Guillermo Sánchez-Delgado

• PhD
• PostDoc Position at Université de Sherbrooke

Background Soluble Alpha-Klotho (S-αklotho) protein and 25-Hydroxyvitamin D (25-OH-D) have emerged as potential modulators for activating and recruiting Brown Adipose Tissue (BAT). The present study aimed to investigate whether circulating S-αklotho and 25-OH-D levels are related to BAT volume, ¹⁸ Fluorine-Fluorodeoxyglucose ( ¹⁸ F-FDG) uptake, and...

Objective Metabolic inflexibility to Western high‐fat diets may contribute to the obesity epidemic. However, validated methods for assessing metabolic flexibility (MetFlex) to high‐fat meals are currently lacking. The purpose of this study was to evaluate the reliability of a novel approach for determining MetFlex to a high‐fat meal and to compare...

Introduction : Le foie joue un rôle crucial dans le maintien de l'homéostasie énergétique en orchestrant une série complexe de cascades métaboliques, alternant entre la production et le stockage d'énergie. L'accumulation excessive de lipides hépatiques, est un facteur de risque majeur pour le développement du diabète de type 2. Les mécanismes sous-...

Early disturbances in the storage of dietary fatty acids within adipose tissue are believed to be a key mechanism linking obesity to the onset of insulin resistance and type 2 diabetes, leading to an increased flux of fatty acids towards lean organs. While exercise is known to improve peripheral insulin sensitivity, its effects on fatty acid fluxes...

Background and aims: The prevalence of paediatric obesity has increased in recent decades. The efficacy of the primary approach based on improving dietary habits and increasing physical activity is limited. Therefore, and given the growing interest in new nutritional strategies such as time-restricted eating (TRE), this study aimed to investigate t...

Objetivos. La restricción temporal de la ingesta de alimentos (TRE) es actualmente objeto de estudio como una estrategia nutricional prometedora para combatir la obesidad y prevenir el riesgo cardio-metabólico en adultos. Sin embargo, su eficacia en población pediátrica aún es desconocida. El objetivo de este estudio fue evaluar los efectos de una...

Objetivos. La restricción horaria de la ingesta de alimentos (TRE por sus siglas en inglés) se está estudiando como una prometedora estrategia nutricional para el tratamiento de la obesidad en población adulta. A pesar de su potencial en la disminución del riesgo cardio-metabólico, resulta necesario explorar sus beneficios y riesgos antes de consid...

Objective The study objective was to investigate the effect of cold exposure on the plasma levels of five potential human brown adipokines (chemokine ligand 14 [CXCL14], growth differentiation factor 15 [GDF15], fibroblast growth factor 21 [FGF21], interleukin 6 [IL6], and bone morphogenic protein 8b [BMP8b]) and to study whether such cold‐induced...

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 lysophospholip...

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 indi...

La restricción temporal de la ingesta de alimentos (TRE) está siendo estudiada como una prometedora estrategia nutricional para el tratamiento de la obesidad en adultos. Sin embargo, su eficacia en población pediátrica aún es desconocida. Este estudio tuvo como objetivo evaluar el efecto de una intervención de TRE de 8 semanas sobre el peso y la co...

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 thro...

Background and aims: Accomplishing a high day-to-day reproducibility is important to detect changes in resting metabolic rate (RMR) and respiratory exchange ratio (RER) that may be produced after an intervention or for monitoring patients' metabolism over time. We aimed to analyze: (i) the influence of different methods for selecting indirect calo...

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. Co...

Purpose The present work examines the associations of dietary habits, sedentarism, physical activity (PA) levels and sleep habits, with thyroid function in young euthyroid adults. Methods A total of 105 young euthyroid adults participated in this cross-sectional study. Thyroid function was determined in fasting conditions (> 6 h). Dietary habits w...

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 objecti...

Objetivos. La restricción horaria de la ingesta de alimentos (TRE por sus siglas en inglés) es un tipo de ayuno intermitente consistente en la concentración de todas las comidas diarias en una ventana temporal determinada, usualmente igual o menor a 10 horas. Aunque se considera una estrategia nutricional muy prometedora para la prevención del ries...

Background Fatty acid-derived lipid mediators including oxylipins, endocannabinoids (eCBs), and their analogues, have emerged as key metabolites in the inflammatory and immune response to physiological stressors. Methods This report was based on a sub-study and secondary analyses the ACTIBATE single-center unblinded randomized controlled trial (Cl...

Objective: Human brown adipose tissue (BAT) has gained considerable attention as a potential therapeutic target for obesity and its related cardiometabolic diseases; however, whether the gut microbiota might be an efficient stimulus to activate BAT metabolism remains to be ascertained. We aimed to investigate the association of fecal microbiota co...

