Energy Expenditure in Humans: Principles, Methods, and Changes Throughout the Life Course.

Humans require energy to sustain their daily activities throughout their lives. This narrative review aims to (a) summarize principles and methods for studying human energy expenditure, (b) discuss the main determinants of energy expenditure, and (c) discuss the changes in energy expenditure throughout the human life course. Total daily energy expenditure is mainly composed of resting energy expenditure, physical activity energy expenditure, and the thermic effect of food. Total daily energy expenditure and its components are estimated using variations of the indirect calorimetry method. The relative contributions of organs and tissues determine the energy expenditure under different physiological conditions. Evidence shows that energy expenditure varies along the human life course, at least in part due to changes in body composition, the mass and specific metabolic rate of organs and tissues, and levels of physical activity. This information is crucial to estimate human energy requirements for maintaining health throughout the life course.

Reproducibility of the energy metabolism response to an oral glucose tolerance test: influence of a postcalorimetric correction procedure.

PURPOSE: Metabolic flexibility (MetF), which is a surrogate of metabolic health, can be assessed by the change in the respiratory exchange ratio (RER) in response to an oral glucose tolerance test (OGTT). We aimed to determine the day-to-day reproducibility of the energy expenditure (EE) and RER response to an OGTT, and whether a simulation-based postcalorimetric correction of metabolic cart readouts improves day-to-day reproducibility. METHODS: The EE was assessed (12 young adults, 6 women, 27 ± 2 years old) using an Omnical metabolic cart (Maastricht Instruments, Maastricht, The Netherlands) after an overnight fast (12 h) and after a 75-g oral glucose dose on 2 separate days (48 h). On both days, we assessed EE in 7 periods (one 30-min baseline and six 15-min postprandial). The ICcE was performed immediately after each recording period, and capillary glucose concentration (using a digital glucometer) was determined. RESULTS: We observed a high day-to-day reproducibility for the assessed RER (coefficients of variation [CV] < 4%) and EE (CVs < 9%) in the 7 different periods. In contrast, the RER and EE areas under the curve showed a low day-to-day reproducibility (CV = 22% and 56%, respectively). Contrary to our expectations, the postcalorimetric correction procedure did not influence the day-to-day reproducibility of the energy metabolism response, possibly because the Omnical's accuracy was ~ 100%. CONCLUSION: Our study demonstrates that the energy metabolism response to an OGTT is poorly reproducible (CVs > 20%) even using a very accurate metabolic cart. Furthermore, the postcalorimetric correction procedure did not influence the day-to-day reproducibility. Trial registration NCT04320433; March 25, 2020.

Association of meal timing with body composition and cardiometabolic risk factors in young adults.

PURPOSE: To investigate the association of meal timing with body composition and cardiometabolic risk factors in young adults. METHODS: In this cross-sectional study participated 118 young adults (82 women; 22 ± 2 years old; BMI: 25.1 ± 4.6 kg/m2). Meal timing was determined via three non-consecutive 24-h dietary recalls. Sleep outcomes were objectively assessed using accelerometry. The eating window (time between first and last caloric intake), caloric midpoint (local time at which ≥ 50% of daily calories are consumed), eating jetlag (variability of the eating midpoint between non-working and working days), time from the midsleep point to first food intake, and time from last food intake to midsleep point were calculated. Body composition was determined by DXA. Blood pressure and fasting cardiometabolic risk factors (i.e., triglycerides, total cholesterol, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, and insulin resistance) were measured. RESULTS: Meal timing was not associated with body composition (p > 0.05). The eating window was negatively related to HOMA-IR and cardiometabolic risk score in men (R2 = 0.348, ß = - 0.605; R2 = 0.234, ß = - 0.508; all p ≤ 0.003). The time from midsleep point to first food intake was positively related to HOMA-IR and cardiometabolic risk score in men (R2 = 0.212, ß = 0.485; R2 = 0.228, ß = 0.502; all p = 0.003). These associations remained after adjusting for confounders and multiplicity (all p ≤ 0.011). CONCLUSIONS: Meal timing seems unrelated to body composition in young adults. However, a longer daily eating window and a shorter time from midsleep point to first food intake (i.e., earlier first food intake in a 24 h cycle) are associated with better cardiometabolic health in young men. CLINICAL TRIAL REGISTRATION: NCT02365129 ( https://www. CLINICALTRIALS: gov/ct2/show/NCT02365129?term=ACTIBATE&draw=2&rank=1 ).

