The usually-skinny star appeared fuller-figured on stage in Amsterdam this week sparking reports that her excessive drinking has caused her weight to balloon.
"Gaga appears to have gained at least 30 pounds (13.6kg)," nutritionist Majid Ali, who has not treated the star, told Radar Online after seeing photos of the 26-year-old.
Gaga has boasted in the past that she follows "the drunk diet", and Ali thinks it's likely booze is the cause of her weight gain.
"I like to drink whiskey and stuff while I am working," Gaga told radio station Sirius FM recently, admitting that she often hits the gym with a hangover.
Earlier this year, the then-slim singer copped criticism when she tweeted, "Just killed back-to-back spin classes. Eating a salad dreaming of a cheeseburger. Pop singers don't eat. I was born this way."
Now that everyone is doing her the favour of pointing out her weight gain (pop singers can't win, huh?) she has reportedly vowed to lose 10lbs (4.5kg) by going on a gluten-free diet.