Lauren Thomas, 28, was horrified when a friend thought a photo of herself which she had posted on Facebook was of her own mother Brenda, 66.
"I knew I'd put on weight but I had no idea I put 30 years on to my life too," Lauren said.
"I immediately changed my privacy settings so no-one could see the photo but I was utterly mortified."
Lauren, from Llanelli, Wales, was struggling with weight issues and had reached 20 stone in early 2012.
She updated her Facebook profile picture with a full length shot of herself and was mortified when a friend commented, "Oh my god, is that your mum? You look like twins."
Lauren said she knew it was just an 'honest mistake' but it left her 'embarrassed beyond words.'
She told The Daily Mail that she grew up surrounded by sweet and savoury treats because her family owned a bakery and her mum rarely said no to her demands for cake and pasties.
Her problems came to a head when her father died when she was 14 years old. Unable to cope with the grief, Lauren started comfort eating. She weighed 19 stone by the time she left school.
"I spent a long time feeling angry but I learned to live with my size, even though deep down I was very unhappy," she said.
Lauren went on to develop bulimia following a trip to the doctors about a pulled muscle in her back.
"A doctor took one look at me and told me he wasn't surprised I'd injured myself because I was so overweight," she said.
"I felt he was quite rude and tried to brush it off but his words stayed with me for a long time afterwards."
She suffered from the eating disorder until she discovered she was pregnant with her daughter Rhiannon, who's now three.
"I had been struggling, and was desperate for control," she said. "But becoming pregnant made me comfortable in myself again. I made sure I ate properly while I was pregnant and after Rhiannon was born I started to put weight on again."
Lauren admits she often ate pieces of chocolate for breakfast and Cornish pasties for lunch.
Then in 2012 she received the comment on Facebook that prompted her to overhaul her diet.
She started the Cambridge Diet, which replaced the fatty and sugary foods she had been filling up on with calorie-controlled milkshakes.
By July 2013 she was down to 10st 7lbs and had dropped six dress sizes, from a size 26 to a 14.
Lauren has since regained two stone, but for the first time in her adult life she is now comfortable with her weight,
"People said I looked ill when I was at my lowest weight," she said. "I'm 5ft 7in and 12 stone is a healthy weight for me.
"I've finally found something which works, and for the first time I feel as if I've got some control."
More on Parentdish