Adults with metabolically healthy overweight or obesity present more brown adipose tissue and higher thermogenesis than their metabolically unhealthy counterparts.

BACKGROUND: There is a subset of individuals with overweight/obesity characterized by a lower risk of cardiometabolic complications, the so-called metabolically healthy overweight/obesity (MHOO) phenotype. Despite the relatively higher levels of subcutaneous adipose tissue and lower visceral adipose tissue observed in individuals with MHOO than individuals with metabolically unhealthy overweight/obesity (MUOO), little is known about the differences in brown adipose tissue (BAT). METHODS: This study included 53 young adults (28 women) with a body mass index (BMI) ≥25 kg/m2 which were classified as MHOO (n = 34) or MUOO (n = 19). BAT was assessed through a static 18F-FDG positron emission tomography/computed tomography scan after a 2-h personalized cooling protocol. Energy expenditure, skin temperature, and thermal perception were assessed during a standardized mixed meal test (3.5 h) and a 1-h personalized cold exposure. Body composition was assessed by dual-energy x-ray absorptiometry, energy intake was determined during an ad libitum meal test and dietary recalls, and physical activity levels were determined by a wrist-worn accelerometer. FINDINGS: Participants with MHOO presented higher BAT volume (+124%, P = 0.008), SUVmean (+63%, P = 0.001), and SUVpeak (+133%, P = 0.003) than MUOO, despite having similar BAT mean radiodensity (P = 0.354). In addition, individuals with MHOO exhibited marginally higher meal-induced thermogenesis (P = 0.096) and cold-induced thermogenesis (+158%, P = 0.050). Moreover, MHOO participants showed higher supraclavicular skin temperature than MUOO during the first hour of the postprandial period and during the cold exposure, while no statistically significant differences were observed in other skin temperature parameters. We observed no statistically significant differences between MHOO and MUOO in thermal perception, body composition, outdoor ambient temperature exposure, resting metabolic rate, energy intake, or physical activity levels. INTERPRETATION: Adults with MHOO present higher BAT volume and activity than MUOO. The higher meal- and cold-induced thermogenesis and cold-induced supraclavicular skin temperature are compatible with a higher BAT activity. Overall, these results suggest that BAT presence and activity might be linked to a healthier phenotype in young adults with overweight or obesity. FUNDING: See acknowledgments section.

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).

Effect of a 24-Week Concurrent Exercise Intervention on Neck Adiposity and Its Distribution in Young Adults: The ACTIBATE Randomized Controlled Trial.

Neck adipose tissue (NAT) accumulation and neck circumference are independent predictors of cardiometabolic risk (CMR) and low-grade chronic inflammation in young adults. The present study examines whether a 24-week concurrent exercise intervention can reduce NAT volume and neck circumference in young adults, and whether any changes in these variables are related to changes in body composition, CMR, and the inflammatory profile. Seventy-four participants (51 women, age 22 ± 2 years) were included in the main analyses, after being randomly assigned to either a (a) control (n = 34), (b) moderate-intensity exercise (n = 19), or (c) vigorous-intensity exercise (n = 21) group. Participants in the exercise groups trained 3-4 days/week (endurance + resistance exercise training). NAT volume and NAT distribution across different depots were estimated using computed tomography before and after the intervention. Anthropometric variables, body composition (determined by dual-energy X-ray absorptiometry), and CMR/inflammatory markers were also recorded. The exercise intervention did not reduce the total NAT volume, nor was NAT distribution affected (p > .05). However, it did reduce neck circumference in the vigorous-intensity exercise group compared with the moderate-intensity exercise and control groups (by 0.8 and 1 cm, respectively, p ≤ .05). Changes in total NAT and neck circumference were positively, albeit weakly, related (adj. R2: .05-.21, all p ≤ .05) to changes in body weight and adiposity, leptin (only total NAT), and CMR (only neck circumference). Altogether 24 weeks of concurrent exercise does not appear to reduce NAT accumulation in young adults, but may slightly reduce neck circumference in those who partake in vigorous exercise.

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 ).