A bout of endurance and resistance exercise transiently decreases plasma levels of bile acids in young, sedentary adults.

Circulating bile acids (BA) are signaling molecules that control glucose and lipid metabolism. However, the effects of acute exercise on plasma levels of BA in humans remain poorly understood. Here, we evaluate the effects of a bout of maximal endurance exercise (EE) and resistance exercise (RE) on plasma levels of BA in young, sedentary adults. Concentration of eight plasma BA was measured by liquid chromatography-tandem mass spectrometry before and 3, 30, 60, and 120 min after each exercise bout. Cardiorespiratory fitness (CRF) was assessed in 14 young adults (21.8 ± 2.5 yo, 12 women); muscle strength was assessed in 17 young adults (22.4 ± 2.5 yo, 11 women). EE transiently decreased plasma levels of total, primary, and secondary BA at 3 and 30 min after exercise. RE exerted a prolonged reduction in plasma levels of secondary BA (p < 0.001) that lasted until 120 min. Primary BA levels of cholic acid (CA) and chenodeoxycholic acid (CDCA) were different across individuals with low/high CRF levels after EE (p ≤ 0.044); CA levels were different across individuals with low/high handgrip strength levels. High CRF individuals presented higher levels of CA and CDCA 120 min after exercise vs baseline (+77% and +65%) vs the low CRF group (-5% and -39%). High handgrip strength levels individuals presented higher levels of CA 120 min after exercise versus baseline (+63%) versus the low handgrip strength group (+6%). The study findings indicate that an individual's level of physical fitness can influence how circulating BA respond to both endurance and resistance exercise. Additionally, the study suggests that changes in plasma BA levels after exercising could be related to the control of glucose homeostasis in humans.

Effect of Moderate Versus Vigorous Exercise Intensity on Body Composition in Young Untrained Adults: The Activating Brown Adipose Tissue Through Exercise (ACTIBATE) Randomized Controlled Trial.

The present study aimed to investigate the effect of a 24-week aerobic + resistance training programs at moderate versus vigorous intensity on body composition, and the persistence of the changes after a 10-month free-living period, in young untrained adults. This report is based on a secondary analysis from the activating brown adipose tissue through exercise (ACTIBATE) single-center unblinded randomized controlled trial. A total of 144 young adults (65.6% women) aged 18-25 years were randomly allocated to three different groups: (a) aerobic + resistance exercise training program based on the international physical activity recommendations at vigorous intensity (Ex-Vigorous group), (b) at moderate intensity (Ex-Moderate group), and (c) control group (no exercise). Body composition outcomes were determined by a dual-energy X-ray absorptiometry scanner. Both Ex-Vigorous and Ex-Moderate decreased body weight, fat mass, and visceral adipose tissue mass in a similar manner (all p < .04). After a 10-month free-living period, these parameters returned to baseline levels in both exercise groups (all ps < .03). No differences between the exercise groups and the control group were noted in lean mass changes (all ps > .1). A 24-week aerobic + resistance training intervention based on the international physical activity recommendations was enough to improve body weight, fat mass, and visceral adipose tissue mass in untrained young adults, independently of the exercise intensity (moderate vs. vigorous).

Association of shivering threshold time with body composition and brown adipose tissue in young adults.

