Comparing Five Generations of ActiGraph Devices using an Orbital Shaker.

Introduction: ActiGraph accelerometers are used extensively to objectively assess physical activity, sedentary behavior, and sleep. Here, we present an objective validation of five generations of ActiGraph sensors to characterize potential differences in output arising from changes to hardware or firmware.

Methods: An orbital shaker generated accelerations from 0 to 3700 milli-g in a randomized order to test the wGT3X-BT, GT9X, CentrePoint Insight Watch (CPIW) 1.

Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome.

Post-infectious myalgic encephalomyelitis/chronic fatigue syndrome (PI-ME/CFS) is a disabling disorder, yet the clinical phenotype is poorly defined, the pathophysiology is unknown, and no disease-modifying treatments are available. We used rigorous criteria to recruit PI-ME/CFS participants with matched controls to conduct deep phenotyping. Among the many physical and cognitive complaints, one defining feature of PI-ME/CFS was an alteration of effort preference, rather than physical or central fatigue, due to dysfunction of integrative brain regions potentially associated with central catechol pathway dysregulation, with consequences on autonomic functioning and physical conditioning.

Glycemia and Gluconeogenesis With Metformin and Liraglutide: A Randomized Trial in Youth-onset Type 2 Diabetes.

Objective: Elevated rates of gluconeogenesis are an early pathogenic feature of youth-onset type 2 diabetes (Y-T2D), but targeted first-line therapies are suboptimal, especially in African American (AA) youth. We evaluated glucose-lowering mechanisms of metformin and liraglutide by measuring rates of gluconeogenesis and β-cell function after therapy in AA Y-T2D.

Methods: In this parallel randomized clinical trial, 22 youth with Y-T2D-age 15.

Does Wrist-Worn Accelerometer Wear Compliance Wane over a Free-Living Assessment Period? An NHANES Analysis.

Purpose: Accelerometers are used to objectively measure physical behaviors in free-living environments, typically for seven consecutive days or more. We examined whether participants experience "wear fatigue," a decline in wear time day over day, during typical assessment period acquired in a nationally representative sample of 6- to 80-yr-olds in the United States.

Methods: Participants were instructed to wear an ActiGraph GT3X+ on their nondominant wrist continuously for seven consecutive days.

Physical Activity Levels (PAL) in US Adults-2019.

Purpose: Physical activity levels (PAL) are associated with mortality risk and were instrumental in estimating national energy requirements, but we are unaware of population-based estimates of PAL in US adults. Thus, we conducted a nationwide survey using a validated previous-day recall method to estimate PAL and the behavioral determinants of low and higher PAL.

Methods: Participants from the AmeriSpeak panel 20-75 yr of age ( N = 2640) completed Activities Completed over Time in 24-hours previous-day recalls.

Effects of interrupting daily sedentary behavior on children's glucose metabolism: A 6-day randomized controlled trial.

Background: Metabolic disease risk in youth is influenced by sedentary behaviors. Acute in-lab studies show that, during a single day, interrupting a sedentary period with short bouts of physical activity improves glucometabolic outcomes.

Objective: To determine if acutely improved glucose metabolism persists after multi-day interruptions of sitting with walking brief bouts.

Activating Human Adipose Tissue with the β3-Adrenergic Agonist Mirabegron.

An appealing strategy for treatment of metabolic disease in humans is activation of brown adipose tissue (BAT), a thermogenic organ best visualized through F-FDG PET/CT. BAT has been activated to varying degrees by mild cold exposure. However, this approach can cause undesirable stress, and there remains no consensus protocol.

Screen Time and Body Image in Icelandic Adolescents: Sex-Specific Cross-Sectional and Longitudinal Associations.

Studies of adolescent body image and screen use are mostly limited to girls, and longitudinal data are scarce. We examined cross-sectional and longitudinal associations between these variables in mid-adolescent boys and girls. Data was collected when participants were at age 15 and 17, by questionnaire and objective measurements ( = 152 had complete data).

Energy expenditure due to gluconeogenesis in pathological conditions of insulin resistance.

Gluconeogenesis (GNG), the formation of glucose from noncarbohydrate precursors, requires adenosine triphosphate (ATP). Previous studies have estimated the energetic cost of GNG in humans based on theoretical calculations of rates of GNG, moles of oxygen consumption by GNG, and average oxygen consumption. Few human studies have measured the energy expenditure (EE) due to GNG.

Sleep timing and consistency are associated with the standardised test performance of Icelandic adolescents.

