Researchers from York University and University of Alberta discovered that staying slim was easier for the parents of today's millennials. In a long-term study, it was found that eating and exercising just like how the 1980's people did will still subject one to gain more weight today.

The goal of the study was to determine if there had been a change in the association between caloric/macronutrient consumption and physical activity with obesity over time.

To achieve this aim, the authors collated data from the National Health and Nutrition Survey (NHANES), which involved 36,377 U.S. adults from 1971 to 2008. Exercise data were only available for 14,419 participants from 1988-2006. They then utilized a model to study if the link between total caloric consumption, percent dietary macronutrient intake and exercise with body mass index (BMI) was altered over time.

The findings of the study showed that between 1971 and 2008, BMI, as well as carbohydrate consumption and total caloric intake rose by about 10-14 percent. During the same time period, protein and fat consumption plummeted by about 5-9 percent. From 1988 to 2006, the number of times that people engage in leisure physical activities increased by 47-120 percent.

The researchers, however, found that for the same caloric/macronutrient consumption and leisure exercise, the predicted BMI increased up to 2.3 kg/m2 in 2006 than in 1988 in the adjusted study design.

Ruth Brown, the study lead author and graduate student from York University in Canada explained that for a specified self-reported food consumption amount, a 10 percent increase in weight was observed in individuals from 2008 compared to those in 1971. Also, a five percent rise in weight was noted among people from 2006 compared to those from 1988, even if they completed a given amount of exercise.

Brown added that these changes may partly explain why obesity rates have gone up drastically.

The researchers said that despite previous researches suggesting that more exercise and less eating may lead to weight loss, the approaches have been proven unsuccessful in the long term.

Professor Jennifer Kuk, the study's corresponding author from York University's School of Kinesiology & Health Science explained that weight management is more than just "energy in" and "energy out." She compared this explanation to investment accounts, which are not only affected by simple deposits and withdrawal transactions; other factors such as inflation, bank fees and exchange rates, also affect the account balance.

In the future additional investigations are warranted to determine the other factors and mechanisms that influence body weight.

Kuk said that lifestyle and environmental factors may have an impact to body weight. These factors may include pollutants, medications taken, eating times, stress and gut bacteria. "Ultimately, maintaining a healthy body weight is now more challenging than ever," she said.

The study was funded by the Canadian Institutes of Health Research was and published in the journal Obesity Research & Clinical Practice on Sept 14, 2015.

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