JOIN USVictor Inzua Canales, a scholar at the National Autonomous University of Mexico, or UNAM's National School of Social Work, said "there are child labourers who are as much as 10 cm shorter than those who don't work".
The study, titled "Ergonomic Exploration in Working Street Children: Mexico City", showed that "the consequences of working at an early age are reflected in (children's) health and biopsychosocial development", UNAM said in a statement.
"Working street children face a variety of risks depending on their occupation, from cramps, bumps and bruises and sprains to muscle tears," Inzua said.
They also are more susceptible to illnesses, "bone deformities, stunted growth, mutilations and accidents, which are often related to food deficiency, deplorable working conditions, rapid temperature changes, uncomfortable positions and prolonged work hours", he said.
During the one-year project, Inzua studied 25 child labourers ranging in age from 8 to 18 who worked on the streets of Mexico City's historical center, mainly as windshield wipers, jugglers, wheelbarrow pushers, tightrope walkers and street vendors.
"I found that children endanger their health with incorrect body positions, uncomfortable movements and malnutrition," he said.
Separately, the scholar conducted a body-mass analysis - crosschecked with height-weight tables - that showed that obesity is a problem among both Mexican children who work and those who do not.
The diet of most child labourers in Mexico is based on bread, coffee, tacos and "garnachas" (fried, high-fat street food); other Mexican children are overweight in large part because of eating too many sweets, Inzua said.
Mexico is considered to have the world's highest level of childhood obesity. Many children from low-income Mexican families are forced to work at an early age to supplement their household earnings.