Physical Activity in Confined Conditions as an Indicator of Free‐Living Physical Activity

Objective: The main determinants of daily energy expenditure are body size and physical activity. Activity energy expenditure is the most variable component of total energy expenditure. It was assessed whether the physical activity level in confined conditions is an indicator of free‐living physical activity. Research Methods and Procedures: Activity energy expenditure was measured over 1 day in a confined environment of a respiration chamber (floor space, 7.0 m²), where activities were restricted to low‐intensity activities of daily living, and over 2 weeks in a free‐living environment using doubly labeled water. Subjects were 16 women and 29 men (age, 31 ± 10 years; BMI, 24.2 ± 2.7 kg/m²). Results: The free‐living activity level of the subjects, as a multiple of resting energy expenditure, was 1.76 ± 0.13. Activity energy expenditure in the chamber was 47 ± 13% of the value in daily life, and the two values were correlated (r = 0.50, p < 0.001; partial correlation corrected for age, gender, and BMI: 0.40, p < 0.01). The chamber value explained 25% of the total variance in free‐living activity energy expenditure. Discussion: The activity level of a subject under sedentary conditions is an indicator of activity energy expenditure in daily life, showing the importance of nonexercise activity for daily energy expenditure.     

Physical activity and subsistence pattern of the Huli, a Papua New Guinea Highland population

Several studies on human energetics have been conducted in developed and developing countries, but very few simultaneously measured time use and energy expenditure. Only a few quantitatively compared subsistence patterns between rural and urban dwellers of an identical population. Here we present the daily physical activity level (PAL), physical exertion, time, and energy expenditure in contrasting subsistence/occupational activities of Papua New Guinea Highlanders, comparing 27 rural villagers (15 men, 12 women) who maintained traditional subsistence agriculture, with 29 urban migrants (14 men, 15 women) who engaged in cash-earning work. A large sex inequality in the division of labor was noted between rural males and females, but not among urban dwellers. Rural-urban comparison indicated sex differences in urbanization. For urban men, the reduction of physical exertion level during work, from energy-consuming agricultural work to sedentary cash-earning work, together with significantly extended work time (by 261 min/day, P < 0.001), led to an increase in work energy expenditure (15-29% of PAL). In contrast, urban women who spent almost equal time at work relative to rural women showed a lower energy expenditure (18% compared to 26% of PAL). The associations with urbanization included a gain in body weight (by 6.4 kg for either sex) and reduced PAL (by 7%, not significant in men; 13%, P < 0.01 in women). Further research is needed to elucidate the effects of urbanization on time use, energy expenditure, and PAL, by comparing rural residents with urban migrants in the same population.     

Daily Energy Expenditure and the Cost of Activity in Mammals

Among 17 species of mammals, field metabolic rates exclusiveof thermoregulatory and productive costs (designated FMR*) averaged2.65 x standard metabolism (SMR). Daily activity costswere calculatedby subtraction from FMR* of the daily energy expenditure associatedwith SMR and assimilation of nutrients. Total expenditure foractivity was of a similar magnitude to that for daily standardmetabolism. Calculations indicate that expenditures by mammalsfor locomotion probably account for less than half of dailyactivity costs. Expenditures by mammals engaged in other kindsof activities are also reviewed. During their daily activityperiods, terrestrial mammals expend energy at a rate of about4.1 x SMR. The utility of energetic increments for activityin time-energy budgets, thermal energy budgets, and analysesof the economics of foraging are discussed.     

Seasonal and sex variation in physical activity levels among agro-pastoralists in Nepal

Considerable attention has been devoted to variation in levels of energy expenditure between and within populations; these are commonly evaluated following international guidelines for grading light, moderate, and heavy physical activity levels (PAL). This study presents activity profiles by season and sex for subsistence agro-pastoralists in Nepal, comparing data for a sample of 20 men observed four times across the year with previously published data on women. Total energy expenditure (TEE) was estimated from direct minute-by-minute observation (totaling 1,679 h for men, 3,601 h for women) and measures of the energy cost of single tasks (117 for men, 168 for women). PAL were calculated and graded as multiples of predicted basal metabolic rate (BMR). Despite an explicitly egalitarian organization of labor, men achieved higher PAL than women (P < .0001), although according to international gradings, both men and women assume moderately heavy PAL in the winter and very heavy PAL in the monsoon. PAL were 1.88 and 2.22 × BMR for men in respective seasons (P < .005; TEE, 11.8 MJ/d and 13.9 MJ/d) and 1.77 and 2.0 × BMR for women (TEE, 9.1 MJ/d and 10.5 MJ/d). High TEE values result from time-consuming work in subsistence tasks, most of which are of moderate energy cost. Results show that the international guideline (FAO/WHO/UNU [1985]) for grading levels of energy expenditure, which adopts discrepant sex-specific values to define thresholds for moderate or heavy PAL, can mask significant gender variation. Male/female ratios of PAL values are suggested instead for population-level comparisons. © 1996 Wiley-Liss, Inc.     

