Background/Objectives:Brown adipose tissue (BAT) is a potential therapeutic target against obesity and diabetes through thermogenesis and substrate disposal with cold exposure. The role of BAT in energy metabolism under thermoneutral conditions, however, remains controversial. We assessed the contribution of BAT to energy expenditure (EE), particularly diet-induced thermogenesis (DIT), and substrate utilization in human adults.Methods:In this cross-sectional study, BAT activity was evaluated in 21 men using 18F-fluoro-2-deoxy-D-glucose positron emission tomography combined with computed tomography (18F-FDG-PET/CT) after cold exposure (19 °C). The subjects were divided into BAT-positive (n=13) and BAT-negative (n=8) groups according to the 18F-FDG-PET/CT findings. Twenty-four hour EE, DIT and respiratory quotient were measured using a whole-room indirect calorimeter at 27 °C.Results:Body composition, blood metabolites and 24-h EE did not differ between groups. DIT (%), calculated as DIT divided by total energy intake, however, was significantly higher in the BAT-positive group (BAT-positive: 9.7±2.5%, BAT-negative: 6.5±4.0%, P=0.03). The 24-h respiratory quotient was significantly lower (P=0.03) in the BAT-positive group (0.861±0.027) than in the BAT-negative group (0.889±0.024).Conclusion:DIT and fat utilization were higher in BAT-positive subjects compared to BAT-negative subjects, suggesting that BAT has a physiologic role in energy metabolism.

To re-evaluate the suitability of calf circumference as a surrogate marker of low muscle mass measured by both bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA). We also examined the effects of obesity and age on low muscle mass screening using calf circumference. Methods: In total, 1239 adults participated in this cross-sectional study. We measured the maximum calf circumference in a standing position and appendicular skeletal muscle mass (ASM) using BIA and DXA. We defined low muscle mass based on the Asian Working Group for Sarcopenia 2019 consensus. Results: Calf circumference was positively correlated with BIA-measured ASM/height 2 (men: r = 0.81, women: r = 0.73) and DXA-measured ASM/height 2 (men: r = 0.78, women: r = 0.76). In the subgroup analyses by obesity and age, calf circumference was also positively correlated with ASM/height 2. The optimal calf circumference cutoffs for low muscle mass screening measured by BIA and DXA were 35 cm (sensitivity 91%, specificity 84%) and 36 cm (sensitivity 82%, specificity 80%) for men, and 33 cm (sensitivity 82%, specificity 84%) and 34 cm (sensitivity 85%, specificity 72%) for women, respectively. Conclusions: Calf circumference is positively correlated with BIA-and DXA-measured muscle mass regardless of obesity and age and is a simple and accurate surrogate marker of muscle mass for diagnosing sarcopenia.

Summary Abdominal adiposity and low cardiorespiratory fitness are assosicated with insulin resistance in people with impaired glucose tolerance and type 2 diabetes. However, little is known about which factor precedes insulin resistance in people with impaired glucose tolerance and type 2 diabetes, and which is the stronger predictor of insulin resistance in non-diabetic people. The purpose of this study was to examine the relationship between insulin resistance and cardiorespiratory fitness, visceral fat, and subcutaneous fat in nondiabetic people. Subjects included 87 men and 77 women aged 30-72 y (mean Ϯ SD, 51.3 Ϯ 12.3 y). Cardiorespiratory fitness was assessed by measuring the maximal oxygen uptake (V · O 2max ) in a progressive continuous test to exhaustion on a cycle ergometer. The visceral and subcutaneous fat areas were measured by magnetic resonance imaging. The homeostasis model assessment of insulin resistance (HOMA-R) was calculated from the fasting concentrations of glucose and insulin. Stepwise multiple linear regression analysis revealed that visceral and subcutaneous fat were significant correlates of HOMA-R, explaining 24% and 6% of the variance, respectively, whereas sex, age, and V · O 2max were not significant independent determinants. Abdominal fat deposition rather than cardiorespiratory fitness is a significant predictor of insulin resistance in non-diabetic people; visceral fat is the most important factor.

