A recent report found that 121,000 people in Cornwall and the Isles of Scilly - 25.9% of the population - are classed as "inactive", which means they get less than 30 minutes of exercise a week.
Cornwall Council is currently leading a physical activity strategy which was launched in 2016 in a bid to encourage more people to get fit.
The council was aiming to get 50,000 more people active by 2020 but has admitted that it is "unlikely" to meet that target.
Details of inactivity among people in Cornwall and the Isles of Scilly were revealed in a report which went before the council's health and wellbeing board this week.
It stated that the focus of the strategy had been on children and early years, although there had been some work done with adults.
The report states that the recent survey found that just 14.1% of young people in Cornwall and the Isles of Scilly are getting the recommended daily levels of activity. That compares with 17.5% nationally.
It adds: "It is estimated that inactivity contributes to 800 deaths in Cornwall and Isles of Scilly each year. Not only can increasing physical activity levels in the population decrease morbidity but reduce hospital admissions and prescriptions."
During 2019 the physical activity strategy is set to focus on active environments - promoting the use of Cornwall's natural landscape and environment for exercise.
The report states that while Cornwall has a natural environment which is well suited for physical activity the county has a lower use of outdoor space.
It adds: "Partnership work and consistent messaging will promote Cornwall’s wonderful environment for outdoor activity to local residents who often perceive it to be for the tourists."
Cornwall Council is also drawing up new planning guidance which will look to have a focus on "activity, accessibility and community" in new developments.