Genetically determined lean mass and dietary response

Weight loss attenuates many obesity-related co-morbidities, but is difficult to sustain with dietary change. Dietary adherence, not macronutrient composition, is a better predictor of weight loss. Weight loss-induced endocrine changes promote food intake and increase energy efficiency, contributing to the difficulty with dietary adherence and weight regain. Macronutrient preference is partly genetically determined, suggesting that personalized dietary interventions might be more successful. In this issue, Li et al. report that a genetic risk score comprising the cumulative weighted effects of variants previously associated with increased lean mass is associated with increased satiety and weight loss 6 months after initiating a low- but not a high-fat diet. The effects were attenuated by 2 years. These findings suggest that genetic variants may influence response to specific diet. Further studies are necessary to assess whether genetically determined lean mass is causally associated with dietary response. Significant progress has recently been made in identifying additional genetic determinants of lean mass, which will enable such investigations and potentially inform future nutritional studies.     

Whole body MRI: Improved lesion detection and characterization with diffusion weighted techniques

Diffusion‐weighted imaging (DWI) is an established functional imaging technique that interrogates the delicate balance of water movement at the cellular level. Technological advances enable this technique to be applied to whole‐body MRI. Theory, b‐value selection, common artifacts and target to background for optimized viewing will be reviewed for applications in the neck, chest, abdomen, and pelvis. Whole‐body imaging with DWI allows novel applications of MRI to aid in evaluation of conditions such as multiple myeloma, lymphoma, and skeletal metastases, while the quantitative nature of this technique permits evaluation of response to therapy. Persisting signal at high b‐values from restricted hypercellular tissue and viscous fluid also permits applications of DWI beyond oncologic imaging. DWI, when used in conjunction with routine imaging, can assist in detecting hemorrhagic degradation products, infection/abscess, and inflammation in colitis, while aiding with discrimination of free fluid and empyema, while limiting the need for intravenous contrast. DWI in conjunction with routine anatomic images provides a platform to improve lesion detection and characterization with findings rivaling other combined anatomic and functional imaging techniques, with the added benefit of no ionizing radiation. J. Magn. Reson. Imaging 2013;38:253–268. © 2013 Wiley Periodicals, Inc.