Toronto, Sep 22 (IANS): If you are around 25 years of age and struggling with weight gain, you would have to eat even less and exercise more than your parents did, suggests new research.

The findings suggest that the older people had it easier -- they could eat more and exercise less, and still avoid obesity.

This could be due to the fact that our body weight is impacted by our changing lifestyle and environment.

"However, it also indicates there may be other specific changes contributing to the rise in obesity beyond just diet and exercise,” said Jennifer Kuk from York University in Toronto, Canada.

The research analysed dietary data of nearly 36,400 US adults collected by the US National Health and Nutrition Survey between 1971 and 2008.

The available physical activity frequency data, of 14,419 adults in the 1988 to 2006 period was also used.

"We observe that for a given amount of self-reported food intake, people will be about 10 percent heavier in 2008 than in 1971,” lead researcher Ruth Brown from York University noted.

The researchers also found that for a given amount of physical activity level, people were about five percent heavier in 2006 than in 1988.

"These secular changes may in part explain why we have seen the dramatic rise in obesity,” Brown noted.

Our body weight is impacted by our lifestyle and environment, such as medication use, environmental pollutants, genetics, timing of food intake, stress, gut bacteria and even nighttime light exposure, Kuk explained.

"Ultimately, maintaining a healthy body weight is now more challenging than ever,” Kuk said.

The findings will be featured in the upcoming issue of the journal Obesity Research & Clinical Practice.