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Obesity is the most common cause of metabolic complications and poor quality of life in Prader-Willi syndrome (PWS). Hyperphagia and obesity develop after an initial phase of poor feeding and failure to thrive. Several mechanisms for the aetiology of obesity in PWS are proposed, which include disruption in hypothalamic pathways of satiety control resulting in hyperphagia, aberration in hormones regulating food intake, reduced energy expenditure because of hypotonia and altered behaviour with features of autism spectrum disorder. Profound muscular hypotonia prevents PWS patients from becoming physically active, causing reduced muscle movements and hence reduced energy expenditure. In a quest for the aetiology of obesity, recent evidence has focused on several appetite-regulating hormones, growth hormone, thyroid hormones and plasma adipocytokines. However, despite advancement in understanding of the genetic basis of PWS, there are contradictory data on the role of satiety hormones in hyperphagia and data regarding dietary intake are limited. Mechanistic studies on the aetiology of obesity and its relationship with disease pathogenesis in PWS are required. . In this review, we focused on the available evidence regarding mechanisms of obesity and potential new areas that could be explored to help unravel obesity pathogenesis in PWS., (© 2016 World Obesity Federation.)

Background/aims: Although childhood obesity is a major problem, routine assessment methods do not reflect fat mass. Body mass index, which is most commonly used, gives an indication of weight for height and not a degree of adiposity., Methods: Bioelectrical impedance and dual-energy X-ray absorptiometry (DEXA) were used in a group of obese children to assess body fat., Results: Comparison between DEXA and commercial bioelectrical impedance scales in 46 children showed a highly significant correlation (R = 0.944, p < 0.001) in fat mass. Fat mass measured using bioelectrical impedance was 2.4 kg lower compared to measurement using DEXA., Conclusion: These bioelectrical scales may prove useful in the management of childhood obesity as they are able to provide important clinical information regarding fat mass and adiposity., (Copyright 2007 S. Karger AG, Basel.)

Objective Traditional methods of bone densitometry may not provide a comprehensive assessment of bone health. We aimed to assess bone micro-architecture and bone marrow adiposity ( BMA) by MRI in adults with osteogenesis imperfecta ( OI) and endocrinopathy including GH deficiency and/or hypogonadism. Measurements High-resolution micro- MRI images were acquired at the tibia using 3T MRI to calculate parameters of bone micro-architecture in seven adults with OI and 10 adults with endocrinopathies. MR Spectroscopy was performed in participants to calculate vertebral BMA, which was expressed as percentage fat fraction (% FF). Lumbar spine DXA was performed to assess bone mineral density. The MRI data were compared with a group of 22 healthy adults who were divided into two age-matched control groups. Results Intra-operator repeatability was high, with an average CoV of 1% for micro- MRI and 2·5% for MRS. The ratio of apparent bone volume to total volume (app BV/ TV) in the endocrinopathy and OI groups was lower than in age-matched control groups ( P = 0·003 and P = 0·008 respectively). A weak association between DXA BMD and app BV/ TV was also observed ( r = 0·5, P = 0·045). % FF was higher in the endocrinopathy group than in the age-matched control group ( P = 0·005), but no difference in % FF was observed between the OI group and their age-matched control group ( P = 0·26). Conclusions MRI provides valuable detailed information on the micro-architecture and adiposity of bones and is capable of showing clear differences in bone parameters in a range of clinical conditions associated with abnormal bone health. [ABSTRACT FROM AUTHOR]