Energy Metabolism

This prospective observational study aims to characterize within-individual variability in resting metabolic rate (RMR) over a 12-week period using high-frequency repeated measurements under standardized conditions. Participants will undergo RMR assessments three times per week using whole-room indirect calorimetry. The study will quantify the magnitude of physiological variability in RMR, distinguish true biological variation from measurement error, and estimate the minimal detectable change required to identify meaningful metabolic adaptations.

Pilates is one of the most popular forms of exercise among older adults worldwide. However, no study has measured how many calories a Pilates session burns or how hard the body works during it in people aged 60 and over. This information is important for exercise professionals who prescribe Pilates for health promotion goals such as weight management and cardiovascular fitness. This study will measure the energy cost and metabolic intensity of two types of Pilates - mat Pilates and equipment-based Pilates - in older adults using a portable indirect calorimetry system (Cosmed K5). Results will be compared to treadmill walking at 4.8 km/h, a well-established moderate-intensity activity. Twenty men and women aged 60 years or older with at least 6 months of continuous Pilates experience will complete three exercise sessions in a randomized order: (1) mat Pilates, (2) equipment-based Pilates, and (3) treadmill walking. Each Pilates session will consist of 9 exercises, with stretching exercises used as warm-up and cool-down and 7 strengthening exercises performed in the main portion of the session (\~50 min). Oxygen consumption, energy expenditure, heart rate, and perceived exertion will be measured throughout each session.

The purpose of this study is to validate previously developed physical function-clustered specific machine-learned accelerometer algorithms to estimate total daily energy expenditure (TDEE) in individuals with general movement and functional limitations.

Bone is a metabolically active tissue undergoing continuous remodeling through the coordinated actions of osteoclasts (resorption), osteoblasts (formation), and osteocytes (regulation). Under physiological conditions, bone formation and resorption are balanced and regulated by systemic hormones (PTH, vitamin D, estrogens) and local mediators. However, aging, metabolic disorders, physical inactivity, or pharmacological treatments may disrupt this equilibrium, leading to the predominance of one process over the other. Circulating biochemical markers of bone turnover-classified into formation markers (P1NP, osteocalcin, bone alkaline phosphatase) and resorption markers (CTx-I, NTx-I, DPD)-provide a means to monitor these dynamics. Beyond its mechanical role, bone also functions as an endocrine organ: osteocalcin, secreted by osteoblasts, modulates insulin secretion and sensitivity, linking bone to muscle and adipose tissue in the regulation of energy metabolism. Adipokines such as leptin and adiponectin further contribute to this complex crosstalk. Bone biomarkers are therefore essential for evaluating skeletal metabolism and identifying conditions such as osteoporosis, though the strict classification into formation versus resorption markers is limited, as some (e.g., osteocalcin) reflect both processes. This study aims to analyze IRCCS San Raffaele database records of urinary and serum biomarkers related to bone, muscle, and energy metabolism, to assess their trends and associations according to age and sex, and to develop statistical models capable of explaining their interrelationships.

KETO-SENSE is a clinical research study investigating how ketone bodies affect energy metabolism and insulin sensitivity in humans. Ketone bodies are naturally produced by the liver during fasting or prolonged exercise and can serve as an alternative fuel for the brain, heart, and muscles. In this study, ten overweight but otherwise healthy adults aged 55-70 years will participate in four study days at Aarhus University Hospital. Participants will receive one of four interventions in a randomized crossover design: 1) growth hormone (GH) and a ketone supplement, 2) GH and placebo, 3) a saline infusion with the ketone supplement, or 4) placebo (saline infusion and placebo supplement). The study uses advanced PET/CT imaging, indirect calorimetry, and tissue biopsies to measure how ketones influence fat breakdown, glucose uptake, and energy expenditure. By understanding these mechanisms, the study aims to clarify whether oral ketone supplementation can improve insulin sensitivity and energy metabolism - findings that could be relevant for common conditions such as overweight, insulin resistance, and type 2 diabetes.

The goals of this clinical trial are: 1. to study lactate kinetic between plasma and erythrocytes during an intervallic exercise and its subsequent recovery, considering the blood pH, the genotype for the T1470A polymorphism of the SLC16A1 gene (rs1049434), and the amount of MCT1 in erythrocytes membrane; 2. to analyze the levels of MCT1 in the erythrocytes membrane according to training status and genotype for the T1470A polymorphism of SLC16A1 (rs1049434). For this, the project will have two phases: * In phase I, trained participants will perform one maximal incremental test and one intervallic submaximal test with a final active recovery. * Phase II, levels of the MCT1 protein in the erythrocyte membrane will be quantified from trained and sedentary participants.

The objective of this observational study is to integrate the doubly labeled water (DLW) database from healthy individuals with multimodal data-including, but not limited to, weight, height, age, sex, race, elevation-from cohorts undergoing rehabilitation following movement impairments or neurological injuries. Machine learning algorithms will be used to develop injury-specific predictive models of energy requirements. The primary research question is: How does energy metabolism change during the rehabilitation process in individuals recovering from traumatic brain injury, stroke, or major surgical procedures? To answer this, participants will undergo a comprehensive set of assessments, including measurements of height and weight, body composition, resting metabolic rate, physical activity levels, total energy expenditure, psychological health, food intake and hunger ratings, sleep quality, cognitive performance, non-invasive brain function monitoring, and gait analysis. Fecal and blood samples will also be collected for untargeted metabolomics analysis.