Arterial stiffening, hypertension and left ventricular (LV) remodelling are associated with increased risk of cardiovascular disease. Cardiorespiratory fitness is associated with cardiovascular function and reduced risk of cardiovascular disease. This cross-sectional study was carried out to determine the relationships between cardiorespiratory fitness, arterial stiffness, blood pressure (BP) and LV remodelling in women. On the basis of peak oxygen uptake, a total of 159 premenopausal (young) and postmenopausal (older) women were categorized into either low (unfit) or high (fit) cardiorespiratory fitness groups. The arterial stiffness and LV remodelling were measured by brachialankle pulse wave velocity (baPWV) and carotid augmentation index (AI) and LV relative wall thickness (RWT). Two-way analysis of variance indicated a significant interaction between age and cardiorespiratory fitness in baPWV, carotid AI, BP and RWT. In the older group, arterial stiffness (baPWV; 1401 ± 231 vs 1250 ± 125 cm s -1 , Po0.01, AI; 32.9±9.9 vs 24.8±10.1%, Po0.01), systolic blood pressure (SBP) (130 ± 22 vs 117 ± 15 mm Hg, Po0.01) and RWT (0.47 ± 0.08 vs 0.42±0.04, Po0.05) in fit women were lower than in unfit women. In older women, RWT was significantly related to baPWV (r ¼ 0.46, Po0.01), carotid AI (r ¼ 0.29, Po0.05), SBP (r ¼ 0.57, Po0.01) .V 2peak (r ¼ À0.32, Po0.05). In young women, they were not significant correlations, except for a weak correlation between RWT and SBP (r ¼ 0.21, Po0.05). These results suggest that higher cardiorespiratory fitness is associated with lower arterial stiffness, BP and RWT in older women.

BackgroundA triaxial accelerometer with an algorithm that could discriminate locomotive and non-locomotive activities in adults has been developed. However, in the elderly, this accelerometer has not yet been validated. The aim were to examine the validity of this accelerometer in the healthy elderly, and to compare the results with those derived in a healthy younger sample.MethodsTwenty-nine healthy elderly subjects aged 60–80 years (Elderly), and 42 adults aged 20–59 years (Younger) participated. All subjects performed 11 activities, including locomotive and non-locomotive activities with a Douglas bag while wearing the accelerometer (Active style Pro HJA-750C). Physical activity intensities were expressed as metabolic equivalents (METs). The relationship between the METs measured using the Douglas bag and METs predicted using the accelerometer was evaluated.ResultsA significant correlation between actual and predicted METs was observed in both Elderly (r=0.85, p<0.001) and Younger (r=0.88, p<0.001). Predicted METs significantly underestimated compared with actual METs in both groups (p<0.001). The mean of the errors was −0.6±0.6 METs in Elderly and −0.1±0.5 METs in Younger. The degree of underestimation increased with increasing METs in Elderly (p<0.001). A stepwise multiple regression analysis revealed that predicted METs, age, and weight were related to actual METs in both groups.ConclusionThe degree of correlation between predicted and actual METs was comparable in elderly and younger participants, but the prediction errors were greater in elderly participants, particular at higher-intensity activities, which suggests that different predicting equations may be needed for the elderly.

To evaluate whether regularly performed rowing exercise affects the trunk muscles size and function, and to examine the effect of rowing exercise on thigh muscle size and function in elderly rowers, we compared the cross-sectional area (CSA) and strength of these muscles in elderly male rowers and in age-matched untrained men. Participants were 16 elderly rowing-trained men (ROW age, 67.8 +/- 2.3 years) and 18 elderly untrained men (CON 66.2 +/- 3.0 years). CSA was measured by MRI in the trunk and thigh muscles. Isometric trunk flexion force and leg extension power were measured. ROW had a 20% larger total trunk muscle CSA than CON (P < 0.01); rectus abdominis was 27% larger, psoas major 64% larger, and erector spinae 14% larger in ROW than in CON (P < 0.05-0.001). Isometric trunk flexion force was related to the CSA of the rectus abdominis (r = 0.777, P < 0.001) and psoas major (r = 0.694, P < 0.001), and was 42% larger in ROW than in CON (P < 0.001). However, force adjusted for the CSA of the muscles did not differ significantly between CON and ROW. In ROW, the CSA was 13% larger in the total thigh muscles (P < 0.01), and leg extension power was 43% higher than in CON (P < 0.001). These results suggest that rowing exercise is a favorable training modality for the trunk muscles, especially psoas major and that it improves thigh muscle size and function in elderly men.