PURPOSE: Brown adipose tissue (BAT) increases metabolic heat production in response to cold exposure. Body size and composition are involved in the human cold response, yet the influence of BAT herein have not fully been explored. Here, we aimed to study the association of the cold-induced shivering threshold time with body composition, BAT, the perception of shivering and skin temperature in young adults. METHODS: 110 young healthy adults (81 females; age = 21.7 ± 2.1 years, BMI = 24.2 ± 4.3 kg/m2) underwent 2 h of individualized cooling, followed by the quantification of BAT using a18F-fluorodeoxyglucose ([18F]FDG) positron emission tomography-computed tomography (PET-CT) scan. Body mass index (BMI), lean mass, fat mass and body surface area (BSA) were also measured. Shivering threshold time was defined as the time until shivering occurred using an individualized cooling protocol. RESULTS: The shivering threshold time was on average 116.1 min for males and 125.8 min for females, and was positively associated to BMI (ß = 3.106; R2 = 0.141; p = 0.001), lean mass (ß = 2.295; R2 = 0.128; p = 0.001) and fat mass (ß = 1.492; R2 = 0.121; p = 0.001) in females, but not in males (all p ≥ 0.409). The shivering threshold time was positively associated with BSA in males (p = 0.047) and females (p = 0.001), but it was not associated with BAT volume or [18F]FDG uptake nor with the perception of shivering and skin temperature perception in both sexes. CONCLUSION: The shivering threshold time is positively associated with whole-body adiposity and lean mass in females, but not in males. The shivering threshold time was positively associated with BSA, but no association was observed with BAT nor with the perception of shivering or skin temperature. Future research should consider the influence of body composition when applying cooling protocols among individuals with different phenotypical features.

Assessment of energy expenditure: are calories measured differently for different diets?

PURPOSE OF REVIEW: The prevalence and burden of obesity has reached alarming levels. The assessment of human energy expenditure enables the identification of obesity-prone and obesity-resistant individuals and helps to explain the short and long-term success of weight loss treatments. In this review, we describe the state-of-the-art methods used in the assessment of human energy expenditure and the impact of dietary intake on the interpretation of the data. RECENT FINDINGS: The reference techniques to assess energy expenditure in humans have not significantly changed during the last century. Today, indirect calorimetry, either using a metabolic chamber or a metabolic cart, is the favored method to assess human energy expenditure and is the only method enabling the assessment of macronutrient oxidation. The doubly labeled water method however provides accurate assessment of human energy expenditure under free living conditions. SUMMARY: Although energy expenditure and macronutrient oxidation can be assessed by simple calculations from oxygen consumption and carbon dioxide production, these calculations can provide erroneous results or require corrections and/or more complex interpretation when several biochemical pathways are simultaneously engaged. Such physiological mechanisms are often elicited by dietary interventions including, among other, gluconeogenesis, lipogenesis, ketogenesis, alcohol oxidation and under or overfeeding.

Endocrine Mechanisms Connecting Exercise to Brown Adipose Tissue Metabolism: a Human Perspective.

PURPOSE OF REVIEW: To summarize the state-of-the-art regarding the exercise-regulated endocrine signals that might modulate brown adipose tissue (BAT) activity and/or white adipose tissue (WAT) browning, or through which BAT communicates with other tissues, in humans. RECENT FINDINGS: Exercise induces WAT browning in rodents by means of a variety of physiological mechanism. However, whether exercise induces WAT browning in humans is still unknown. Nonetheless, a number of protein hormones and metabolites, whose signaling can influence thermogenic adipocyte's metabolism, are secreted during and/or after exercise in humans from a variety of tissues and organs, such as the skeletal muscle, the adipose tissue, the liver, the adrenal glands, or the cardiac muscle. Overall, it seems plausible to hypothesize that, in humans, exercise secretes an endocrine cocktail that is likely to induce WAT browning, as it does in rodents. However, even if exercise elicits a pro-browning endocrine response, this might result in a negligible effect if blood flow is restricted in thermogenic adipocyte-rich areas during exercise, which is still to be determined. Future studies are needed to fully characterize the exercise-induced secretion (i.e., to determine the effect of the different exercise frequency, intensity, type, time, and volume) of endocrine signaling molecules that might modulate BAT activity and/or WAT browning or through which BAT communicates with other tissues, during exercise. The exercise effect on BAT metabolism and/or WAT browning could be one of the still unknown mechanisms by which exercise exerts beneficial health effects, and it might be pharmacologically mimicked.

