Older women who are obese but otherwise “metabolically healthy” — they do not have type 2 diabetes, high blood pressure or high cholesterol — are at higher risk of developing cardiovascular disease than healthy women who are not obese, according to a new study.
The study also found that the risk of cardiovascular disease, which includes heart disease, stroke and other conditions affecting the heart and blood vessels, is much higher in older women who are metabolically unhealthy, regardless of their weight.
These findings cast doubt on the controversial concept of “healthy obesity” — the idea that it’s possible to be fit and healthy even if you’re obese.
They also underscore how important it is for everyone — including those who aren’t overweight — to take steps to improve their metabolic health, such as exercising regularly and eating a healthy, balanced diet.
“Our large cohort study confirms that metabolically healthy obesity is not a harmless condition, and even women who remain free of metabolic diseases for decades face an increased risk of cardiovascular events,” said Matthias Schulze, the study’s senior author and a molecular epidemiologist at the German Institute of Human Nutrition Potsdam-Rehbruecke, in a released statement.
“What’s more, we observed that most healthy women are likely to develop type 2 diabetes, high blood pressure, or high cholesterol over time, irrespective of their [body mass index], putting them at much higher risk for cardiovascular disease,” he added.
The study was published in The Lancet Diabetes and Endocrinology.
For the study, Schulze and his colleagues, which included researchers at Harvard University, analyzed health data collected from 1980 to 2010 on almost 100,000 women who were participating in Harvard’s Nurses’ Health Study, which has been ongoing since 1976. Every two years, the women answered detailed questionnaires about their weight, height, lifestyle and medical history.
None of the women included in the current study had a history of cardiovascular disease when they entered the Nurses’ Health Study. But over the period of the study (the women were followed for a median average of 24 years), 3,304 of them had a heart attack and 3,080 had a stroke.
Schulze and his colleagues looked to see if there was any association between the women’s weight and metabolic health and their risk of having one of those cardiovascular “events.” There’s no clear definition of metabolic health, but this study defined it as not having type 2 diabetes, high blood pressure and/or high cholesterol.
The researchers found that being metabolically unhealthy increased the women’s risk of developing cardiovascular disease. Both normal-weight (non-overweight) and overweight women who were metabolically unhealthy were about 2.5 more likely to have a heart attack or stroke as their equal-weighted peers who were metabolically healthy.
For women who were obese and metabolically unhealthy, the risk was even greater. They were 3.15 times more likely to have a heart attack or stroke.
Interestingly, the study found that women who developed type 2 diabetes or high blood pressure were more likely to have a heart attack or stroke than the women who stayed metabolically healthy. But women who developed only high cholesterol were not.
The study also found that most of the women who began the study metabolically healthy — including 68 percent of the non-overweight women and 84 percent of the obese women — went on to become metabolically unhealthy.
That finding suggests not only that everyone needs to be concerned about developing type 2 diabetes, high blood pressure and high cholesterol, but also that obesity worsens the risk.
“Long-term maintenance of metabolic health is a challenge for overweight/obese [women], but also for normal-weight women,” said Schulze. “Our findings highlight the importance of preventing the development of metabolic diseases, and suggest that even individuals in good metabolic health may benefit from early behavioral management to improve their diet and increase physical activity in order to guard against progression to poor metabolic health.”
Not an end to the debate
The study comes with several caveats. Although the study was large and had a long follow-up period, it was still an observational study, which means it doesn’t prove obesity raises the risk for heart problems. It shows only a correlation. Furthermore, the study relied on the women to provide their own health information. Such self-reports are not always accurate.
Another major limitation is that the data obtained from the women did not include detailed information about physical activity, cardiorespiratory (heart-lung) fitness or incidents of heart failure, which, as a commentary accompanying the study points out, is probably the cardiovascular disease most affected by obesity.
Given all these limitations, it’s unlikely that this study will end the debate about whether obesity can be healthy. Indeed, as the authors of the accompanying commentary point out, several other studies have suggested that people “with metabolically healthy obesity and decent levels of cardiorespiratory fitness have a quite good overall prognosis from cardiovascular disease and overall survival.”
What those studies — and the current one — do seem to agree upon is how important it is for individuals to take steps to prevent metabolic syndrome and to improve their cardiorespiratory fitness. And the best way to do that, the authors of the commentary stress, is to keep excess pounds off, get plenty of physical activity and eat a healthy diet, especially by reducing calories from simple sugars and carbohydrates.
That advice is for everyone, no matter what your weight.