Singaporean blogger Xiaxue has previously lobbed brickbats at targets, from singer Adele to climate activist Greta Thunberg.
Adele has reportedly looked thinner recently, despite her previous comments that she did not want to look like a model.
Xiaxue, 35, has also called out Thunberg, 17, as a young child who views matters one-dimensionally.
Now, she has taken aim at people who are, in her own words, "morbidly overweight", citing plus-size model La'Shaunae Steward, 23, as an example.
Posting on Instagram, Xiaxue, whose real name is Wendy Cheng, wrote: "It's one thing to be chubby or fat but this is way past that. Most morbidly obese people don't live past 40."
She took umbrage at "irresponsible" people who "gorge themselves with 30 burgers a day", saying that when their health fails, taxpayers have to help them settle their medical bills.
"The morbidly obese (like La'Shaunae Steward) should never be seen as attractive. Irresponsibility isn't attractive," Xiaxue added.
She did not think it was appropriate for Instagram to put up a photo of Steward on its wall to promote body positivity, reported The Daily Mail.
American model Steward did not take the attack from Xiaxue lightly.
"Why are thin people this obsessed with letting me know indirectly they think I'm unattractive to them, therefore I'm not worthy of love, a career, being visible and literally telling me the age I'm going to die?
"I don't owe weight loss to anyone. I don't owe anyone an explanation for why I'm fat or don't exercise. I don't have to prove my health."
The war of words continued, with Xiaxue putting up a defence, saying her comments were "reserved for the morbidly obese only".
She also posted a picture of herself after she digitally altered her face, body, arms and legs to look bigger.
"I maintain my stance. Morbid obesity isn't attractive because it leads to death and disease. This isn't personal against anyone so it isn't fat-shaming.
"And I did not ever talk about chubby or regular fat people."
Amid a backdrop of the modelling industry making moves to embrace diversity, Xiaxue's comments have irked netizens.
One person echoed the views of others by posting that Xiaxue is "deliberately spouting hate against plus-size women, encouraging bullying and discrimination".
But even as some netizens have asked Instagram to suspend her account, Xiaxue has not backed down, also hitting out at Singapore actress Oon Shu An, 33.
The latter had posted a different take on the Steward issue, praising the model's bravery to not fit into people's perceptions of the "right" body image.
In response, Xiaxue posted: "If she's so beautiful, why don't you gain 150kg to go look like her? Practise what you preach."