摘要:Topic: Psychological and stressful social situations, as well as factors of an unhealthy lifestyle (such as insufficient exercise, weight increase and/or social isolation) are potential causes of MUS (Medically Unexplained Symptoms) and obesity, usually overlooked by general practitioners. Obesity is often underestimated using BMI, since it does not reflect the real loss of fat mass after nutritional strategies. Scope: We analyzed the changes in fat mass (FM) and fat-free mass (FFM) in the presence of decreasing BMI, using a novel advanced bio-impedance device, BIA-ACC (Bioelectric Impedance Analyzer for Analisi Composizione Corporea) that measures numerous parameters of body composition. Methods: 109 patients were enrolled at the center for primary care for a routine check-up, all apparently free of disease but with problems of excess weight and MUS to varying degrees. The evaluation of the parameters BIA-ACC was performed at the first visit T0, and at follow-up T1, after about 2 months of a standard nutritional strategy. Results: BMI decreased in all patients. FFM, particularly skeletal muscle, was the 1st principal component (PCA1: 58%) that determines the well-being of the patients and a decrease of MUS. The 2nd component (PCA2: 22%) is the FM. We found 3 different patterns of patient response to BMI reduction: 75.23% showed loss of FM and minimally FFM; 17.43% showed loss of FM with preservation or increase FFM; 7.34% showed loss of FFM alone. Conclusions: Body composition analysis is a valuable non-invasive tool to monitor patients in the early stages of immune-metabolic dysregulation when clinical symptoms are not yet evident. Our results demonstrate the importance of the maintenance of FFM rather than the loss of FM alone during weight loss therapy. Preservation of skeletal muscle is essential to facilitate the stabilization of loss of only fat and thus to eliminate the MUS correlated to chronic stress.