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 interventio...

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 po...

The effects of the different electrical frequencies of whole-body electrical stimulation (WB-EMS) on energy expenditure (EE) and the respiratory exchange ratio (RER) remain poorly understood. This study aimed to determine the effects of different WB-EMS electrical frequencies on EE and the RER during supine resting and uphill walking. A total of 10...

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 v...

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 per...

New appetite‐regulating antiobesity treatments such as semaglutide and agents under investigation such as tirzepatide show promise in achieving weight loss of 15% or more. Energy expenditure, fat oxidation, and lean mass preservation are important determinants of weight loss and weight‐loss maintenance beyond appetite regulation. This review discus...

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 y...

In 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 maxi...

Background & aims The validity of most commercially available metabolic cart is mostly unknown. Thus, we aimed to determine the accuracy, precision, within-subject reproducibility, and concordance of RMR and RER measured by four commercially available metabolic carts [Cosmed Q-NRG, Vyaire Vyntus CPX, Maastricht Instruments Omnical, and Medgraphics...

This review summarizes the effects of different types of intermittent fasting (IF) on human cardiometabolic health, with a focus on energy metabolism. First, we discuss the coordinated metabolic adaptations (energy expenditure, hormonal changes and macronutrient oxidation) occurring during a 72 h fast. We then discuss studies investigating the effe...

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 all...

Objectives To investigate the feasibility and acceptability of three different 8h time-restricted eating (TRE) schedules (i.e., early TRE, late TRE, and self-selected TRE) over 4 weeks in adults with overweight/obesity from southern Spain. Methods A total of 22 adults with overweight/obesity and a baseline eating window ≥12h (13 women; 48 ± 10 yea...

Purpose: Thyroid hormones (THs) are important mediators of brown adipose tissue (BAT) differentiation. However, the association of TH concentrations with human BAT is unclear. The present work examines the associations between circulating thyroid-stimulating hormone (TSH) and THs concentrations (i.e. free tri-iodothyronine, FT3, and free thyroxine,...

Human brown adipose tissue (BAT) volume has been consistently claimed as 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-...

The present work examines the relationships between maximal fat oxidation during a graded exercise test (MFO), the intensity of exercise that elicits MFO (Fatmax), and traditional cardiometabolic risk factors in healthy, sedentary adults. A total of 119 (81 women) young, sedentary adults (22.1±2.2 years old), and 71 (37 women) middle-aged, sedentar...

Regular physical activity (PA) is an important part of the treatment of several medical conditions, including overweight and obesity, in which there may be a weakened appetite control. Eating behaviour traits influence weight control and may be different in active and sedentary subjects. This paper reports the relationships between the time spent i...

Objective: This study aimed to describe the energy expenditure (EE) and macronutrient oxidation response to an individualized nonshivering cold exposure in young healthy adults. Methods: Two different groups of 44 (study 1: 22.1 [SD 2.1] years old, 25.6 [SD 5.2] kg/m2 , 34% men) and 13 young healthy adults (study 2: 25.6 [SD 3.0] years old, 23.6...

Objective To study the association between usual dietary factors (dietary energy density, nutrient intake, food group consumption, and dietary pattern) and brown adipose tissue (BAT) volume/18F-fluorodeoxyglucose (18F-FDG) uptake after personalized cold exposure in young healthy adults. Methods A total of 122 young adults (n=82 women; 22.0±2.1 yea...

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 variet...

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 i...

Background: Due to a clinical and public health interest of neck circumference (NC), a better understanding of this simple anthropometric measurement, as a valid marker of body composition is necessary. Methods: A total of 119 young healthy adults participated in this study. NC was measured over the thyroid cartilage and perpendicular to the lon...

The method used to select representative gas exchange data from large datasets influences the resting metabolic rate (RMR) returned. This study determines which of three methods yields the lowest RMR (as recommended for use in human energy balance studies), and in which method the greatest variance in RMR is explained by classical determinants of t...

Background & aims: This study compares the influence of different exercise training programs on basal metabolic rate (BMR) and fat oxidation, in basal conditions (BFox) and during exercise (MFO), in sedentary, middle-aged adults. Methods: The study subjects of this 12 week-long, randomised controlled trial, were 71 middle-aged adults (age 53.5 ±...

This cross-sectional study investigates the relationship between the shed form of the Klotho protein (S-Klotho) in plasma, and cardiometabolic risk in healthy, sedentary adults. The study subjects were 214 healthy, sedentary adults (~64% women). Data were collected during the baseline assessments of two randomized controlled trials: The FIT-AGEING...

