-age years. Second, the age-related decline in RMR was primarily associated with the loss of FFW. Third, the loss of FFW was partially related to a decrement in VO2max and nutritional factors. Therapeutic interventions designed to increase VO2max by elevating physical activity may preserve fat-free weight and thus offset the decline of RMR in aging women.

Adolescent↗

PubMed1993

Examination of data normalization procedures for expressing peak VO2 data.

Peak O2 uptake (VO2) has traditionally been compared among individuals differing in body composition by dividing measured values (1/min) by fat-free mass (FFM) (i.e., ratio method). However, the ability of the ratio method to mathematically remove the confounding influence of FFM from peak VO2 has recently been questioned. Therefore, we compared the effectiveness of the ratio method vs. regression modeling to normalize peak VO2 in a large cohort of males and females for differences in FFM. Regression modeling adjusts peak VO2 according to the relationship derived from the regression of peak VO2 on FFM. Results showed that peak VO2 was 60% higher in males (3.53 +/- 1.01/min) than in females (2.22 +/- 0.6 l/min; P < 0.01). With the ratio method (i.e., peak VO2/FFM), peak VO2 was 15% higher in males (54.6 +/- 12 ml.kg FFM-1.min-1) than in females (47.4 +/- 11 ml.kg FFM-1.min-1; P < 0.01). In contrast, when a regression-based approach was employed to normalize values, no significant difference in adjusted peak VO2 was observed between males and females (3.04 +/- 0.9 vs. 3.01 +/- 1.0 l/min). In conclusion, dividing peak VO2 by FFM can produce spurious results, because this approach does not take into account the nonzero intercept. Therefore, a regression-based approach should be used to normalize peak VO2.

Adolescent↗

PubMed1993

Sodium-potassium pump activity contributes to the age-related decline in resting metabolic rate.

We examined the hypothesis that a decline in Na-K pump activity contributes to the lower resting metabolic rate (RMR) in older males, independent of the loss of fat-free mass. Plasma and erythrocyte Na and K concentrations were measured using flame photometry. Changes in these concentrations after incubation with and without ouabain were used to calculate erythrocyte Na-K pump rate and rate constant in 27 younger (28 +/- 7 yr) and 25 older (67 +/- 6 yr) men. Older men showed an 18% lower erythrocyte Na-K pump rate constant (0.32 +/- 0.09 vs. 0.39 +/- 0.10 h-1; P < 0.01), a 12% lower RMR (1.10 +/- 0.14 vs. 1.25 +/- 0.14 kcal/min; P < 0.01) and an 8% lower level of fat-free mass (61.7 +/- 5.8 vs. 67.4 +/- 8.1 kg; P < 0.01) relative to younger men. A lower RMR persisted in older men (1.14 +/- 0.12 kcal/min) compared to younger men (1.21 +/- 0.12 kcal/min; P < 0.05) after control for the effect of fat-free mass. No differences in RMR were found, however, between older (1.17 +/- 0.13 kcal/min) and younger men (1.20 +/- 0.13 kcal/min) after controlling for both fat-free mass and the erythrocyte Na-K pump rate constant. A positive relation was noted between RMR and the erythrocyte Na-K pump rate constant, after removing the effects of fat-free mass (partial r = 0.30; P < 0.05). Our results support the conclusions that: 1) the in vivo activity of the Na-K pump is related to RMR, and 2) the age-related reduction in Na-K pump activity is a partial contributor to the decline in RMR in older men.

Adult↗

PubMed1990

A mutation in the small (alpha) subunit of glycyl-tRNA synthetase affects amino acid activation and subunit association parameters.

