When it comes to living a longer life, staying active may matter far more than what the scale says.

Per the largest study yet on fitness, body weight, and longevity published recently in the British Journal of Sports Medicine, researchers found that people who are aerobically fit (i.e., how well your heart, lungs, and muscles work together to supply oxygen during exercise) significantly reduce their risk of premature death, even if they are obese.

In fact, being fit cut the risk of premature death by half for people with obesity, compared to those of normal weight who were unfit.

"This tells us that it’s much more important, all things considered, to focus on the fitness aspect” of health and longevity, “rather than the fatness aspect,” Siddhartha Angadi, senior author of the study and an exercise physiologist at the University of Virginia, told The Washington Post.

The review pooled data from 20 prior studies involving nearly 400,000 midlife and older adults from multiple countries, about 30% of whom were women.

Participants were grouped based on their aerobic fitness, which was objectively measured through cardiovascular stress tests, and their body mass index (BMI).

They also pulled data about who’d died during follow-up periods of up to about two decades.

The findings were clear:

People who were fit and overweight or obese had similar risks of death as fit people at a normal weight

But people who were unfit — no matter their weight — had 2 to 3 times higher risks of dying early from any cause or heart disease

“From a statistical standpoint, fitness largely eliminated the risk” of early death from obesity-related conditions, Angadi said in a media report.

Encouragingly, the study suggests that achieving better fitness doesn’t require extreme effort. Even moving from the bottom 20% of fitness for someone’s age to just slightly above that threshold can offer substantial health benefits, Angadi explained.

For most of us, that could mean "brisk walks," he added. Moderate exercise, such as walking at a pace where you can talk but not sing, is enough to boost fitness.

Barry Braun, executive director of the Human Performance Clinical Research Laboratory at Colorado State University, who wasn't involved in the study, called the findings "important" because they confirm the protective role of fitness across genders and body sizes.