This book provides an approach to the research work carried out with school children by performing an intervention with muscle strength training to reduce body fat in a school population, specifically in an elementary school in the State of Hidalgo, Mexico. The World Health Organization defines obesity as an abnormal or excessive accumulation of fat that constitutes a health risk. The increase of overweight and obesity in childhood is a public health problem in industrialized and developing countries. The National Health and Nutrition Survey 2018-2019, found that overweight and obesity continue to be a highly prevalent problem in the Mexican population in all regions of the country and in urban and rural areas. To measure changes in dietary practices, instruments that measure knowledge, consumption, culinary skills, habits and food expenditures in private or public sector schools are required. As can be seen, overweight and obesity is a chronic disease that mainly affects children at different stages of growth.