Mrs Henson's husband Brian said she was delighted after losing weight
A mother died after drinking four litres of water in under two hours, an inquest has heard
Jacqueline Henson, 40, from Huddersfield, wanted to slim down from 14st (89kg) when she started the meal replacement diet plan LighterLife.
Huddersfield Coroner's Court was told she died from brain swelling.
A verdict of accidental death was recorded and the coroner said LighterLife had given clear guidance on how much water should be consumed.
The LighterLife diet plan is aimed at people who are three or more stones overweight and involves consuming 500 calories a day for 12 weeks by replacing meals with shakes, soups and bars, as well as drinking water.
Mrs Henson's husband Brian told BBC News that she was delighted when she lost 11.5lbs (5.2kg) during the first week of her diet.
He said: "It had been going brilliant, she loved it because she was losing weight. She was over the moon."
The inquest heard how on 14 November last year Mrs Henson began drinking two two-litre bottles of water out of a pint glass while watching television at her home in Almondbury.
She complained that her stomach was "solid" and was later sick.
Mrs Henson said she had a headache and went upstairs to the toilet where she collapsed. She died in hospital the next day.
West Yorkshire Coroner Roger Whittaker said no-one should drink water in the quantities involved over such a short period.
A spokesman for LighterLife said: "We are so sorry to hear about Jacqueline and extend our sympathies to her family.
"Our programme gives clear guidance that water should be consumed regularly over the course of the day, and the coroner confirmed that the events were a tragic accident."
Mr Henson said he now wanted to warn others of the danger of drinking too much water.
He said: "I had no idea that much water could kill someone. If I'd have known that I would not have let her drink it."