Negative energy balance in male and female rangers: effects of 7 d of sustained exercise and food deprivation

Hoyt, Reed W.; Opstad, P. K.; Haugen, Ann-Helen; DeLany, James P.; Cymerman, Allen; Friedl, Karl E.

doi:10.1093/ajcn/83.5.1068

Cited by 81 publications

(90 citation statements)

References 45 publications

(64 reference statements)

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“…19 Research on both lean and obese cohorts has demonstrated that RMR reduces rapidly when individuals are placed in energy restriction, with the magnitude of the decrease being greater than can be accounted for by tissue loss. 16,34 RMR of overweight women has been reported to fall by 6% within 10 days of commencing energy restriction (800 kcal per day; B40% WM baseline ), 16 and a comparable (B6%) decrease in resting oxygen consumption was reported after only 4 days of severe energy restriction (450 kcal per day; o25% WM baseline ) in very obese women. 35 In obese women, Bray et al 35 noted that a weight loss of 1 kg every 4 days would be expected based on the baseline-calculated EDef.…”

Section: Discussionmentioning

confidence: 94%

Does metabolic compensation explain the majority of less-than-expected weight loss in obese adults during a short-term severe diet and exercise intervention?

et al. 2012

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OBJECTIVE:We investigated to what extent changes in metabolic rate and composition of weight loss explained the lessthan-expected weight loss in obese men and women during a diet-plus-exercise intervention. DESIGN: In all, 16 obese men and women (41 ± 9 years; body mass index (BMI) 39 ± 6 kg m À 2 ) were investigated in energy balance before, after and twice during a 12-week very-low-energy diet(565-650 kcal per day) plus exercise (aerobic plus resistance training) intervention. The relative energy deficit (EDef) from baseline requirements was severe (74%-87%). Body composition was measured by deuterium dilution and dual energy X-ray absorptiometry, and resting metabolic rate (RMR) was measured by indirect calorimetry. Fat mass (FM) and fat-free mass (FFM) were converted into energy equivalents using constants 9.45 kcal per g FM and 1.13 kcal per g FFM. Predicted weight loss was calculated from the EDef using the 0 7700 kcal kg À 1 rule 0 . RESULTS: Changes in weight ( À 18.6 ± 5.0 kg), FM ( À 15.5 ± 4.3 kg) and FFM ( À 3.1 ± 1.9 kg) did not differ between genders. Measured weight loss was on average 67% of the predicted value, but ranged from 39% to 94%. Relative EDef was correlated with the decrease in RMR (R ¼ 0.70, Po0.01), and the decrease in RMR correlated with the difference between actual and expected weight loss (R ¼ 0.51, Po0.01). Changes in metabolic rate explained on average 67% of the less-than-expected weight loss, and variability in the proportion of weight lost as FM accounted for a further 5%. On average, after adjustment for changes in metabolic rate and body composition of weight lost, actual weight loss reached 90% of the predicted values. CONCLUSION: Although weight loss was 33% lower than predicted at baseline from standard energy equivalents, the majority of this differential was explained by physiological variables. Although lower-than-expected weight loss is often attributed to incomplete adherence to prescribed interventions, the influence of baseline calculation errors and metabolic downregulation should not be discounted.

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Section: Discussionmentioning

confidence: 94%

Does metabolic compensation explain the majority of less-than-expected weight loss in obese adults during a short-term severe diet and exercise intervention?

et al. 2012

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“…cadets (22 AE 2 MJ/day), but weight-specific TEEs ($350 kJ/kg per day), and physical activity levels (TEE/resting metabolic rate ¼ $3.5) were similar [6 ]. A study of Marine recruits participating in a demanding physically demanding 54 h training exercise also found that men and women performing similar high-intensity activities had similar weight-specific TEEs (men 350 AE 40 kJ/kg per day; women 340 AE 40 kJ/kg per day) [15].…”

Section: Norwegian Ranger Trainingmentioning

confidence: 93%

“…The effects of underfeeding have also been investigated in soldiers participating in military training courses in which study durations are shorter, at 3-62 days, and sleep deprivation and sustained physical activity are added stressors. Study populations range from Norwegian cadets participating in a training course that involves a week of food and sleep deprivation and approximately 23 h/day of marching and other activities [4, 5,6 ], to soldiers participating in 8 weeks of physically demanding US Army Ranger training, in which sleep is restricted to 4 h/day and food is in short supply [7,8]. Others have studied long-range patrols by Swedish ski troops [9], hot weather training by Zimbabwean recruits [10], and a variety of other extremes [11][12][13][14][15] (see Table 1).…”

