A new study has found if there's one thing you should not not do, it's exercise.
Researchers in the US have found a lack of exercise increases your chances of an early death even more than smoking, diabetes and heart disease.
"Being unfit on a treadmill or in an exercise stress test has a worse prognosis, as far as death, than being hypertensive, being diabetic or being a current smoker," lead researcher cardiologist Wael Jaber told CNN.
"We've never seen something as pronounced as this and as objective as this."
The study looked at data from more than 122,000 patients who'd jumped on a treadmill in previous studies - 23 years' worth of data.
Dr Jaber said although it's well-known a sedentary lifestyle is bad for you, the magnitude of the benefits the study uncovered were surprising. Sedentary people have twice the risk of death than people with kidney dialysis, for example.
And if you think some people push their fitness to far, think again.
"There actually is no ceiling for the benefit of exercise' - including in the case of 'ultra' exercisers, who are sometimes said to be at higher risk of death due to the extremes they push their bodies," he said.
The benefits were greatest for women, and age didn't matter.
"You should demand a prescription from your doctor for exercise," Dr Jaber told CNN.
The study was published in journal JAMA Network Open.
Newshub.