Human energetics methods in biological anthropology

Nutritional anthropology in the world

Nutritional anthropology is the study of human subsistence, diet and nutrition in comparative social and evolutionary perspective. Many factors influence the nutritional health and well-being of populations, including evolutionary, ecological, social, cultural and historical ones. Most usually, biocultural approaches are used in nutritional anthropology, incorporating methods and theory from social science as well as nutritional and evolutionary science. This review describes approaches used in the nutritional anthropology of past and present-day societies. Issues of concern for nutritional anthropology in the world now include: understanding how undernutrition and food insecurity are produced at local, regional and international levels; how food systems are constructed using social, biological and biocultural perspectives; and obesity from a biocultural viewpoint. By critiquing framings of present-day diet in an evolutionary context, nutritional anthropology asks 'what should be eaten?', rather than 'what can be eaten?', and 'how cheaply can people be fed?'.

Age related decline in female lar gibbon great call performance suggests that call features correlate with physical condition

BACKGROUND

White-handed gibbons (Hylobates lar) are small Asian apes known for living in stable territories and producing loud, elaborate vocalizations (songs), often in well-coordinated male/female duets. The female great call, the most conspicuous phrase of the repertoire, has been hypothesized to function in intra-sexual territorial defense. We therefore predicted that characteristics of the great call would correlate with a caller's physical condition, and thus might honestly reflect resource holding potential (RHP). Because measurement of RHP is virtually impossible for wild animals, we used age as a proxy, hypothesizing that great call climaxes are difficult to produce and maintain over time, and that older adults will therefore perform lower quality great calls than young adults. To test this we analyzed the great call climaxes of 15 wild lar gibbon females at Khao Yai National Park, Thailand and 2 captive females at Leo Conservation Center, Greenwich, CT.

RESULTS

Findings show that call climaxes correlate with female age, as young animals (n = 8, mean age: 12.9 years) produced climaxes with a higher frequency range (delta F0), maximum F0 frequency and duty cycle than old animals (n = 9, mean age: 29.6 years). A permuted discriminant function analysis also correctly classified calls by age group. During long song bouts the maximum F0 frequency of great call climaxes' also decreased. Additional data support the hypothesis that short high notes, associated with rapid inhalation as an individual catches its breath, reflect increased caller effort. Older females produced more high notes than younger females, but the difference only approached statistical significance, suggesting that calling effort may be similar across different ages. Finally, for the first time in this species, we measured peak intensity of calls in captive females. They were capable of producing climaxes in excess of 100 dB at close range (2.7 m).

CONCLUSIONS

Age and within-bout differences in the lar gibbon great call climax suggest that call features correlate with physical condition and thus the call may have evolved as an honest signal in the context of intra-sexual territorial defense and possibly also in male mate choice via sexual selection, although further testing of these hypotheses is necessary.

Human eating behaviour in an evolutionary ecological context

Present-day human eating behaviour in industrialised society is characterised by the consumption of high-energy-density diets and often unstructured feeding patterns, largely uncoupled from seasonal cycles of food availability. Broadly similar patterns of feeding are found among advantaged groups in economically-emerging and developing nations. Such patterns of feeding are consistent with the evolutionary ecological understanding of feeding behaviour of hominids ancestral to humans, in that human feeding adaptations are likely to have arisen in the context of resource seasonality in which diet choice for energy-dense and palatable foods would have been selected by way of foraging strategies for the maximisation of energy intake. One hallmark trait of human feeding behaviour, complex control of food availability, emerged with Homo erectus (1.9 x 10(6)-200000 years ago), who carried out this process by either increased meat eating or by cooking, or both. Another key trait of human eating behaviour is the symbolic use of food, which emerged with modern Homo sapiens (100000 years ago to the present) between 25000 and 12000 years ago. From this and subsequent social and economic transformations, including the origins of agriculture, humans have come to use food in increasingly elaborate symbolic ways, such that human eating has become increasingly structured socially and culturally in many different ways.

Influence of urbanisation on physical activity and dietary changes in Huli-speaking population: a comparative study of village dwellers and migrants in urban settlements

The influence of urbanisation on physical activity and dietary changes was examined in a Papua New Guinea Highland population. Adult male and female subjects (n 56) were selected, including twenty-seven rural villagers and twenty-nine urban migrants. BMR was calculated from values measured in similar samples of Huli-speaking population, according to gender and body weight. Total daily energy expenditure (TEE) was assessed by 24 h heart rate (HR) monitoring (flex-HR method) and physical activity level (PAL) calculation was based on BMR. Energy, protein and fat intakes were measured by weighing food on a single day. Urban subjects were heavier and taller than their rural counterparts; significant differences were found in stature in men (P < 0.05) and body weight in women (P < 0.05). Urban subjects had longer sedentary periods (HR < or = flex-HR) and shorter active periods (HR > flex-HR) than rural subjects. Consequently, the former had lower TEE and PAL than the latter; significant differences were found in women (TEE, P < 0.05, PAL, P < 0.01) but not in men. Total daily energy intake and TEE were well balanced (<7 %) in all groups, whereas protein and fat intakes were considerably higher in urban subjects than rural subjects. Reduced PAL and increased fat intake by urban dwellers may increase the risks of obesity and chronic degenerative diseases.