Prevalence of severe/morbid obesity and other weight status and anthropometric reference standards in Spanish preschool children: The PREFIT project.

BACKGROUND: Childhood obesity has become a major health problem in children under the age of 5 years. Providing reference standards would help paediatricians to detect and/or prevent health problems related to both low and high levels of body mass and to central adiposity later in life. Therefore, the aim of this study was to examine the prevalence of different weight status categories and to provide sex- and age-specific anthropometry reference standards for Spanish preschool children. METHODS: A total of 3178 preschool children (4.59±0.87 years old) participated in this study. Prevalence of different degrees of obesity (mild, severe, and morbid) and other weight status categories were determined. RESULTS: Reference standards were obtained. Prevalence of overweight and obese preschool children in the Spanish population ranged from 21.4 to 34.8%. Specifically, the obesity prevalence was 3.5, 1.2, and 1.3% of these subjects were categorized as mild, severe, and morbid obese. Sex- and age-specific reference standards for anthropometric parameters are provided for every 0.25 years (i.e. every trimester of life). CONCLUSION: Our results show a high prevalence of overweight/obese preschoolers. The provided sex- and age-specific anthropometric reference standards could help paediatricians to track and monitor anthropometric changes at this early stage in order to prevent overweight/obesity.

Association between brown adipose tissue and bone mineral density in humans.

BACKGROUND: Brown adipose tissue (BAT) seems to play a role in bone morphogenesis. A negative association has been reported between BAT and bone mineral density (BMD) in women, but not in men. A panel of experts has recently published a set of recommendations for BAT assessment, and thus, to re-address previously reported associations is needed. This study aimed to investigate the association between cold-induced BAT 18F-Fluorodeoxyglucose (18F-FDG) uptake and BMD in young healthy adults. METHODS: Ninety-eight healthy adults (68 women; 22 ± 2.2 years old; 24.3 ± 4.5 kg/m2) cold-induced BAT was assessed by means of an 18F-FDG positron emission tomography-computed tomography (PET-CT) scan preceded by a personalized cold stimulation. The cold exposure consisted in 2 h in a mild cold room at 19.5-20 °C wearing a water perfused cooling vest set 4 °C above the individual shivering threshold. Total body and lumbar spine BMD were assessed by a whole-body DXA scan. RESULTS: We found no association between BMD and cold-induced BAT volume, mean, and maximal activity (all P > 0.1) in neither young and healthy men nor women. These results remained unchanged when adjusting by height, by body composition, and by objectively assessed physical activity. Sensitivity analyses using the criteria to quantify cold-induced BAT-related parameters applied in previous studies did not change the results. CONCLUSIONS: In summary, our study shows that there is no association between cold-induced BAT and BMD in young healthy adults. Moreover, our data support the notion that previously shown associations between BAT and BMD in healthy non-calorically restricted individuals, could be driven by methodological issues related to BAT assessment and/or sample size limitations.

Evidence of high 18 F-fluorodeoxyglucose uptake in the subcutaneous adipose tissue of the dorsocervical area in young adults.

NEW FINDINGS: What is the central question of this study? In some studies, biopsies have been performed of the subcutaneous adipose tissue in the abdomen, and they failed to find browning markers. Is the abdomen the right place to take biopsies? What is the main finding and its importance? For first time, we observed that the glucose uptake in the dorsocervical subcutaneous adipose tissue is higher in comparison to other areas of subcutaneous adipose tissue. ABSTRACT: Neonates have subcutaneous brown adipose tissue (BAT) in the dorsocervical area, and it is thought that these depots gradually disappear with age. Here, we determined that young adults have high 18 F-flurodeoxyglucose (18 F-FDG) uptake in the subcutaneous adipose tissue (SAT) of the dorsocervical area. A total of 133 young adults (age 22 ± 2 years; body mass index 25 ± 5 kg m2 ) were included in the study. We performed a shivering threshold test for every participant. Later, we performed 2 h of personalized cold exposure, immediately before a positron emission tomography/computed tomography scan. We showed that 23 of 133 participants had 18 F-FDG uptake in the dorsocervical area that achieved the criteria to be considered BAT, mainly in women (96%, n = 22 of 23). In the whole sample, the glucose uptake in the SAT of the dorsocervical area was positively correlated with BAT volume and activity located in the supraclavicular area. We showed that the 18 F-FDG uptake of the SAT of the dorsocervical area in humans is different from that of other SAT areas. Future studies are warranted to confirm the brown signature of this tissue.