Dairy products are thought to improve recovery after both resistance and endurance exercises due to their nutritional proprieties. We systematically reviewed the effects of dairy product intake on exercise performance and recovery of muscle function in humans. A literature search was conducted in the MEDLINE (via PubMed) and Web of Science database...

Background: Several studies have explored the role of human brown adipose tissue (BAT) in energy expenditure. However, the link between BAT and appetite regulation needs to be more rigorously examined. Objectives: We aimed to investigate the associations of BAT volume and 18F-fluordeoxyglucose (18F-FDG) uptake after a personalized cold exposure...

Objectives Short sleep duration and sleep disturbances have been related to obesity and metabolic disruption. However, the behavioural and physiological mechanisms linking sleep and alterations in energy balance and metabolism are incompletely understood. In rodents, sleep regulation is closely related to appropriate brown adipose tissue (BAT) ther...

Humans have metabolically active brown adipose tissue (BAT). However, what is the relation between exercise or physical activity with this tissue remains controversial. Therefore, the main aim of the present study is to examine whether cardiorespiratory fitness and muscular strength are associated with brown adipose tissue (BAT) volume and activity...

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. T...

Purpose: We examined whether obese individuals have a reduced maximal fat oxidation (MFO) and the intensity that elicit MFO (Fatmax) compared to normal weight and overweight persons, taking into account their level of cardiorespiratory fitness. Methods: The study subjects were 138 sedentary adults (87 women) aged 30.1 ± 13.6 years. Based on thei...

Maximal fat oxidation during exercise (MFO) and the exercise intensity eliciting MFO (Fatmax) are considered important factors related to metabolic health and performance. Numerous MFO and Fatmax data collection and analysis approaches have been applied, which may have influenced their estimation during an incremental graded exercise protocol. Desp...

[This corrects the article DOI: 10.1371/journal.pone.0217029.].

The time spent in sedentary behaviour represents an important public health burden. To reduce sedentary time in the general population, the simplest, most effective, and most accessible method is to decrease lying and sitting time. We aimed to compare differences on energy expenditure (EE) across lying, sitting, and standing positions; and to analy...

Purpose Nowadays, 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) positron emission tomography (PET)/X-ray computed tomography (CT) is considered the best available technique to in vivo determination of human BAT volume. The most used Hounsfield unit (HU) threshold for BAT quantification is from – 250 to − 50 HU. Therefore, the main objective of the pre...

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...

Objective This study aimed to examine whether brown adipose tissue (BAT) or skeletal muscle activity mediates the relationship between personal level of environmental temperature (Personal‐ET) and wrist skin temperature (WT). Moreover, we examined whether BAT and skeletal muscle have a mediating role between Personal‐ET and WT (as a proxy of periph...

Currently, 18 [F]-Fluorodeoxyglucose ( ¹⁸ F-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...

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...

An iButton is a temperature sensor of small dimensions (button-sized; 16 × 6 mm2), relatively low cost (˜US50$), with a stable and autonomous system that measures temperature and records the data in a protected memory section. These devices are used in different fields and the company offers a software (One-Wire Viewer) with several limitations. Th...

The maximal fat oxidation (MFO), and the exercise intensity that elicits MFO (Fatmax), are considered excellent markers of fat metabolism during exercise. Besides individual’s biological characteristics (e.g. fed state, physical fitness level, sex, or age), data selection and analysis can affect MFO and Fatmax estimations, yet the effect is unknown...

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 prevalenc...

Purpose To analyze the diurnal variation of maximal fat oxidation (MFO) and the intensity that elicit MFO (Fat max ) in trained male athletes. Methods A total of 12 endurance-trained male athletes aged 24.7±4.1 participated in the study. We measured MFO, Fat max , maximum oxygen uptake (VO 2 max) and oxygen uptake percentage at ventilatory thresho...

Having valid and reliable resting energy expenditure (REE) estimations is crucial to establish reachable goals for dietary and exercise interventions. However, most of the REE predictive equations were developed some time ago and, as the body composition of the current population has changed, it is highly relevant to assess the validity of REE pred...

Human brown adipose tissue (BAT) has attracted clinical interest not only because it dissipates energy but also for its potential capacity to counteract obesity and related metabolic disorders (e.g., insulin resistance and dyslipidemia). Cold exposure is the most powerful stimulus for activating and recruiting BAT, and this stimulatory effect is me...

Obesity and related metabolic diseases are considered to be a pandemic that has exponentially increased during the last decades. Our current knowledge and strategies to combat obesity and to reduce cardiovascular disease are insufficient and new approaches have to be harnessed and exploited. Since the rediscovery of human brown adipose tissue in 2...

