***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: Background Cold-stimulated adaptive thermogenesis in brown adipose tissue ( BAT ) to increase energy expenditure is suggested as a possible therapeutic target for the treatment of obesity . We have recently shown high prevalence of BAT in adult humans , which was inversely related to body mass index ( BMI ) and body fat percentage ( BF% ) , suggesting that obesity is associated with lower BAT activity . Here , we examined BAT activity in morbidly obese subjects and its role in cold-induced thermogenesis ( CIT ) after applying a personalized cooling protocol . We hypothesize that morbidly obese subjects show reduced BAT activity upon cold exposure . Methods and Findings After applying a personalized cooling protocol for maximal non-shivering conditions , BAT activity was determined using positron-emission tomography and computed tomography ( PET-CT ) .  Cold-induced BAT activity  was detected in three out of 15 morbidly obese subjects . Combined with results from lean to morbidly obese subjects ( n = 39 ) from previous study , the collective data show a highly significant correlation between BAT activity and body composition ( P<0.001 ) , respectively explaining 64 % and 60 % of the variance in BMI ( r = 0.8 ; P<0.001 ) and BF% ( r = 0.75 ; P<0.001 ) . Obese individuals demonstrate a blunted CIT combined with low BAT activity . Only in BAT-positive subjects ( n = 26 ) mean energy expenditure was increased significantly upon cold exposure ( 51.5±6.7 J/s versus 44.0±5.1 J/s , P = 0.001 ) , and the increase was significantly higher compared to BAT-negative subjects ( + 15.5±8.9 % versus + 3.6±8.9 % , P = 0.001 ) , indicating a role for BAT in CIT in humans . Conclusions This study shows that in an extremely large range of body compositions , BAT activity is highly correlated with BMI and BF% . BAT-positive subjects showed higher CIT , indicating that BAT is also in humans involved in adaptive thermogenesis . Increasing BAT activity could be a therapeutic target in ( morbid ) obesity BACKGROUND Studies in animals indicate that brown adipose tissue is important in the regulation of body weight , and it is possible that individual variation in adaptive thermogenesis can be attributed to variations in the amount or activity of brown adipose tissue . Until recently , the presence of brown adipose tissue was thought to be relevant only in small mammals and infants , with negligible physiologic relevance in adult humans . We performed a systematic examination of the presence , distribution , and activity of brown adipose tissue in lean and obese men during exposure to cold temperature .  Brown-adipose-tissue activity was studied in relation to body composition and energy metabolism . METHODS We studied 24 healthy men--10 who were lean ( body-mass index [ BMI ] [ the weight in kilograms divided by the square of the height in meters ] , < 25 ) and 14 who were overweight or obese ( BMI , > or = 25)--under thermoneutral conditions ( 22 degrees C ) and during mild cold exposure ( 16 degrees C ) . Putative brown-adipose-tissue activity was determined with the use of integrated (18)F-fluorodeoxyglucose positron-emission tomography and computed tomography .  Body composition and energy expenditure were measured with the use of dual-energy x-ray absorptiometry and indirect calorimetry . RESULTS Brown-adipose-tissue activity was observed in 23 of the 24 subjects ( 96 % ) during cold exposure but not under thermoneutral conditions . The activity was significantly lower in the overweight or obese subjects than in the lean subjects ( P=0.007 ) . BMI and percentage of body fat both had significant negative correlations with brown adipose tissue , whereas resting metabolic rate had a significant positive correlation . CONCLUSIONS The percentage of young men with brown adipose tissue is high , but its activity is reduced in men who are overweight or obese . Brown adipose tissue may be metabolically important in men , and the fact that it is reduced yet present in most overweight or obese subjects may make it a target for the treatment of obesity The ability to alter the amount and activity of brown adipose tissue ( BAT ) in human adults is a potential strategy to manage obesity and related metabolic disorders associated with food , drug , and environmental stimuli with BAT activating/recruiting capacity . Infrared thermography ( IRT ) provides a non-invasive and inexpensive alternative to the current methods ( e.g. 18F-FDG PET ) used to assess BAT . We have quantified BAT activation in the cervical-supraclavicular ( C-SCV ) region using IRT video imaging and a novel image computational algorithm by study ing C-SCV heat production in healthy young men after cold stimulation and the ingestion of capsinoids in a prospect i ve double-blind placebo-controlled r and omized trial . Subjects were divided into low-BAT and high-BAT groups based on changes in IR emissions in the C-SCV region induced by cold . The high-BAT group showed significant increases in energy expenditure , fat oxidation , and heat output in the C-SCV region post-capsinoid ingestion compared to post-placebo ingestion , but the low-BAT group did not . Based on these results , we conclude that IRT is a promising tool for quantifying BAT activity Brown adipose tissue ( BAT ) can be identified by (18)F-fluorodeoxyglucose (FDG)-positron emission tomography ( PET ) in adult humans . Thirteen healthy male volunteers aged 20 - 28 years underwent FDG-PET  after 2-h cold exposure at 19 ° C with light-clothing and intermittently putting their legs on an ice block . When exposed to cold , 6 out of the 13 subjects showed marked FDG uptake into adipose tissue of the supraclavicular and paraspinal regions ( BAT-positive group ) , whereas the remaining seven showed no detectable uptake ( BAT-negative group ) . The BMI and body fat content were similar in the two groups . Under warm conditions at 27 ° C , the energy expenditure of the BAT-positive group estimated by indirect calorimetry was 1,446 ± 97 kcal/day , being comparable with that of the BAT-negative group ( 1,434 ± 246 kcal/day ) . After cold exposure , the energy expenditure increased markedly by 410 ± 293 ( P < 0.05 ) and slightly by 42 ± 114 kcal/day ( P = 0.37 ) in the BAT-positive and -negative groups , respectively . A positive correlation ( P < 0.05 ) was found between the cold-induced rise in energy expenditure and the BAT activity quantified from FDG uptake . After cold exposure , the skin temperature in the supraclavicular region close to BAT deposits dropped by 0.14 ° C in the BAT-positive group , whereas it dropped more markedly ( P < 0.01 ) by 0.60 ° C in the BAT-negative group . The skin temperature drop in other regions apart from BAT deposits was similar in the two groups . These results suggest that BAT is involved in cold-induced increases in whole-body energy expenditure , and , thereby , the control of body temperature and adiposity in adult humans Historically , brown adipose tissue has been elusive and not easy to detect , hence its relative obscurity in human physiology until its rediscovery in 2009 . At that point , it was proven that the symmetrical artefacts frequently detected on positron emission tomography-computed tomography ( PET-CT ) , which resolved if the environment was kept warm , were brown adipose tissue deposits . PET-CT has remained the stalwart of human brown adipose tissue research and is still considered the gold st and ard . However , PET-CT exposes the participant to ionising radiation , limiting studies to large , but retrospective , review of clinical imaging or a small-scale , but prospect i ve , design . Within this context , alternative imaging modalities have been sought . Due to the heat-generating properties of brown adipose tissue , infrared thermography is a natural c and i date for measuring its activity and the supraclavicular depot is relatively superficial , allowing detection of the heat signature . Infrared thermography is a non-invasive , non-contact technique for measuring temperature remotely . Recent developments in image analysis techniques have facilitated the use of infrared thermography to study  brown adipose tissue activation in population s , and in ways , not previously feasible 
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Conclusion : Despite the large number of published method ologies , IRT is a promising method for detecting BAT activation .