It has been observed relationship between weight at birth, which is the result of the fetal environment, and the occurrence of obesity. However, the most important factors appear to be related to dietary and energy expenditure. The results on the relationship between high intake of energy and obesity are not conclusive, seems to have more effect the proportion of energy provided by fat. With regard to energy expenditure, factor that determines further the development of obesity in children and adolescents is a sedentary lifestyle and in particular the practice of sedentary activity such as watching television, using the computer or video games. The Western lifestyle is characterized by physical inactivity, excessive heat and food supply neutrality, linked to a strong advertising pressure. The first two features, reflecting a decrease of daily expenditure that can represent up to 500 Kcal between sedentary children and children athletes, this being a trigger for obesity.
The process of modernization and socio-economic restructuring in the developed and developing, have modified dietary habits and physical activity. These new dietary habits and physical inactivity are associated with overweight and obesity. The reduction of energy expenditure may be the most important determinant of the current epidemic of childhood obesity. As dietary and nutritional factors in childhood associated with a higher rate of obesity, for example, the consumption of low-calorie diets rich in fat and sugar, consuming energy-dense foods, especially those such as the "fast food" or "junk food" and a low consumption of fruits and vegetables. With respect to physical activity factors, there is a clear link between physical inactivity and fat accumulation. Children have decreased their physical activity in the past two decades, practiced increasingly sedentary games (video games, computer games), and decreased the sport, spending many hours watching television. It is documented that over 95% of childhood obesity is due to this cause
In Mexico the risk factor most associated with obesity in children is the change in eating patterns diets with a high calorific value, and the decline in physical activity levels. As for food, the study from the National Household Income and Expenditure Survey in Mexico, in 1998, described the increase in the percentage of refined carbohydrate foods such as soft drinks, while decreased fruits, vegetables, meats and dairy. Another interesting contribution of this study describes the products in which they spend most Mexicans do not meet all the nutritional needs of a large group of households. With respect to physical activity, obesity, sedentary lifestyle is associated with product outline the conditions of urban life, which leads to more time spent watching television and video games, in the Mexican population was estimated that each hour of television 12% increases the risk of obesity in children aged 9-16 years, which were found to spend an average of 4.1 + / - 2.2 hours / day watching TV or playing video games.
Obesity is favored by low socioeconomic status, the event is recorded in the increased incidence of it, especially in women, is linked to inadequate nutrition habits and physical inactivity. In men of high social class has seen more cases, however, the most severe forms do not appear to be related to social class, but that is probably due to genetic factors.The physical environment as the season, geographic region and population density, population, are associated with increased occurrence of obesity, for example, lower prevalence occurs in the summer and spring, and increases in autumn and winter.
Other factors such as excessive weight of the mother during pregnancy, advanced age (> 35 years), the children of separated parents and only children are at increased risk of obesity, is by overprotection or affection with excess supply of food. " . Other causes of obesity are related to intrauterine influences, such as maternal obesity, exposure to famine during the first or third trimester and gestational diabetes mellitus in a study by Marza Dowda and Col., 2791 with a group of young between 8 and 16 years, participants in NHANES III, found that girls who watched more than four hours of television were more overweight than those who spent less time, and children who participated in a program of exercise and sport were less overweight than their peers who did not participate in the program. According to research, the increased time spent on video games and television and increased consumption of foods high in calories, are related to excess adiposity (88). In the late 90s, new data were analyzed worried related to sedentary behavior, an increase in the predominance of obesity and daily hours of television