Intermittent fasting has been a popular diet plan since the 5:2 diet, where you eat normally for 5 days and fast for 2, hit the headlines. But intermittent fasting is not safe or suitable for all people, such as those with long-term health conditions or a history of eating disorders. And the researchers involved in this study made the point of warning that alternate day fasting should not be tried without medical advice. Speak to a GP for advice before starting.