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1.
  • Speakman, John R., et al. (författare)
  • Total daily energy expenditure has declined over the past three decades due to declining basal expenditure, not reduced activity expenditure
  • 2023
  • Ingår i: Nature Metabolism. - : NATURE PORTFOLIO. - 2522-5812. ; 5:4, s. 579-588
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Obesity is caused by a prolonged positive energy balance(1,2). Whether reduced energy expenditure stemming from reduced activity levels contributes is debated(3,4). Here we show that in both sexes, total energy expenditure (TEE) adjusted for body composition and age declined since the late 1980s, while adjusted activity energy expenditure increased over time. We use the International Atomic Energy Agency Doubly Labelled Water database on energy expenditure of adults in the United States and Europe (n = 4,799) to explore patterns in total (TEE: n = 4,799), basal (BEE: n = 1,432) and physical activity energy expenditure (n = 1,432) over time. In males, adjusted BEE decreased significantly, but in females this did not reach significance. A larger dataset of basal metabolic rate (equivalent to BEE) measurements of 9,912 adults across 163 studies spanning 100 years replicates the decline in BEE in both sexes. We conclude that increasing obesity in the United States/Europe has probably not been fuelled by reduced physical activity leading to lowered TEE. We identify here a decline in adjusted BEE as a previously unrecognized factor.
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2.
  • He, Rebecca S. S., et al. (författare)
  • Allometric scaling of metabolic rate and cardiorespiratory variables in aquatic and terrestrial mammals
  • 2023
  • Ingår i: Physiological Reports. - : WILEY. - 2051-817X. ; 11:11
  • Tidskriftsartikel (refereegranskat)abstract
    • While basal metabolic rate (BMR) scales proportionally with body mass (M-b), it remains unclear whether the relationship differs between mammals from aquatic and terrestrial habitats. We hypothesized that differences in BMR allometry would be reflected in similar differences in scaling of O-2 delivery pathways through the cardiorespiratory system. We performed a comparative analysis of BMR across 63 mammalian species (20 aquatic, 43 terrestrial) with a M-b range from 10 kg to 5318 kg. Our results revealed elevated BMRs in small (>10 kg and <100 kg) aquatic mammals compared to small terrestrial mammals. The results demonstrated that minute ventilation, that is, tidal volume (V-T)center dot breathing frequency (f(R)), as well as cardiac output, that is, stroke volume center dot heart rate, do not differ between the two habitats. We found that the "aquatic breathing strategy", characterized by higher V-T and lower f(R) resulting in a more effective gas exchange, and by elevated blood hemoglobin concentrations resulting in a higher volume of O-2 for the same volume of blood, supported elevated metabolic requirements in aquatic mammals. The results from this study provide a possible explanation of how differences in gas exchange may serve energy demands in aquatic versus terrestrial mammals.
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