Exercise-induced changes on exerkines that might influence brown adipose tissue metabolism in young sedentary adults.

ABSTRACTIn rodents, exercise alters the plasma concentration of exerkines that regulate white adipose tissue (WAT) browning or brown adipose tissue (BAT) metabolism. This study aims to analyse the acute and chronic effect of exercise on the circulating concentrations of 16 of these exerkines in humans. Ten young sedentary adults (6 female) performed a maximum walking effort test and a resistance exercise session. The plasma concentration of 16 exerkines was assessed before, and 3, 30, 60, and 120 min after exercise. Those exerkines modified by exercise were additionally measured in another 28 subjects (22 women). We also measured the plasma concentrations of the exerkines before and after a 24-week exercise programme (endurance + resistance; 3-groups: control, moderate-intensity and vigorous-intensity) in 110 subjects (75 women). Endurance exercise acutely increased the plasma concentration of lactate, norepinephrine, brain-derived neurotrophic factor, interleukin 6, and follistatin-like protein 1 (3 min after exercise), and musclin and fibroblast growth factor 21 (30 and 60 min after exercise), decreasing the plasma concentration of leptin (30 min after exercise). Adiponectin, atrial natriuretic peptide (ANP), ß-aminoisobutyric acid, meteorin-like, follistatin, pro-ANP, irisin and myostatin were not modified or not detectable. The resistance exercise session increased the plasma concentration of lactate 3 min after exercise. Chronic exercise did not alter the plasma concentration of these exerkines. In sedentary young adults, acute endurance exercise releases to the bloodstream exerkines that regulate BAT metabolism and WAT browning. In contrast, neither a low-volume resistance exercise session nor a 24-week training programme modified plasma levels of these molecules.HighlightsAcute endurance exercise increases the plasma concentration of lactate, norepinephrine, brain-derived neurotrophic factor, interleukin 6, follistatin-like protein 1, musclin, and fibroblast growth factor 21, and decrease the plasma concentration of leptin.The exercise-induced change in lactate plasma concentration is positively associated with brown adipose tissue volume, glucose uptake and radiodensity.Neither acute resistance exercise nor chronic exercise significantly alter the plasma concentration of these exerkines.Trial registration: ClinicalTrials.gov identifier: NCT02365129.

Nef enhances HIV-1 replication and infectivity independently of SERINC5 in CEM T cells.

A primary function of HIV-1 Nef is the enhancement of viral infectivity and replication. Whether counteraction of the antiretroviral proteins SERINC3 and SERINC5 is the cause of this positive influence on viral growth-rate and infectivity remains unclear. Here, we utilized CRISPR/Cas9 to knockout SERINC3 and SERINC5 in a leukemic CD4-positive T cell line (CEM) that displays nef-related infectivity and growth-rate phenotypes. Viral replication was attenuated in CEM cells infected with HIV-1 lacking Nef (HIV-1ΔNef). This attenuated growth-rate phenotype was observed regardless of whether the coding regions of the serinc3 or serinc5 genes were intact. Moreover, knockout of serinc5 alone or of both serinc5 and serinc3 together failed to restore the infectivity of HIV1ΔNef virions produced from infected CEM cells. Our results corroborate a similar study using another T-lymphoid cell line (MOLT-3) and indicate that the antagonism of SERINC3 and SERINC5 does not fully explain the virology of HIV-1 lacking Nef.

No evidence of brown adipose tissue activation after 24 weeks of supervised exercise training in young sedentary adults in the ACTIBATE randomized controlled trial.

