Brits are at their fittest when they are in their thirties, a study has revealed.
Adults in their mid to late thirties are more likely to exercise regularly, be members of gyms and sport clubs and eat a healthier diet than their counterparts in their twenties.
A quarter of those polled said that having children had a big impact on their fitness levels and more than one in ten started leading a more active lifestyle once they knew they were having children.
Thirty something's also said that they were at their least fit at the age of 29 due to eating too much junk food and consuming too much alcohol.
Half of adults aged 30-39 now rate themselves as fit and spend more time exercising than people in their twenties.
A spokesman for the Gym Group who conducted the poll said: ''It certainly seems that people have a wake-up call when it comes to healthy living when approaching middle age.
''When you are in your twenties you can get away with not doing as much exercise, late nights and too much junk food.
''But as you creep in to your thirties, the pounds can pile on and it's not as easy to burn the candle at both ends.
''Starting a family and having young children definitely keeps you on your toes and not only is it important to keep fit to physically keep up with them it's about the long-term effects.
''Knowing that there are people relying on you is a huge incentive to live a healthy lifestyle.''
The study found that adults in their 30's, 40's and 50's all agreed that they burnt the candle at both ends in their 20's and a third of fifty something's still rate themselves as healthy.
By comparison 15 per cent of people aged 18-29 declared themselves as unhealthy.
More than half of all age groups said they felt 'ok' with their current weight although they would like to lose a few pounds.
Those in their twenties were the least likely to eat enough fruit and vegetables with more than half claiming to not eating enough healthy food.
They were also the group that eats more take-aways.
A quarter of under 29's have two take-aways a week, compared to 25 per cent of 30 plus adults never eating these types of meals.
Younger adults were also the biggest snackers according to the poll.
It emerged that adults in their forties were the biggest smokers followed by those in their fifties.
Forty something's were also revealed to be the heaviest drinkers with the average 40-49 year old consuming nine units of alcohol a week.
Those in the 30-39 age group exercised more frequently than the other age groups - the average person works out nearly three times a week.
Although one in five thirty something's does physical exercise four or five times in a typical week.
Those aged 18-29 were the group most likely to shun any form of exercise what so ever.
A spokesman for the Gym Group added: ''It's a perfect time of year to address your lifestyle and to question your fitness levels and diet.
''This poll highlights that as people get older they do become more aware of leading a healthy and balanced lifestyle.
''Of course everyone enjoys treats now and then but as you get older it becomes harder to shift extra pounds and you realise you have to work at maintaining the physique you have been used to.''
