The congressional candidate and former White House physician said he does not want the government telling him he needs to wear a mask.
Ronny Jackson told reporters White House medical staff took various measures to improve the president's diet and help him lose pounds.
Trump reportedly ordered Dover sole for dinner recently instead of his go-to steak at Trump International Hotel.
The first daughter has faced ethics questions about her fashion brand's recent wave of trademark approvals in China.
Jackson's nomination as veterans affairs secretary was withdrawn last week.
Ronny Jackson's nomination to head the VA has become engulfed in controversy.
"He's never held a command or led anything remotely close...in scope or complexity to the VA," said AMVETS in a statement.
White House officials said Wednesday evening that Veterans Affairs Secretary David Shulkin will resign and that President Donald Trump will nominate his personal physician, Ronny Jackson, to succeed him.