Resting and exercise energy use in Antarctica: effect of 50% restriction in temperate climate energy requirements

Case, H. Samuel; Reed, H. L.; Palinkas, Lawrence A.; Reedy, Kathleen R.; Do, Nhan; Finney, Nancy S.; Seip, Richard L.

doi:10.1111/j.1365-2265.2006.02588.x

Cited by 11 publications

(12 citation statements)

References 43 publications

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“…Further, Antarctic workers have generally been reported to have expended more energy than workers in the United Kingdom (13,14). With the exception of the extrapolated data from the McMurdo study (2) and the work of Taylor et al (15) (which itself was performed 15 years ago), none of these studies is less than 29 years old. While the polar environment has not changed greatly in this period of time, the work and living conditions of polar residents have.…”

Section: Food Intakementioning

confidence: 99%

“…Metabolic rate is known to increase in response to cold environmental conditions as a means of maintaining thermal balance (2,3,18). Since basal metabolic rate (BMR, roughly equivalent to resting metabolic rate, RMR) forms a large percentage of total energy expenditure, it may well contribute to an increased energy requirement of personnel living in polar regions.…”

Section: Increase In Basal Metabolismmentioning

confidence: 99%

“…Those living and working in Antarctica are exposed to environmental stressors including cold temperatures, extremes of photoperiod, seasonally affected activity levels, dry air and high electromagnetic radiation. Psychological factors such as geographic and social isolation also have a significant impact (2,3). For several months of the year there is 24-hour daylight or 24-hour darkness.…”

Section: Introductionmentioning

confidence: 99%

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The effect of Antarctic residence on energy dynamics and aerobic fitness

Simpson

2010

International Journal of Circumpolar Health

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Objective. To review the current literature that describes the effect of Antarctic residence on energy dynamics and aerobic fitness. Study design. Literature review. Methods. Published literature on energy dynamics and aerobic fitness in the polar environment was reviewed. Energy dynamics were represented by body weight, body fat, food intake and energy expenditure. Consideration was given to seasonal variation and possible explanations for the apparent high metabolic cost of Antarctic residence. The influence of cold exposure was discussed and comment was made on the differences between temperate and polar residence. Results. Food intake and energy expenditure are found to increase with Antarctic residence. There is often an associated increase in body weight and body fat. Seasonal variation is common but not universal, with an increase in body weight and body fat in winter. Variation in aerobic fitness appears to be related to the specific study sample rather than Antarctic residence per se. Conclusions. In most instances, Antarctic residence has effects on energy dynamics and aerobic fitness. Explanations for the observed changes may include physiological adaptations, such as a raised basal metabolic rate and increased thermogenesis. However, cold-induced changes are less likely when cold exposure is minimized by heated buildings and insulated clothing. Activity patterns related to work and leisure thus represent a more likely cause. The majority of the research is several decades old; further research would help to elucidate the patterns of energy dynamics of modern Antarctic workers. (Int J Circumpolar Health 2010; 69(3):220-235)

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Section: Food Intakementioning

confidence: 99%

Section: Increase In Basal Metabolismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The effect of Antarctic residence on energy dynamics and aerobic fitness

Simpson

2010

International Journal of Circumpolar Health

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“…Additionally, a small decline in serum-free triiodothyronine (fT 3 ) and free thyroxine (fT 4 ), a doubling in both T 3 distribution volume and plasma appearance and clearance rate, as well as a small decrease in T 4 distribution volume further help define this condition (4,7). Physiologically, and presumably as part of hypothermic cold adaptation (5), polar expeditioners in the Antarctic have been found to experience a fall in body temperature (8) and an apparent 70% increase in daily energy requirements (3,9). A similar seasonal pattern of alteration in thyroid hormones has also been observed in residents living in the Arctic (10).…”

Section: Introductionmentioning

confidence: 99%

Psychoneuroendocrine effects of combined thyroxine and triiodothyronine versus tyrosine during prolonged Antarctic residence