In 2009, brown adipose tissue (BAT) was discovered to be present and active in human adults. Since then, BAT has been regarded as a promising target for therapies against obesity and related diseases. However, whether BAT is able to significantly influence human energy balance and metabolism regulation is still unclear. Moreover, there is biologica...

Cold induced thermogenesis (CIT) in humans results mainly from the combination of both brown adipose tissue (BAT) and skeletal muscle thermogenic activity. The relative contribution of both tissues to CIT and to cold induced nutrient oxidation rates (CI-NUTox) remains, however, to be elucidated. We investigated the association of BAT and skeletal m...

Skin temperature parameters during cold-induced thermogenesis. P for one-way analysis of variance. min: minute.

The aim of this study was to study the effects of a 6-session (one per week) WB-EMS training intervention on maximum oxygen uptake, aerobic and gas exchange thresholds, running economy, and muscular power in male recreational runners. Twelve men were randomized into WB-EMS intervention (n = 6; 27.0 ± 7.5 years; 70.1 ± 11.1 kg; 1.75 ± 0.5 m) or cont...

New findings: What is the central question of this study?Some studies have performed biopsies of the subcutaneous adipose tissue (SAT) in the abdomen and they failed to find browning markers. Is 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 SAT is hi...

Brown adipose tissue (BAT) activity is influenced by the outdoor temperature variation. However, people spend most of their time indoors, especially in colder regions/seasons. Therefore, outdoor temperature is probably not an accuracy tool to quantify the exposure of the participants before BAT quantification. We studied the association of wrist an...

Background & aims: Since the discovery of active brown adipose tissue in human adults, non-shivering cold-induced thermogenesis (CIT) has been regarded as a promising tool to combat obesity. However, there is a lack of consensus regarding the method of choice to analyze indirect calorimetry data from a CIT study. We analyzed the impact of methods...

Purpose Human BAT has gained considerable attention as a potential therapeutic target for obesity and type 2 diabetes. However, whether physical activity (PA) might be an efficient stimulus to activate and recruit brown adipose tissue (BAT) remains to be ascertained. We aimed to examine whether objectively measured PA levels were associated with BA...

[This corrects the article DOI: 10.1371/journal.pone.0196543.].

Human brown adipose tissue (BAT) was re-discovered in 2009 by several independent groups, who showed that it is present and active in adults, as judged from the profound uptake of the glucose analogue radiotracer 18F-fluorodeoxyglucose in positron-emission tomography and computed tomography scan analysis after cold exposure. A potential clinical im...

Purpose: Near-infrared spectroscopy (NIRS) has recently been proposed as an indirect technique to assess brown adipose tissue (BAT) in young men. NIRS arises as a novel technique to avoid the limitations of the "gold-standard" 2-deoxy-2-[18F]fluoro-D-glucose ([18F]DG) positron emission tomography combined with X-ray computed tomography (PET/CT). T...

The popularity of whole-body electromyostimulation is growing during the last years, but there is a shortage of studies that evaluate its effects on physical fitness and sport performance. In this study, we compared the effects of a periodized and functional whole-body-electromyostimulation training on maximum oxygen uptake (VO2max), ventilatory th...

Human brown adipose tissue (BAT) is commonly assessed by cold-induced 18F-fluorodeoxyglucose (FDG) PET-CT using several quantification criteria. Uniform criteria for data analysis became available recently (BARCIST 1.0). We compared BAT volume and activity following BARCIST 1.0 criteria against the most commonly used criteria [Hounsfield Units (HU)...

Background & aim: The thermic effect of food (TEF) refers to the increase of the metabolic rate and body temperature in response to a single meal. To date, most of the studies have focused to determine the TEF in terms of energy expenditure, but little is known about which is the response in terms of skin temperature. The aim of this study was to...

The aim of this study was to comprehensively describe the physiological responses to an acute bout of mild cold in young lean men (n = 11, age: 23 ± 2 years, body mass index: 23.1 ± 1.2 kg/m²) to better understand the underlying mechanisms of non-shivering thermogenesis and how it is regulated. Resting energy expenditure, substrate metabolism, skin...

Equations used to measure skin temperature. Table adapted from Martinez-Tellez et al. [64]. (PDF)

Time domain parameters of heart rate variability rate across study periods. Values are mean ± standard deviation (n = 7). Repetead measures analysis of variance was performed, using Bonferroni post-hoc tests for pairwise comparisons. No significant differences were observed across periods (P>0.05). Mean RR: mean length of all RR intervals, pNN50: p...

Body anatomical points where the iButtons were attached to the skin. 26 different positions can be distinguished. Panel (A): distribution of the iButtons over the whole body, Panel (B): distribution of the iButtons on the right clavicular sites. (PDF)