Excess body weight increases risk for cardiovascular disease (CVD), as well as type 2 diabetes, certain cancers, and many other illnesses. However, not everyone who is overweight or obese develops these illnesses; and simply having a “normal” body weight or body mass index (BMI)-a measure of body weight relative to height-is no guarantee of low risk. “The relationship between BMI and risk for CVD and death is complex,” says Edward Saltzman, MD, academic dean for education at Tufts’ Friedman School of Nutrition Science and Policy. “Elevated BMI does increase CVD risk, but risk is also impacted by things like body-fat percentage, waist circumference, age, duration of obesity, race, ethnicity, gender, and other genetic factors,” as well as lifestyle elements such as smoking and level of physical activity.
Metabolic Health: Risk for CVD is closely tied to metabolic health. High blood pressure, low HDL cholesterol levels, elevated triglyceride levels, and high blood sugar are all indicators of metabolic abnormalities associated with increased risk of heart attack and stroke. The more of these metabolic risk factors a person has, the higher their CVD risk, no matter what they weigh. It is estimated that 65 to 80 percent of people with a BMI in the “obese” range (>30) have at least two common metabolic abnormalities, and a study published in European Heart Journal in March of 2018 found that only six percent of individuals with obesity had no metabolic problems at all. “While it is possible to be metabolically healthy at an elevated BMI,” says Saltzman, “there is still a strong association between BMI and metabolic health.”
One reason for the correlation between higher body weight and metabolic problems is that excess body fat is associated with chronic low-grade inflammation. This inflammation increases risk of insulin resistance, diabetes, and developing CVD. In 2017, the landmark CANTOS trial gave over 10,000 heart attack survivors with laboratory evidence of chronic inflammation a drug designed to lower that inflammation. The drug lowered the risk of future cardiovascular events, demonstrating that inflammation is an important, and modifiable, risk factor for CVD.
BMI and Cardiovascular Disease: The European study cited above, which included nearly 300,000 white adults, found that risk of high blood pressure, heart attack, and stroke each increase as BMI and waist size increase. Participants with a BMI in the normal range had the lowest risk of CVD. But having a normal body weight is no guarantee of good metabolic health. A July 2018 study of over 23,000 Chinese adults published in the journal Nutrition, Metabolism & Cardiovascular Disease found that normal weight individuals who have a high percentage of body fat are at increased risk for several cardiometabolic conditions including diabetes and high blood pressure.
What You Can Do: Fortunately, metabolic CVD risk factors (like blood pressure, HDL cholesterol levels, triglyceride levels, blood sugar, and inflammation) can be modified by diet and lifestyle changes and appropriate medical care. Although people with an elevated BMI are more likely to have metabolic risk factors and cardiovascular disease, people with a healthier diet pattern, greater activity, and higher fitness (ability to exercise vigorously) have much lower metabolic risk, regardless of their weight or BMI; and people with poor diets, sedentary lifestyle, and low fitness have much higher metabolic risk, even if lean. A 2017 study in Preventing Chronic Disease found that overweight or obese individuals who had healthy habits (being a non-smoker, only drinking alcohol in moderation, getting 30 minutes of exercise daily, and eating five or more servings of fruits and vegetables daily) had disease risk similar to their normal-weight peers. So help protect your heart by making healthy lifestyle choices, no matter what the scale says.