Try This: The Do’s and Don’ts of Intermittent Fasting

Hi ,

Intermittent fasting (IF) can be a powerful tool for supporting weight loss and shifting overall body composition. 

But did you know there’s a right way and a wrong way to practice it depending on your goals?

I recently sat down with intermittent fasting expert Thomas DeLauer, who served up a masterclass on the topic. Because there is a lot of nuance surrounding intermittent fasting, I highly recommend listening to the full episode.

Today, I’m giving you a recap of our conversation and the do’s and don’ts of intermittent fasting so you can reap its incredible benefits. 

Let’s jump right in!

What Is Intermittent Fasting?

Intermittent fasting is a sustainable way to reap the benefits of fasting without the discomfort of a prolonged fast. How it works is you have a set window of time when you eat your calories for the day, followed by a period of time where you abstain from food entirely.

What Are the Most Common Forms of Intermittent Fasting?

The most popular form of intermittent fasting is the 16:8 window (16 hours of fasting and an eight-hour feeding window). However, 14:10 and 12:12 fasting-to-eating windows might be more manageable when first getting started. It’s important to note that your eating window should ideally be during the day and your fasting window at night to sync up with your circadian rhythm. 

How Does Intermittent Fasting Work?

The short- and long-term benefits of intermittent fasting are well established. When we give our bodies a break from digesting food, it allows our immune systems to focus on important tasks like autophagy (the process of clearing damaged cells). It also enhances insulin sensitivity, blood sugar balance, and metabolic flexibility. 

Combined, the immune and metabolic benefits of intermittent fasting have an outstanding impact on overall health and risk for chronic diseases like cancer, type 2 diabetes, and Alzheimer’s.

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Intermittent Fasting and Weight Loss: Where Calories Matter

When it comes to weight loss, however, the mechanism behind intermittent fasting’s benefits is hotly debated. We used to think its impact on immunity and metabolic health was primarily responsible.Although this could have something to do with the initial weight loss, Thomas believes the main way intermittent fasting shifts body composition is through a net reduction in calories and ultra-processed food consumption. 

By narrowing our eating window, it’s easier to reach a calorie deficit. This was the case for Thomas, who credits his over 100 lb. weight loss to intermittent fasting.But after several months, his weight loss plateaued. He eventually learned that the quality of the food we eat to break a fast is just as important as the fast itself. This leads me to the first “don’t” of intermittent fasting.

The Don’ts of Intermittent Fasting

1. Don’t take the “Standard American” approach to fasting. When Thomas first started intermittent fasting, he still ate the Standard American Diet and broke his fasts with ultra-processed food, fast food, and fried foods.  Just shortening his eating window led to a 50-pound weight loss in six months, but his weight loss eventually plateaued. This is why Thomas is now super vocal about the quality of foods that make up your diet.  By moving toward a whole-food diet and away from ultra-processed foods that are designed to make us overeat, we naturally consume fewer calories.

2. Don’t break your fast with large amounts of refined carbs, sugar, or saturated fat. When breaking a fast, Thomas recommends avoiding large amounts of carbs and sugar that will send you on a blood sugar roller coaster for the rest of the day.  Breaking a fast with saturated fat increases blood lipopolysaccharide levels (LPS), bacterial components that bypass our gut lining and trigger inflammation.  A little inflammation after a fast is normal. But, as Thomas says here, research suggests that if LPS enters the bloodstream after a fast it can lead to double the levels of inflammation.  This is why Thomas recommends avoiding MCT oil, butter, and fatty meats to break a fast. (See the first “do” below for what you should eat to break your fast.)

3. Don’t overconsume calories from “healthy” processed food. With my friends who claimed intermittent fasting didn’t work for them, I noticed they were overeating calories from processed “health” foods (think gluten-free chips, high-fat protein bars, keto snacks, etc.).  Focusing on eating whole foods during their feeding window while keeping an eye on calories helped them shift their body composition in the direction they ultimately wanted.

The Do’s of Intermittent Fasting

1. Do break your fast with lean protein and healthy fats. This is Thomas’s top suggestion for breaking a fast. Lean protein helps promote fullness and starts your eating window off with balanced blood sugar, which helps combat cravings for the rest of the day.   When it comes to fats, Thomas recommends monounsaturated fats from olive oil or avocado oil to break your fast. Not only are these easier to digest, but they also help to mitigate LPS from passing through the gut and into the bloodstream. 

2. Do plan your fasts ahead of time and be intentional about them. Failing to plan equals planning to fail! We need to ensure we’re being intentional about our fasts. This means knowing when your fasting window will start and end and having meals prepped and planned for the day.

3. Do fast with your circadian rhythm. While planning your fasts, remember that eating with your circadian rhythm is key. Eating most of your calories earlier in the day is best because this is when insulin sensitivity is highest and when our digestive system is most primed to break down and absorb nutrients from our food.  Based on Dr. Satchin Panda’s research in circadian biology, he recommends stopping eating two-to-three hours before bed to promote weight loss further. 

4. Do start with a 12-hour fasting window and work your way up. Thomas began his fasting journey with the 16:8 fasting window. If you can jump right in and follow this, great! If not, don’t worry.  Dr. Satchin Panda suggests starting with a 12:12 or a 14:10 window and then gradually working your way up to 16:8. Then, once you conquer the 16:8, feel free to throw in a longer fast.

What about Women in Their Reproductive Years?

Dr. Mindy Pelz, Dave Asprey, and Cynthia Thurlow suggest fasting in the follicular phase when the body is better equipped to handle stressors and avoiding fasting during the luteal phase.

However, Thomas takes a different stance. He says that fasting during the luteal phase could be beneficial when done right. This is a super-personalized topic, so I recommend listening to what the experts say when planning your fasts.

Final Thoughts: Why Calories Matter

I’ve done many interviews over the years on the power of fasting. What I appreciate about Thomas’s approach is that he doesn’t discount the importance of calories, especially when it comes to weight loss, if that’s your goal. 

This doesn’t mean that we have to go crazy counting calories. Tracking your calorie intake with an app or a food scale for a few days every couple of months is enough to get an idea of the quantity of food you’re eating.

What about Longer Fasts? 

As far as longer fasts go, those in their 50s and older have a higher risk of losing lean muscle as a part of the weight loss. This is why past podcast guests like Donald Layman, PhD, and Cynthia Thurlow do not recommend longer fasts for older adults.That doesn’t mean you can’t practice intermittent fasting; you just need to make sure you’re reaching your daily protein goal in your feeding window. 

My Approach to Intermittent Fasting 

Growing up vegetarian, I underate on protein for most of my young adult life, but now that I’m in my 40s, I’m focused on increasing muscle and building strength. Because longer fasts would make it harder for me to hit my daily protein goal, I’m not doing much fasting beyond the normal 8–12 hour feeding window, and I’m totally okay with that.Here's to your health,Dhru Purohit