She grew up in Camborne, Cornwall, which she described growing up as "pretty working class and basic in a small town".
[7][3][5][8][9] As a child Joanna had chronic asthma and was unable to do any sort of strenuous physical activities at a young age, but had always wanted a bigger build for her body.
When she was 14 years old, she saw for the first time pictures of female bodybuilders in a magazine that belonged to a college student who was staying with her family.
[10][11] Three months later, at 107 lb (8 st; 49 kg), Joanna worked up the courage to go to a local gym and told the owner she wanted to build muscle.
The gym owner's wife dismissed her goal of building muscle by saying it should be left to the men, however, her husband began to train her.
At the 1996 English Federation of Bodybuilders (EFBB) British Championships, her sister Nicola, who had only qualified 2 weeks prior, got second place in the lightweight category.
[10][1][8][5] Joanna spent the next 2 years, including completing 2 years of nursing school and eventually stopped going to school in order concentrate on her bodybuilding career, in Manchester making a living as a care worker and honing her physique, packing on more size, improving her shape and increasing her muscle maturity.
At the 2001 Jana Tana Classic, at the age of 24 years old, she won her pro debut by getting 1st in the lightweight title, which qualified her for the Ms. Olympia.
After winning the Jana Tana Classic, she began doing photo and video shoots and started receiving fan mail.
In June 2004, she began training with professional bodybuilder Charles Glass and Chad Nicholls for the 2004 GNC Show of Strength.
She was injured in a car crash and started taking strong pain relief medication that was not available in the United Kingdom.
The documentary covered her childhood, modeling for her website and her training and competing at the 2004 GNC Show of Strength and 2004 Ms. Olympia.
After a 2 year break from competing, she attended the 2007 Atlantic City Pro, where she got 4th place in the lightweight category.
In 2011, she moved her home from Fort Lauderdale to Sarasota and was focusing on improving her physique in order to compete in the near future.
She is sometimes incorrectly cited by sources as being the youngest female bodybuilder to ever win an IFBB pro card.
Thus Joanna retained her record as youngest British female bodybuilder to ever to win her IFBB pro card.
[22][9] In April 2020 Thomas was found dead in her flat in Camborne, Cornwall by a police officer conducting a wellness check.
In a short article in Robert Kennedy's MuscleMag International Thomas talked of finding a small level of fame after appearing in the documentary.