A quarter of the adult population in industrialized countries experiences mental health issues during their lifetime. In France, despite the existence of specialized legislation, mental/neuro-psychiatric disorders are estimated to contribute to 32% of the global disease burden. Yet overall, and in France in particular, mental illness receives insufficient attention despite its substantial contribution to the nonfatal disease burden, chronic nature, and estimated 20-year reduction in life expectancy. To a large extent, in fact, premature mortality in individuals with mental illness is due to non-communicable physical disorders that have not been properly diagnosed or treated. In turn, in the Covid-19 pandemic context, the mental illness burden seems to be growing at an alarming rate and will likely continue to do so in the coming years. Another deleterious aspect of the current situation is that it exacerbates existing risk behaviors (i.e., increased smoking, alcohol use, snacking, sedentariness). MEMORIES is a 4-year multi-disciplinary project with 5 inter-related work packages; its main working hypothesis addresses the role of mental health status as a potentially modifiable determinant of nutrition-related chronic disorders such as obesity and type 2 diabetes among adults. MEMORIES has 3 specific aims: (1) estimate and rank the relative risk of nutrition-related chronic disorders associated with different mental disorders; (2) develop and validate an epidemiological, prospectively applicable mental multi-morbidity index; (3) investigate the prospective association of mental multi-morbidity with nutrition-related chronic disorders (obesity, type 2 diabetes and their comorbidity) in general (the French NutriNet-Santé e-cohort) and vulnerable (e.g., smokers, heavy alcohol users, individuals with poor dietary quality and/or high levels of sedentariness) population samples, and estimate the proportion of avoidable morbidity and mortality related to these disorders. The overarching goal of MEMORIES is to contribute to the reduction of morbidity and premature mortality rates in individuals with mental illnesses, based on new scientific tools and knowledge derived from a rigorous multidisciplinary approach encompassing epidemiology, nutrition, psychology, endocrinology, biostatistics, preventive medicine, and public health. The results can thus guide clinical practice, primary and secondary prevention, epidemiological and intervention research, and public health policy.