Zoe Salmon used to drink up to eight litres of water a day until a doctor advised her to cut down "straight away".
The ‘Blue Peter’ presenter was "pretty alarmed" to discover she had been downing more than double the maximum amount of water recommended on a daily basis, which can lead to fatal water intoxication.
The 40-year-old star told the Daily Mirror newspaper: "I felt quite silly when I sat down, taking an appointment to say I might be drinking too much water.
"I’d been drinking more than double the maximum. The doctor told me to act straight away – come down gradually by 200mls and work my way back to two litres. It was pretty alarming."
Zoe always believed drinking lots of water would improve her complexion and stop her from snacking, but had no idea how deadly her habit could become.
She explained: "I grew up having really bad skin, and I’d always heard that drinking loads of water would help.
"There was the old wives’ tale about how when you feel hungry you might actually be thirsty – although I was sipping so much water throughout the day I don’t think that was a significant factor for me."
Now she is determined to stick to the recommended two litres a day.
She added: "Each day I’d begin with a litre to kick-start my digestive system, I’d have another after my first coffee to balance out the effect of the caffeine and another after a smoothie.
"I’d drink a litre at the gym, fill up my water bottle with another litre for the drive home and if I went for a night out and had three or four glasses of wine, I’d have three or four glasses of water to counteract it."