Working Out While Intermittent Fasting – Is it Safe?

Author: Reema Behl

From Intermittent Fasting (IF) to One Meal A Day (OMAD), the wellness world boasts an impressive number of fasting plans, aimed at helping you lose weight, maintain muscle mass, reduce the risk of diabetes and fight inflammation.

When we exercise, our body uses carbohydrates as the primary source of fuel.

This is because they break down easily for energy. However, in a fasted state, when our bodies are depleted of carbohydrates or glycogen, fat is relied on for energy. Therefore, working out in a fasted state may increase fat oxidation. Studies indicate that fasting can also improve insulin sensitivity, and increase Human Growth Hormone production (HGH), which plays a vital role in metabolism.

But can you train effectively while fasted?

Muscle and Health investigates.

“If you are doing slow and steady cardio or a light workout then working out in a fasted state is usually alright,” suggests Siva Subramanian, founder at Potential Health Development. “For high-intensity sessions, it is recommended to eat something light 30-45 minutes before the workout. Today, with devices like Ultrahuman Cyborg, you can check how optimally fuelled you are for your workout and log your fuel scores too.

“If your workout is cardio-based or high intensity, plan the timing of the workout so that a meal can be had post-workout which will fit in the IF window,” says Siva.

“Alternatively, plan for a higher carbohydrate intake earlier in the day during the feeding window. For example: if you do a morning workout in a fasted state, break your fast with a post-workout meal consisting of carbohydrates and protein which will help replenish glycogen stores and aid in muscle recovery. Or you can plan a strength workout between lunch and dinner to ensure adequate fuel and optimal recovery.”

The Pros and Cons of Training Fasted


Studies have shown that working out in a fasted state can increase fat oxidation which can be useful for optimizing body composition. This also depends on the intensity of the workout. Fasted state workouts prevent indigestion, making life easier for people with existing GI conditions such as acid reflux.


You may experience muscle loss. Working out on an empty stomach depletes the body’s glycogen stores and it may need to break down protein for fuel which is not ideal. A fasted workout may reduce performance as fat oxidation requires a greater amount of oxygen to be used.

Working out in a fasted state increases the production of cortisol, which is detrimental to muscle mass.

A note about Type 2 Diabetes and Metabolic Syndrome

If you wake up with unstable blood glucose levels, this potentially prevents your ability to perform fasted exercise of any kind. People with type 2 diabetes/metabolic syndrome or those taking medication/insulin therapy for the same should talk with a physician before starting workouts in a fasted state. Fasted training could cause low blood glucose levels (hypoglycemia) and your overall health may be impacted.

Fasted state workouts alone may not reverse metabolic disorders. Optimizing the hormonal imbalances depends on cumulative factors such as nutrition and lifestyle along with fasting.

It is possible to go hypoglycemic during training in a fasted state?

It is important to be conscious of how you are feeling throughout your workout. Symptoms such as dizziness/ weakness/ and nausea could indicate low blood glucose levels. Wearing continuous glucose monitors, like the Ultrahuman Cyborg, can help avoid such situations.

Professional comments courtesy of Siva Subramanian (founder) and Alia Abreo (director) at Potential Health Development. Working on preventative healthcare and personalized intervention with cutting-edge diagnostics, Potential Health Development works alongside Ultrahuman, the world’s most advanced metabolic fitness platform.


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