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American Journal of Clinical Nutrition, Vol. 83, No. 5, 1068-1075, May 2006
© 2006 American Society for Nutrition

ORIGINAL RESEARCH COMMUNICATION

Negative energy balance in male and female rangers: effects of 7 d of sustained exercise and food deprivation1,2,3,4

Reed W Hoyt, Per Kristian Opstad, Ann-Helen Haugen, James P DeLany, Allen Cymerman and Karl E Friedl

1 From the US Army Research Institute of Environmental Medicine, Natick, MA (RWH, AC, and KEF); the Norwegian Defence Research Establishment, Kjeller, Norway (PKO and A-HH); and the Pennington Biomedical Research Center, Baton Rouge, LA (JPD)

Background:A challenging 7-d ranger field exercise (FEX) by cadets in the Norwegian Military Academy provided a venue in which to study the effects of negative energy balance.

Objective:We quantified total energy expenditure (TEE), food intake, and changes in body composition in male and female cadets.

Design:TEE (measured by doubly labeled water), food intake, activity patterns (measured by accelerometry), and body composition (measured by dual-energy X-ray absorptiometry) were measured in 16 cadets (10 men and 6 women aged 21–27 y).

Results:The physically active ({approx}23 h/d) and semistarved (0.2–2.2 MJ/d) cadets lost weight (x ± SD: men, –7.7 ± 1.1 kg; women, –5.9 ± 1.1 kg; P < 0.05). Absolute TEE differed by sex (men, 26.6 ± 2.0 MJ/d; women, 21.9 ± 2.0 MJ/d; P < 0.05) but body weight–specific TEE did not (men, 343 ± 26 kJ · kg–1 · d–1; women, 354 ± 18 kJ · kg–1 · d–1; NS). Fat-free mass (FFM) loss differed significantly by sex (men, –4.0 ± 1.2 kg; women, –2.5 ± 1.1 kg; P < 0.05), but percentage FFM loss did not (men, –6.3 ± 1.9%; women, –5.6 ± 2.4%). In contrast, absolute FM loss did not differ significantly by sex (men, –3.45 ± 0.72 kg; women, –3.42 ± 0.22 kg), but fat oxidation (men, 5.2 ± 1.0 mg · min–1 · kg FFM–1; women, 7.3 ± 0.5 mg · min–1 · kg FFM–1) and the relative contribution of FM to TEE (men, 74 ± 14%; women, 89 ± 6%) were significantly greater in women than in men (P < 0.05).

Conclusion:Female cadets maintained a significantly more fat-predominant fuel metabolism than did male cadets in response to sustained exercise and semistarvation.

Key Words: Starvation • sustained exercise • body composition • sex • water intake • military rangers • Norway






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