Want to add years to your life? Following a few healthy habits could do just that, according to a new study.

The observational study presented Monday at the American Society for Nutrition's annual meeting in Boston examined data on more than 700,000 U.S. veterans and how their life expectancy shifted based on the number of healthy habits followed. 

The findings? Adopting eight healthy lifestyle habits by middle age can result in a substantially longer life than those with few or none of the habits. Those habits include: 

• Being physically active
• Being free from opioid addiction
• Not smoking
• Managing stress
• Having a good diet
• Not regularly binge drinking
• Having good sleep hygiene
• Having positive social relationships

While the habits aren't groundbreaking — you've likely heard health experts advise similar wellness practices — the amount of lifespan expected to be gained from them is impressive.

According to the results, men with all eight habits at age 40 are expected to live 24 years longer on average compared with those with none. Women with all eight habits are predicted to live an 21 additional years.

"We were really surprised by just how much could be gained with the adoption of one, two, three, or all eight lifestyle factors," Xuan-Mai T. Nguyen, health science specialist at the Department of Veterans Affairs and rising fourth-year medical student at Carle Illinois College of Medicine, said in a news release. "Our research findings suggest that adopting a healthy lifestyle is important for both public health and personal wellness."

Low physical activity, opioid use and smoking had the biggest impact on lifespan, according to the release, with a 30-45% higher risk of death during the study period.

"Stress, binge drinking, poor diet, and poor sleep hygiene were each associated with around a 20% increase in the risk of death, and a lack of positive social relationships was associated with a 5% increased risk of death," the release added.

In terms of when to take action, "the earlier the better," Nguyen noted, "but even if you only make a small change in your 40s, 50s, or 60s, it still is beneficial."

That's because adopting healthier habits at an older age can still help you live longer, researchers found, even if the life expectancy gain grew slightly smaller with age.

"It is never too late to adopt a healthy lifestyle," Nguyen said.

This study has not yet been published by a peer-reviewed publication, but was evaluated and selected by a committee of experts to be presented at the meeting.