Chukars (Alectoris chukar) and Sand Partridges (Ammoperdix heyi), two ground—dwelling phasianids, are permanent residents of the Negev desert and are sympatric over much of their ranges. Sand Partridges (body mass = 150—250 g), however, inhabit only arid and very arid areas, whereas Chukars (mb = 350—600 g) are widely distributed and inhabit deserts only at the margins of their ranges. We compared some of the desert adaptations of these phasianids by measuring the seasonal field metabolic rates (FMR) and water influxes (using doubly labelled water), diet selection, and food requirements of free—living Chukars and Sand Partridges at a site where both species occurred. Both species showed adaptation in the form of low energy metabolism, which ranged from 43 to 81% of that expected for birds of similar body mass. During summer, Sand Partridges had lower energy expenditures (5.47 kJ°g— ⁰ . ⁶ ¹°d— ¹) and water influxes 72.3 mL°kg— ⁰.⁷ ⁵°d— ¹) than did Chukars (6.42 kJ°g— ⁰ . ⁶ ¹°d— ¹ and 93.5 mL°kg— ⁰ . ⁷ ⁵°d— ¹, respectively), indicating more pronounced adjustments to arid conditions in the desert specialist. However, both species obtained more than half of their water influx in summer by drinking. Their summer diet was relatively dry, consisting mainly of seeds (80%) along with some green vegetation (18%) and, in Chukars, occasional arthropods. This situation changed abruptly after winter rains, which induced germination and reduced the availability of seeds. Chukars were unable to maintain energy balance in the face of low ambient temperatures and a diet (90% green vegetation) that contained much water but comparatively little energy, and they mobilized fat reserves to meet energy requirements. Most Sand Partridges left the study area after winter rains, apparently migrating to the lower elevation, warmer, and drier Arava (part of the Rift Valley). The winter rainy season appears to be the most stressful time of the year for both species. The adaptations to hot, dry conditions possessed by Sand Partridges may be accompanied by constraints on their abilities to cope with cool, wet conditions, and this may restrict them to arid and very arid habitats.

Information on the macronutrient composition of the diet is needed in doubly labeled water studies to convert measured rates of carbon dioxide production into values for total energy expenditure. There is no general consensus, however, about the best method to determine food intake for this purpose. Four common methods of measuring food intake (7-day weighed food intake, 24-hour recall, and Fred Hutchinson Cancer Research Center/Block and Willett food frequency questionnaires) were tested for their ability to provide comparable food quotient and total energy expenditure data in doubly labeled water studies in 10 young and 10 older women. All methods gave mean values for total energy expenditure that were within 1% of each other. Individual values obtained using the 24-hour recall and food frequency questionnaires were within +/-3% (standard deviation) of values determined using data from the 7-day weighed food record. These results suggest that it is not necessary to use time-consuming and expensive 7-day food records in doubly labeled water studies; instead, food intake data obtained more easily by 24-hour recall or food frequency questionnaire can provide comparable data.

The use of food quotients (FQ) calculated from dietary records is proposed for predicting respiratory quotients (RQ) that are needed for calculating free-living energy expenditure determined by the doubly-labeled water method which predicts respiratory CO2 production. This approach is based on the fact that, over the relatively long periods of double-isotope measurements (10-20 days), FQ (which can be obtained from a single 4-day measurement of dietary composition) must equal RQ in subjects in energy balance. It is shown that FQ can easily be adjusted to account for anabolism or catabolism for subjects not in energy balance. Typical RQ values are reported for various population sub-groups residing in the United Kingdom (omnivorous adults, vegetarians, vegans, Asian immigrants, and weaned and breast- and bottle-fed infants).(wz)

Objective: To study whether eating or physical-activity (PA) habits differ between obese and non-obese monozygotic (MZ) co-twins independent of genetic effects. Methods: Rare MZ pairs discordant for obesity (n=14, body mass index difference 5.2±1.8 kg m–2) and weight-concordant control pairs (n=10, 1.0±0.7 kg m–2), identified through a population-based registry of 24–28-year-old twins (n=658 MZ pairs), completed 3-day food and PA diaries and eating behavior questionnaires. Each twin was asked to compare his/her own eating and PA patterns with the co-twin's behavior by structured questionnaires. Accuracy of energy intake was validated by doubly labeled water. Results: Non-obese co-twins consistently reported that their obese twin siblings ate more food overall, consumed less healthy foods and exercised less than the non-obese co-twins do. However, no differences in energy intake (9.6±1.0 MJ per day vs 9.8±1.1 MJ per day, respectively) in the food diaries or in the mean PA level (1.74±0.02 vs 1.79±0.04, respectively) in the PA diaries were found between obese and non-obese co-twins. A considerable underreporting of energy intake (3.2±1.1 MJ per day, P=0.036) and overreporting of PA (1.8±0.8 MJ per day, P=0.049) was observed in the obese, but not in the non-obese co-twins. Conclusions: On the basis of rare MZ twin pairs discordant for obesity, the co-twin assessments confirmed substantial differences in eating and PA behavior between obese and non-obese persons. These may be overlooked in population studies using food and PA diaries because of considerable misreporting by the obese.

Background: Measurements of dietary intake in obese and overweight populations are often inaccurate because food intakes are underestimated. Objective: The purpose of this study was to evaluate the validity of the combined use of observer-recorded weighed-food records and 24-h snack recalls in estimating energy intakes in overweight and obese individuals. Design: Subjects were 32 healthy women and 22 healthy men with mean body mass indexes (in kg/m2) of 29.5 and 30.3, respectively. Energy intake (EI) was measured over 2 wk in a university cafeteria. No restrictions were made on meal frequency or EI. To document food consumed outside the cafeteria, 24-h snack recalls were conducted before meals. Energy expenditure (EE) was measured with the doubly labeled water (DLW) method (EEDLW). Energy balance was determined by measuring body weight at the beginning and end of the 2-wk period. Results: The mean EI in the women (10.40 +/- 1.94 MJ/d) and men (14.37 +/- 3.21 MJ/d) was not significantly lower than the EEDLW in the women (10.86 +/- 1.76 MJ/d) and men (14.14 +/- 2.83 MJ/d). The mean EI represented 96.9 +/- 17.0% and 103 +/- 18.9% of the measured EE for women and men, respectively. There were no significant changes in weight in the group as a whole or by sex at the end of the testing period; the men lost 0.23 +/- 1.58 kg and the women lost 0.25 +/- 1.09 kg. Conclusion: The combination of observer-recorded food records and 24-h snack recalls is a valid method for measuring EI in overweight and obese individuals.