Kim Kardashian busted her ass to lose 16 pounds for The Met Gala, and anyone accusing her of doing it in an unhealthy manner just doesn't get it ... so says her longtime trainer.
We got DON-A-MATRIX out in L.A. Wednesday who says Kim dropped some serious lbs the old-fashioned way ... hard work and dieting. Don was with Kim through the three-week process, and says at no point did she "starve" herself.
Not only that, Don says Kim was an animal in the gym -- working out 2 times a day -- and sticking to a well-balanced diet.
He says Kim's not his only client who lost a lot of weight in a short period of time ... other clients have lost even more -- the key is exercise and healthy eating.
TMZ broke the story, when Kim first tried on Marilyn Monroe's "Happy Birthday, Mr. President" dress back in March, it didn't fit, and The Ripley's Museum actually rejected her request to borrow the dress for the Met Gala.
Ripley's Believe It or Not!
Determined, Kim dropped the weight, and came back a few weeks later -- and the dress fit, and Ripley's was down with the Met.
Not everyone was impressed, however, by Kim's weight loss -- "Riverdale" star Lili Reinhart slammed her, saying, "To walk on a red carpet and do an interview where you say how starving you are ... because you haven't eaten carbs in the last month ... all to fit in a f*****g dress?" She continued, "Please stop supporting these stupid, harmful celebrities whose entire image revolves around their bodies."