The First Minister decided to reduce his weight after staff became concerned that he was piling on the pounds while fulfilling his many engagements.
But it was only after meeting the former governor of the Bank of England, Sir Mervyn king, at Wimbledon this year, that he pledged to take action.
King suggested that Salmond should try the diet - known as the 5:2 diet as it requires slimmers to restrict calorie intake to 600 for two days out of every seven - that is also popular with celebrities such as actors Jennifer Lopez and Ben Affleck.
Mr Salmond said: "I know Mervyn from Wimbledon and he is now my dietary adviser.
"It works for me because I love food.
"It is difficult as I am at functions every day but I can say to myself 'I'm not having this delicious meal now because I can have it tomorrow'.
"It is easier psycho- logically.
"It can be a struggle but I've dropped about two stone and two collar sizes."
The First Minister is believed to have adopted the diet not because of health fears but because staff want him to be in better physical condition for the arduous campaign for independence.
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