For years the singer has been trying to get out of her record deal over claims he sexually and emotionally abused her.
In the leaked messages he criticises her for having "Diet Coke and turkey while on an all juice fast", and says songwriters "are reluctant to give [her] songs because of her weight".
He has always denied mistreating her and says the emails have been taken out of context.
Kesha argues she should be free from her contract with Dr Luke so she can release music elsewhere.
He says Kesha's allegations of abuse are malicious lies and "defamatory".
The emails leaked to The New York Post are between Dr Luke and Kesha's manager, Monica Cornia.
Two refer to Kesha's struggle with the eating disorder bulimia - something which she says he didn't support her over.
"Nobody was calling anybody out," Dr Luke says in an email dated 28 June 2012.
"We were having a discussion on how she can be more disciplined with her diet.
"There have been many times we have all witnessed her breaking her diet plan. This particular time - it happened to be Diet Coke and turkey while on an all juice fast."
An earlier email claims: "A-List songwriters and producers are reluctant to give Kesha their songs because of her weight."
The third email discusses an argument over lyrics, in which Dr Luke allegedly tells the singer he doesn't care what she wants: "If you were smart you would go in and sing it."
In a statement released through his lawyer, the record producer denies these emails demonstrate abuse.
"Kesha and her attorneys continue to mislead by refusing to disclose the larger record of evidence showing the bad faith of Kesha Sebert and her representatives which is greatly damaging to them," the statement says.
"It also shows the tremendous support that Dr Luke provided Kesha regarding artistic and personal issues, including Kesha's own concerns over her weight.
"Rather than agree to a thorough disclosure, Kesha and her representatives improperly publicized, without court permission, three out-of-context emails which do not present the full picture regarding the events they concern.
"Dr Luke looks forward to full vindication in court."