TORONTO, Sept. 21 (UPI) -- Members of the millennial generation may have more trouble fighting obesity than those older than them, having to eat less and exercise more in order to stay fit.
Researchers found that when eating the same amount of food, young people will gain more weight than their forebears 35 years ago. While a new study by researchers at York University, published in Obesity Research and Clinical Research, does not determine a cause, it suggests that food and exercise are not the only variables at play in people's weight.
"This is because weight management is actually much more complex than just 'energy in' versus 'energy out'," said Jennifer Kuk, a professor in the School of Kinesiology and Health Science at York University, in a press release. "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."
Researchers used data from the U.S. National Health and Nutrition Survey on diet collected between 1971 and 2008 for 36,377 people and on physical activity for 14,149 people between 1988 and 2006, comparing dietary intake, physical activity, and body mass index over time in the participants.
The researchers found that BMI, total caloric intake and carbohydrate intake increased between 10 and 14 percent from 1971 to 2008, while fat and protein intake decreased between 5 and 9 percent in that time. They also found that from 1988 to 2006, leisure time physical activity had increased between 47 and 120 percent.
The data showed that, over time, for a given intake of calories or nutrients, BMI was 10 percent more in 2008 than in 1971. For a set amount of physical activity, participants also were predicted to weigh 5 percent more in 2006 than in 1998.
Kuk said this suggests factors other than diet and exercise are causing the large increase in obesity during the last several years. At fault, she said, could be a wide range of factors in lifestyle and environment, from medications and environmental pollutants to stress, genetics or the food itself.
"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," said Kuk. "However, it also indicates there may be other specific changes contributing to the rise in obesity beyond just diet and exercise."
Other recent studies have shown that diet and exercise are not entirely at fault for higher BMIs. A study conducted at Mount Sinai hospital in New York that showed the body can be conditioned for obesity -- making it more difficult to hold it off.
New data released by the Centers for Disease Control and Prevention showed obesity estimates in the United States ranging from 21.3 percent in Colorado to 35.9 percent in Arkansas and no state had less than 20 percent of its population classifying as obese.
"Ultimately, maintaining a healthy body weight is now more challenging than ever," Kuk said.