A strategy was designed to isolate mutants of glycyl-tRNA synthetase that are altered at the amino acid binding site, including a class with altered amino acid specificity. For this purpose, the plasmid pBR322 was mutated so that the codon (AGC) of the active site Ser-68 in the beta-lactamase gene was changed to the glycine codon GGC to inactivate the encoded enzyme. Suppressors that increase the amount of beta-lactamase activity of the Gly-68 allele of beta-lactamase were isolated and some mapped to the gene encoding glycyl-tRNA synthetase (glyS). While in vitro misaminoacylation of tRNA(Gly) with serine was not detected for any of the mutants, glycyl-tRNA synthetase activity was altered. One severely affected glyS mutant (N302) was studied in more detail. For this mutant, a single Pro-61----Leu substitution in the alpha chain confers an elevation of the Km values for glycine (25-fold) and for ATP (45-fold) in the aminoacylation reaction, but only a minor perturbation of the Km for tRNA. There also was a severely reduced adenylate synthesis activity (greater than 100-fold). In addition, a nonlinear dependence between aminoacylation activity and enzyme concentration was observed which implies that the alpha chain Pro-61----Leu mutation has disrupted the functionally essential subunit interactions of the holoenzyme. The results of the preceding paper have shown that the alpha chain and parts of the beta chain are required for aminoacylation and adenylate synthesis activity. The results of this study suggest that the alpha chain specifically contributes to amino acid and to ATP binding in a way that is affected by proper subunit interactions.

Alleles↗

PubMed1990

Deletions in the large (beta) subunit of a hetero-oligomeric aminoacyl-tRNA synthetase.

Glycyl-tRNA synthetase is one of two aminoacyl-tRNA synthetases in Escherichia coli that is comprised of heterologous subunits which are organized in an alpha 2 beta 2 quaternary structure. The two subunits are encoded by a single mRNA with the region for alpha (303 codons) subunit followed by that for beta (689 codons) subunit. Five COOH-terminal deletions in the beta subunit coding region have been created. Each deletion protein has been investigated for its synthesis and stability in vivo, adenylate synthesis activity in vitro, and aminoacylation activity in vivo and in vitro. This has been done in the presence of free alpha subunit and, additionally, with alpha subunit that is fused by its carboxyl terminus to the amino terminus of each of the beta subunit deletion proteins. With a fused or unfused alpha chain, over 100 amino acids can be deleted from the carboxyl terminus of the beta chain without loss of in vivo complementation of a delta glyS (deletion) strain. Further analysis shows that the alpha subunit and approximately the amino-terminal half of the beta subunit are sufficient for the adenylate synthesis activity. In particular, a deletion of 306 amino acids from the COOH terminus of the beta subunit has little effect on the Km parameter for ATP or glycine in the pyrophosphate exchange reaction. The tRNA-dependent step in aminoacylation requires additional beta subunit sequences on the COOH-terminal side of those needed for adenylate synthesis. In these respects, the functional organization of the beta chain parallels that of several aminoacyl-tRNA synthetases which have only homologous subunits. In the case of the glycine enzyme, however, the heterologous alpha subunit is required for the elucidation of activities encoded by functional determinants of the beta chain.

Amino Acyl-tRNA Synthetases↗

PubMed1988

Evidence for a unique first position codon-anticodon mismatch in vivo.

The Ser68(AGC) codon of the beta-lactamase gene was changed to the glycine codons GGA and GGC. With glycine at position 68, beta-lactamase is inactive because it does not have a nucleophilic side-chain to function in the reaction mechanism. The mutant SG68(GGA) allele had no detectable beta-lactamase activity; however, the mutant SG68(GGC) did produce a small amount of activity. Both mutant alleles produce comparable amounts of beta-lactamase protein in a maxi-cell system. To identify why these two "same-sense" beta-lactamase mutants differ phenotypically, we introduced the alleles into Escherichia coli strains with mutations that affect translational fidelity. The rpsD mutation, which decreases fidelity, significantly increased activity with the SG68(GGC) allele, while the rpsL mutation, which increases translational fidelity, had little effect on the beta-lactamase activity. The rpsD and rpsL alleles had no effect on the SG68(GGA) allele. From the allele specificity of the activity produced by the bla mutants, and from the differential effect of translational fidelity on the activity of the SG68(GGC) allele, we infer that tRNA(GCU)Ser, the AGU/C reading tRNA(Ser), mistranslates SG68(GGC) at a frequency of about 0.1%, and subsequently produces active beta-lactamase. This is the first observation of an A/G wobble with a wild-type tRNA at the first position of the codon-anticodon interaction.

