The fitness industry is worth millions today and gyms are overflowing with ambitious young professionals. So it may come as a surprise to find the origins of the keep-fit craze were born out of poverty.
Diet more, do yoga, run off some pounds, have a facelift.
The messages urging us to get in shape are constant and pervasive. Never has there been such a pressure to look good.
Or so we think. Today's fears about obesity and the effects of our sedentary lives are, in fact, an echo of 1930s Britain when austerity, rather than over-indulgence, sparked a similar neurosis about public health, and led to the first ever fitness craze.
During World War I the authorities were shocked by the feebleness of military recruits, with 40% in the lowest medical category. But by 1939, the country had been transformed from a nation of anaemic weaklings to one with an obsession for public health.
This change was due to several factors, but none greater than Mollie Bagot Stack, founder of the Women's League of Health and Beauty in 1930, and foremother of today's fitness obsession.
Mrs Bagot Stack promoted her philosophy of exercise structured and graded to the needs of all ages and abilities, and taught by trained physicians, through huge public displays. The first, in Hyde Park, drew 160,000 members whose activities were documented on the newsreels of the day, and form part of a new BBC television series.
Mollie Bagot Stack - foremother of today's fitness craze
Mrs Bagot Stack had long been interested in exercise when, in the 20s, she moved to Manchester, where she saw that women working in mills could benefit from systematic exercise to invigorate them after a hard day.
A trip to the Himalayas had also opened her eyes to the better posture of Indian women and yoga techniques which she incorporated into her system.
As her daughter Prunella recalls today, it was "very, very necessary. There was nothing like it at the time because there were private lessons if you could afford them, but there was nothing that was popular and cheap and that everybody could join".
"That was amazingly popular and cheap because it cost half a crown to join, 3/6 for an entrance badge and then sixpence a class. Well it just took off like a bomb. It was incredible."
Prunella Stack, now 90, inherited her mother's work aged 20
The craze gathered pace as Europe began to re-arm and the threat of war loomed large again. Finally, in 1937, the government harnessed the momentum built by the Women's League and began a national health campaign. Prunella, who inherited the running of the league from her mother, was appointed to the campaign to stress physical exercise as "a matter of national importance".
This 20-year leap by the British from weaklings to fitness fanatics owed a debt to other factors. The burgeoning Boy Scout and Girl Guide movement, which placed an emphasis on outdoor life, saw its membership shoot to a million in the 1920s. Healthy eating was also being pushed. Bermondsey Borough Council in London released a series of films to encourage its poverty-stricken residents to, among other things, brush their teeth
The cinema was a key propaganda tool, and women made up three-quarters of the audience in the 1920s. Pathe began Eve's Film Review, which ran for about 10 minutes and focused on things it thought women would enjoy like fashion films, beauty or women's sports.
Pathe cataloguer Jenny Hammerton says in the aftermath of World War I, women were partly motivated to get fit out of self-interest.
"During the 20s there weren't many men to go round because of the loss of male life during [the war]," says Ms Hammerton. "There was what was known as the two million superfluous women, I think a lot of the films focus on the body beautiful. They were really encouraging women to look their best in order to snare a man."
The Fitness League's legacy
In the 50s and 60s the attitude seemed to change. Len Almond, of the British Heart Foundation National Centre for Physical Activity & Health, says there was shift in schools to games such as netball and hockey, rather than dance and movement - something that put many women off exercising.
But with the aerobics craze of the 80s, the pendulum swung back again. Today the influence of the Women's League - now called the Fitness League - can be seen in every gym workout room around the country.
Newly uncovered film footage of the Women's League of Health and Beauty will feature in Nation on Film, to be broadcast on BBC Two on Tuesday 15 February at 1930 GMT.