Basal metabolic adaptation of the Evenki reindeer herders of Central Siberia

Previous research has suggested that basal metabolic rates (BMRs of indigenous circumpolar populations are elevated, perhaps as an adaptation to chronic, severe cold stress. This study examines variation in BMR among indigenous (Evenki) and nonindigenous (Russian immigrant) populations living in Central Siberia to determine: 1) whether the Evenki show evidence of increased metabolic rates, and 2) whether the metabolic responses of the Evenki are different from those of the recent Russian migrants ("controls"). BMRs were measured among 58 Evenki (19 men, 39 women) and 24 Russian (8 men, 16 women) adults (18-56 years of age) from three Siberian villages. Measured BMRs were compared to those predicted based on body weight and body SA (Consolazio et al., 1963; Schofield, 1985a,b). BMRs per unit weight and FFM were similar in Evenki and Russian men, whereas Evenki women had higher BMRs than their Russian peers. Relative to the Schofield (body weight) norms, Evenki men and women and Russian men all showed modest elevations in BMR, whereas Russian women had lower than expected BMRs. Compared to the Consolazio (surface area) estimates, both Evenki men and women showed significant elevations in BMR. Russian men also showed higher than expected BMRs, while those of Russian women were slightly below predicted levels. Age-related declines in BMR were evident among the women of both ethnic groups, but not among the men. Additionally, residence location was an important predictor of metabolic variation in the Evenki, with those of the more traditional village showing greater elevations in BMR. These results suggest that the Evenki display elevated metabolic needs, and this long-term adaptation reflects the interaction of genetics and level of acculturation. Am. J. Hum. Biol. 12:75-87, 2000. Copyright 2000 Wiley-Liss, Inc.

Daily energy expenditure across the course of lactation among urban Bangladeshi women

Measures of energy intake of lactating women in developing countries show that intakes are often lower than those recommended by international bodies, while fat-mass losses are often substantially less than the 3-4 kg used in the calculations of recommendations, suggesting that physiological adaptation must be commonplace among such women. The cost of lactation may be met by reduction in energy expenditure, including reduced physical activity, as well as by mobilization of bodily soft tissue. However, daily energy expenditure of lactating women has been shown to increase across the course of lactation among women in a rural population in the Philippines and an urban population in India, with a decline in body weight across the course of lactation in both studies. In the present study, total daily energy expenditure and anthropometric body composition were measured longitudinally in 68 mothers from a poor urban area of Dhaka, Bangladesh, at 0, 1, 2, 4, and 8 months of lactation, to determine whether the increasing energy expenditure across lactation observed elsewhere also occurs in Bangladeshi women. In addition, the extent to which an extended period of lactation was accompanied by weight and body fat change in these women was determined. Energy expenditure by heart-rate monitoring and activity report, and body composition from anthropometry was carried out four times across the 8-month period of lactation. A small decline in body fat mass and a significant increase in total energy expenditure across this period were observed, confirming similar observations elsewhere in the developing world.

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 x BMR for men in respective seasons (P <.005; TEE, 11.8 MJ/d and 13.9 MJ/d) and 1.77 and 2.0 x 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.

Differences between observed and predicted energy costs at rest and during exercise in three subsistence-level populations

Estimates of daily energy expenditure are important for many areas of research in human ecology and adaptability. The most common technique for estimating human energy expenditure under field conditions, the factorial method, generally relies on activity-specific energy costs derived from published sources, based largely on North American and European subjects. There is concern that such data may not be appropriate for non-Western populations because of differences in metabolic costs. The present study addresses this concern by comparing measured vs. predicted energy costs at rest and during sub-maximal exercise in 83 subjects (52 males, 31 females) from three subsistence-level populations (Siberian herders and highland and coastal Ecuadorian farmers). Energy costs at rest (i.e., lying, sitting and standing) and while performing a standard stepping exercise did not significantly differ among the three groups. However, resting energy costs were significantly elevated over predicted levels (+ 16% in men, + 11% in women), whereas exercising costs were comparable to predicted values (-6% in men, + 3% in women). Elevations in resting energy needs appear to reflect responses to thermal stress. These results indicate that temperature adjustments of resting energy costs are critical for accurately predicting daily energy needs among traditionally living populations.