Critical Periods for the Development of Obesity

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Childhood Obesity 96 demonstrated that birth weight can have a significant effect on the interaction between fat and muscle metabolism (Symonds et al., 2006). Programming of obesity from early stages in lifeIn the early 50's, Widdowson & McCance, 1963, began to study in animal models the influence of pre-and postnatal diet on the development of obesity.These researchers found that rats born with low weight and subsequently overfed during postnatal life, developed a large size and body weight in adulthood; the rats overfed during early lactation, showed high concentrations of insulin and cholesterol.Since then, numerous studies have shown that obesity, a plague in Western countries, may have its roots before birth (Cottrell & Ozanne, 2008).However, much remains to be elucidated about how the human body records these impressions.Given that obesity is primarily a disorder of energy balance, where energy intake exceeds energy expenditure, its mechanisms may involve the regulation of appetite and a disruption of energy expenditure together with an alteration of tissue metabolism and physical activity (Taylor & Poston, 2007).Currently there is scientific evidence from both epidemiological and animal studies suggesting that programming of obesity is caused by environmental influences that occur from the embryonic stage to neonatal life and childhood.Studies in animal models show that the foetus and newborn may be receiving different hormonal and dietary insults that converge in a common phenotype of hyperphagia, obesity, impaired adipocyte function and alteration of physical activity.Although the programming of obesity is clearly a multifactorial process, the diversity of models with a common goal allows suggesting some common metabolic pathways.The change in adipocyte development and the stimulation of the secretion of glucocorticoids seems to play an important role in the plasticity of the hypothalamus at the end of gestation and early postnatal life and is also clearly involved in programming appetite and metabolism to establish a higher body weight, which may or may not be adjusted over time (Taylor & Poston, 2007).Different mechanisms during critical stages of development may be involved in the early programming of adult obesity, including: 1. Impairment of placental function, 2. Formation of foetal adipose tissue and regulation of leptin synthesis and secretion before birth (McMillen et al.,

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