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It’s okay to be heavy, as long as you don’t have diabetes or hypertension–right? Not so fast, says the latest research.

There are always exceptions to the rule, and that’s true of health issues too. While the bulk of studies warn about the dangers — to the heart, liver, kidneys and other body systems — of gaining weight, a small number of trials suggested that some overweight or obese individuals may be as healthy as their normal weight counterparts, since they had normal blood pressure, no diabetes and relatively stable cholesterol levels. In fact, one study found that overweight individuals (but not obese people) tended to live longer than those of normal weight.

But in a comprehensive review of studies dating back to the 1950s, scientists contradict that idea, with evidence that it’s not possible to be both overweight and healthy.

(MORE: You Can Be Fat and Fit–and Thin and Unhealthy)

The researchers, from Lunenfeld-Tanenbaum Research Institute at Mount Sinai Hospital in Toronto, Canada, found that people who tipped the scales at above their recommended body mass index (BMI) but did not have abnormal cholesterol or blood pressure, for example, still had a higher risk of dying from heart disease over an average of about 10 years compared to metabolically healthy individuals within normal weight ranges. In their analysis, published in Annals of Internal Medicine, the researchers separated individuals in the previous studies into six groups: normal weight and healthy, normal weight and unhealthy, overweight and healthy, overweight and unhealthy, obese and healthy, and obese and unhealthy. Their results showed that regardless of the person’s BMI, an unhealthy metabolic state — such as having hypertension, diabetes or high cholesterol levels — was consistently linked to an increased risk of dying during the study period or having a heart event. And contrary to previous studies that suggested that heavier people with normal metabolic readings could have “benign obesity” or “metabolically healthy obesity,” the team also reported that metabolically healthy obese participants had a higher risk of dying earlier or having heart-related problems than those who were normal weight and also metabolically healthy.

Why did previous studies suggest that people could be fit and fat? According to the current study’s lead author, Dr. Caroline Kramer, the discrepancy likely has to do with how the various studies were set up. For instance, some large studies only compared weight and the risk of adverse events instead of looking closely at people’s metabolic health. So some of the apparently healthy but overweight or obese individuals might have had signs of diabetes or hypertension or high cholesterol that simply weren’t recorded in the study. Other trials compared healthy obese people to unhealthy obese people, instead of comparing them to people of normal or healthy weights, and other studies relied on small groups of participants who were only studied over short time periods.

“This concept of healthy obesity came in the last 10 years, and it compares people who are obese but metabolically healthy to only metabolically unhealthy overweight people,” says Dr. Kramer. “Some studies report that if you are obese but metabolically healthy, you are protected in a way. We don’t think that that is true. And I don’t think it will come as much of a surprise.”

But since obesity has different effects on the body for different people, researchers are still investigating how weight gain and its health effects may vary among people whose obesity is due primarily to things such as genetics and environmental exposures as opposed to unhealthy diets and lack of physical activity. Even the studies in the current meta-analysis, for example, did not all include follow-up with the participants, so the final mortality and heart disease rates may be slightly higher or lower than they should be. But for now, the advice about maintaining a healthy weight in order to avoid premature death and disease seems sound — there may not be a way to heavy and healthy at the same time.