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There is accumulating evidence showing that obesity is due not merely to increased food intake, but could have a more complex pathophysiology possibly originating from the gut. Due to its microbiological, hormonal, and nutritional aspects, the gut could represent a starting point for the treatment of weight excess. Obesity is associated with a change of microbiota composition that not only could increase the calorie extraction from food but also could create a functional derangement resulting in irritable bowel syndrome (IBS). Several mechanisms have been postulated to explain this association, such as specific foods that are poorly absorbed, i.e., carbohydrates and lipids, as well as conditions of psychological stress which could stimulate colonic hypersensitivity giving rise to IBS symptoms. Another factor involved in this link could be the subclinical inflammation typical of obesity, characterized by the release of inflammatory mediators that can irritate intestinal nerve endings. The change of levels of some anorexigenic hormones, as well as the alterations of the gut microbiota with the reduction of the bacteroides/Firmicutes ratio, could also contribute to the pathogenesis of IBS related to obesity. Thus, the aim of this manuscript is to review the current evidence on the association between obesity and IBS while providing physiopathological hypotheses that may explain this link. Further, we will report the effect of weight loss on IBS symptoms, highlighting the importance of an accurate assessment of gut function in obese patients.

Study of the interactions between the gut microbiota and brain-gut axis represents a very appealing approach to increasing our knowledge about the mechanisms leading to obesity and obesity-related diseases. The aim of this review is to focus on the effects of short-chain fatty acids (SCFAs), which are the main products of gut microbial fermentation from non-digestible carbohydrates in the colon, on the gut-brain axis. Evidence is accumulating regarding the role of SCFAs in the fine-tuning of the gut-brain axis, a feedback system which is vital not only for the proper maintenance of gastrointestinal and metabolic functions, but also for the regulation of food intake and energy expenditure. SCFAs are thought to play a key role in increasing the host capacity to harvest excess energy from the diet. SCFAs, however, can exert their effects on the host metabolism via multiple complementary pathways. Metabolic, inflammatory, and neural pathways can be regulated by SCFAs, which can act by sensing nutritional status, thereby maintaining body energy homeostasis. SCFA production from prebiotic consumption is the rationale for targeting intestinal mechanisms to increase energy expenditure and thereby reduce obesity risk.

Aim: The objective of this study was to investigate the effect of implementation of short-term patient empowerment as applied to Mediterranean diet (MD) adherence on metabolic and anthropometric parameters in prediabetic overweight or obese subjects., Methods: The sample included 42 subjects with prediabetes, aged 18-75 years and with body mass index (BMI) > 25 kg/m 2 , who received dietary advice on MD by nutritionists during session groups every 2 weeks for 4 months. Data on energy caloric intake and macronutrient consumption were collected using a 7-day food diary record. Adherence to MD was investigated through the PREvención con DIeta MEDiterránea (PREDIMED) questionnaire. No advice was given regarding caloric restriction and physical activity. At baseline and at the end of the study, each subject underwent anthropometric, metabolic, and nutritional assessments., Results: Approximately 40.5% of subjects had achieved restoration of normal glucose tolerance by the end of the study. Fasting plasma glucose, glycated hemoglobin (HbA1C), BMI, waist circumference, blood pressure, visceral adiposity index, triglycerides, and total and LDL cholesterol levels were significantly decreased, while HDL cholesterol had significantly increased by the end of the study. The subjects significantly increased adherence to MD, as assessed by the PREDIMED questionnaire at follow-up. A reduction of prevalence of the metabolic syndrome was also reported. Interestingly, the PREDIMED score correlated with HbA1C values at follow-up, after adjusting for BMI and total caloric intake., Conclusions: Implementation of short-term patient empowerment as applied to MD adherence was shown to improve anthropometric and metabolic parameters in prediabetic overweight or obese subjects. This is of considerable importance, given that diet must be the cornerstone of treatment in patients at high risk of developing type 2 diabetes.