She wrote: “Bulimia and anorexia since I was 15.”
Fans on the site immediately heaped praise on the singer, with user Ida writing: “I can’t stop crying. Gaga I’m battling the same thing right now.”
Fellow fan Dylan Appleby added: “to be perfectly honest i don’t see the weight gain and even if i could it doesn’t matter (sic)”
Lady Gaga recently revealed the reason behind her weight increase was down to her father’s restaurant in New York.
She said: “I love eating pasta and I'm a New York Italian girl. That's why I have been staying out of New York.
"My father opened a restaurant. It's so amazing ... it's so freaking delicious, but I'm telling you I gain five pounds every time I go there.
"So my dad wants me to eat at the restaurant, and I'm like, 'I've got to go where I can drink green juice.' "