Science, like all things, is imperfect. Through experimentation and research, we make our best guesses. Sometimes we think we understand, only to find out later that the reality may be quite different from what we thought. Obesity appears to be one of those things.
For decades, we’ve believed that obesity is a plague on Americans and our health care system – and in some ways, this is so. For some, obesity can increase the risk for diabetes, high blood pressure, heart disease, stroke and other health problems. However, growing attention is being given to the “obesity paradox” so named because, as strange as it sounds, it is possible to be overweight, even mildly obese by clinical standards, and have a lower risk of death than people who are leaner.
What We Think We Know
Since the 1800s, the body mass index has been one of the primary tools used to determine whether someone is a healthy weight. People with a BMI less than 18.5 are considered underweight, 18.5 to 24.9 is the normal range, and 25 to 29.9 is considered overweight. People with a BMI over 30 are considered obese, a category which has now been further sub-divided into three grades.
What We’re Learning
As one-size-fits-all categorizations, BMI may be an inaccurate indicator of health in some cases. Its downfall is that it ignores age, gender, disability, disease history and body composition, not to mention activity level and where the extra pounds came from (e.g., nutrient-dense whole foods or processed foods). Additionally, it doesn’t account for other factors that can influence health, including blood pressure, lipid levels, waist circumference and blood sugar, among others.
While BMI can be a useful guideline, it is only one small part of the overall health story. This was one important lesson gleaned from a recent review of nearly 100 past studies assessing almost three million people, in which researchers found that Grade 1 obesity (a BMI of 30 to 34.9) did not increase the risk of death. In fact, people who were overweight or slightly obese were at about 6 percent lower risk of dying than people of normal weight.
But don’t run for the refrigerator just yet. The researchers found that Grade 2 or 3 obesity (a BMI over 35) was associated with a nearly 30 percent higher risk of death. However, even in these levels of obesity, what’s more important is lifestyle, not the number on the scale.
So is it possible that being moderately overweight could actually have a protective effect on health? Studies have been conducted on a variety of populations, including those with heart failure, chronic kidney or liver disease, hypertension, stroke, diabetes and other conditions, all of which show that overweight patients live longer than their leaner peers.
How could this be? The answers remain uncertain, but there are a number of possible explanations:
- Body fat might create a protective barrier from injury or secrete hormones or other chemicals that protect against disease.
- Having energy reserves could provide nutritional support in times of illness.
- Obese individuals may get more aggressive treatment earlier on since medical professionals recognize obesity as a risk factor for health problems.
- Thinner individuals who develop chronic diseases may have genetic variants that make them more vulnerable to illness.
Weight loss isn’t necessarily the best prescription for people who are overweight or moderately obese, especially if they have a chronic disease.
An additional possibility is that science is missing something. There are a number of factors that could be confounding study findings, including age, socioeconomic factors, fat distribution (the apples vs. pears comparison), medication use, smoking status and the presence of comorbidities.
What the Obesity Paradox Means to You
Despite the limitations of existing research and the many unanswered questions, the obesity paradox merits further consideration. For individuals trying to maximize their health and longevity, the recommendation isn’t as simple as “Don’t eat too much” or “Lose weight.” If you eat a diet rich in fruits, vegetables, lean protein and whole grains and are physically active, being slightly overweight may not be a problem.
As health care professionals, we must look at the whole picture when advising our patients, not simply the number on the scale. Most studies would support the recommendation that severely obese individuals would benefit from changes in lifestyle that could not only improve their health but also their quality of life. But for those who are moderately overweight, particularly if they have a chronic disease or are of advanced age, weight loss may not be the first line of treatment.