 For patients who benefit , half achieve a seizure reduction within five days ( if the diet starts with an initial fast of one to two days ) , three @-@ quarters achieve a reduction within two weeks , and 90 % achieve a reduction within 23 days . If the diet does not begin with a fast , the time for half of the patients to achieve an improvement is longer ( two weeks ) but the long @-@ term seizure reduction rates are unaffected . Parents are encouraged to persist with the diet for at least three months before any final consideration is made regarding efficacy . 
