The following correction was printed in the Guardian's Corrections and clarifications column, Wednesday February 14 2007

We were wrong to refer to Gillian McKeith as a dietician in the headline above - a mistake on our part. There was no suggestion in the text that Ms McKeith had used the description. In Britain dietitians (the spelling they prefer) are registered, and regulated under the Health Professions Order 2001.

Gillian McKeith, the You Are What You Eat presenter, has agreed to drop the title Dr from her company's advertising after a complaint to the industry watchdog. She has made millions from book and health food spin-offs, but her credentials have been questioned by some experts.

After the Advertising Standards Authority came to the provisional conclusion that the honorific was likely to mislead the public, McKeith Research said it planned to drop it from its advertising, obviating the need for a full investigation. The complaint was brought by a Guardian reader who learned of Ms McKeith's academic credentials from a recent Bad Science column by Ben Goldacre.

The self-styled health guru has consistently argued she is entitled to call herself a doctor because of her distance learning PhD in holistic nutrition from the American Holistic College of Nutrition.

It is understood the ASA was minded to rule that the adverts were misleading, because the college was not accredited by any recognised educational authority at the time she took the course, and she does not hold a general medical qualification. While the adverts usually stated somewhere in the text Ms McKeith was not a medical doctor, the initial impression given was that she was, it said.

According to documents seen by the Guardian, the agreement prevents Ms McKeith calling herself a doctor in any advertising or mailshots relating to her company and its products. They include a Dr Gillian McKeith-branded range of health foods and the Dr Gillian Club, which offers online health plans.

She told the Guardian she understood the offending ad was a leaflet without the usual disclaimer she was not a medical doctor. She said she understood the honorific had to go from leaflets, but not from all adverts. "As far as I'm concerned, because of the hard work I have done, I'll continue to put PhD after my name; I'm entitled to use the word Dr as and when I choose."

She said she had become a target for critics of her brand of nutrition because of her public profile. "I am on a mission to change this country's eating habits. I've been doing it for 15 years, and I have had amazing results. I believe strongly and passionately in my mission."

Her PR representative, Max Clifford, said her degree had not played a part in her career. "Personally, I wish it had never been mentioned. She never needed it, and it's done nothing but cause her embarrassment."

Ms McKeith is on her fourth series of the Channel 4 show.