Experts also said that people with a healthy weight should also workout in order to avoid health problems later in life.
According to a survey of 2,100 people, brisk walking was found to be the favourite way of exercising and after that dancing, swimming or going to the gym was considered the fun way to exercise.
A third of 18 to 24-year-olds said that they would exercise if they saw an unflattering photo of themselves or were told they looked fat - meaning that good body shape is what it would take for young adults to exercise. And, only 4 percent said they found exercise fun.
Another motivation to exercise included fancying someone at the gym. Only 13 percent of men and 7 percent of women reported that keeping a healthy heart was their main inspiration. The most prominent way of avoiding exercise was excuses such as not having enough time and one in seven people blamed bad weather for not working out.
A campaign is now being launched by The British Heart Foundation to encourage people to up their heart rate for 30 minutes a day, It also said that someone dies every 15 minutes as a direct result of physical inactivity.
Dr Mike Knapton, director of prevention and care at The British Heart Foundation, said it was a "deadly serious" problem. "With our busy lifestyles and labour-saving devices we've stopped getting the exercise our bodies desperately need," BBC quoted Knapton, as saying.
"For many people, exercise has become an ugly word, something to avoid at all costs - but you'd be amazed how easy it is to up the tempo of your heartbeat. "Just 30 minutes a day will do you and your heart the world of good," Knapton added.
The government advises a minimum of 30 minutes of moderate-intensity exercise five times a week. Dr David Haslam, clinical director of the National Obesity Forum, said that it was depressing to know that even those who had a heart attack did not change their lifestyles.
"Children instinctively exercise when left to their own devices, but they don't because they're stopped from doing that by the school curriculum and parents scared of child abductors and murderers lurking on every corner. "So, if it doesn't become a habit, you're not going to work hard to go against the tide and introduce it as an adult."
He added that exercise should be incorporated into everyday life because if not, it also increases the risk of cancer and cardiovascular disease. "Physical activity and obesity are too different risk factors, so even if you're lean, if you're inactive you increase your risk of cancer and cardiovascular disease," Haslam said.