Brain and high metabolic rate organ mass: contributions to resting energy expenditure beyond fat-free mass

An enduring enigma is why the ratio of resting energy expenditure (REE) to metabolically active tissue mass, expressed as the REE/fat-free mass (FFM) ratio, is greater in magnitude in subjects with a small FFM than it is in subjects with a large FFM. This study tested the hypothesis that a higher REE/FFM ratio in subjects with a small body mass and FFM can be explained by a larger proportion of FFM as high-metabolic-rate tissues compared with that observed in heavier subjects. REE was measured by indirect calorimetry, FFM by dual-energy X-ray absorptiometry (DEXA), and tissue/organ contributions to FFM by whole body magnetic resonance imaging (MRI) in healthy adults. Four tissue heat-producing contributions to FFM were evaluated, low-metabolic-rate fat-free adipose tissue (18.8 kJ/kg), skeletal muscle (54.4 kJ/kg), and bone (9.6 kJ/kg); and high-metabolic-rate residual mass (225.9 kJ/kg). Initial evaluations in 130 men and 159 women provided strong support for two key, developed models, one linking DEXA FFM with MRI FFM estimates and the other linking REE predicted from the four MRI-derived components with measured REE. There was an inverse association observed between measured REE/FFM and FFM ( r 2 = 0.17, P < 0.001). Allometric models revealed a similar pattern of tissue change relative to body mass across males and females with greater proportional increases in fat-free adipose tissue and skeletal muscle than in FFM and a smaller proportional increase in residual mass than in FFM. When examined as a function of FFM, positive slopes were observed for skeletal muscle/FFM and pooled low-metabolic-rate components, and a negative slope for residual mass. Our linked REE-body composition models and associations strongly support the hypothesis that FFM varies systematically in the proportion of thermogenic components as a function of body mass and FFM. These observations have important implications for the interpretation of between-individual differences in REE expressed relative to metabolically active tissue mass.

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Small organs with a high metabolic rate explain lower resting energy expenditure in African American than in white adults

American Journal of Clinical Nutrition ◽

10.1093/ajcn/83.5.1062 ◽

2006 ◽

Vol 83 (5) ◽

pp. 1062-1067 ◽

Cited By ~ 82

Author(s):

Dympna Gallagher ◽

Jeanine Albu ◽

Qing He ◽

Stanley Heshka ◽

Lawrence Boxt ◽

...

Keyword(s):

African American ◽

Energy Expenditure ◽

Metabolic Rate ◽

Resting Energy Expenditure ◽

High Metabolic Rate ◽

White Adults ◽

Resting Energy

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Current Predictive Resting Metabolic Rate Equations Are Not Sufficient to Determine Proper Resting Energy Expenditure in Olympic Young Adult National Team Athletes

Frontiers in Physiology ◽

10.3389/fphys.2021.625370 ◽

2021 ◽

Vol 12 ◽

Author(s):

Aydın Balci ◽

Ebru Arslanoğlu Badem ◽

Ayfer Ezgi Yılmaz ◽

Aslı Devrim-Lanpir ◽

Bihter Akınoğlu ◽

...

Keyword(s):

Energy Expenditure ◽

Metabolic Rate ◽

Female Athletes ◽

Resting Metabolic Rate ◽

Resting Energy Expenditure ◽

Mean Difference ◽

Fat Free Mass ◽

Male Athletes ◽

National Team ◽

Resting Energy

Predictive resting metabolic rate (RMR) equations are widely used to determine athletes’ resting energy expenditure (REE). However, it remains unclear whether these predictive RMR equations accurately predict REE in the athletic populations. The purpose of the study was to compare 12 prediction equations (Harris-Benedict, Mifflin, Schofield, Cunningham, Owen, Liu’s, De Lorenzo) with measured RMR in Turkish national team athletes and sedentary controls. A total of 97 participants, 49 athletes (24 females, 25 males), and 48 sedentary (28 females, 20 males), were recruited from Turkey National Olympic Teams at the Ministry of Youth and Sports. RMR was measured using a Fitmate GS (Cosmed, Italy). The results of each 12 prediction formulas were compared with the measured RMR using paired t-test. The Bland-Altman plot was performed to determine the mean bias and limits of agreement between measured and predicted RMRs. Stratification according to sex, the measured RMR was greater in athletes compared to controls. The closest equation to the RMR measured by Fitmate GS was the Harris-Benedict equation in male athletes (mean difference -8.9 (SD 257.5) kcal/day), and Liu’s equation [mean difference -16.7 (SD 195.0) kcal/day] in female athletes. However, the intra-class coefficient (ICC) results indicated that all equations, including Harris-Benedict for male athletes (ICC = 0.524) and Liu’s for female athletes (ICC = 0.575), had a moderate reliability compared to the measured RMR. In sedentary subjects, the closest equation to the measured RMR is the Nelson equation in males, with the lowest RMSE value of 118 kcal/day [mean difference: 10.1 (SD 117.2) kJ/day], whereas, in females, all equations differ significantly from the measured RMR. While Nelson (ICC = 0.790) had good and Owen (ICC = 0.722) and Mifflin (calculated using fat-free mass) (ICC = 0.700) had moderate reliability in males, all predictive equations showed poor reliability in females. The results indicate that the predictive RMR equations failed to accurately predict RMR levels in the participants. Therefore, it may not suitable to use them in determining total energy expenditure.