Amino Acid Sequence↗

PubMed1986

Internal structural features of E. coli glycyl-tRNA synthetase examined by subunit polypeptide chain fusions.

In contrast to most aminoacyl-tRNA synthetases which are monomers or oligomers of a single polypeptide, Escherichia coli glycyl-tRNA synthetase has an alpha-2, beta-2 structure. The enzyme requires both subunits for catalysis of either adenylate or aminoacyl-tRNA synthesis. The head-to-tail arrangement of the alpha- and beta-chain coding regions in the genome suggests that the two-subunit protein may be tantamount to a single chain. We fused the carboxyl terminus of the alpha-chain to the amino terminus of the beta-chain, through a short peptide linker. Five different amino acid substitutions were placed in the linker. In all instances, the fusion polypeptide is stable in maxicell extracts. In a glyS null strain, a gene encoding any of the fusion proteins substitutes for the wild-type gene. Assays confirm that, in vitro, the engineered polypeptide fusion is active to within 2- to 3-fold of the wild-type, unfused chains. Oligomers of the fusion protein are observed and may be required for activity. Because the creation and limited manipulation of the artificial peptide linker region does not destroy the activity, we also conclude that the C-terminal part of the alpha-chain and the amino-terminal part of the beta-chain are not important for activity.

Amino Acyl-tRNA Synthetases↗

PubMed1983

Physical characterization of plasmids isolated from Streptosporangium.

Plasmids were isolated from two species of Streptosporangium by CsCl-ethidium bromide equilibrium density gradient centrifugation. A plasmid isolated from S. brasiliense, designated pSgB-1, was characterized by electron microscopy and agarose gel electrophoresis. The pSgB-1 plasmid is a closed circular DNA molecule of 9.4 X 10(6) Da. A restriction endonuclease map was generated and unique cleavage sites were found for EcoRI, ClaI, XbaI, and MstII. Another plasmid, pSgV-1, isolated from S. viridognriseum, has an estimated Mr of 54 X 10(6). The pSgB-1 plasmid is phenotypically cryptic but an unusual phenotypic trait, resembling phage plaques, may be associated with the S. viridogriseum plasmid pSgV-1.

Actinomycetales↗

PubMedDate not supplied

Influence of physiological factors on the age-related increase in blood pressure in healthy men.

The independent and collective influences of several physiological factors on the age-related increase in blood pressure in healthy men were examined. Twenty-seven younger and 25 older, mostly normotensive, healthy men were studied. Blood pressure, body fat, body fat distribution, maximal oxygen consumption (VO2max), plasma norepinephrine, dietary Na, and erythrocyte Na-K pump activity were measured. Older men showed 57% higher percent body fat, 40% higher plasma norepinephrine concentration, 14% greater mean arterial blood pressure (MAP), and 5% higher plasma K concentration than younger men (all p < 0.01). Older men showed a 38% (p < 0.01) lower VO2max, 19% (p < 0.05) lower energy intake, 18% (p < 0.05) lower Na-K pump rate constant, and a 17% (p < 0.05) lower Na-K pump rate. Group means for MAP were adjusted for combinations of plasma norepinephrine, waist:thigh ratio, VO2max, and the Na-K pump rate constant, to determine if any one variable or combination could account for the age related increase in MAP. Statistical adjustment for plasma norepinephrine, waist:thigh ratio, and Na-K pump rate constant eliminated the significant difference between MAPs for the two groups. Thus, alterations in sympathetic nervous system activity, body fat distribution, and the membrane Na-K pump activity independently contribute to the age-related increase in MAP in healthy men.

