If you want to live to a ripe old age, the healthiest weight to be may be…modestly overweight.


Isn’t being overweight by definition unhealthy?

Indeed it is. But a new study suggests that the healthiest weight has shifted upward since the 1970s. So we might need to reclassify “slightly overweight” as “healthy weight.”

Skeptical? So were we. That’s why we reached out to the lead study author, Børge G. Nordestgaard, MD, DMSc, a professor at the University of Copenhagen.


In the new study, Dr. Nordestgaard and colleagues analyzed three sets of Danish data—from 1976-1978, 1991-1994 and 2003-2013—to find the link between people’s body mass index (BMI) and death from any cause during three decades. “I think the data would also apply to people living in the US, as the two countries have a similar standard of living and health-care systems,” he said.

BMI is an imperfect measure, but for most people it’s a reasonable gauge of body fatness. Normal healthy weight is defined by the National Institutes of Health (NIH) and the World Health Organization (WHO) as having a BMI of 18.5 up to 24.9—which translates to up to 150 pounds if you’re 5’5″ or 174 pounds if you’re 5’10”. The BMI for “overweight” is 25 to 29.9, and for “obese,” it’s over 30.

Here’s what the study found…

  • In the 1970s, the BMI associated with the lowest risk of dying was 23.7.
  • In the 1990s, it was 24.6.
  • By the 2000s, it had reached 27—i.e., “overweight.”

For the record, the difference between a BMI of 24 and 27 for an average height woman of 5’5″ is 18 pounds—from 144 to 162 pounds. For a 5’10” man, it’s 21 pounds—from 167 to 188.


Why the change? The data doesn’t tell us, but Dr. Nordestgaard points to two trends. First, there have been great improvements in the medical management of risk factors for cardiovascular disease and diabetes, as well as the treatment of these conditions, which are keeping people from getting these diseases and helping them live longer if they do get them. The second is a trend toward people getting more exercise, which helps prevent these diseases.

Still, that’s not enough to explain the shift. It may explain why slightly heavier people are healthier than they used to be…but it doesn’t explain why they would live longer than people who weigh less.

The answer may come from a little appreciated but consistent research fact. Having some extra weight can be protective—when you’re older than 65 or 70. Why? It helps you survive infections and other illnesses, including cancer. Per Dr. Nordestgaard, “Being overweight may have beneficial effects on survival.” (Being overweight over age 70, it turns out, may also protect against dementia.)


More research will definitely be required before the WHO, or the NIH in the US, changes the definition of overweight. In the meantime, Dr. Nordestgaard emphasizes that preventing weight from creeping up as you age is still a good idea. As you gain weight, you’re at increased risk for knee and hip problems, and your risk for cardiovascular disease and diabetes goes up, too. It’s easy for weight to creep up, so keeping it under control is still the best policy, he said, “Don’t push your weight up too high.”

On the other hand, if your weight is a little above normal, don’t fret. Said Dr. Nordestgaard, “Our data suggest that people with a BMI of 25 to 27 should not be too worried about their weight.” Instead, he said, focus on exercise and healthy eating. (To easily determine your BMI, click on this NIH calculator.)