For a woman who preferred to remain behind the scenes, Audrey Eyton, who has died aged 83, did more to revolutionise British eating habits than any television chef in the past 40 years. A powerhouse in the nascent UK diet industry, she co-founded Slimming magazine, wrote The F-Plan Diet and used her wealth to challenge our disregard for farm animals’ welfare and appetite for meat.

Slimming magazine began as a kitchen-table operation with her then husband, Tom Eyton, in Caterham, Surrey. It was 1969 and the two faced considerable cynicism that readers would want their local newsagent to know they were worried about their weight. It was the first display of the former beauty editor’s pin-sharp ability to recognise a change in public taste and the opening of a lucrative new market: within three issues it was selling 140,000 copies.

In part Eyton’s success at Slimming was due to her understanding that whatever diet fad was being discussed, slimmers craved the scientific evidence that the self-denial would work. The couple packed the editorial board with experts, including a nutritionist, medical adviser and psychiatrist. They also extended the brand across a wide range of enterprises, from a health club – Ragdale Hall in Leicestershire – to local slimming clubs. When they sold the business in 1980, four years after their divorce, it was reputed to be worth £4m.

Two things inspired Eyton to turn her attention to high-fibre diets. One was a horror of the low-carb diets favoured since the 1960s. “There is something that stays in my mind called the ‘Hawaiian Circle’,” she once told an interviewer. “It was a thick circle of pineapple with about half a pound of cheese on top. You were taught this did you good.”

Facebook Twitter Pinterest The F2 Diet by Audrey Eyton, 2006. The original book came out in 1982. Photograph: Martin Lee/Alamy

The second was her son Matthew’s health problems at boarding school. Eyton was convinced they were caused by a bad diet, though she failed to convince the matron that he needed to eat better food.

The result was her 1982 blockbuster The F-Plan Diet, which built upon research by the medical scientist Denis Burkitt that suggested that fibre, not reduced carbohydrates, led to slimming success. A global bestseller, the book had an immediate impact on supermarket shelves, as consumers hunted out pulses, wholemeal bread, high fibre cereals and vegetables. The book, which also led to a slot for Eyton on the BBC Breakfast Time television show, pioneered a market for evidence-based diets.

Born in Blackburn, Lancashire, Audrey was the daughter of Evelyn and Melville Gray. Her father was a travelling salesman and both parents were animal lovers. As a child she developed a passion for horses that took her away from her “pebble-dashed home” to the stables, which she hung around like “a groupie”, she would later tell friends.

Her father died when she was 12. Four years later Audrey left Blackburn girls’ high school to work as a reporter for the Accrington Observer, where her beat included obituaries. A sign of her personal charm was that bereaved families would frequently invite her into their homes .

By 19 she had moved to London to work for the magazine Woman, eventually rising to the role of beauty editor, though the subject did not interest her. What did fascinate her were diets, which was why, when Tom tired of working night shifts as a chief subeditor at the Telegraph, they set up Slimming. They also had two sons; the first, Richard, who was born with a disability, died after only 10 days.

At 15 her remaining child, Matthew, was diagnosed with an obsessive compulsive disorder. Described as “fiercely intelligent”, he won a postgraduate place at Cambridge University, though his passion was for animal welfare. He had mental health problems and the psychiatric treatments he received were “unendurable”, according to Eyton.

In 1991, aged 24, he took his own life, leaving a note entreating his mother to look after the animals. She fulfilled his request by setting up the Matthew Eyton Animal Welfare Trust, which, over the past 25 years, has raised £250,000 for various animal charities. She also made a plea for the end of factory farming in The Kind Food Guide (1991), which revealed the farming conditions of animals produced for meat.

“I decided I couldn’t spend my time weeping and the best memorial is the way you live your life. I wouldn’t want to go on living if I wasn’t contributing to this cause,” Eyton told Juliet Gellatley, who set up the vegan charity Viva with £25,000 from the trust.

Through the foundation, Eyton helped to achieve reforms that have made a material difference to the lives of farmed animals, such as the introduction of CCTV cameras into slaughterhouses. However, her involvement was not only financial.

She took part in demonstrations, such as against the export of live animals from Dover, and raised several rescue pigs at her home in Canterbury, Kent. Her considerable marketing nous proved invaluable, especially to vegan causes, helping the movement become mainstream through initiatives such as Veganuary. She was also a trustee of Compassion in World Farming.

In 2006 she published The F2 Diet, a follow-up to her 1980s bestseller, which claimed to harness “twenty-first century cutting-edge science”.

However her driving passion, which she continued to work at even after her diagnosis with Parkinson’s disease five years ago, remained animal welfare.

Eyton is survived by her sister, Valerie, and by two nieces.

• Audrey Eyton, journalist, writer and animal welfare campaigner, born 11 January 1936; died 30 June 2019