Being obese or overweight may have its advantages, suggests one new study.
Despite this, some researchers maintain that excessive body fat can have a protective cardiovascular effect.
In fact, the authors of a 2002 reference paper coined the phrase "obesity paradox" to describe the observation that people with a higher body mass index (BMI) are less likely to die from cardiovascular conditions than people with a normal weight.
Since then, the theory has been the subject of much controversy. However, new evidence appears to support it.
Dr. Zuolu Liu — from the University of California, Los Angeles — and her colleagues wanted to see how the obesity paradox applies to stroke. Previous research into the same issue, explain the researchers, yielded mixed results.
They will present their new findings at the American Academy of Neurology's 71st Annual Meeting, which this year takes place in Philadelphia, PA.
Up to 62 percent lower chance of death
Dr. Liu explains the motivation for their study, saying, "It was first noticed that carrying extra weight may play a role in survival for people who had suffered from kidney and heart disease, so we felt the need to investigate whether it also was tied to improved stroke survival."
To do so, the researchers examined 1,033 people who had experienced an ischemic stroke — that is, a condition wherein the arteries that pump blood to the brain are blocked.
The participants were 71 years old, on average, and their average BMI was 27.5. People whose BMI is between 25 and 29.9 are considered overweight, while a BMI of over 29.9 indicates obesity.
Dr. Liu and team grouped the participants into five categories — "underweight, normal, overweight, obese, and severely obese" — according to their BMI. The researchers monitored the participants' survival and recovery for 3 months after their stroke.
Overall, people with severe obesity had a 62 percent lower chance of dying from a stroke than people with a normal BMI, people with obesity had a 46 percent lower chance of death, and those who were overweight had a 15 percent lower chance of dying.
However, those who were underweight had a 67 percent higher chance of dying following a stroke than people with a normal BMI. Dr. Liu and colleagues conclude:
"Outcome from acute ischemic stroke is characterized by an obesity paradox: elevated BMI is associated with reduced 3-month mortality over all, and reduced disability over most weight ranges."
The study was observational, so it cannot account for causality. However, a "possible explanation is that people who are overweight or obese may have a nutritional reserve that may help them survive during prolonged illness," says Dr. Liu.
The researchers also caution that their results may not be applicable to the general population, as the study sample was limited to people from southern California.
"More research is needed to investigate the relationship between [BMI] and stroke," says Dr. Liu.