Exercise modulates both brown adipose tissue (BAT) metabolism and white adipose tissue (WAT) browning in murine models. Whether this is true in humans, however, has remained unknown. An unblinded randomized controlled trial (ClinicalTrials.gov ID: NCT02365129) was therefore conducted to study the effects of a 24-week supervised exercise intervention, combining endurance and resistance training, on BAT volume and activity (primary outcome). The study was carried out in the Sport and Health University Research Institute and the Virgen de las Nieves University Hospital of the University of Granada (Spain). One hundred and forty-five young sedentary adults were assigned to either (i) a control group (no exercise, n = 54), (ii) a moderate intensity exercise group (MOD-EX, n = 48), or (iii) a vigorous intensity exercise group (VIG-EX n = 43) by unrestricted randomization. No relevant adverse events were recorded. 97 participants (34 men, 63 women) were included in the final analysis (Control; n = 35, MOD-EX; n = 31, and VIG-EX; n = 31). We observed no changes in BAT volume (Δ Control: -22.2 ± 52.6 ml; Δ MOD-EX: -15.5 ± 62.1 ml, Δ VIG-EX: -6.8 ± 66.4 ml; P = 0.771) or 18F-fluorodeoxyglucose uptake (SUVpeak Δ Control: -2.6 ± 3.1 ml; Δ MOD-EX: -1.2 ± 4.8, Δ VIG-EX: -2.2 ± 5.1; p = 0.476) in either the control or the exercise groups. Thus, we did not find any evidence of an exercise-induced change on BAT volume or activity in young sedentary adults.

A larger brown fat volume and lower radiodensity are related to a greater cardiometabolic risk, especially in young men.

Objectives: Brown adipose tissue (BAT) is important in the maintenance of cardiometabolic health in rodents. Recent reports appear to suggest the same in humans, although if this is true remains elusive partly because of the methodological bias that affected previous research. This cross-sectional work reports the relationships of cold-induced BAT volume, activity (peak standardized uptake, SUVpeak), and mean radiodensity (an inverse proxy of the triacylglycerols content) with the cardiometabolic and inflammatory profile of 131 young adults, and how these relationships are influenced by sex and body weight. Design: This is a cross-sectional study. Methods: Subjects underwent personalized cold exposure for 2 h to activate BAT, followed by static 18F-fluorodeoxyglucose PET-CT scanning to determine BAT variables. Information on cardiometabolic risk (CMR) and inflammatory markers was gathered, and a CMR score and fatty liver index (FLI) were calculated. Results: In men, BAT volume was positively related to homocysteine and liver damage markers concentrations (independently of BMI and seasonality) and the FLI (all P ≤ 0.05). In men, BAT mean radiodensity was negatively related to the glucose and insulin concentrations, alanine aminotransferase activity, insulin resistance, total cholesterol/HDL-C, LDL-C/HDL-C, the CMR score, and the FLI (all P ≤ 0.02). In women, it was only negatively related to the FLI (P < 0.001). These associations were driven by the results for the overweight and obese subjects. No relationship was seen between BAT and inflammatory markers (P > 0.05). Conclusions: A larger BAT volume and a lower BAT mean radiodensity are related to a higher CMR, especially in young men, which may support that BAT acts as a compensatory organ in states of metabolic disruption.

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.

Dihydrocapsiate does not increase energy expenditure nor fat oxidation during aerobic exercise in men with overweight/obesity: a randomized, triple-blinded, placebo-controlled, crossover trial.

Background: Prior evidence suggests that capsinoids ingestion may increase resting energy expenditure (EE) and fat oxidation (FATox), yet whether they can modulate those parameters during exercise conditions remains poorly understood. We hypothesized that dihydrocapsiate (DHC) ingestion would increase EE and specifically FATox during an acute bout of aerobic exercise at FATmax intensity (the intensity that elicits maximal fat oxidation during exercise [MFO]) in men with overweight/obesity. Since FATmax and MFO during aerobic exercise appear to be indicators of metabolic flexibility, whether DHC has an impact on FATox in this type of population is of clinical interest. Methods: A total of 24 sedentary men (age = 40.2 ± 9.2 years-old; body mass index = 31.6 ± 4.5 kg/m2 [n = 11 overweight, n = 13 obese]) participated in this randomized, triple-blinded, placebo-controlled, crossover trial (registered under ClinicalTrials.gov Identifier no. NCT05156697). On the first day, participants underwent a submaximal exercise test on a cycle ergometer to determine their MFO and FATmax intensity during exercise. After 72 hours had elapsed, the participants returned on 2 further days (≥ 72 hours apart) and performed a 60 min steady-state exercise bout (i.e. cycling at their FATmax, constant intensity) after ingesting either 12 mg of DHC or placebo; these conditions were randomized. Respiratory gas exchange was monitored by indirect calorimetry. Serum marker concentrations (i.e. glucose, triglycerides, non-esterified fatty acids (NEFAs), skin temperature, thermal perception, heart rate, and perceived fatigue) were assessed. Results: There were no significant differences (P > 0.05) between DHC and placebo conditions in the EE and FATox during exercise. Similarly, no significant changes were observed in glucose, triglycerides, or NEFAs serum levels, neither in the skin temperature nor thermal perception across conditions. Heart rate and perceived fatigue did not differ between conditions. Conclusions: DHC supplementation does not affect energy metabolism during exercise in men with overweight/obesity.

