The growth promoting effects of antibiotics were first discovered in the 1940s. Since then, many antimicrobials have been found to improve average daily weight gain and feed efficiency. The total production of antibiotics can be estimated between 100,000-200,000 tons annually and the human population is being influenced, directly or indirectly (from the environment) by this amount of drug. The twentieth-century increase in human height and the obesity of the population is roughly observed since the mass consumption of antibiotics 40-50 years ago. The association between antibiotic consumption and the increase of human growth/obesity is suspected.