Low birth weight and obesity: causal or casual casual association?

OBJECTIVE: To present the conceptual foundations that explain how events occurring during intrauterine life may influence body development, emphasizing the interrelation between low birth weight and risk of obesity throughout life. DATA SOURCES: Google Scholar, Library Scientific Electronic Online (SciELO), EBSCO, Scopus, and PubMed were the databases. “Catch-up growth”, “life course health”, “disease”, “child”, “development”, “early life”, “perinatal programming”, “epigenetics”, “breastfeeding”, “small baby syndrome”, “phenotype”, “micronutrients”, “maternal nutrition”, “obesity”, and “adolescence” were isolated or associated keywords for locating reviews and epidemiological, intervention and experimental studies published between 1934 and 2014, with complete texts in Portuguese and English. Duplicate articles, editorials and reviews were excluded, as well as approaches of diseases different from obesity. DATA SYNTHESIS: Within 47 selected articles among 538 eligible ones, the thrifty phenotype hypothesis, the epigenetic mechanisms and the development plasticity were identified as fundamental factors to explain the mechanisms involved in health and disease throughout life. They admit the possibility that both cardiometabolic events and obesity originate from intrauterine nutritional deficiency, which, associated with a food supply that is excessive to the metabolic needs of the organism in early life stages, causes endocrine changes. However, there may be phenotypic reprogramming for low birth weight newborns from adequate nutritional supply, thus overcoming a restrictive intrauterine environment. Therefore, catch-up growth may indicate recovery from intrauterine constraint, which is associated with short-term benefits or harms in adulthood. CONCLUSIONS: Depending on the nutritional adequacy in the first years of life, developmental plasticity may lead to phenotype reprogramming and reduce the risk of obesity.