It is more difficult for millennial to lose weight than it was for their parents, according to a recent study.

Researchers from York University found that when eating the same amount of food, millennials "will gain more weight than their forebears 35 years ago," UPI reported.  This shows that it is biologically more difficult for 25 year olds to lose weight than it was for their parents and grandparents.

"Our study results suggest that if you are 25, you'd have to eat even less and exercise more than those older, to prevent gaining weight," researcher Jennifer Kuk said in a statement. "However, it also indicates there may be other specific changes contributing to the rise in obesity beyond just diet and exercise."

For the study, researchers collected and analyzed dietary data from nearly 36,400 American adults. They also looked at physical activity frequency data of between 1988 to 2006 period.

They found that when eating the same amount of food, people will be about 10 percent heavier in 2008 than in 1971, and about 5 percent heavier for a given amount of physical activity level in 1988 than 2006.

"These results are clearly in contrast with the common notion that weight management is simply about what you eat and how much you exercise," Kuk an associate professor in the School of Kinesiology and Health Science at Canada's York University, told Yahoo News reported.

Ruth Brown, lead researcher of the study, said these secular changes may "explain why we have seen the dramatic rise in obesity."

The researchers point out that although several studies have shown that eating less and exercising more results in weight loss, in the long term, they are proven to be ineffective.

"This is because weight management is actually much more complex than just 'energy in' versus 'energy out'," Kuk said. "

Kuk said a person's body weight is impacted by their lifestyle and environment, such as medication use, environmental pollutants, genetics, timing of food intake and stress.

The findings are detailed in the journal Obesity Research & Clinical Practice.