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The effect of fasting diets on medication management


To the Editor: Fasting diets have been used by humans for millennia for religious and medical purposes and are now gaining popularity for wellbeing and weight loss purposes. With increasing use of short- and long-term courses of medication to manage a multitude of conditions, a question that needs to be asked is will fasting diets impact on medication regimens?

The 5 : 2 diet, where calorie intake is unrestricted 5 days a week and limited to 500 calories for women and 600 calories for men 2 days a week, is becoming increasingly popular due to widespread publicity. In humans, there is some evidence that intermittent fasting (mainly alternate day fasting rather than the 5 : 2 regimen) could lead to weight reduction, decreased insulin resistance and prevention of type 2 diabetes.1,2

It is possible that patients who are taking medication and intermittently fasting each week could encounter adverse effects or therapeutic failure. Medications of concern generally fall into two categories: those for which absorption may be significantly altered by administration on an empty stomach, and those for which increased gastrointestinal3 or other4 adverse effects may result when taken on an empty stomach (Box).