Is Intermittent Fasting Safe When Working Out?


It’s quite beneficial to work out during intermittent fasting as studies show the correlation between intermittent fasting and exercise can be a deadly combination. In this two-pronged approach, hormone optimization and autophagy, which is the process of breaking down cancerous and unwanted cells, can shoot to a whole new level.

When going on intermittent fasting, the stored glucose in the body can go down, and sugar levels will decrease. As a result, levels of insulin are reduced as well as levels of leptin. This will allow one’s body to break down body fat into ketones for energy. You become more and more sensitive to insulin as the days progress; this will enable you to burn fat and build muscle at much more elevated rates.

A study cited in Science daily highlighted that male human growth hormone (HGH) levels increase by a staggering 2000% in males, and 1300% in females who supplemented intermittent fasting with a moderate workout. Add to that the testosterone boost you get, and you have a serious contender for the best gym partner. Testosterone is a steroid hormone that regulates your energy levels, libido, muscle mass, memory, and other critical bodily functions.

Fasting, coupled with a good workout, allows HGH and Testosterone to collaborate and provide the best conditions for weight loss and muscle gain. Here’s a complete overview of how intermittent fasting impacts different kinds of training.

HIIT and Intermittent Fasting

High-intensity interval training (HIIT) involves short bouts of intense physical activity followed by rest for about half an hour. Not only is this type of training highly effective, but it also provides unparalleled health benefits that are simply impossible to get from aerobic exercises alone.

In addition to an enormous upshot in HGH levels, HIIT builds increased stamina and strength, improves body function and composition, increases testosterone levels, and diminishes stress.

When coupled with intermittent fasting, all these benefits are amplified, with little to no side effects. HIIT is one of the best workout routines to incorporate in your fasting schedule, according to many experts.

To take things up a notch and yield even more benefits with a combination of HIIT and intermittent fasting, you can also carry on fasting two to three hours post-workout.

One thing you should take care of after a good HIIT session is your protein intake. According to the International Society of Sports Medicine, you should consume between .14 and .23 grams of protein per pound of body weight within 1-2 hours of a workout (that’s 30g of protein for a 150-pound woman).

Cardio and Intermittent Fasting

The first cardio theory was presented by Bill Philips, a renowned bodybuilder, and author of Body for Life. In his book, he talks about how exercising in a fasted state helps with maximizing weight loss. His theory has gathered massive traction over the years and carved an essential place in fasting science in recent years.

According to Bill, the science behind the theory is simple. Fasting overnight lowers your insulin levels, blood sugar, and glycogen reserves, which lets the body directly tap into its secondary source of fuel (fat) for energy and fast-tracks the weight loss process. Before you go jumping on the fasted-cardio bandwagon, you should consider a few things, though.

The founder of the Brave Body Project and a certified gym instructor, Lindsey Clayton, believes that cardio is safe in a fasted state. Still, you should keep the intensity of your workout minimal.

She adds that instead of a fast sprint, or running a marathon, opt for a light jog instead. Clayton cautions that if you’re quickly getting tired and light-headed and are afraid you’re not going to keep your performance up, it’s better to exercise post-meal or snack to tip the balance in your favor.

In one Loughborough University study, runners who engaged in an hour-long treadmill session without having a meal first felt more starved than those who ate ahead of the exercise.

Additionally, fasting while doing cardio not only depletes your stored fats and carbs, but it also takes a big chunk of your protein reserves in the form of lean muscle. For most people who exercise, this is a deal-breaker. Having a branched-chain amino acid (BCCA) drink during fasted-workout can slow down this process. Look for a supplement that has at least 5g of BCCAs as a general recommendation.

Weight Training and Intermittent Fasting

Lifting weights while fasting is manageable, but you have to be careful about the glucose reserves in your body. They deplete pretty fast after an intense lifting session, especially if you’re knee-deep in intermittent fasting. During a fast, your glycogen stores are already being used up. And if you resort to weight training in addition to that, it might put an unfair burden on your body. What you can do is schedule your workout in such a way that it immediately follows a heavy meal. Heavy lifting is different than a burst session; it demands an immediate refill from your end.

As with cardio, your body might need some time to adapt to lifting weights at full strength. So, it’s advisable to go easy on yourself in the beginning.

Studies show that fasted weight lifting evokes a higher anabolic response to a post-workout meal than regular training. This means that your body reacts a lot better to your post-workout steaks and veggies, and begins building and replenishing energy a lot faster, which leads to massive gains.

 has great significance in the gym. Essentially, VO2 max your body’s ability to use oxygen. Those who have a higher VO2 capacity burn a lot more fat from exercise than those who don’t. From this, we can conclude that fasted weight lifting provides better results and improved performance in the gym.

To Sum, it All Up

Exercising while fasting is safe and beneficial. It provides many benefits from hormone optimization to improving VO2 max levels and lifting output. However, you need to be wary of specific details. While cardio, HIIT, and weight lifting are great while fasting, your body will need time getting used to them if you’ve only recently stumbled upon the holy grail of fasted-training.

Therefore, it’s recommended to take things slowly and listen to your body, instead of starving yourself for fuel and oxygen to the point that it completely breaks down. The excellent news, intermittent fasting gives you a lot of room and space to experiment and find the right approach — all you need is some curiosity and initiative.

About Vanessa Davis

Vanessa Davis is 32 years old, lives in New York and is currently a full-time content writer at Her areas of expertise are fitness, nutrition and leading a healthy lifestyle, and in her free time she enjoys yoga, skiing and mountain climbing.

Leave a Reply

Your email address will not be published. Required fields are marked *