Impact of Food-Based Weight Loss Interventions on Gut Microbiome in Individuals with Obesity: A Systematic Review.

The observation that the gut microbiota is different in healthy weight as compared with the obese state has sparked interest in the possible modulation of the microbiota in response to weight change. This systematic review investigates the effect of food-based weight loss diets on microbiota outcomes (α-diversity, ß-diversity, relative bacterial abundance, and faecal short-chain fatty acids, SCFAs) in individuals without medical comorbidities who have successfully lost weight. Nineteen studies were included using the keywords 'obesity', 'weight loss', 'microbiota', and related terms. Across all 28 diet intervention arms, there were minimal changes in α- and ß-diversity and faecal SCFA concentrations following weight loss. Changes in relative bacterial abundance at the phylum and genus level were inconsistent across studies. Further research with larger sample sizes, detailed dietary reporting, and consistent microbiota analysis techniques are needed to further our understanding of the effect of diet-induced weight loss on the gut microbiota.

Orthorexia Nervosa: An Examination of the Prevalence, Correlates, and Associated Impairment in a University Sample.

Orthorexia nervosa is characterized by an obsession with eating "pure" or "healthy" foods. Despite emergent interest, few studies have been published about orthorexia to date. This study examined the phenomenology, correlates, and associated impairment of orthorexia in 404 undergraduate students. A battery of self-report questionnaires assessed orthorexia symptoms, related functional impairment, disordered eating, perfectionism, obsessive-compulsive symptoms, appearance anxiety, fear of negative evaluation, anxiety, and depressive symptoms. In total, 35.4% of participants endorsed elevated orthorexia symptoms, with primary concerns related to guilt associated with dietary transgressions and experiencing control when eating in a desired manner. Orthorexia symptoms demonstrated small to medium correlations with associated impairment variables, perfectionism, disordered eating, appearance anxiety, and obsessive-compulsive symptoms. Mean differences were observed across all variables (except depressive symptoms) between individuals elevated and not elevated on orthorexia symptoms. Collectively, this study suggests a relatively high frequency of orthorexia symptoms using current methods (which have significant limitations) and demonstrate fairly modest associations with psychological symptomology.