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Resting and exercise energy use in Antarctica: effect of 50% restriction in temperate climate energy requirements
Author(s) -
Case H. Samuel,
Reed H. Lester,
Palinkas Lawrence A.,
Reedy Kathleen R.,
Van Do Nhan,
Finney Nancy S.,
Seip Richard
Publication year - 2006
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.2006.02588.x
Subject(s) - basal metabolic rate , medicine , zoology , endocrinology , resting energy expenditure , energy requirement , basal (medicine) , energy expenditure , chemistry , energy metabolism , biology , psychology , regression , insulin , psychoanalysis
Summary Objective To determine the impact of energy restriction (ER) upon the previously reported increased resting and exercise‐related oxygen utilization, reduced body temperature, increased serum TSH, and reduced serum free T3 concentrations found during Antarctic residence (AR). Design Prospective, intervention with both paired controls and a similar reference control group (RG). Patients and measurements Seven subjects were assessed before and after a 50% ER period of 60 h. This ER was carried out within 30 days of arriving in Antarctica in October (OCT) and again after 10 months AR in August (AUG). During the periods of ER, mean energy consumption was 5662 ± 1344 kJ/day in OCT and 5529 ± 967 kJ/day in AUG. Resting metabolic rate (RMR), a calculated resting metabolic rate (RMR reg ) using a submaximal work regression, serum TSH, FT3 and tympanic temperature (Tty) were measured. These values were compared with a similar RG of 12 subjects reported previously who were studied in California, USA before and then again during AR. Results Weight declined by 1·1 ± 0·1 kg/day (OCT) and 0·92 ± 0·2 kg/day (AUG) with ER, resulting in a reduction of body weight by 3·1 ± 0·4% in OCT ( P = 0·0001) and 2·5 ± 0·4% in AUG ( P = 0·0015) during AR. The RMR before ER did not change with AR and it was not significantly different from the RG studied in California. With ER the RMR tended to decline in both OCT (132 ± 5 to 122 ± 4 mlO 2 /min/m 2 ) and AUG (134 ± 5 to 126 ± 5 mlO 2 /min/m 2 ), but these were not significant. By contrast, RMR reg obtained before ER was increased with AR by 22·5 ± 7·8% ( P = 0·01) in OCT and by 28·1 ± 7·0% ( P = 0·0008) in AUG over the RG values obtained in California. RMR reg did not decrease with ER in either OCT or AUG. The total energy expenditure derived from these measures of weight loss suggests that 24‐h energy requirements are 74·4%[95% confidence interval (CI) 2·6–146·3; P < 0·05] more than those expected in temperate climates. Tty declined by 0·6 ± 0·2 °C ( P < 0·01) with AR compared with the RG measured in California, but was not affected by either period of ER. ER had no effect on FT3 but tended to decrease serum TSH in AUG ( P = 0·06). Conclusions 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.