Intermittent fasting (IF) is a pattern of eating that focuses on meal timing and does not change the amount of calories and nutrients you need each day. Instead, the eating pattern simply adjusts the window of time you eat.
IF is highly individualized but can be beneficial when it comes to losing weight and maintaining weight loss. Research also shows a myriad of health benefits aside from weight loss such as improved insulin sensitivity, blood pressure, lipids, inflammation, and oxidative stress to name a few.
Our bistroMD protocol typically recommends a 10-14 hour fast from dinner/snack to breakfast the next morning. Therefore, if you eat breakfast at 8:00 am, you will stop eating between 6:00-10:00 pm that evening. This is often a timeframe that is much more sustainable long term. We do not recommend significantly longer than 14 hours of fasting for a few reasons:
1. Going longer than 14 hours allots less than 10 hours in the day to consume adequate protein. Research shows the body does not really absorb more than 30-45 grams of protein at one sitting/meal. For example, someone having one meal a day will not absorb a much larger amount of protein at that meal and the glucose and insulin load of the meal is high.
2. The risk of muscle breakdown in a prolonged fast.
3. Too restrictive eating can lead to "binge" days or cause excessive calorie and sugar/fat/protein intake on non-fasting days.
4. Sets the scene for an unhealthy or dysfunctional relationship with food.
Overall, what you eat always matters no matter the timeframe in which you eat. So, it’s important to ensure you are not skipping your meals and snacks and eating whole foods with adequate protein, controlled complex carbohydrates, and healthy fats.
Once someone’s insulin resistance improves and blood sugar becomes more stable with adequate protein, fiber, and meal timing, extending the fast to 10-14 hours can be helpful depending on the person.
For those with hypoglycemia, are pregnant, breastfeeding, underweight, or have a history of disordered eating we do not recommend intermittent fasting. For members with chronic diseases and on medications, we recommend always discussing with your doctor first before making any extreme dietary changes.