A YouGov poll carried out on behalf of the BHF found that almost one-third of people aged 50 to 64 believe they do not have the time to exercise.
Yet if people were given a spare half an hour of free time they would choose inactive pursuits such as reading or watching the television, the survey revealed.
The results of the poll come as the BHF launches its '30 A Day' campaign to encourage people to exercise. Individuals over 50 are particularly targeted as the charity argues that with a growing ageing population people need to ensure their health and independence in their later life.
Exercise such as swimming and gardening can help people to fight against heart disease and other illnesses.
Dr Mike Knapton, director of prevention and care at the BHF, described the number of people dying from inactivity as an "alarming thought".
"These deaths are avoidable and the solution is simple and achievable," he said.
"We can all make excuses, but at the end of the day it's up to individuals to make the change, to get up and to get active."
From today the BHF is sending out 2.5 million leaflets to households to outline the ways they can get fit.
Lending her support to the campaign, broadcaster Angela Rippon said: "Finding your own way to enjoy being physically active is key - be it dancing, swimming, long country walks - or whatever suits you. It's an investment in your future health, which you will never ever regret."
As well as launching its own campaign, the BHF will present MPs with a 'blueprint' on Wednesday outlining steps it wants the government to take to encourage activity in people, especially in the over-50s.
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