Adolescent↗

PubMedDate not supplied

Central markers of body fat distribution are important predictors of plasma lipids in elderly men and women.

We determined the contribution of body fat distribution, peak VO2, fat mass, and dietary intake to variation in plasma lipids in elderly individuals. Volunteers were a healthy cohort of older Caucasian women (n = 75, mean age +/- SD, 72 +/- 5 years) and older men (n = 101, 72 +/- 5 years). We determined fat mass from underwater weighing, fat patterning from waist circumference, as well as peripheral and truncal skinfolds, exercise capacity from peak VO2, and dietary intake from three-day food diaries. Plasma lipid levels were measured in the fasting state and included total cholesterol, high density lipoprotein (HDL-C), low density lipoprotein (LDL-C), and fasting triglycerides. Older women weighted less than older men, but had higher fat mass, truncal, and peripheral skinfolds. Waist circumference and peak VO2 were lower in older women than older men. Older women had higher total cholesterol (217 +/- 31 vs. 197 +/- 30; p < 0.01), HDL-C (54 +/- 12 vs. 49 +/- 14; p < 0.05), and LDL-C (133 +/- 26 vs. 121 +/- 27; p < 0.01) when compared with older men. No gender differences were noted in fasting triglycerides. Truncal skinfolds were the best predictor of plasma lipids in older men, accounting for between 9% and 30% (r2) of the variation in plasma lipids. Similarly, in older women, central markers of fatness (i.e., waist circumference and truncal skinfolds) were the best predictors of plasma lipids (r2 = 3% to 24%). Total fat mass, peak VO2 and dietary intake were not independent predictors of plasma lipids in older men and women. Indices of central body fatness, rather than total fat mass, peak VO2 or dietary intake are stronger predictors of plasma lipids in healthy older men and women.

Adipose Tissue↗

PubMedDate not supplied

Physiological predictors of increasing total and central adiposity in aging men and women.

BACKGROUND: Increasing levels of total and central body fat with advancing age contribute to the development of cardiovascular and metabolic disease. We examined gender-related differences and physiological predictors of the rate of increase in total and central body fat in men and women. METHODS: We studied 427 healthy men (age range, 17 to 90 years) and 293 women (age range, 18 to 88 years). We measured body fatness by hydrostatic weighing, central adiposity from the waist circumference, peak volume of oxygen utilization (VO2) from a treadmill test, leisure time physical activity (LTA) from a questionnaire, resting metabolic rate and respiratory quotient from indirect calorimetry, and energy intake from 3-day food diaries. RESULTS: Fat mass increased with age, and the rate was greater in women (r = .61; slope = 0.25 kg/y; P < .01) than in men (r = .43; slope = 0.16 kg/y; P < .01). Increasing fat mass in men and women was most strongly associated with declines in peak VO2 and LTA. Controlling for these variables reduced the increase in fat mass from 17% to 3% per decade in men and from 26% to 5% per decade in women. The increase in waist circumference with age was also greater in women (r = .53; slope = 0.28 cm/y) than in men (r = .39; slope = 0.18 cm/y; P < .01). Increasing waist circumference with age in men and women was most strongly associated with declines in LTA and peak VO2, respectively. Control for these variables reduced the age-related increase in waist circumference from 2% to 1% per decade in men and from 4% to 1% per decade in women. We observed no independent contribution of resting metabolic rate, respiratory quotient, menopause status, energy, or macronutrient intake to the age-related increase in fat mass and waist circumference. CONCLUSIONS: Our findings suggest that (1) the age-related increase in fat mass and waist circumference is greater in women than in men and (2) the physiological characteristics that reflect a decline in physical activity-related energy expenditure, rather than resting energy expenditure, are important predictors of the increases in total and central fatness. Lifestyle changes that increase the level of physical activity may be advantageous in blunting age-related increases in total and central body fatness.

Adipose Tissue↗