The business entrepreneur and The Apprentice star, 68, tweeted his opinion while watching The X Factor on Saturday night (21 November).
During the live shows, Lord Sugar simply wrote: "Catching up on X Factor. Cheryl is now too thin."
And while some of his 4.68million followers agreed with him, others were quick to defend the former Girls Aloud singer.
catching up on X-factor . Cheryl is now too thin.— Lord Sugar (@Lord_Sugar) November 21, 2015
One follower called Lord Sugar a "sizest", while another asked: "Her body is your business why exactly Shugs?"
A female fan replied: "Is there any need to say that? She's perfect."
A more angry response came from one tweeter, who blasted: "@Lord_Sugar Cheryl isn't too skinny!!! Leave her alone now!!! Stop being horrible! #stopbodyslammingnow!!!"
And another said: "@Lord_Sugar oh shut up. She is absolutely beautiful regardless of her size. What matters is that she is healthy."
However, there were many who agreed with the BBC star, including one who joined the debate saying: "Oh come off it, she's lost loads of noticeable weight which is not her natural size, that's clear!"
While one fan said being thin made Cheryl look "old", another added: "He's obvs noticed she's remarkably smaller than her Girls Aloud days. She's a public figure, he's allowed comment."
The first live show of the weekend saw Mason Noise voted off in a shock elimination.
He said: "Thank you to everyone who voted, thank you to everyone who didn't vote as well."
Another act will leave on Sunday (22 November).
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