It’s important to be flexible. Intermittent fasting is ideally a lifestyle, not a fad diet. In Dr. Krista Varady’s studies of alternate day fasting, she tells people not to worry if they miss two or three fast days in a month. Sometimes your fast days might land on a holiday or during another family event, and it may be more stressful to stringently stick to your fast than to enjoy a piece of cake.
However, some people find that “cheating” derails their whole fasting schedule. If you are the type of person who needs a lot of structure to succeed at a healthy behavior, Varady suggests not skipping your fast days for family events or other occasions. However, for most people the occasional cheat day won’t significantly impede weight loss progress or metabolic health.