Keto flexing refers to a dietary approach that involves cycling between periods of low and high carbohydrate intake to promote metabolic flexibility. The 5-1-1 rule is one such method that can help maintain this state, enhancing the body's ability to switch between burning carbohydrates and fats effectively.

The rule consists of the following routine for each week:

• Five days of a ketogenic diet consisting of low-carb, protein-rich meals with less than 50 grams of carbohydrates from non-starchy vegetables.
• One day dedicated to fasting, typically a 24-hour fast chosen based on individual stress levels.
• One day of increased carbohydrate intake, with total carbs exceeding 150 grams while maintaining protein levels and reducing fat intake.

One notable effect of this method is its impact on thyroid hormone conversion. By intermittently introducing carbohydrates into the diet, the body is prompted to support the conversion of inactive T4 hormone to active T3 hormone. Additionally, insulin plays a role in this process, further assisting in thyroid function.

The 5-1-1 rule may also provide benefits for women, particularly in terms of hormonal balance. Variations in carbohydrate intake are linked with improved levels of progesterone and estrogen, especially beneficial during the menstrual cycle. Planning flex days around the premenstrual phase could optimize these hormonal benefits.