Palinkas

Reedy

Smith

et al. 2007

International Journal of Circumpolar Health

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Objectives. We previously reported that cognitive function improves with thyroxine and that there is a circannual pattern to mood and human TSH during Antarctic residence. To extend these findings, we examined the effects of tyrosine and a combined levothyroxine/ liothyronine supplement in euthyroid men and women who spent the austral summer (n=43) and/or winter (n=42) in Antarctica. Study Design. Randomized, placebo-controlled, clinical trial. Methods. Subjects were randomized to receive the following each day for 91.6±3.2 days in summer and/or 138.0± 3.2 days in winter: (1) 12g tyrosine mixed in 113g applesauce; (2) 50ug of levothyroxine and 12.5ug of liothyronine (T4-T3 Supplement); or (3) placebo. Cognitive performance and mood were assessed using the Automatic Neuropsychological Assessment Metric -Isolated and Confined Environments. Effectiveness of thyroid supplement and tyrosine in Antarctica Results. With placebo in summer, mood did not change while TSH decreased by 28%; in winter, there was a 136% degradation in mood (p<0.01) and TSH increased by 18%. With combined T4-T3 supplement, there was a 51% degradation in mood in summer compared with placebo (p<0.05) and TSH decreased by 57%; in winter there was a 135% degradation in mood while TSH was reduced by 26% (p<0.05). Tyrosine use in summer was associated with no change in mood and a 30% decline in TSH, while in winter there was a 47% improvement in mood and TSH decreased by 28% along with a 6% increase in fT3 (p<0.05). Conclusions. Administration of tyrosine leads to a significant reduction in serum TSH and improvement in mood in winter compared with placebo, while the combined T4-T3 supplement leads to a worsening of mood in summer and no improvement in winter. There appears to be a seasonal influence on the psychological response to interventions and the relationship to changes in TSH reductions. (Int J Circumpolar Health 2007; 66(5):401-417)

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“…Human beings adapt to prolonged exposure to a cold environment by increasing metabolic and physiologic responses; after moving to the Antartic, energy requirements increase, as well as T 3 production, clearance and distribution, TRH-stimulated TSH release, TSH and thyroglobulin serum levels, while altered total and free TH levels may depend on altitude differences (Palinkas et al 2007). When exposed for 60 h to 50% energy restriction, humans loose considerable body weight but do not decrease TH or TSH serum levels as in temperate conditions, which indicates that cold stimulation overcomes the inhibition produced by food restriction (Case et al 2006).…”

Section: Stress and The Hpt Axismentioning

confidence: 93%

Regulation of TRH neurons and energy homeostasis-related signals under stress

Joseph‐Bravo

Jaimes-Hoy

Charlí

2015

Journal of Endocrinology

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Energy homeostasis relies on a concerted response of the nervous and endocrine systems to signals evoked by intake, storage, and expenditure of fuels. Glucocorticoids (GCs) and thyroid hormones are involved in meeting immediate energy demands, thus placing the hypothalamo-pituitary-thyroid (HPT) and hypothalamo-pituitary-adrenal axes at a central interface. This review describes the mode of regulation of hypophysiotropic TRHergic neurons and the evidence supporting the concept that they act as metabolic integrators. Emphasis has been be placed on i) the effects of GCs on the modulation of transcription of Trh in vivo and in vitro, ii) the physiological and molecular mechanisms by which acute or chronic situations of stress and energy demands affect the activity of TRHergic neurons and the HPT axis, and iii) the less explored role of non-hypophysiotropic hypothalamic TRH neurons. The partial evidence gathered so far is indicative of a contrasting involvement of distinct TRH cell types, manifested through variability in cellular phenotype and physiology, including rapid responses to energy demands for thermogenesis or physical activity and nutritional status that may be modified according to stress history.

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Resting and exercise energy use in Antarctica: effect of 50% restriction in temperate climate energy requirements

Abstract: Exercise-related energy requirements are increased with AR. Moderate ER may reduce resting but not exercise-related energy expenditure and it is associated with a weight loss exceeding expectations for 50% restriction of temperate climate energy predictions.

Cited by 11 publications

References 43 publications

The effect of Antarctic residence on energy dynamics and aerobic fitness

The effect of Antarctic residence on energy dynamics and aerobic fitness

Psychoneuroendocrine effects of combined thyroxine and triiodothyronine versus tyrosine during prolonged Antarctic residence

Regulation of TRH neurons and energy homeostasis-related signals under stress

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