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Background/Objectives:Brown adipose tissue (BAT) is a potential therapeutic target against obesity and diabetes through thermogenesis and substrate disposal with cold exposure. The role of BAT in energy metabolism under thermoneutral conditions, however, remains controversial. We assessed the contribution of BAT to energy expenditure (EE), particularly diet-induced thermogenesis (DIT), and substrate utilization in human adults.Methods:In this cross-sectional study, BAT activity was evaluated in 21 men using 18F-fluoro-2-deoxy-D-glucose positron emission tomography combined with computed tomography (18F-FDG-PET/CT) after cold exposure (19 °C). The subjects were divided into BAT-positive (n=13) and BAT-negative (n=8) groups according to the 18F-FDG-PET/CT findings. Twenty-four hour EE, DIT and respiratory quotient were measured using a whole-room indirect calorimeter at 27 °C.Results:Body composition, blood metabolites and 24-h EE did not differ between groups. DIT (%), calculated as DIT divided by total energy intake, however, was significantly higher in the BAT-positive group (BAT-positive: 9.7±2.5%, BAT-negative: 6.5±4.0%, P=0.03). The 24-h respiratory quotient was significantly lower (P=0.03) in the BAT-positive group (0.861±0.027) than in the BAT-negative group (0.889±0.024).Conclusion:DIT and fat utilization were higher in BAT-positive subjects compared to BAT-negative subjects, suggesting that BAT has a physiologic role in energy metabolism.

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The thermogenic effects of green tea catechin have been repeatedly reported, but their mechanisms are poorly understood. The aim of this study was to investigate the acute and chronic effects of catechin on brown adipose tissue (BAT), a site specialized for nonshivering thermogenesis, in humans. Fifteen healthy male volunteers underwent fluorodeoxyglucose-positron emission tomography to assess BAT activity. To examine the acute catechin effect, whole-body energy expenditure (EE) after a single oral ingestion of a beverage containing 615 mg catechin and 77 mg caffeine (catechin beverage) was measured. Next, to investigate the chronic catechin effects, 10 men with low BAT activity were enrolled. Before and after ingestion of the catechin beverage 2 times/d for 5 wk, cold-induced thermogenesis (CIT) after 2 h of cold exposure at 19°C, which is proportional to BAT activity, was examined. Both the acute and chronic trials were single-blinded, randomized, placebo-controlled, season-matched crossover studies. A single ingestion of the catechin beverage increased EE in 9 subjects who had metabolically active BAT (mean ± SEM: +15.24 ± 1.48 kcal, < 0.01) but not in 6 subjects who had negligible activities (mean ± SEM: +3.42 ± 2.68 kcal). The ingestion of a placebo beverage containing 82 mg caffeine produced a smaller and comparative EE response in the 2 subject groups. Multivariate regression analysis revealed a significant interaction between BAT and catechin on EE (β = 0.496, = 0.003). Daily ingestion of the catechin beverage elevated mean ± SEM CIT (from 92.0 ± 26.5 to 197.9 ± 27.7 kcal/d; = 0.009), whereas the placebo beverage did not change it. Orally ingested tea catechin with caffeine acutely increases EE associated with increased BAT activity and chronically elevates nonshivering CIT, probably because of the recruitment of BAT, in humans. These trials were registered at www.umin.ac.jp/ctr/ as UMIN000016361.

The increase in obesity and lipid disorders in industrialized countries may be due to irregular eating patterns. Few studies have investigated the effects of nighttime snacking on energy metabolism. We examined the effects of nighttime snacking for 13 days on energy metabolism. Eleven healthy women (means ± SD; age: 23 ± 1 yr; body mass index: 20.6 ± 2.6 kg/m(2)) participated in this randomized crossover trial for a 13-day intervention period. Subjects consumed a specified snack (192.4 ± 18.3 kcal) either during the daytime (10:00) or the night time (23:00) for 13 days. On day 14, energy metabolism was measured in a respiratory chamber without snack consumption. An oral glucose tolerance test was performed on day 15. Relative to daytime snacking, nighttime snacking significantly decreased fat oxidation (daytime snacking: 52.0 ± 13.6 g/day; nighttime snacking: 45.8 ± 14.0 g/day; P = 0.02) and tended to increase the respiratory quotient (daytime snacking: 0.878 ± 0.022; nighttime snacking: 0.888 ± 0.021; P = 0.09). The frequency of snack intake and energy intake, body weight, and energy expenditure were not affected. Total and low-density lipoprotein (LDL) cholesterol significantly increased after nighttime snacking (152 ± 26 mg/dl and 161 ± 29 mg/dl; P = 0.03 and 76 ± 20 mg/dl and 83 ± 24 mg/dl; P = 0.01, respectively), but glucose and insulin levels after the glucose load were not affected. Nighttime snacking increased total and LDL cholesterol and reduced fat oxidation, suggesting that eating at night changes fat metabolism and increases the risk of obesity.