Sleep has been shown to affect cognitive function in laboratory studies; however, its association to the academic performance of adolescents has largely been demonstrated using self-reported measures. Studies with objective measures of both sleep and academic performance are limited. The aim of the present study was to determine whether the free-living sleep quantity, quality, and timing of 15-year-old adolescents measured with wrist actiography are associated with their scores on national standardised examinations as an objective measure of academic achievement.

Leptin Decreases Energy Expenditure Despite Increased Thyroid Hormone in Patients With Lipodystrophy.

Context: Leptin is an adipokine that signals energy sufficiency. In rodents, leptin deficiency decreases energy expenditure (EE), which is corrected following leptin replacement. In humans, data are mixed regarding leptin-mediated effects on EE.

Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake.

The carbohydrate-insulin model of obesity posits that high-carbohydrate diets lead to excess insulin secretion, thereby promoting fat accumulation and increasing energy intake. Thus, low-carbohydrate diets are predicted to reduce ad libitum energy intake as compared to low-fat, high-carbohydrate diets. To test this hypothesis, 20 adults aged 29.

Association between free-living sleep and memory and attention in healthy adolescents.

In laboratory studies, imposed sleep restriction consistently reduces cognitive performance. However, the association between objectively measured, free-living sleep and cognitive function has not been studied in older adolescents. To address this gap, we measured one week of sleep with a wrist-worn GT3X+ actigraph in 160 adolescents (96 girls, 17.

Room Indirect Calorimetry Operating and Reporting Standards (RICORS 1.0): A Guide to Conducting and Reporting Human Whole-Room Calorimeter Studies.

Whole-room indirect calorimeters have been used to study human metabolism for more than a century. These studies have contributed substantial knowledge to the assessment of nutritional needs and the regulation of energy expenditure and substrate oxidation in humans. However, comparing results from studies conducted at different sites is challenging because of a lack of consistency in reporting technical performance, study design, and results.

Changes in sleep and activity from age 15 to 17 in students with traditional and college-style school schedules.

Objectives: Sleep duration and physical activity decline with age during adolescence. Earlier school schedules may contribute to these declines. The aim of this longitudinal study was to track changes in sleep and activity of Icelandic youth from primary to secondary school and compare students who enrolled in secondary schools with traditional and college-style schedules.

Less physical activity and more varied and disrupted sleep is associated with a less favorable metabolic profile in adolescents.

Background: Sleep and physical activity are modifiable behaviors that play an important role in preventing overweight, obesity, and metabolic health problems. Studies of the association between concurrent objective measures of sleep, physical activity, and metabolic risk factors among adolescents are limited.

Objective: The aim of the study was to examine the association between metabolic risk factors and objectively measured school day physical activity and sleep duration, quality, onset, and variability in adolescents.

Less screen time and more physical activity is associated with more stable sleep patterns among Icelandic adolescents.

Objectives: Emerging evidence suggests that inconsistent sleep may affect physical and psychological health. Thus, it is important to identify modifiable determinants of sleep variability. Screen time and physical activity are both thought to affect sleep, but studies of their relationship to sleep variability using objective measures are lacking.

The Effects of Interrupting Sitting Time on Affect and State Anxiety in Children of Healthy Weight and Overweight: A Randomized Crossover Trial.

Purpose: Sedentary time relates to higher anxiety and more negative affect in children. This study assessed whether interrupting sitting over 3 hours is sufficient to influence state anxiety, positive affect, or negative affect, and tested weight status as a moderator.

Methods: Analyses were the second (preplanned) purpose of a larger study.

Sexual Dimorphisms in Adult Human Brown Adipose Tissue.

Objective: This study aimed to quantify and compare the amount, activity, and anatomical distribution of cold-activated brown adipose tissue (BAT) in healthy, young, lean women and men.

Methods: BAT volume and F-fluorodeoxyglucose uptake were measured by positron emission tomography and computerized tomography in 12 women and 12 men (BMI 18.5-25 kg/m , aged 18-35 years) after 5 hours of exposure to their coldest temperature before overt shivering.

Chronic mirabegron treatment increases human brown fat, HDL cholesterol, and insulin sensitivity.

BACKGROUNDMirabegron is a β3-adrenergic receptor (β3-AR) agonist approved only for the treatment of overactive bladder. Encouraging preclinical results suggest that β3-AR agonists could also improve obesity-related metabolic disease by increasing brown adipose tissue (BAT) thermogenesis, white adipose tissue (WAT) lipolysis, and insulin sensitivity.METHODSWe treated 14 healthy women of diverse ethnicities (27.