Millennials, Gen Y need to eat less, work out more to stave off obesity, researchers say

"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," says Professor Jennifer Kuk in the School of Kinesiology and Health Science. "However, it also indicates there may be other specific changes contributing to the rise in obesity beyond just diet and exercise."

The study, funded by the Canadian Institutes of Health Research, analyzed dietary data of nearly 36,400 American adults collected by the 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 per cent heavier in 2008 than in 1971, and about five per cent heavier for a given amount of physical activity level in 1988 than 2006," notes Ruth Brown, lead researcher and York U graduate student, adding, "These secular changes may in part explain why we have seen the dramatic rise in obesity."

The study, "Secular differences in the association between caloric intake, macronutrient intake and physical activity with obesity," is featured in the upcoming issue of Obesity Research & Clinical Practice.

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'," says Kuk. "That's similar to saying your investment account balance is simply your deposits subtracting your withdrawals and not accounting for all the other things that affect your balance like stock market fluctuations, bank fees or currency exchange rates."

Kuk further explains that 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. "Ultimately, maintaining a healthy body weight is now more challenging than ever."