Infant feeding, appetite and satiety regulation, and adiposity during infancy: a study design and protocol of the 'MAS-Lactancia' birth cohort.

Introduction The prevalence of childhood obesity has risen dramatically in recent years. A proportion of this burden has been attributed to factors that occur during the first 1000 days of life such as genetic predisposition, breast feeding and complementary feeding. Although the mechanisms by which these factors affect weight and adiposity are less well understood, appetite and satiety regulation may be a key to understanding them. This cohort study aims to investigate the role of appetite and satiety regulation as a mediator in the association between infant feeding practices and genetic polymorphisms with children's growth, adiposity and metabolic risk factors. METHODS AND ANALYSIS: 'MAS-Lactancia' (the first word means 'more' and is also an acronym in Spanish for 'Appetite and Satiety Mechanisms', the second word is 'breastfeeding') is an open, ongoing, prospective birth cohort that began the enrolment in 2016 of mother-child pairs affiliated to the Mexican Social Security Institute and that live in the city of Cuernavaca, Mexico. Pregnant women between 16-week and 22-week gestation are followed during the second half of their pregnancies, at birth and throughout their infant's first 48 months of life (at 1 month, 3 months, 6 months, 9 months, 12 months, 18 months, 24 months, 36 months and 48 months) at the clinic and at-home visits that include questionnaires, anthropometric measurements and biospecimen collection. The main exposure variables are infant feeding (breast feeding and complementary feeding) and genetic polymorphisms (fat mass and obesity-associated, leptin and adiponectin genes). Outcome variables include infant's growth, adiposity and metabolic risk factors. We will conduct longitudinal models and path analyses to identify the potential mediating role of satiety and appetite indicators (leptin, adiponectin, insulin concentrations, appetite and satiety perception). Ethics and dissemination The study protocol, data collection instruments, consent forms and procedures were approved by the institutional review boards of the National Institute of Public Health and the Mexican Social Security Institute in Mexico. Findings will be disseminated through conferences, peer-reviewed publications and meetings with stakeholders.