Samantha Clowe, from Leeds, weighed more than 17 stones when she began the LighterLife 500-calorie-a-day plan. Miss Clowe died on June 28 last year after collapsing at her home.

An inquest at Wakefield Coroner’s Court has heard a post-mortem examination failed to establish a cause of death but it was likely Ms Clowe died from cardiac arrhythmia.

A pathologist told the inquest Ms Clowe’s death could have been related to the diet and her weight loss but coroner David Hinchliff recorded a narrative verdict, saying it was not clear whether the diet caused or contributed to her death in any way.

The inquest heard Ms Clowe checked with her doctor before starting the diet and saw her GP for two monthly check-ups.

The diet involves eating a combination of soups, shakes and snack bars averaging around 530 calories a day.

Yesterday, LighterLife said that, although Ms Clowe’s Body Mass Index (BMI) had reduced from 37 to 32 during the diet, she was still clinically obese at the time of her death and her weight may have already affected her health before starting the plan.

A spokesman said: “We were very sad to hear the news about Samantha. The coroner said Samantha was clinically obese, which increased the risk of cardiac death.

“It had been suggested that there was a possible link to the diet but the coroner said it was very difficult to make such a connection. LighterLife is a clinically monitored programme and has helped 150,000 people lose weight effectively and safely during the past 12 years.”

Dr David Haslam, chairman of the National Obesity Forum, added: “Modern very low calorie diets are a safe and proven way to lose weight and have a valuable role in the fight against obesity.

“Samantha’s death tragically shows the real dangers of being obese, and the need to maintain a healthy weight.”

The inquest heard a statement from Ms Clowe’s mother in which she said her daughter had embarked on the diet because she was due to get married and did not want to be a “fat bride”.