Is being a few pounds overweight actually better for you? According to a number of studies in the past few years, the answer is yes.
One study reported ideal weight carries a higher risk for early death than being overweight, suggesting being overweight may actually be protective. Some have taken this and similar studies to mean gaining weight may actually be good for you.
In an almost emotional reaction, subsequent studies were produced that showed the exact opposite. One such study of over 10 million participants found that being ideal weight had the lowest risk for early death, while being overweight was associated with a 7% to 20% increased risk.
So which is it?
While studies fueling both sides of the argument have their flaws, the fact that there is such inconsistency suggests to me the issue is far more nuanced than we think.
First, let’s define what we mean by being overweight. For health and medicine we use the body mass index (BMI), which is a ratio between height and weight (BMI equals weight [in kg] divided by height [in m] squared). A BMI between 25 and 30 kg/m2 is considered overweight while a BMI equal to or greater than 30 kg/m2 is obese. A BMI between 18.5 and 25 kg/m2 is considered normal weight, although now that more than half of adults are overweight or obese, there is nothing ‘normal’ about the normal weight category, so I use the term ‘ideal weight’. And then, there is the extreme of being underweight which is a BMI less than 18.5.
Now before going further, let’s get out of the way where most scientists and health experts do agree; being underweight or obese is not good for one’s health. Both are associated with increased risk for disease and early death.
The studies that have found overweight to be potentially beneficial are generally of the same kind; observational and longitudinal, in which scientists take a measure (in this case BMI) at one time point and then follow people until the end of the study. For these studies, the outcome of interest is death. Once the study has finished, the BMI of the different study participants is compared to the death rates. In the above mentioned study, there was a lower proportion of overweight people in the study dying than normal weight.
The caveat with these studies is they can only show association and not cause. Which came first, the chicken or the egg? In this case the following contrasting questions unanswered:
- Do sick people become thinner and then die?
- Does being thin lead to a disease that causes death?
Now observational studies are used a lot in research (I do many of them myself), and especially in fields like nutrition where it is hard to do intervention studies. But we generally find that when numerous observational studies conducted by different researchers around the world agree, we feel it is safe to assume that the findings are most likely true.
The problem here is that we don’t have consistent agreement and it could be due to slightly different study methods and/or not being able to control for every factor, which may be important.
For example, we know that overweight people tend to have higher levels of cholesterol, blood pressure and blood sugar than people in the ideal range. And, it is more common for overweight people with these risk factors to be taking medications to treat them. Many of these medications are so effective at reducing early death, that the overweight person taking a cholesterol-lowering medication may be at lower risk than an ideal weight person not taking a medication.
One study conducted over 30 years, found the BMI associated with the lowest risk for early death has increased over time. The authors speculated this may be to the greater availability and use of medications to lower risk factors in people who are overweight.
For people who are overweight and have risk factors, diabetes, heart disease and other conditions, prescribing weight loss (or should I say, the doctor tells the patient to lose weight) is one of the most common treatments. Therefore, a subset of people in the ideal weight range may actually have been overweight and reduced their weight because of their disease. When people who were ever overweight (even if not overweight at the time) were compared to people who were always ideal weight, those in the ideal weight had a lower risk for early death.
So by now I’ve probably made the issue more confusing than it was before and failed to answer my original question. While being overweight is associated with greater risk factors, we don’t have great studies to tell us about long term impact on early death. The one thing that no study has shown, is that going from ideal weight to overweight makes someone healthier. Indeed, none of the authors of any of the studies on either side are suggesting that people who are in the ideal weight range put on a few pounds.
But does it mean that we should still ask/demand people who are overweight (not obese) to lose weight in an effort to improve their health? There may still be some value to that in terms of reducing risk factors, as well as reducing risk for orthopedic conditions like osteoarthritis of the knee, and even psychological issues and stigma that overweight people may face.
That being said, losing weight is terribly hard and the common wisdom is to support people who are overweight live a healthy lifestyle in terms of mental well-being, nutrition and physical activity, and not have them focus on their weight.