Is the Atkins Diet hurting alcohol sales in Britain?
That's the question the drinks industry is puzzling over at the moment as an estimated three million people attempt the diet and its ban on alcohol.
For an industry that prides itself on understanding consumers, there's a surprising ignorance about the impact of Atkins.
Interbrew can throw little light on the issue.
It says: "A number of factors can impact on beer sales and it is difficult to attribute the effects of the Atkins diet to direct sales performance."
Allied Domecq is similarly baffled.
"We don't believe any company will be able to say whether this diet is affecting volumes."
Helpfully, it adds: "There could be a whole range of issues affecting consumer choice."
The Atkins Diet says you should not drink alcohol when you start.
After a while, an occasional glass of wine is acceptable.
As alcohol can increase yeast-related symptoms, such as bloating, gas and craving for sweets, beer is unacceptable at any stage.
Adam Collett, Greene King pub company marketing director, says he believes there's been no impact on sales.
"While we recognise the popularity of things like the Atkins Diet, in our experience people who are on such a diet tend to leave it at the pub door when they go out for a drink or a meal."
That view was confirmed by one industry figure, who told the MA: "Atkins is bad for you.
I prefer the Adnams diet myself.