Men's time allocation to subsistence work among the Ache of Eastern Paraguay

Quantitative data on men's time allocation among the Ache of Paraguay are presented. The data indicate that Ache men work almost 7 hours daily in direct food acquisition, which is the major daily activity. The amount of time Ache men work is compared with the amount reported for other modern hunter-gatherers and tribal horticulturalists. The characterization of hunter-gatherers as the original affluent society does not agree with currently available data. The results show high variance across societies, both hunting and horticultural, and suggest that time spent in subsistence work is not simply a function of food needs. We propose that the value of time spent in potential alternative activities must be considered in order to predict time spent in subsistence tasks.     

Estimates of Daily Energy Expenditure in Birds: The Time-Energy Budget as an Integrator of Laboratory and Field Studies

SYNOPSIS. Measures of energy expenditure by free-living birdscan provide quantitative testsof a number of ecological theories,regarding such diverse phenomena as foraging strategies, resourcecompetition, or parental investment. Our confidence in thesetests rests heavily on the confidence we have in the estimatedrates of energy expenditure. The most common approach to obtainingsuch estimates is the construction of time-energy budgets, inwhich the durations of ananimal's daily activities are multipliedby the respective energy costs of the activities, and thesecosts are summed. Our knowledge of the energy costs of activities,particularly locomotion, has greatly advanced in recent years,as has the ability to adequately assess thermoregulatory costs.Comparisons between timeenergy budgets and direct measures ofenergy expenditure obtained using doubly labeled water indicatethat time-energy budgets can yield accurate estimates of energyexpenditure. However, this is likely to be achieved only underfairly rigorous conditions in which resting costs, activitycosts, and thermoregulatory costs are all well described.Evidenceis accumulating to suggest that, under some conditions, energyexpenditure by birds reaches a maximum sustainable level, atwhich point it is limited by the physiological capacitiestoingest and assimilate energy. Under these conditions, behavioralresponses to changing physical environments and resource availabilitymay be critical to the maintenance of energy balance.     

Non-exercise daily energy expenditure and physical activity pattern in male endurance athletes.

The present study was performed to determine whether differences in non-exercise daily energy expenditure (Md,ne) exist between trained and untrained individuals. The data from seven cross-country skiers were compared with those from eight sedentary men. Daily energy expenditure (Md) was determined using the heart rate-oxygen consumption relationship; resting metabolic rate (Mr) was measured using indirect calorimetry. A physical activity questionnaire and ratios of Md or Md,ne to Mr were used as indices of physical activity. Md and Mr were significantly higher in the trained subjects whereas Md,ne was identical in the two groups. The ratio of Md,ne to Mr and the data from the physical activity questionnaire showed that there was no significant difference in daily energy expenditure and physical activity pattern during the non-exercise time. These results suggest that the exercise-induced increase in daily energy requirements is not compensated by a more sedentary life during the other daily activities in these trained men.     

Physical work causes suppression of ovarian function in women.

The suppression of reproductive function is known to occur in women engaging in activities that require high energetic expenses, such as sport participation and subsistence work. It is still unclear, however, if reproductive suppression is a response to high levels of energy expenditure, or only to the resulting state of negative energy balance. To our knowledge, this study provides the first evidence that work-related energy expenditure alone, without associated negative energy balance, can lead to the suppression of reproductive function in women. We document suppression of ovarian function expressed as lowered salivary progesterone levels in women from an agricultural community who work hard, but remain in neutral energy balance. We propose two alternative evolutionary explanations (the ''pre-emptive ovarian suppression'' hypothesis and the ''constrained down-regulation'' hypothesis) for the observed results.     

