Sitting down is no worse for you than standing up as long as you take regular exercise, according to a study.
This casts doubt on the health benefits of sit-stand work stations that are becoming increasingly popular.
It also challenges NHS advice that states: "Remaining seated for too long is bad for your health, regardless of how much exercise you do."
Exeter University and University College London researchers followed more than 5,000 people over a 16-year period and their findings were published in the International Journal of Epidemiology.
The research found there was no influence on mortality risk for participants from sitting at work, during leisure time or watching television.
The NHS said on its website in advice published last year that there was "increasing evidence" linking excessive sitting with being obese, type 2 diabetes, some types of cancer, and premature death.
It recommends an active break from sitting every 30 minutes, citing expert Professor Stuart Biddle saying: "Sitting needs breaking up."
"Do some tasks standing, like having coffee and chats, or even writing a letter –- Ernest Hemingway wrote his novels standing," he added.