The Influence of Exercise, Lifestyle Behavior Components, and Physical Fitness on Maternal Weight Gain, Postpartum Weight Retention, and Excessive Gestational Weight Gain.

This study examines (a) the influence of exercise, lifestyle behavior components (sedentary time, physical activity, and sleep and dietary patterns), and physical fitness on maternal weight gain, postpartum weight retention, and excessive gestational weight gain and (b) whether exercise protects against the adverse effects of impaired metabolism and nonoptimal body composition related to excessive gestational weight gain. Subjects were assigned to either a supervised concurrent (aerobic + resistance) exercise program followed 3 days/week (n = 47) or a control group (n = 54). Sedentary time, physical activity, sleep and dietary patterns (assessed by accelerometry and questionnaires), muscle strength (handgrip test), and cardiorespiratory fitness (Bruce test) were determined at gestational Weeks 16 and 33 (early-middle and late pregnancy, respectively), and at 6 weeks postpartum. Weight gain and weight retention were calculated using recorded weights at prepregnancy, early-middle, and late pregnancy, and at 6 weeks postpartum. Birth complications, maternal postpartum body composition, cardiometabolic, and inflammatory markers in maternal and umbilical cord arterial and venous blood, and in colostrum, and mature milk were also recorded. The exercise intervention reduced late weight gain (B = -2.7, SE = 0.83, p = .003) and weight retention (B = -2.85, SE = 1.3, p = .03), independent of any lifestyle behavior component or physical fitness, but did not prevent excessive weight gain. Increasing cardiorespiratory fitness, muscle strength, and sleep duration were associated with a smaller mean weight gain and lower excessive weight gain values (p < .05). Among the participants who experienced excessive weight gain, those who were exercisers had a lower body mass index and systemic tumor necrosis factor-alpha concentration, lower umbilical cord venous tumor necrosis factor-alpha and arterial interferon gamma levels, higher cord arterial interleukin-10 levels, and improved placental function compared with controls (p < .05). In summary, exercise may help optimize gestational weight gain and weight retention, and may attenuate the impaired phenotype related to excessive weight gain. Increasing cardiorespiratory fitness, muscle strength, and sleep duration might help to prevent excessive weight gain during pregnancy.

Plasma Levels of Endocannabinoids and Their Analogues Are Related to Specific Fecal Bacterial Genera in Young Adults: Role in Gut Barrier Integrity.

OBJECTIVE: To investigate the association of plasma levels of endocannabinoids with fecal microbiota. METHODS: Plasma levels of endocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), as well as their eleven analogues, and arachidonic acid (AA), were measured using liquid chromatography-tandem mass spectrometry in 92 young adults. DNA extracted from stool samples was analyzed using 16S rRNA gene sequencing. Lipopolysaccharide levels were measured in plasma samples. RESULTS: Plasma levels of endocannabinoids and their analogues were not related to beta or alpha diversity indexes. Plasma levels of AEA and related N-acylethanolamines correlated positively with the relative abundance of Faecalibacterium genus (all rho ≥ 0.26, p ≤ 0.012) and Akkermansia genus (all rho ≥ 0.22, p ≤ 0.036), and negatively with the relative abundance of Bilophila genus (all rho ≤ -0.23, p ≤ 0.031). Moreover, plasma levels of 2-AG and other acylglycerols correlated positively with the relative abundance of Parasutterella (all rho ≥ 0.24, p ≤ 0.020) and Odoribacter genera (all rho ≥ 0.27, p ≤ 0.011), and negatively with the relative abundance of Prevotella genus (all rho ≤ -0.24, p ≤ 0.023). In participants with high lipopolysaccharide values, the plasma levels of AEA and related N-acylethanolamines, as well as AA and 2-AG, were negatively correlated with plasma levels of lipopolysaccharide (all rho ≤ -0.24, p ≤ 0.020). CONCLUSION: Plasma levels of endocannabinoids and their analogues are correlated to specific fecal bacterial genera involved in maintaining gut barrier integrity in young adults. This suggests that plasma levels of endocannabinoids and their analogues may play a role in the gut barrier integrity in young adults.