Differences in daily energy expenditure in lean and obese women: the role of posture allocation

Objective: A low resting metabolic rate (RMR) is considered a risk factor for weight gain and obesity; however, due to the greater fat‐free mass (FFM) found in obesity, detecting an impairment in RMR is difficult. The purposes of this study were to determine the RMR in lean and obese women controlling for FFM and investigate activity energy expenditure (AEE) and daily activity patterns in the two groups. Methods and Procedures: Twenty healthy, non‐smoking, pre‐menopausal women (10 lean and 10 obese) participated in this 14‐day observational study on free‐living energy balance. RMR was measured by indirect calorimetry; AEE and total energy expenditure (TEE) were calculated using doubly labeled water (DLW), and activity patterns were investigated using monitors. Body composition including FFM and fat mass (FM) was measured by dual energy X‐ray absorptiometry (DXA). Results: RMR was similar in the obese vs. lean women (1601 ± 109 vs. 1505 ± 109 kcal/day, respectively, P = 0.12, adjusting for FFM and FM). Obese women sat 2.5 h more each day (12.7 ± 3.2 h vs. 10.1 ± 2.0 h, P < 0.05), stood 2 h less (2.7 ± 1.0 h vs. 4.7 ± 2.2 h, P = 0.02) and spent half as much time in activity than lean women (2.6 ± 1.5 h vs. 5.4 ± 1.9 h, P = 0.002). Discussion: RMR was not lower in the obese women; however, they were more sedentary and expended less energy in activity than the lean women. If the obese women adopted the activity patterns of the lean women, including a modification of posture allocation, an additional 300 kcal could be expended every day.     

Low Resting and Sleeping Energy Expenditure and Fat Use Do Not Contribute to Obesity in Women

Objective: Determine whether sleeping and resting energy expenditure and sleeping, resting, and 24‐hour fuel use distinguish obesity‐prone from obesity‐resistant women and whether these metabolic factors explain long‐term weight gain. Research Methods and Procedures: Forty‐nine previously overweight but currently normal‐weight women were compared with 49 never‐overweight controls. To date, 87% of the 98 women have been re‐evaluated after 1 year of follow‐up, without intervention, and 38% after 2 years. Subjects were studied at a General Clinical Research Center after 4 weeks of tightly controlled conditions of energy balance and macronutrient intake. Forty‐nine obesity‐prone weight‐reduced women were group‐matched with 49 never‐overweight obesity‐resistant controls. All were premenopausal, sedentary, and normoglycemic. Energy expenditure and fuel use were assessed using chamber calorimetry. Body composition was assessed using DXA. Results: At baseline, percent body fat was not different between the obesity‐prone and control women (33 ± 4% vs. 32 ± 5%, respectively; p = 0.22). Analysis of covariance results show that after adjusting for lean and fat mass, sleeping and resting energy expenditure of obesity‐prone women was within 2% of controls. Neither sleeping nor resting energy expenditure nor sleeping, resting, or 24‐hour fuel use was significantly different between the groups (p > 0.25). None of the metabolic variables contributed significantly to patterns of weight gain at 1 or 2 years of follow‐up. Discussion: The results suggest that when resting and sleeping energy expenditure and fuel use are assessed under tightly controlled conditions, these metabolic factors do not distinguish obesity‐prone from obesity‐resistant women or explain long‐term weight changes.     

Energetics of the annual cycle of Dippers Cinclus cinclus

Time-activity budgets and energy expenditure of Dippers Cinclus cinclus were studied in all months of the year and for every stage of the annual cycle. The commonest daytime activity was feeding (54%), then resting (43%) and flying (4%). On a 24-hr day basis the most marked changes in activity followed from changing daylengths. DEE (Daily Energy Expenditure), derived from time-activity budgets through the year and laboratory estimates of metabolism, averaged 201 kj d ^-1 in females and 228 kj d ^-1 in the larger males. Over a more restricted range of circumstances, direct estimates of DEE obtained from 77 Dippers using the doubly labelled water technique averaged 205 ± 43 kj d^-1 and 251 ± 55 kj d^-1 in females and males, respectively. Overall, the correspondence between these largely independent estimates of energy expenditure was reasonably close. DEE was highest during breeding (laying-females; rearing-males) and in late winter for both sexes. The lowest energy expenditures occurred during moult, amongst juveniles and in early winter. Incubating females and mate-guarding males also had low energy costs. Across all stages of the annual cycle body size, activity patterns, ambient temperature and river flow had significant effects on energy expenditure. The rate at which food was gathered to meet these changing energy demands varied widely. While some of this variation was imposed by a seasonal environment, it was also likely to reflect adaptive shifts in rates of food gathering, in some cases consequent upon the changing fitness benefits of various non-feeding activities.     

