An athlete’s guide to intermittent fasting

Although intermittent fasting is a method best known to help promote weight loss, fasting has also been said to help with energy levels, mental clarity, as well as additional long-term benefits.

But is it right for you and your fitness goals? Find out everything you need to know about intermittent fasting to help you decide below.

Intermittent fasting (IF) is an eating pattern that alternates between periods of fasting, or not eating, and eating. Simply put, it’s limiting your food intake to a specific time window each day.

And while this way of eating may sound extreme, we’ll let you in on a little secret you might not realize yet…you’re already fasting every day.

Think about it: when you’re asleep, you’re not eating – that’s fasting. Then, when you wake up, you start eating again, breaking your fast. Intermittent fasting is more or less the same, just with a bit more structure.

Traditionally, intermittent fasting is a dietary pattern that your ancestors would have followed, not out of choice but because of food scarcity.

Various studies have suggested that intermittent fasting can have powerful health benefits for your body and your brain,¹ including improved:

• insulin sensitivity
• blood pressure
• oxidative stress
• Appetite²

One of the most talked about benefits of intermittent fasting – especially in the fitness world – is the effect it has on metabolism. During the longer fasting period, the body turns to existing excess fat reserves as a source of energy and burns these.

Sounds awesome, right? After all, who wouldn’t want to get rid of some excess body fat?! But how does it work?

Usually, your body relies on the intake of carbohydrates as its primary source of energy. These are broken down into glucose and released into the bloodstream.

As a response to the blood sugar in the veins, the body increases insulin, the fat-synthesizing and storage-promoting hormone.

Longer periods of not eating mean you are depriving your body of a substantial part of its glucose intake, which previously served as an energy source. Glucose levels drop – insulin drops.

This means your body looks for another source of energy and turns to burning fat for fuel. So, if you can control insulin levels through a decrease in carbs, you can control and actively stimulate fat burn.

Beyond weight loss, the lesser-known benefit of intermittent fasting is increased energy. When we eat several times a day, our metabolism goes through cycles of breaking down carbohydrates and turning them into blood sugar.

Eventually, it’s used for energy or stored in cells for later. After blood sugar is consumed or stored by the body, it drops, taking your energy and mental performance down with it. This triggers a “hunger signal,” and the whole process starts all over again.

The constant up-and-down cycle of blood sugar throughout the day stresses our metabolism and results in overall lower energy levels and mental performance.

Intermittent fasting changes that by using fat for energy. Fat is digested slowly and must be sent to the liver for processing (to ketones) before it can be used for energy.

This process happens steadily and consistently with no fluctuations, meaning we have more energy, feel better, and our concentration levels and cognitive function are also higher.

When you exercise in a fasted state, you’re training without readily available glucose. So, your body will break down its glycogen stores or fat reserves.

And while fasted workouts can help burn more fat during exercise, research shows that people tend to store more fat afterward. Burning fat during exercise, unfortunately, does not necessarily equal losing body fat. ⁶

What’s more, working out fasted might leave you with less energy and could affect your ability to truly get after your training. Whether it’s a good idea also depends on the type of exercise you are doing, since carbohydrates are the primary fuel source for high-intensity activities.

It’s recommended that fasted workouts be reserved for low-intensity activities, such as light stretching, walking, or yoga, and for sessions less than 45 minutes. Consequently, athletes should avoid high-intensity exercise when fasting.⁵

With intermittent fasting, the window of eating is decreased, and the window of fasting is increased.

While you can technically fast for any length of time, some methods are more popular than others because they are easier to stick with and are often more effective.

Here are a few common types of intermittent fasting:

16:8 method

This type of IF involves eating during an 8-hour window and then fasting for 16 hours. So, you may choose to eat between the hours of 9 a.m. and 5 p.m. and then drink water, tea, coffee, or milk for the remaining time.

5:2 method

The 5:2 method involves eating normally for 5 days a week and then restricting your calorie intake for the other 2 days and is a popular plan for weight management.

It involves eating just 25% of your usual daily calories for 2 days, typically 500 calories for women and 600 calories for men.

Research shows that the 5:2 diet is as effective as calorie restriction in promoting weight loss in overweight and obese people.³

Alternate day fasting

A type of intermittent fasting that requires you to fast every other day and eat normally on non-fasting days.

Some modified versions of this type of IF, allow you to eat around 20 to 30% of your usual calories on the fasting days.

Studies show that alternate-day fasting and the modified version can induce weight loss of 0.77% to 12.97% over 3 to 26 weeks compared to other IF regimens.⁴

Eat Stop Eat

A regimen that involves fasting for 24 hours twice per week, then eating a well-balanced diet for the remaining 5 days. Although you don’t need to be dieting on the eating days, you do need to eat responsibly.

As with anything in health and fitness, whether or not to give intermittent fasting a try is 100% individual and depends heavily on your goals.

Intermittent fasting isn’t for everyone, and each of these “benefits” comes with a caveat. There are a lot of benefits to fueling before a workout, so you need to decide what works best for you and your lifestyle.

If you do decide to give intermittent fasting a go, ease into it and give your body enough time to adjust. Feeling low on energy or extra hungry at first is normal, but make sure to pay attention to how you feel overall.

It can take a few weeks to notice the benefits, so be patient. The most important thing is to find a way of eating that you can stick to in the long run.