Section: Introductionmentioning

confidence: 99%

Field studies of exercise and food deprivation

Hoyt

Friedl

2006

Current Opinion in Clinical Nutrition &Amp; Metabolic Care

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Purpose of reviewThe increase in obesity in developed societies drives interest in the interplay of energy intake, metabolic energy expenditure, and body energy stores. A better understanding of energy management in physically active and undernourished humans should help guide strategies to manage obesity safely and effectively. This review focuses on field studies of men and women engaged in prolonged strenuous activities, ranging from ranger training to extreme expeditions. Recent findingsAlthough scientifically unconventional and limited, field studies of exercise and food deprivation have yielded interesting findings: 4-5% body fat is the normal lower limit to fat reserves in physically active underfed young adult men, and in response to exercise and underfeeding, women used more fat mass and less fat-free mass to meet metabolic fuel requirements. Summary Field studies have shown that fat energy reserves in young adult men can be estimated as percentage body fat minus 5%, and initial body fat mass has a significant positive influence on fat oxidation rates per kilogram of fat-free mass during rapid weight loss associated with underfeeding and exercise. Data logging pedometers, activity monitors, global positioning systems, and wireless body and personal-area networks promise to make it easier to study and care for free-living humans. Keywords body composition, free-living, negative energy balance, physical work, semi-starvation, soldiers

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“…Before their eventual rescue they had lost over 20kg each. Although humans can endure several days of heavy physical exercise with limited food rations (Guezennec et al, 1994;Hoyt et al, 2006), by day 95 of the expedition Stroud and Fiennes showed considerable reductions in muscle power, reductions that were linked to marked decreases in cytoplasmic and mitochondrial enzyme activities (Stroud et al, 1997). Two other studies on endurance exercise levels that approach or exceed those of the Arctic explorers, on Tour de France cyclists (Westerterp et al, 1986) and Swedish cross-country skiers (Sjodin et al, 1994), respectively, show somewhat smaller deficits, or even complete energy balance.…”

Section: Introductionmentioning

confidence: 99%

Why marathon migrants get away with high metabolic ceilings: towards an ecology of physiological restraint

Piersma¹

2011

Journal of Experimental Biology

101

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SummaryAnimals usually are not willing to perform at levels, or for lengths of time, of which they should be maximally capable. In stating this, exercise performance and inferred capacity are gauged with respect to body size and the duration of particular levels of energy expenditure. In such relative terms, the long-term metabolic ceiling of ca. 7 times basal metabolic rate in challenged but energy-balanced individuals may be real and general, because greater performance over long periods requires larger metabolic machinery that is ever more expensive to maintain. Avian marathon migrants relying on stored fuel (and therefore not in energy balance) that work for 9 consecutive days at levels of 9-10 times basal metabolic rate are exceptional performers in terms of the 'relative expenditure' on 'duration of a particular activity' curve nevertheless. Here I argue that metabolic ceilings in all situations (energy balanced or not) have their origin in the fitness costs of high performance levels due to subsequently reduced survival, which then precludes the possibility of future reproduction. The limits to performance should therefore be studied relative to ecological context (which includes aspects such as pathogen pressure and risk of overheating), which determines the severity of the survival punishment of over-exertion. I conclude that many dimensions of ecology have determined at which performance levels (accounting for time) individual animals, including human athletes, begin to show physiological restraint. Using modern molecular techniques to assay wear and tear, in combination with manipulated work levels in different ecological contexts, might enable experimental verification of these ideas.

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Negative energy balance in male and female rangers: effects of 7 d of sustained exercise and food deprivation

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

Cited by 81 publications

References 45 publications

Does metabolic compensation explain the majority of less-than-expected weight loss in obese adults during a short-term severe diet and exercise intervention?

Does metabolic compensation explain the majority of less-than-expected weight loss in obese adults during a short-term severe diet and exercise intervention?

Field studies of exercise and food deprivation

Why marathon migrants get away with high metabolic ceilings: towards an ecology of physiological restraint

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