Trends over 5 decades in U.S. occupation-related physical activity and their associations with obesity

Background

The true causes of the obesity epidemic are not well understood and there are few longitudinal population-based data published examining this issue. The objective of this analysis was to examine trends in occupational physical activity during the past 5 decades and explore how these trends relate to concurrent changes in body weight in the U.S.

Methodology/Principal Findings

Analysis of energy expenditure for occupations in U.S. private industry since 1960 using data from the U.S. Bureau of Labor Statistics. Mean body weight was derived from the U.S. National Health and Nutrition Examination Surveys (NHANES). In the early 1960''s almost half the jobs in private industry in the U.S. required at least moderate intensity physical activity whereas now less than 20% demand this level of energy expenditure. Since 1960 the estimated mean daily energy expenditure due to work related physical activity has dropped by more than 100 calories in both women and men. Energy balance model predicted weights based on change in occupation-related daily energy expenditure since 1960 for each NHANES examination period closely matched the actual change in weight for 40–50 year old men and women. For example from 1960–62 to 2003–06 we estimated that the occupation-related daily energy expenditure decreased by 142 calories in men. Given a baseline weight of 76.9 kg in 1960–02, we estimated that a 142 calories reduction would result in an increase in mean weight to 89.7 kg, which closely matched the mean NHANES weight of 91.8 kg in 2003–06. The results were similar for women.

Conclusion

Over the last 50 years in the U.S. we estimate that daily occupation-related energy expenditure has decreased by more than 100 calories, and this reduction in energy expenditure accounts for a significant portion of the increase in mean U.S. body weights for women and men.     

Rates of water turnover and energy expenditure of free-living male common seals (Phoca vitulina)

The water and energy metabolism of free-living male common seals ( Phoca vitulina ) during the mating season was investigated using labelled water methods. All three seals, which were captured on two occasions, were in negative energy balance during the study. The daily energy expenditure of one animal, estimated using doubly-labelled water was 52·5 MJ. This is equivalent to six times the basal metabolic rate predicted from Kleiber's (1975) allometric equation. Rates of water turnover were slightly lower than predicted from the allometric equation of Richmond, Langham & Trujillo (1962). The observed rates of water turnover and energy expenditure are considerably higher than those of seals which fast during the mating season, and are consistent with the observed differences in behaviour between males of the common seal and other pinniped males during mating.     

Compensation in resting metabolism for experimentally increased activity

To study zebra finch allocation of energy to day and night at two different workloads, we assessed the daily energy turnover from: (1) metabolizable energy of the food, and (2) doubly-labeled water. In both experiments we imposed two levels of activity on captive zebra finches (Taeniopygia guttata), by applying different computer-controlled workload schedules. A low workload required 20 hops, and a high workload 40 hops to obtain 10 s access to food. In experiment 1, we further measured nocturnal energy expenditure by overnight oxygen consumption. From experiment 2 we derived an estimate of the costs of hopping activity, from inter-individual association of daily amount of hopping and daily energy expenditure. Surprisingly, the daily energy budget was, on average, reduced slightly when birds were subjected to a high workload. Since hopping activity was 50% higher during the high workload than during the low workload, the birds apparently compensated, even over-compensated, for the increased energetic demands of activity. Nocturnal energy expenditure was indeed reduced for the high workload, which was largely due to a reduction in resting metabolic rate. Economizing on energy was more than could have been accomplished by a reduction in mass alone, and we discuss the occurrence and potential mechanisms of physiological compensation. The amount of energy saved during the night did account for part of the total amount of energy saved. We surmise that the strategy of energetic compensation observed during the night was extended into the inactive hours of the day. Accepted: 10 July 1998     