Thermogenic responses to different clamped skin temperatures in cold-exposed men and women.

Despite many decades of research examining thermoregulatory responses under varying cold stresses in humans, very little is known about the variability in metabolic heat production and shivering activity. Here, we used a novel closed-loop mean skin temperature clamping technique with a liquid-conditioned suit to isolate the effects of mean skin temperature on the subjective evaluation of thermal sensation, heat production, shivering responses, and oxidative fuel selection in young, lean, and healthy men (n = 12) and women (n = 12). Our results showed a skin temperature-dependent increase in metabolic heat production (5.2 ± 1.2 kJ/min, 5.9 ± 1.5 kJ/min, and 7.0 ± 1.8 kJ/min with skin temperature maintained at 31 ± 0.1°C, 29 ± 0.2°C, and 27 ± 0.1°C, respectively; P < 0.0001) and shivering intensity in both men and women [0.6 ± 0.1% maximal voluntary contraction (MVC), 1.1 ± 0.4% MVC, and 2.5 ± 0.7% MVC, respectively; P < 0.0001], including sex-dependent differences in heat production at all three temperatures (P < 0.005). Even when controlling for lean body mass and fat mass, sex differences persisted (P = 0.048 and P = 0.004, respectively), whereas controlling for differences in body surface area eliminated these differences. Interestingly, there were no sex differences in the cold-induced change in thermogenesis. Despite clamping skin temperature, there was tremendous variability in the rate of heat production and shivering intensity. Collectively this data suggests that many of the interindividual differences in thermogenesis and shivering may be explained by differences in morphology and body composition.

Circulating concentrations of free triiodothyronine are associated with central adiposity and cardiometabolic risk factors in young euthyroid adults.

Thyroid dysfunction is associated with classic cardiometabolic risk factors in humans. However, this relationship remains unclear in young euthyroid adults. The present work examines the associations of circulating thyroid hormones (THs) and thyroid-stimulating hormone (TSH) concentrations with body composition and cardiometabolic risk factors in young euthyroid adults. A total of 106 sedentary, euthyroid adults (72 women; 22 ± 2 years old) participated in this cross-sectional study. THs and TSH serum concentrations were determined in fasting conditions (6 h). Body composition (fat mass (FM), lean mass (LM), and visceral adipose tissue (VAT)) was determined by dual-energy X-ray absorptiometry, anthropometric parameters (weight, height, and waist circumference) were measured, and neck adipose tissue mass was quantified through computed tomography (CT) scanning. Cardiometabolic risk factors including fasting glucose and lipid metabolism markers, hepatic phosphatase and transaminases, and blood pressure were also assessed. Free triiodothyronine (FT3) concentration was positively associated with body mass index, LM, VAT, and waist circumference (all P ≤ 0.038). FT3 was also associated with glucose, insulin, HOMA-IR, fatty liver index, and blood pressure (all P < 0.024). All the associations were attenuated when adjusting for sex. In contrast, we found no associations of TSH or free thyroxine with any body composition parameter or cardiometabolic risk factors. In conclusion, FT3 is associated with central adiposity and cardiometabolic risk factors including insulin resistance, fatty liver index, and mean, systolic and diastolic blood pressure in young euthyroid adults. ClinicalTrials.gov identifier: NCT02365129.

