You’ve dabbled in various fitness programs, taste-tested an array of fad diets, and educated yourself on the latest nutrition and fitness studies, but you’re just left frustrated, wondering why your body isn’t rivaling the fit figures infiltrating your Instagram account. (Check out these 6 Body Positive Fitness Instagram Accounts for a refreshing change.) So what gives?

The lack of progress despite your efforts may leave you feeling disheartened, but a recent study reveals there may be other factors at play in your weight loss woes. Published in the journal Obesity Research & Clinical Practice, the York University study found that modern environmental factors—like sleep deprivation and increased stress—are weighing heavily on American waistlines and keeping us from losing weight.

After examining dietary information from over 36,000 people from 1971 to 2008, and the fitness practices of roughly 14,000 people from 1988 to 2006, researchers found that despite ingesting the same amount of calories and having identical physical activity levels, a person from 2006 had a BMI 2.3 points higher than someone from 1988.

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They also found that an individual from 2008 was 10 percent heavier than someone from 1971, regardless of having identical diets (and get this: not only were your parents able to eat more, but they were also Having More Sex).

“Of the factors listed, there is significant evidence that lack of quality sleep and increased stress levels alter hormone balance,” says Amanda Foti, R.D., senior dietitian and expert for Selvera. “Individuals struggling with sleep deprivation and/or high stress levels can experience the affect it has on food cravings, satiety, energy levels and even metabolism.”

She further expands on additional factors that may be thwarting American weight loss efforts, acknowledging that though more research is needed, the elevated exposure to pesticides and chemicals have been linked in some studies with obesity (not to mention a drop in your man’s sperm count).

Foti also points out that food and sugar addictions have become a bit of an epidemic, due to constant exposure to processed foods and sweets. “They are finding that consuming sugar has a similar effect on the brain to some drugs, causing the individual to crave and ‘need’ the sugar even when they are not hungry.”

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Other possible factors include medication use, genetics, timing of food intake, gut bacteria and nighttime light exposure, according to Dr. Jennifer Kuk, researcher and associate professor at York University.

She also states: “Our study results suggest that if you are 40 years old now, you’d have to eat even less and exercise more than if you were a 40-year old in 1971, to prevent gaining weight.”

So, how do we combat these factors contributing to our growing waistlines? “We are in an era of yo-yo dieting with fad diets and short term solutions,” says Foli. “Weight loss should be viewed as a comprehensive lifestyle change addressing diet, activity, habits, stress management and sleep. In order to counteract the factors that we do not have control over we must focus on the areas we do.”

Start by educating yourself on the healthier choices you can make. “Choosing to eat a whole foods diets, understanding proper portion sizes, working exercise into your routine, taking the proper steps to manage stress and sleep are just a few steps that can be taken,” she says. “It does not happen overnight and it is not easy, but taking responsibility for your health and making wellness a priority is the first step. Whether that means tackling it on your own, with your family, or with help from an expert.”

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