Physical Activity Levels Are Low in Free‐Living Adults with Chronic Paraplegia

Objectives: To compare physical activity levels (PALs) of free‐living adults with chronic paraplegia with World Health Organization recommendations and to compare energy expenditure between persons with complete vs. incomplete paraplegia. Research Methods and Procedures: Twenty‐seven euthyroid adults (17 men and 10 women) with paraplegia (12.5 ± 9.5 years since onset; 17 with complete lesions and 10 with incomplete lesions) participated in this cross‐sectional study. Resting metabolic rate was measured by indirect calorimetry and total daily energy expenditure (TDEE) by heart rate monitoring. PAL was calculated as TDEE/resting metabolic rate. Total body water was measured by deuterium dilution and fat‐free mass (FFM) and fat mass (FM) by calculation (FFM = total body water/0.732; FM = weight ? FFM). Obesity was defined using the following percentage FM cutoffs: men 18 to 40 years >22% and 41 to 60 years >25%; and women 18 to 40 years >35% and 41 to 60 years >38%. Results: Nineteen subjects (70.4%; 13 men and six women) were obese. Fifteen subjects (56%) engaged in structured physical activity 1.46 ± 0.85 times during the observation period for a mean of 49.4 ± 31.0 minutes per session. Despite this, mean PAL of the group was 1.56 ± 0.34, indicative of limited physical activity. TDEE was 24.6% lower in subjects with complete paraplegia (2072 ± 505 vs. 2582 ± 852 kcal/d, p = 0.0372). Discussion: PAL of the group was low, indicating that persons with paraplegia need to engage in increased frequency, intensity, and/or duration of structured physical activity to achieve a PAL ≥1.75 and, thereby, to offset sedentary activities of daily living.     

Seasonal variations in the energetics of an Australian nectarivorous bird, Lichmera indistincta

1. Seasonal variations in unit perching costs, flying costs and energy budgets for Lichmera indistincta were investigated. 2. Unit perching and flying costs were greatest in winter and least in summer. Variations in perching costs occurred principally because of changes in conductance. Flying cost variations may have been due to changes in wing disc loading and/or the integrity of wing feathers. 3. Rates of net energy intake were greatest in winter and least in summer. Variations in these rates were such that they offset changes in the rates of total energy expenditure to provide diurnal energy balance. 4. Regardless of the season, net daytime energy storage proceeded at a uniform rate and resulted in the storage of sufficient energy to offset overnight expenditure.     

Activity budgets and activity rhythms in red ruffed lemurs (Varecia rubra) on the Masoala Peninsula, Madagascar: seasonality and reproductive energetics

The activity budgets and daily activity rhythms of Varecia rubra were examined over an annual cycle according to season and reproductive stage. Given the relatively high reproductive costs and patchy food resources of this species, I predicted that V. rubra would 1) travel less and feed more during seasonal resource scarcity in an attempt to maintain energy balance, and 2) show sex differences in activity budgets due to differing reproductive investment. Contrary to the first prediction, V. rubra does not increase feeding time during seasonal food scarcity; rather, females feed for a consistent amount of time in every season, whereas males feed most during the resource-rich, hot dry season. The results are consistent with other predictions: V. rubra travels less in the resource-scarce cold rainy season, and there are some pronounced sex differences, with females feeding more and resting less than males in every season and in every reproductive stage except gestation. However, there are also some provocative similarities between the sexes when activity budgets are examined by reproductive stage. During gestation, female and male activity budgets do not differ and appear geared toward energy accumulation: both sexes feed and rest extensively and travel least during this stage. During lactation, activity budgets are geared toward high energy expenditure: both sexes travel most and in equal measure, and rest least, although it remains the case that females feed more and rest less than males. These similarities between female and male activity budgets appear related to cooperative infant care. The high energetic costs of reproduction in V. rubra females may require that they allot more time to feeding year round, and that their overall activity budget be more directly responsive to seasonal climate change, seasonal food distribution, and reproductive schedules.     

Energy Expenditure during Sexual Activity in Young Healthy Couples

Objective

To determine energy expenditure in kilocalories (kcal) during sexual activity in young healthy couples in their natural environment and compare it to a session of endurance exercise.

