Jonah Hill before and after

The 27-year-old is estimated to have lost close to 40 lbs. (18,1kg) since last December, according to the Daily Mail.

Hill, who lost the weight through diet and exercise, started his weight loss earlier this year because he 'thought it was important to be healthier,' he told the Los Angeles Times.

'It's not fun,' he said of his efforts. 'I wouldn't say it's the most fun endeavor I've ever took on in my life—but its important. And I'm enjoying it. If I eat something unhealthy now, I kind of feel a little weird and my body hurts.'

Besides striving to get healthier, Hill may have shed the weight for his new role in the upcoming film '21 Jump Street,' co-starring Channing Tatum.