Assessment of maximal fat oxidation during exercise: A systematic review.

Maximal fat oxidation during exercise (MFO) and the exercise intensity eliciting MFO (Fatmax ) are considered biological markers of metabolic health and performance. A wide range of studies have been performed to increase our knowledge about their regulation by exercise and/or nutritional intervention. However, numerous data collection and analysis approaches have been applied, which may have affected the MFO and Fatmax estimation. We aimed to systematically review the available studies describing and/or comparing different data collection and analysis approach factors that could affect MFO and Fatmax estimation in healthy individuals and patients. Two independent researchers performed the search. We included all original studies in which MFO and/or Fatmax were estimated by indirect calorimetry through an incremental graded exercise protocol published from 2002 to 2019. This systematic review provides key information about the factors that could affect MFO and Fatmax estimation: ergometer type, metabolic cart used, warm-up duration and intensity, stage duration and intensities imposed in the graded exercise protocol, time interval selected for data analysis, stoichiometric equation selected to estimate fat oxidation, data analysis approach, time of the day when the test was performed, fasting time/previous meal before the test, and testing days for MFO/Fatmax and maximal oxygen uptake assessment. We suggest that researchers measuring MFO and Fatmax should take into account these key methodological issues that can considerably affect the accuracy, validity, and reliability of the measurement. Likewise, when comparing different studies, it is important to check whether the above-mentioned key methodological issues are similar in such studies to avoid ambiguous and unacceptable comparisons.

Supraclavicular skin temperature measured by iButtons and 18F-fluorodeoxyglucose uptake by brown adipose tissue in adults.

Currently, 18 [F]-Fluorodeoxyglucose (18F-FDG) in combination with a positron emission tomography/computed tomography (PET/CT) scan analysis is the most commonly used method to quantify human BAT volume and activity. However, this technique presents several drawbacks which negatively affect participant's health. The aim of the present work is to determine whether supraclavicular skin temperature can be used as an indirect marker of cold-induced BAT and skeletal muscle 18F-FDG uptake in adults, while taking into account body composition. We performed a personalized cooling protocol just before an 18F-FDG-PET/CT scan, and we measured supraclavicular skin temperature before (in warm conditions) and after the cooling protocol in 88 adults (n = 57 women, mean age: 21.9 ±â€¯2.1 years old, body mass index: 24.5 ±â€¯4.3 km/m2). We found that supraclavicular skin temperature at the warm and cold periods was weakly and positively associated with BAT activity (SUVmean and SUVpeak: ß = 3.000; R2 = 0.072; P = 0.022 and ß = 2.448; R2 = 0.060; P = 0.021), but not with skeletal muscle 18F-FDG uptake, after controlling for body composition. We performed further analyses and the positive associations persisted only in the group of women. In conclusion, supraclavicular skin temperature in warm and cold conditions seems to be related with cold-induced 18F-FDG uptake by BAT only in women, although the low explained variance of these associations means that there are other factors involved in the supraclavicular skin temperature.

Concurrent validity of supraclavicular skin temperature measured with iButtons and infrared thermography as a surrogate marker of brown adipose tissue.

