A chef who has cooked for Oprah Winfrey and Prime Minister Jacinda Ardern has opened up on how she lost 30kg without exercising.

Speaking with Mike Hosking, Bridget Davis said she has lost 30kg in just five months.

She attributes her success to eating lots of protein and adding lots of flavour to her meals.

"Brain fog gone, bloating gone, stomach upsets gone, mood swings gone, tiredness gone," she wrote on her website Bridget's Healthy Kitchen.

"They say it takes 21 days to form a habit. I can tell you that after 90 days, I have left my old self behind eating little to no gluten, dairy and/or sugar."

Davis spoke with Mike Hosking about her top tips for weight loss:

* Cutting out gluten, especially bread or anything with white flour in it
* Cutting out sugar
* Reducing the amount of dairy
* Start the day with protein, like chicken or eggs
* Lunch should be the largest meal of the day and include protein

Her latest cookbook is Bridget's Healthy Kitchen.