The skinny on Oprah's slimline look: How a new chef has helped the star drop 25lbs in just SIX weeks

By Tamara Abraham

PUBLISHED: 10:34 EST, 20 June 2012 | UPDATED: 10:34 EST, 20 June 2012

If you thought Oprah Winfrey had been looking slimmer of late, then it seems you'd be right.

The TV host, 58, has lost 25lbs in just six weeks, it was revealed today, shedding much of the weight she had gained over the past 18 months due to the pressures of running her OWN network.

The secret to her success, sources say, is a lean, low-calorie diet implemented by her new chef.

Slimline new look: Oprah Winfrey, pictured in April (left) and more recently on June 8 (right), has lost 25lbs in just six weeks after embracing a new diet and exercise regime, it was revealed today

The fast results were also thanks to the fact that she has resumed her regular treadmill workouts with trainer Bob Greene, they added.

'Oprah has absolutely flipped for the new chef,' a source told the National Enquirer.

'The personalized diet Oprah's been following uses a combination of fruits and vegetables, fish, chicken and lean meat.

'It's low in fat and calories, but still leaves her feeling full.'

It is a positive turn for the star, who has spoken publicly about her struggle to maintain a healthy weight.

Yo-yo weight: Oprah at her thinnest in 1988 (left) and in 2008, when a thyroid problem caused her weight to balloon to 200lbs (right)

Once rakishly thin in 1988, Oprah's weight has been a yo-yo ever since, not helped by a thyroid problem, diagnosed in 2008, that caused the scales to soar to 200lbs.

She wrote at the time in O Magazine: 'The thyroid diagnosis felt like some kind of prison sentence. I was so frustrated that I started eating whatever I wanted - and that's never good. My drug of choice is food. I use food for the same reasons an addict uses drugs: to comfort, to soothe, to ease stress.'

Now, though, it appears that she has struck the right balance of a healthy, lean diet that does not feel restrictive, and a workout programme that is equally sustainable.

'Deep down, Oprah knew she had the willpower to lose it again if she took the right approach, and she's finally found a plan she really likes,' the Enquirer's source explained.

'This program is a lifestyle change and it stresses eating the right kind of foods to sustain energy and good health.'