Now the whole of Scotland has cause to be worried about getting on the wrong side of the Perthshire-born nutritionist. McKeith’s new year resolution is to cure her homeland’s obesity epidemic — and that could involve the food police paying you a house call.

If Britain’s problem with junk food is scary, Scotland’s is truly terrifying. Over the past decade, £100m has been spent on healthy living campaigns, but Scots are said to be eating less fruit and vegetables than they did 10 years ago. Obesity is responsible for more cases of cirrhosis of the liver than excessive alcohol consumption.

Through her television programmes — which regularly attract up to 3m viewers — McKeith has used shock tactics to challenge people’s complacency about their weight. From forensic analysis of their faeces to confronting people with a vat of oil to show how much fat they consume, no measure is too extreme.

The same in-your-face approach is needed to tackle obesity on a national scale, argues McKeith. She is currently developing an action plan to be put to the Scottish government early in the new year designed to shake some sense into lardy Scots.

“In 2020 we will be looking at a disaster in terms of child obesity in Scotland unless we act now,” she warns. “If we can reach children there is hope for saving that generation.”

McKeith is not short of confidence and sees herself as the right woman for this toughest of challenges.

“It needs planning, it needs education and someone at the helm to pull this off. I know I could make it happen,” she says. “I would pioneer such a movement. It is my dream to change the eating habits of the people of this country and give them a healthier life. That’s why I do what I do.”

Her most radical proposal is one that will raise the ire of those who believe Scotland is becoming a nanny state. She proposes to recruit an army of nutritionists who would march into fat people’s homes and sort out their lives, like foodie social workers.

“Why can’t we have nutritionists go into all the homes of people who are suffering from obesity and whose children are obese?” she says. They could be identified and helped.

“We are talking about a lot of disenfranchised people who have not got the education. These people need to be re-educated and the only way to do that is to have a plan of action funded by the government.”

The failure of government campaigns over the past decade is proof, she says, that what is needed is direct hands-on help for the families with the most serious dietary problems.

“One of the biggest problems is that people have to be shown. Sometimes, if they just sit and watch something, it is not as easy to learn,” she says.

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