New research has found that early exposure to chemicals that are used in making baby bottles may initiate obesity.
Three separate studies presented at the European Congress on Obesity in Geneva found that mice which were exposed during early development to chemicals used in products such as plastic food containers or even boat paint tended to become fat later in life.
The findings could change how obesity is viewed and dealt with, according to an expert on the subject.
Jerry Heindel from the United States National Institute of Environmental Health Sciences said: "If these findings are proven to be true in humans, then the focus must change from losing weight as adults to prevention of weight gain during development, through reducing the exposure to such substances."
In one study, female mice whose mothers were exposed to bisphenol A -- commonly used in plastic good containers and bottles -- were found to grow up into fat mice.
Food intake and activity levels were no different between the mice who became fat and those that did not, according to the study by Beverly Rubin from the US Tufts University.
Another study found that pregnant mice which were exposed to the chemical perfluorooctanoic acid -- used as a greaseproofing agent in products such as microwave popcorn bags -- had mice which were unusually small at birth but then became overweight as adults.
Suzanne Fenton from the US Environmental Protection Agency, who conducted the research, pointed out that the effect is only seen when low doses are applied.
This indicates that different doses may "trigger health problems in the body by various mechanisms or that the high doses cause more serious problems, and potentially mask the abnormal weight gain", she said.
A third study found that when pregnant mice were treated with doses of tributylin that is comparable to that found in humans, a genetic programme would be triggered in their offspring, causing them to become fat as adults.
Tributylin is a chemical used in plastic food wrap and as a fungicide.
"Developmental exposure is probably more serious than adult exposure because the data with other such exposures suggest that the pro-obesity reprogramming is irreversible, which means you will spend your life fighting weight gain," said Bruce Blumberg from the University of California at Irvine who conducted the research.
The World Health Organization has estimated that over 700 million people would be obese by 2015.
The European Conference on Obesity is meeting in Geneva from May 14-17.