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Effects of Television on Metabolic Rate: Potential Implications For Childhood Obesity

PEDIATRICS ◽

10.1542/peds.91.2.281 ◽

1993 ◽

Vol 91 (2) ◽

pp. 281-286

Author(s):

Robert C. Klesges ◽

Mary L. Shelton ◽

Lisa M. Klesges

Keyword(s):

Energy Expenditure ◽

Metabolic Rate ◽

Television Viewing ◽

Resting Energy Expenditure ◽

Normal Weight ◽

Laboratory Setting ◽

Obese Children ◽

Two Measures ◽

The Relationship ◽

Resting Energy

The effects of television viewing on resting energy expenditure (metabolic rate) in obese and normal-weight children were studied in a laboratory setting. Subjects were 15 obese children and 16 normal-weight children whose ages ranged from 8 to 12 years. All subjects had two measures of resting energy expenditure obtained while at rest and one measurement of energy expenditure taken while viewing television. Results indicated that metabolic rate during television viewing was significantly lower (mean decrease of 211 kcal extrapolated to a day) than during rest. Obese children tended to have a larger decrease, although this difference was not statistically significant (262 kcal/d vs 167 kcal/d, respectively). It was concluded that television viewing has a fairly profound lowering effect of metabolic rate and may be a mechanism for the relationship between obesity and amount of television viewing.

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Resting Energy Expenditure in Obese Women with Primary Hypothyroidism and Appropriate Levothyroxine Replacement Therapy

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/clinem/dgaa097 ◽

2020 ◽

Vol 105 (4) ◽

pp. e1741-e1748 ◽

Cited By ~ 3

Author(s):

Emanuele Muraca ◽

Stefano Ciardullo ◽

Alice Oltolini ◽

Francesca Zerbini ◽

Eleonora Bianconi ◽

...

Keyword(s):

Body Composition ◽

Energy Expenditure ◽

Replacement Therapy ◽

Resting Energy Expenditure ◽

Primary Hypothyroidism ◽

Normal Serum ◽

Fat Free Mass ◽

Model Assessment ◽

Obese Women ◽

Resting Energy

Abstract Context Growing evidence suggests that appropriate levothyroxine (LT4) replacement therapy may not correct the full set of metabolic defects afflicting individuals with hypothyroidism. Objective To assess whether obese subjects with primary hypothyroidism are characterized by alterations of the resting energy expenditure (REE). Design Retrospective analysis of a set of data about obese women attending the outpatients service of a single obesity center from January 2013 to July 2019. Patients A total of 649 nondiabetic women with body mass index (BMI) > 30 kg/m2 and thyrotropin (TSH) level 0.4–4.0 mU/L were segregated into 2 groups: patients with primary hypothyroidism taking LT4 therapy (n = 85) and patients with normal thyroid function (n = 564). Main outcomes REE and body composition assessed using indirect calorimetry and bioimpedance. Results REE was reduced in women with hypothyroidism in LT4 therapy when compared with controls (28.59 ± 3.26 vs 29.91 ± 3.59 kcal/kg fat-free mass (FFM)/day), including when adjusted for age, BMI, body composition, and level of physical activity (P = 0.008). This metabolic difference was attenuated only when adjustment for homeostatic model assessment of insulin resistance (HOMA-IR) was performed. Conclusions This study demonstrated that obese hypothyroid women in LT4 therapy, with normal serum TSH level compared with euthyroid controls, are characterized by reduced REE, in line with the hypothesis that standard LT4 replacement therapy may not fully correct metabolic alterations related to hypothyroidism. We are not able to exclude that this feature may be influenced by the modulation of insulin sensitivity at the liver site, induced by LT4 oral administration.

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