Purpose The purpose of this study was to evaluate acute effects of coffee with a high content of chlorogenic acids and different hydroxyhydroquinone contents on postprandial endothelial dysfunction. Methods This was a single-blind, randomized, placebo-controlled, crossover-within-subject clinical trial. A total of 37 patients with borderline or stage 1 hypertension were randomized to two study groups. The participants consumed a test meal with a single intake of the test coffee. Subjects in the Study 1 group were randomized to single intake of coffee with a high content of chlorogenic acids and low content of hydroxyhydroquinone or coffee with a high content of chlorogenic acids and a high content of hydroxyhydroquinone with crossover. Subjects in the Study 2 group were randomized to single intake of coffee with a high content of chlorogenic acids and low content of hydroxyhydroquinone or placebo coffee with crossover. Endothelial function assessed by flow-mediated vasodilation and plasma concentration of 8-isoprostanes were measured at baseline and at 1 and 2 h after coffee intake. Results Compared with baseline values, single intake of coffee with a high content of chlorogenic acids and low content of hydroxyhydroquinone, but not coffee with a high content of chlorogenic acids and high content of hydroxyhydroquinone or placebo coffee, significantly improved postprandial flow-mediated vasodilation and decreased circulating 8-isoprostane levels. Conclusions These findings suggest that a single intake of coffee with a high content of chlorogenic acids and low content of hydroxyhydroquinone is effective for improving postprandial endothelial dysfunction.

The effects of sleep restriction on energy metabolism and appetite remain controversial. We examined the effects of shortened sleep duration on energy metabolism, core body temperature (CBT), and appetite profiles. Nine healthy men were evaluated in a randomised crossover study under two conditions: a 3.5-h sleep duration and a 7-h sleep duration for three consecutive nights followed by one 7-h recovery sleep night. The subjects’ energy expenditure (EE), substrate utilisation, and CBT were continually measured for 48 h using a whole-room calorimeter. The subjects completed an appetite questionnaire every hour while in the calorimeter. Sleep restriction did not affect total EE or substrate utilisation. The 48-h mean CBT decreased significantly during the 3.5-h sleep condition compared with the 7-h sleep condition (7-h sleep, 36.75 ± 0.11 °C; 3.5-h sleep, 36.68 ± 0.14 °C; p = 0.016). After three consecutive nights of sleep restriction, fasting peptide YY levels and fullness were significantly decreased (p = 0.011), whereas hunger and prospective food consumption were significantly increased, compared to those under the 7-h sleep condition. Shortened sleep increased appetite by decreasing gastric hormone levels, but did not affect EE, suggesting that greater caloric intake during a shortened sleep cycle increases the risk of weight gain.

The components of roasted or green coffee beans that promote abdominal fat reduction are not clear. We investigated the effects of daily consumption of coffee enriched in chlorogenic acids (CGA) on abdominal fat area in a randomized, double-blind, parallel controlled trial. Healthy, overweight men and women (n = 150, body mass index (BMI) ≥25 to <30 kg/m2) were randomly allocated to high-CGA (369 mg CGA/serving) or control (35 mg CGA/serving) coffee groups. Instant coffee was consumed once daily for 12 weeks, with four-week pre- and post-observation periods. Abdominal fat area and anthropometric measurements were analyzed at baseline and at four, eight, and 12 weeks, and 142 subjects completed the trial. Visceral fat area (VFA), total abdominal fat area (TFA), body weight, and waist circumference significantly decreased in the CGA group compared with the control group, with a group × time interaction (p < 0.001, p = 0.001, p = 0.025, and p = 0.001, respectively). Changes in VFA and TFA from baseline to 12 weeks were significantly greater in the CGA group than in the control group (−9.0 ± 13.9 cm2 vs. −1.0 ± 14.3 cm2, p < 0.001; −13.8 ± 22.9 cm2 vs. −2.0 ± 16.2 cm2, p < 0.001). No severe adverse events occurred. Consumption of high-CGA coffee for 12 weeks by overweight adults might lower VFA, TFA, BMI, and waist circumference.