According to traditional Chinese belief, oolong tea is effective in the control of body weight. Few controlled studies, however, have been conducted to measure the impact of tea on energy expenditure (EE) of humans. A randomized cross-over design was used to compare 24-h EE of 12 men consuming each of four treatments: 1) water, 2) full-strength tea (daily allotment brewed from 15 g of tea), 3) half-strength tea (brewed from 7.5 g tea) and 4) water containing 270 mg caffeine, equivalent to the concentration in the full-strength tea treatment. Subjects refrained from consuming caffeine or flavonoids for 4 d prior to the study. Tea was brewed each morning; beverages were consumed at room temperature as five 300 mL servings. Subjects received each treatment for 3 d; on the third day, EE was measured by indirect calorimetry in a room calorimeter. For the 3 d, subjects consumed a typical American diet. Energy content of the diet was tailored to each subject's needs as determined from a preliminary measure of 24-h EE by calorimetry. Relative to the water treatment, EE was significantly increased 2.9 and 3.4% for the full-strength tea and caffeinated water treatments, respectively. This increase over water alone represented an additional expenditure of 281 and 331 kJ/d for subjects treated with full-strength tea and caffeinated water, respectively. In addition, fat oxidation was significantly higher (12%) when subjects consumed the full-strength tea rather than water.

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Background: Various methods are used by epidemiologists to estimate the energy cost of physical activity; these include physical activity records and recalls. However, there is limited validation of these methods against the doubly labeled water technique for determining energy expenditure (EE). Objective: We compared EE as estimated by indirect methods (physical activity records and recall questionnaires) used in epidemiologic studies with EE obtained from doubly labeled water (EE DLW ) in free-living men. Design: We determined EE DLW , energy intake at weight maintenance, and EE from 7-d physical activity records (EE Record ) and a 7-d physical activity recall questionnaire (EE Recall ) in 24 men aged 41 ± 2.0 y (x -± SEM) with a body mass index (in kg/m 2 ) of 25.1 ± 0.5. Results: There was excellent agreement between EE DLW (13.27 ± 0.35 MJ/d) and energy intake (13.19 ± 0.36 MJ/d), with a difference of 0.5 ± 1.0% (x -± SE). The indirect measures of physical activity and EE were 14.17 ± 0.37 MJ/d for EE Record (difference from EE DLW : 7.9 ± 3.2%) and 17.40 ± 1.45 MJ/d for EE Recall (difference from EE DLW : 30.6 ± 9.9%). Conclusions: Seven-day physical activity records provide an acceptable estimate of EE in free-living adults compared with EE DLW , but 7-d physical activity recalls have limited application to estimate daily EE. For optimal validity, the 7-d physical activity records require good subject compliance and the provision of careful instructions for their use.Am J Clin Nutr 2002;75:519-25. KEY WORDSExercise, energy intake, Stanford 7-d physical activity questionnaire, physical activity records, physical activity recall, doubly labeled water, basal metabolic rate, men

This article addresses a number of key problems commonly confronted in the literature on international demand analysis. These include data issues and requirements, multistage budgeting, outliers, group heteroskedasticity, and model selection. A two-stage demand system is fit to International Comparison Programme data for 114 countries for nine aggregate categories and eight food sub-categories of goods. Outliers are identified and omitted from the sample. Parameter estimates for the two stages are obtained with a maximum-likelihood procedure that corrects for group heteroskedasticity. Countryspecific income and own-price elasticities are calculated and indicate that poor countries are more responsive to changes in income and prices than rich countries. We also find evidence for the strong version of Engel's law; when income doubles, the budget share of food declines by approximately 0.10.

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A calorimeter suitable for measuring human energy expenditure has been assembled by the US Department of Agriculture in Beltsville, Maryland. The room-sized calorimeter is 3.05 X 2.74 X 2.44 m (20.39 m3). Direct and indirect calorimetry methods are used to simultaneously measure heat emission and energy expenditure. A water-cooled gradient layer chamber is used to measure human heat production directly. Indirect calorimetry is ascertained by measuring the changes in gas composition of the air entering and existing the chamber. The inlet and outlet air are each sampled three times every 100 s with a multiple gas analyzer to determine carbon dioxide and methane production and oxygen consumption within the chamber. A total of 30 measurements, which include temperature, pressure, gas fractions, flow rates, direct heat transfer, electrical power, and motion within the chamber, are converted from electrical to digital signals and recorded on magnetic disk nine times each minute. Real-time calculations for directly and indirectly measured energy expenditure are continuously updated and displayed. The performance of the calorimeter is assessed by the combustion of alcohol within the chamber. Results of these tests indicate that the direct heat recovery is 99.7 +/- 2.6 (SD) % and the indirect heat recovery is 100.3 +/- 1.3 (SD) %.

To estimate sources and extent of variation in energy expenditure (EE), as measured by indirect calorimetry in a room-sized human calorimeter, a number of 24-h measurements were compiled. Measured oxygen consumption and carbon dioxide production from alcohol combustion experiments averaged 101.5% of the theoretical value with a coefficient of variation (CV) of 1.4%. Experiment 1 consisted of four men who had the following averages: age, 41 y; height, 179 cm; weight, 84.6 kg; and fat, 23.5%. Five measurements, separated by 1 d, were made on each subject. Daily and basal EE averaged 2852 and 1691 kcal/d, respectively, with a within-subject CV of 2.7% and 2.4%, respectively. Experiment 2 consisted of five men who had the following averages: age, 48 y; height, 181.6 cm; weight, 87 kg; and fat, 23%. Five measurements made on each subject were separated by 1-3 wk. Daily and basal EE averaged 2619 and 1837 kcal/d, respectively, with a within-subject CV of 4.6% and 2.9%, respectively.

Objectives: The purpose of this study was to compare estimates of daily energy expenditure (EE) using energy intake from self reported diet records, metabolizable energy intake balance, doubly labeled water and room calorimetry methods. Design: Cross sectional design. Setting: Beltsville Human Nutrition Research Center, Beltsville, MD USA. Interventions: Energy intake was measured using seven-day self reported diet records (EI), and metabolizable energy (ME) intake balance. EE was measured using doubly labeled water (TEE) and 24 h indirect room calorimetry (24 EE). Body composition was measured using stable isotope dilution and DEXA. Results: EI measured by self reported diet records was 22% less than ME intake balance, 23% less than TEE by doubly labeled water and 8% less than 24 EE by room calorimetry. 24 EE was 16% less than TEE and 16% less than ME. TEE was not signi®cantly greater than ME (0.3%). While mean ME, TEE and 24 EE measurements were signi®cantly lower in female compared to male subjects, mean EI and the mean percent difference between measurement methods were not. Conclusions: Direct comparison of these methods indicate self reported diet records and room calorimetry underestimate daily energy expenditure. While EI balance accurately estimates energy expenditure, EE measured by doubly labeled water is a more direct approach.