Methods

The study population consisted of twenty one heterosexual couples (age: 22.6 ± 2.8 years old) from the Montreal region. Free living energy expenditure during sexual activity and the endurance exercise was measured using the portable mini SenseWear armband. Perceived energy expenditure, perception of effort, fatigue and pleasure were also assessed after sexual activity. All participants completed a 30 min endurance exercise session on a treadmill at a moderate intensity.

Results

Mean energy expenditure during sexual activity was 101 kCal or 4.2 kCal/min in men and 69.1 kCal or 3.1 kCal/min in women. In addition, mean intensity was 6.0 METS in men and 5.6 METS in women, which represents a moderate intensity. Moreover, the energy expenditure and intensity during the 30 min exercise session in men was 276 kCal or 9.2 kCal/min and 8.5 METS, respectively and in women 213 kCal or 7.1 kCal/min and 8.4 METS, respectively. Interestingly, the highest range value achieved by men for absolute energy expenditure can potentially be higher than that of the mean energy expenditure of the 30 min exercise session (i.e. 306.1 vs. 276 kCal, respectively) whereas this was not observed in women. Finally, perceived energy expenditure during sexual activity was similar in men (100 kCal) and in women (76.2 kCal) when compared to measured energy expenditure.

Conclusion

The present study indicates that energy expenditure during sexual activity appears to be approximately 85 kCal or 3.6 kCal/min and seems to be performed at a moderate intensity (5.8 METS) in young healthy men and women. These results suggest that sexual activity may potentially be considered, at times, as a significant exercise.     

Young But Not Old Adult African Striped Mice Reduce Their Activity in the Dry Season When Food Availability is Low

An individual′s survival and fitness depend on its ability to effectively allocate its time between competing behaviors. Sex, social tactic, season and food availability are important factors influencing activity budgets. However, few field studies have tested their influences. The African striped mouse (Rhabdomys pumilio) lives in highly seasonal habitats in southern Africa, and individuals can adopt different social tactics. We investigated seasonal changes in activity budgets of different tactics and predicted that individuals will reduce their activity in the non‐breeding season to save energy when food availability is low and that young non‐breeding adults (‘philopatrics’) invest mainly in activities related to gaining body mass to increase survival probability. We predicted old adults (‘breeders’), which bred during the previous breeding season, to invest mainly in maintenance of their social status. We conducted 90 focal observations during the non‐breeding season and 73 during the breeding season. Activity budgets of striped mice were season and tactic specific, with philopatrics, but not breeders, reducing activity when food availability was low, possibly to decrease energy expenditure. Philopatrics of both sexes foraged and basked more in the breeding season than during the non‐breeding season. Male philopatrics gained body mass and female philopatrics maintained their body mass in both seasons. Sex‐specific differences occurred during the breeding season, when female breeders foraged more than male breeders, while male breeders chased other individuals more than female breeders. These findings indicate that individuals adopting different social tactics display distinct behaviors to fulfill tactic‐specific energetic needs .     

Association of eating frequency with body fatness in pre- and postmenopausal women

Objective: To examine associations between eating frequency (EF) and body fatness in pre‐ and postmenopausal women, after excluding potential low‐energy reporters. Research Methods and Procedures: In this cross‐sectional study of 220 free‐living women, 64 pre‐ and 50 postmenopausal non‐low‐energy‐reporting women were further analyzed (age, 24 to 74 years; BMI, 18.5 to 38.6 kg/m²). Anthropometric and body composition measurements (DXA) were performed in all study participants. EF, energy, and macronutrient intake were assessed by 3‐day food record. Physical activity level and energy expenditure were assessed by self‐reported questionnaire. Results: No association between EF and adiposity indices was detected in premenopausal women. In contrast, EF was positively correlated with percentage body fat in postmenopausal women (r = 0.30, p = 0.03). EF was positively correlated with total energy intake in both groups and with total energy expenditure in premenopausal women only (r = 0.34, p = 0.02). Multivariate analysis revealed that, in postmenopausal women, EF was a significant predictor of body fatness (standardized β = 0.41, p = 0.01). Discussion: Frequent eating was not found to be related to adiposity in premenopausal women, but it was associated with increased body fat in postmenopausal women. Possible explanations could be that the frequent eating is not associated with a physically active lifestyle in postmenopausal women or that frequent eating predisposes women after menopause to a higher energy intake by increasing food stimuli and rendering it more difficult for them to control energy balance.