In an era of food abundance, uncontrolled appetite and overeating is an issue We hypothesize that environmental factors modify gut hormones incretion, which in turn affect appetite and obesity  over the first two decades of life Data from two ongoing cohorts will be used: a 4y follow-up birth cohort and a 10y follow-up in adolescents We will test whether psychological (stress) and physiological (greenness/pollution) environmental factors influence gut hormones and consequently  body composition, while also checking moderation by diet/activity and mediation by gut microbiota and inflammation Strengths are 1) data on four critical periods in human’ lifespan: in utero life, infancy, childhood and adolescence using existing cohorts, 2) an integrative view of several exposures, 3) a mechanistic focus Our proposal is committed to the concept of “geing from early life onwards”supported by the EU The project will (a) Raise public health awareness to the problem of uncontrolled eating in our highly palatable food environment, air pollution and stress; (b) Help basic science to enable mechanistic insights in the appetite pathways; (c) Inform clinical practice on pharmacological targets (gut hormones and related physiology), psychological interventions and dietary guidelines, (d) methodological improvements in population studies by the validation of carbon load in fecal samples as indicator of direct exposure in the intestine