A client recently asked me if a change in his diet could help his mental agility.

We started to dive in a bit deeper into this subject and realized that the composition of his meals was very high performance, but the timing of his meals was not ideal. He was eating dinner quite late and then having an early breakfast the next morning. So, we outlined an intermittent feeding approach and realized that skipping breakfast, and then planning a substantial early lunch, would fit his schedule well. He was up for trying this new approach, and after only a few days, he saw a marked improvement in his mental clarity and his quality of sleep. Why would this be?

Intermittent fasting or, to be more accurate, intermittent feeding (IF), is a popular topic in the performance and health news feeds. It has become one of the most frequent High Performance Nutrition questions I am asked.

For me, there are 3 key questions:

1. Is there evidence that IF helps human performance?
2. Are there any negatives?
3. Is there a “best practice” for IF and human performance?

IF is advocated in functional medicine and personalized nutrition to help control inflammation, improve digestive performance, and support glucose and insulin metabolism. This is based on peer-reviewed evidence and clinical practice.

There is a growing consensus that the restriction of calories brings about what is called a xenohormetic effect. A what effect? A xenohormetic effect simply means that calorie restriction has a low-dose stressor effect on the cells that boosts their longevity. IF can create a simple system to build habits around a low-level calorie restriction.

Plus, something interesting happens to the microbiome when we limit our time of eating and provide a greater resting time for the gut. Certain bacteria, which have an important “housekeeping” function in the gut, prosper during the fasting hours. These bacteria help to optimize digestive function and the gut-brain connection. At the same time, the cell membrane may increase its sensitivity to insulin so the pancreas can create less and get the same desired effect.

Is there a potential downside to IF? This approach is not recommended (without the support of your doctor) if you have a history of eating disorders, if you are pregnant or nursing, or if you are a diabetic on insulin. Even with IF, we always advocate the Eat, Feel, Perform approach as a way of improving your awareness as to how YOUR body responds to food. Similarly, we always recommend increasing the nutrient richness of your food by eating a lot of vegetables and fruits.

When thinking about best practices, one recent paper really caught my eye. A group of adults was asked to either restrict their energy intake by 500 calories a day or follow a 5:2 regime (where 2 days of the week they consumed only 600 calories a day and the other 5 days they ate as they normally would). The researchers monitored the impact on their cognition and used a proxy marker for neurogenesis in the hippocampus (an area of the brain heavily involved in memory). The results showed very little difference between the two groups. In other words, IF had a positive impact on cognitive function, regardless of the style used.

In the case of my client, the way that IF worked for him was to use what is often referred to as the 16/8 method. He skipped breakfast, which meant he had an extended overnight fast of 15-16 hours. He had a high performance early lunch (see recipe below for an example) to maintain nutrient richness throughout the day and to set his brain up for the day ahead. He tested it, found it worked well for him, and recognized the desired effect on his cognitive function (eat, feel, perform). And by being so aware of the benefits, this became a high performance habit for him.

1. Have you experimented with IF, and if so, what was your experience?
2. I often recommend starting with a 12-hour overnight fast, and then extending that hour by hour as an initial approach to IF.
3. Be aware of how your approach affects your cognitive function, your energy level, and your digestive function. If there is a benefit in any of these areas, then extend the fasting hours or try a 5:2 approach.

*Disclaimer: Always check with your healthcare provider before starting a new diet regime, especially if you have any underlying health conditions (diabetes, heart disease, etc.) or are taking any medications. We always recommend trying this out on a weekend or light day until you know how your body will respond.

Strategic IF means having a well-planned meal where you break the fast. In the case of an extended overnight fast, an egg-based meal will provide good nutrients for brain function. The recipe below is a favorite of my clients.

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Braised Eggs with Leek (based on an Ottolenghi recipe)

Ingredients

• 1 Tablespoon olive oil
• 1 leek, sliced
• 3/8 cup baby spinach leaves
• 4 eggs
• ½ pack of feta cheese
• ½ teaspoon cumin seeds or powder
• salt
• pepper
• half a lemon, diced (whole lemon)
• 1/2 cup vegetable stock (1/2 stock cube and 1/2 cup boiling water)
• sumac (optional)

Directions

1. Heat oil in a pan, and then add leeks, salt, and pepper. Fry for 3 minutes, stirring frequently. Add cumin, lemon, and stock; boil rapidly for 4 minutes. Most of the stock will have reduced.
2. Lower heat, and then add spinach (it will wilt within 1 minute).
3. Create four indentations in the mix. Break an egg into each one. Sprinkle feta cheese around each egg. Cover the pan and cook for 5 minutes, on low to medium heat. The whites should be solid, but the yolks still runny.
4. Sprinkle with sumac if available. Serve over bread with the rest of the olive oil.

As always, we’d love to know what you think.