The Protective Role of Physical Fitness on Cardiometabolic Risk During Pregnancy: The GESTAtion and FITness Project.

Physical fitness (PF) is a cornerstone of metabolic health. However, its role in maternal-fetal metabolism during pregnancy is poorly understood. The present work investigates: (i) the association of PF with maternal and fetal cardiometabolic markers, and with clustered cardiometabolic risk during pregnancy, and (ii) whether being fit counteracts cardiometabolic abnormalities associated with overweight/obesity. Several PF components (flexibility, lower and upper body strength, and cardiorespiratory fitness [CRF]) were objectively assessed in 151 pregnant women at gestational weeks 16 and 33, and an overall PF cluster score calculated. At the same times, maternal glycemic and lipid markers, cortisol, and C-reactive protein were assessed with standard biochemical methods, along with blood pressure and a proxy for insulin resistance, and a cardiometabolic risk cluster score determined. These analytes were also measured in maternal and umbilical cord arterial and venous blood collected at delivery. PF was found to be associated with several maternal and a small number of fetal cardiometabolic markers (p < .05). Lower and upper body muscle strength, CRF, overall PF (week 16), and CRF changes (weeks 16-33) were inversely associated with clustered cardiometabolic risk (p < .05). Normal weight fit women had lower values for insulin level, insulin resistance, triglycerides, low-density lipoprotein cholesterol, C-reactive protein, and diastolic blood pressure than did overweight/obese unfit women at week 16 (p < .05). In conclusion, greater PF, especially muscle strength and CRF in early-middle pregnancy, appears to be associated with a better metabolic phenotype, and may protect against maternal cardiometabolic risk. "Keep yourself fit and normal weight before and during early pregnancy" should be a key public health message.

Heart rate rather than heart rate variability is better associated with cardiorespiratory fitness in adults.

This study aimed to examine the association of heart rate (HR) and heart rate variability (HRV) with cardiorespiratory fitness (CRF) in adults. This cross-sectional study included 204 participants: 132 young adults (67% women; 22.3 ± 2.3 years) and 72 middle-aged adults (53% women; 53.2 ± 5 years). HR and HRV were measured using a Polar RS800CX heart rate monitor. CRF was assessed using a metabolic cart during an incremental test. HR was negatively associated with CRF relative to body weight (BW) in young adults adjusting for sex, age, and physical activity (ß ranged from -0.200 to -0.195; all P ≤ 0.022). These associations disappeared after including fat mass as a covariate (all P ≥ 0.106) while remained significant after adjusting for fat-free mass (FFM; all P ≤ 0.008). Neither HR nor HRV variables were associated with CRF expressed as absolute values or relative to FFM in young and middle-aged adults after adjusting for the abovementioned covariates (all P ≥ 0.074). Our results suggest that HR rather than HRV is better associated with CRF relative to BW in young adults. However, this association seems to be explained by the inclusion of fat mass in the calculation of CRF relative to BW. HighlightsHeart rate and heart rate variability variables have been associated with cardiorespiratory fitness.Our present results, and previous literature, suggest that the "simple" measurement of the heart rate could be easier to obtain and interpret than the heart rate variability variables.The heart rate variable rather than the heart rate variability variables is better associated with cardiorespiratory fitness relative to body weight in healthy young adults.

Diurnal variations of cold-induced thermogenesis in young, healthy adults: A randomized crossover trial.