Brown adipose tissue (BAT) thermogenic activity is commonly assessed with a positron emission tomography with computed tomography scan (PET/CT). This technique has several limitations and alternative techniques are needed. Supraclavicular skin temperature measured with iButtons and infrared thermography (IRT) has been proposed as an indirect marker of BAT activity. We studied the concurrent validity of skin temperature measured with iButtons vs. IRT and the association of supraclavicular skin temperature measured with iButtons and IRT with BAT. We measured skin temperature upon a shivering threshold test with iButtons and IRT in 6 different regions in 12 participants (n = 2 men). On a separate day, we determined supraclavicular skin temperature with an iButton and IRT after 2 h of a personalized cooling protocol. Thereafter, we quantified BAT volume and activity by PET/CT. We observed that the absolute differences between the devices were statistically different from 0 (all P < 0.05) after the shivering threshold test. Moreover, we did not find any association between supraclavicular skin temperature measured with iButtons or IRT and BAT 18F-FDG activity (r = -0.213; P = 0.530 and r = -0.079; P = 0.817). However, we observed a negative association of supraclavicular skin temperature measured by IRT with BAT 18F-FDG volume (r = -0.764; P = 0.006), but not with supraclavicular skin temperature measured with iButtons (r = -0.546; P = 0.082). In light of these results, we concluded that the measurement of skin temperature obtained by iButtons and IRT are not comparable. Furthermore, it seems that supraclavicular skin temperature is not associated with BAT 18F-FDG activity, but it appears to be negatively associated with BAT 18F-FDG volume in the case of IRT.

Association of wrist and ambient temperature with cold-induced brown adipose tissue and skeletal muscle [18F]FDG uptake in young adults.

Brown adipose tissue (BAT) activity is influenced by the outdoor temperature variation. However, people spend most of their time indoors, especially in colder regions and during cold seasons. Therefore, outdoor temperature is probably not an accurate tool to quantify the exposure of the participants before BAT quantification. We studied the association of wrist and personal environmental temperatures with cold-induced BAT and skeletal muscle [18F]fluorodeoxyglucose ([18F]FDG) uptake in adults. A total of 74 participants wore two iButtons during 7 days to measure wrist temperature (WT) and personal level of environmental temperature (Personal-ET). Thereafter, we performed a 2-h personalized cooling protocol before performing an [18F]FDG-PET/CT scan. WT was negatively associated with BAT volume ( R2 = 0.122; P = 0.002) and BAT activity [standardized uptake value (SUV)peak, R2 = 0.083; P = 0.012]. Moreover, Personal-ET was negatively associated with BAT volume ( R2 = 0.164; P < 0.001), BAT activity (SUVmean and SUVpeak, all R2 ≥ 0.167; P < 0.001), and skeletal muscle activity (SUVpeak, R2 = 0.122; P = 0.002). Interestingly, the time exposed to a certain Personal-ET (16-20°C) positively correlated only with [18F]FDG uptake by BAT (volume and activity; all P ≤ 0.05), whereas the time exposed to 12-15°C positively correlated only with measures of [18F]FDG uptake by skeletal muscle activity (all P ≤ 0.05). This study shows that WT and Personal-ET are associated with [18F]FDG uptake by BAT and skeletal muscle activity in adults within certain temperature thresholds. Moreover, our results suggest that [18F]FDG uptake by human BAT or skeletal muscle can be activated or inhibited in different ranges of ambient temperatures exposures. Results should be taken with caution because the observed associations were relatively weak.

Estimating VO2max in children aged 5-6 years through the preschool-adapted 20-m shuttle-run test (PREFIT).