The aim of this cross-sectional study was to compare body composition and risk factors of lifestyle-related diseases between young and older male rowers and sedentary controls. Healthy males aged 19-73 years participated in the study, and were divided into four groups: 26 young rowers, 24 senior rowers, 23 young sedentary controls, and 22 senior sedentary controls. Total and regional lean soft tissue, fat mass, and bone mineral density were measured using dual-energy X-ray absorptiometry. The HDL-cholesterol of senior rowers (67.4 +/- 13.4 mg . dl(-1)) was significantly (P < 0.05) higher than that of senior sedentary controls (59.2 +/- 11.9 mg . dl(-1)), while HDL-cholesterol was similar in senior rowers and young rowers (66.1 +/- 10.8 mg . dl(-1)). Arm, leg, and trunk lean soft tissue mass were significantly higher in senior rowers (5.6 +/- 0.6 kg, 18.2 +/- 1.8 kg, and 27.3 +/- 3.2 kg respectively) than in senior sedentary controls (5.1 +/- 0.4 kg, 16.3 +/- 1.4 kg, and 24.6 +/- 1.7 kg respectively; P < 0.05). Bone mineral density was also significantly higher in senior rowers than in senior sedentary controls (ribs, lumbar spine, and pelvic segments; P < 0.05). We conclude that age-related increases in the risk of lifestyle-related diseases, such as osteoporosis and sarcopenia, are attenuated in male rowers. These results suggest that regular rowing exercise may have a positive influence in the prevention of lifestyle-related diseases in older Japanese people.

SummaryThe number of lean young women has been increasing. Fear of being fat may induce unnecessary attempts to reduce body weight, which can cause several types of illness. Many investigations have demonstrated dysfunction of the hypothalamus and metabolic differences in patients with anorexia nervosa. However, it is unclear whether there are any differences in physical characteristics between women with lower body weight and no illness compared to those of normal body weight. In this study, we investigated the differences in body composition, biochemical parameters, and resting energy expenditure (REE) between young women with low and normal body mass index (BMI). Twenty lean women (BMI Ͻ 18.5 kg/m 2 ) and 20 normal women (18.5 Ϲ BMI Ͻ 25 kg/m 2 ) were recruited for this study. Body composition, biochemical parameters, and REE (REEm: measurement of REE) were measured, and the REE (REEe: estimation of REE) was estimated by using a prediction model. Marked differences were found in body composition. All of the values of blood analysis were in the normal ranges in both groups. REEm (kcal/d and kcal/kg BW/d) was significantly lower in lean than in normal women, but there were no significant differences in the REEm to fat free mass (FFM) ratio between the two groups. In addition, there was good agreement between REEm and REEe obtained from the specific metabolic rates of four tissue organs. These data indicate that the lean women without any illness have normal values of biochemical parameters and energy metabolism compared to women with normal BMI. Key Words lean women, body mass index, body composition, resting energy expenditureThe National Health and Nutritional Examination Survey of Japan in 2008 indicated that the number of lean women aged 20-30 y has been increasing. The ideal body mass index (BMI) is also lower in the young women compared to age matched men and even to women in other age groups. In fact, Takimoto et al.( 1 ) reported that the BMI, collected every 10 y between 1976 and 2000, has been decreasing among women between 20 and 30 y old. In addition, recent studies indicated that many young Japanese women overestimate their current BMI and express a their desire to lose weight ( 1 , 2 ). Fear of being fat may induce unnecessary attempts to reduce body weight ( 3 ). Going on a crash diet to lose weight causes illness and health incidents. In some cases, attempts to become thin are associated with nutritional deficiencies, irregular menstruation, osteoporosis and decreased resting energy expenditure (REE) ( 4-7 ). Moreover, previous studies suggested that low pre-pregnancy BMI and gestational weight gain are associated with low birth weight ( 8 , 9 ). Therefore, extreme weight loss may have an impact on not only the women themselves but also on their children. Many investigations indicated a dysfunction of hypothalamus and metabolic changes in patients with anorexia nervosa (AN) associated with excessive weight loss. Most AN patients have low level of estradiol and show amenorrhea or irregular menstr...