BACKGROUND: Harnessing cold-induced thermogenesis (CIT) and brown adipose tissue (BAT) activity has been proposed as a means of counteracting a positive energy balance, and thus of combating obesity and its related comorbidities. However, it has remained unclear whether CIT and BAT activity show diurnal variation in humans - knowledge that might allow treatments based on these factors to be time-optimized. METHODS: A randomized crossover experiment was designed to examine whether CIT shows morning/evening variation in young, healthy adults (n = 14, 5 women). On the first experimental day, subjects' shivering thresholds were determined following a cooling protocol. After ≈96 h had elapsed, the subjects then returned on two further days (approx. 48 h apart) at 08:00 h or 18:00 in random order. On both the latter days, the resting energy expenditure (REE) was measured before the subjects underwent personalized cold exposure (i.e., according to their shivering threshold). CIT was then assessed for 60 min by indirect calorimetry. In an independent cross-sectional study (n = 133, 88 women), subjects came to the laboratory between 8:00 and 18:00 h and their BAT 18F-fluordeoxyglucose (18F-FDG) uptake was assessed after personalized cold stimulation. RESULTS: Both the REE and CIT were similar in the morning and evening (all P > 0.05). Indeed, 60 min of personalized-mild cold exposure in the morning or evening elicited a similar change in energy expenditure (16.8 ± 12.8 vs. 15.7 ± 15.1% increase above REE, P = 0.72). BAT 18F-FDG uptake was also similar in the morning, evening and afternoon (all P > 0.05). CONCLUSION: CIT does not appear to show morning/evening variation in young healthy adults, with the current study design and methodology. BAT 18F-FDG uptake appears not to change across the day either, although experiments with a within-subject study design are needed to confirm these findings. Registered under ClinicalTrials.gov Identifier no. NCT02365129.

Deciphering the constrained total energy expenditure model in humans by associating accelerometer-measured physical activity from wrist and hip.

The constrained total energy expenditure (TEE) model posits that progressive increases in physical activity (PA) lead to increases in TEE; but after certain PA threshold, TEE plateaus. Then, a compensatory reduction in the expenditure of non-essential activities constrains the TEE. We hypothesized that high PA levels as locomotion associate with a compensatory attenuation in arm movements. We included 209 adults (64% females, mean [SD] age 32.1 [15.0] years) and 105 children (40% females, age 10.0 [1.1] years). Subjects wore, simultaneously, one accelerometer in the non-dominant wrist and another in the hip for ≥ 4 days. We analyzed the association between wrist-measured (arm movements plus locomotion) and hip-measured PA (locomotion). We also analyzed how the capacity to dissociate arm movements from locomotion influences total PA. In adults, the association between wrist-measured and hip-measured PA was better described by a quadratic than a linear model (Quadratic-R2 = 0.54 vs. Linear-R2 = 0.52; P = 0.003). Above the 80th percentile of hip-measured PA, wrist-measured PA plateaued. In children, there was no evidence that a quadratic model fitted the association between wrist-measured and hip-measured PA better than a linear model (R2 = 0.58 in both models, P = 0.25). In adults and children, those with the highest capacity to dissociate arm movements from locomotion-i.e. higher arm movements for a given locomotion-reached the highest total PA. We conclude that, in adults, elevated locomotion associates with a compensatory reduction in arm movements (probably non-essential fidgeting) that partially explains the constrained TEE model. Subjects with the lowest arm compensation reach the highest total PA.

Brown Adipose Tissue Volume and Fat Content Are Positively Associated With Whole-Body Adiposity in Young Men-Not in Women.

Human brown adipose tissue (BAT) volume has consistently been claimed to be inversely associated with whole-body adiposity. However, recent advances in the assessment of human BAT suggest that previously reported associations may have been biased. The present cross-sectional study investigates the association of BAT volume, mean radiodensity, and 18F-fluorodeoxyglucose (18F-FDG) uptake (assessed via a static positron emission tomography [PET]-computed tomography [CT] scan after a 2-h personalized cold exposure) with whole-body adiposity (measured by DXA) in 126 young adults (42 men and 84 women; mean ± SD BMI 24.9 ± 4.7 kg/m2). BAT volume, but not 18F-FDG uptake, was positively associated with BMI, fat mass, and visceral adipose tissue (VAT) mass in men but not in women. These associations were independent of the date when the PET-CT was performed, insulin sensitivity, and body surface area. BAT mean radiodensity, an inverse proxy of BAT fat content, was negatively associated with BMI, fat mass, and VAT mass in men and in women. These results refute the widely held belief that human BAT volume is reduced in obese persons, at least in young adults, and suggest that it might even be the opposite in young men.