PURPOSE: (1) To examine the comparability, i.e., discriminatory power, in a preschooler test (PREFIT 20-m shuttle-run test) and the 20mSRT-Original in 5-6-year-olds; (2) to provide an equation to estimate VO2max from the 20mSRT-PREFIT. METHODS: 138 participants aged 5-6 years performed the 20mSRT-PREFIT and the 20mSRT-Original in a counterbalanced order. Total test duration, completed stages, maximum speed and maximum heart rate were registered. RESULTS: Participants finished stages from 2-10 in the 20mSRT-PREFIT, whereas stages 1-5 were completed in the 20mSRT-Original and a null was registered, showing the original version a lower discriminatory power. We also observed that the higher the cardiorespiratory fitness level the more comparable were the tests, i.e., - 0.04 km h-1 difference between tests in the fittest participants (i.e., maximum speed ≥ 9.5 km h-1). Using the original equation proposed by Leger and colleagues in 1988 and based on the estimation regression of maximum speed in the 20mSRT-Original from the PREFIT version, we computed a new equation to estimate VO2max from the 20mSRT-PREFIT: Y = 44.657 + 1.795X 1 - 2.601X 2 + 0.0852X 1 X 2 (r = 0.77; r 2 = 0.59; SEE = 1.25 ml kg-1 min-1 or 2.59% of estimated mean VO2max = 48.38 ml kg-1 min-1), where X 1 is the 20mSRT-PREFIT maximum speed (km h-1) and X 2 is the age of participants. The 20mSRT-PREFIT resulted in a significantly higher maximum heart rate than the 20mSRT-Original. CONCLUSIONS: The 20mSRT-PREFIT has higher discriminatory power than the 20mSRT-Original. Our study provides for the first time an opportunity to estimate VO2max in preschoolers and children based on the 20mSRT-PREFIT maximum speed and the age of participants.

Role of Exercise in the Activation of Brown Adipose Tissue.

BACKGROUND: The energy-burning capacity of brown adipose tissue (BAT) makes it an attractive target for use in anti-obesity therapies. Moreover, due to its ability to oxidize glucose and lipids, BAT activation has been considered a potential therapy to combat type 2 diabetes and atherogenesis. SUMMARY: BAT is mainly regulated by the sympathetic nervous system (SNS); yet, recent findings have shown a group of novel activators that act independently of the stimulation of the SNS such as cardiac natriuretic peptides, irisin, interleukin-6, ß-aminoisobutyric acid and fibroblast growth factor 21 that could influence BAT metabolism. Several strategies are being examined to activate and recruit BAT with no side effects. In this review, we postulate that exercise might activate and recruit human BAT through the activation of SNS, heart and skeletal muscle. KEY MESSAGES: Epidemiological and well-designed exercise-based randomized controlled studies are needed to clarify if exercise is able to activate BAT in humans.

The hidden cost of coaching: intentional training of shot adequacy discrimination in basketball hampers utilization of informative incidental cues.

The goal was to identify the advantages and disadvantages of using intentional guidance to teach to discriminate between good and bad circumstances to shoot in basketball. A simulated shot-adequacy learning task was developed, in which participants were asked to decide, in each trial, whether the player in possession of the ball should shoot or not. After each decision, they received feedback on their response (determined by five cues: Opposition, Rebound, Balance, Alternative, and Distance). 65 naïve participants (M age = 18.6 yr., SD = 1.3) were divided into two groups. The Incidental group received no guiding instructions. The Intentional group was instructed to utilize four of the five cues. The Distance cue was kept incidental for both groups. Participants effectively incorporated the cues into their decisions. Guidance had a markedly different effect across cues. The Intentional group utilized Distance less efficiently than the Incidental group, i.e., intentional instructions on the other four cues nearly blocked the utilization of Distance.

Cold-induced changes in plasma signaling lipids are associated with a healthier cardiometabolic profile independently of brown adipose tissue.

Cold exposure activates brown adipose tissue (BAT) and potentially improves cardiometabolic health through the secretion of signaling lipids by BAT. Here, we show that 2 h of cold exposure in young adults increases the levels of omega-6 and omega-3 oxylipins, the endocannabinoids (eCBs) anandamide and docosahexaenoylethanolamine, and lysophospholipids containing polyunsaturated fatty acids. Contrarily, it decreases the levels of the eCBs 1-LG and 2-LG and 1-OG and 2-OG, lysophosphatidic acids, and lysophosphatidylethanolamines. Participants overweight or obese show smaller increases in omega-6 and omega-3 oxylipins levels compared to normal weight. We observe that only a small proportion (∼4% on average) of the cold-induced changes in the plasma signaling lipids are slightly correlated with BAT volume. However, cold-induced changes in omega-6 and omega-3 oxylipins are negatively correlated with adiposity, glucose homeostasis, lipid profile, and liver parameters. Lastly, a 24-week exercise-based randomized controlled trial does not modify plasma signaling lipid response to cold exposure.