If you’ve ever hopped out of bed and straightaway headed to the treadmill with your cup of coffee in hand, then you’ve inadvertently dabbled in fasted cardio. Working out on an empty stomach is not always deliberate. However, fitness experts suggest trying it, especially if you have endurance goals or aim for body recomposition.
What Does Fasted Cardio Involve?
The nature of the exercise and the time passed since your last meal play a crucial role here. To classify as fasted cardio, the workout should involve rhythmic, single movement activities like cycling, running, or rowing, as stated by certified strength and conditioning coach and personal trainer Josh Schlottman.
So, how long do you need to abstain from food? According to John Gardner, a NASM-certified trainer and the CEO of the fitness platform Kickoff, it depends on the time taken for your stomach to empty and for your digestive system to go into “off” mode. “Your body might enter a fasted state within four to six hours, based on your digestive system’s pace or your last meal,” he explains. Nevertheless, the most effective results typically come from exercising after a 12-hour fast, most frequently on an empty stomach in the morning.
For those who can’t start their day without caffeine, there’s no need to worry. Schlottman suggests that drinking coffee (without creamers or sugar) before the workout and staying hydrated is permissible before a fasted cardio session. In fact, it might be advantageous, as many people struggle with low energy levels during fasted cardio. “A bit of caffeine can provide the energy boost you require to power through your workout,” he mentions.
Firstly: Is Engaging in Fasted Cardio Safe?
If you are in good health, trying fasted cardio should pose no issues. However, if you have any pre-existing medical conditions, Gardner advises consulting a healthcare professional. “Fasted cardio can be highly unsafe for individuals with medical conditions that are affected by low blood sugar,” he warns. Additionally, if you feel lightheaded or dizzy when exercising on an empty stomach, it’s best to avoid it,” he adds.
It Might Help in Achieving Your Body Recomposition Objectives
If your goal is to reduce your body fat percentage, fasted cardio could be advantageous. When you work out after fasting, your body utilizes the calories from your last meal to power your workout, Schlottman explains. “In a fasted state, your body lacks the quick carbohydrates or other calories for immediate fuel,” he elaborates. Consequently, it turns to glycogen, the long-term storage form of carbohydrates in muscles and the liver. Once your glycogen reserves are depleted, your body resorts to burning fat for energy, resulting in increased fat burning. A study in the British Journal of Nutrition revealed that individuals who performed fasted treadmill running burned 20% more fat than those who ate beforehand.
It Might Enhance Your Endurance
Engaging in fasted cardio could also boost your endurance capabilities. This is attributed to training your body to depend less on quick-burning carbohydrates and sugars for energy and more on fat as the primary energy source, Schlottman clarifies. Fats are more abundant in the body compared to glycogen reserves, which helps endurance athletes avoid depletion or “bonking.” A study published in the Journal of Applied Physiology demonstrated that individuals who exercised while fasted exhibited greater endurance improvements than those who exercised after eating.
Keep in Mind…
It’s essential to note that utilizing fat for energy is a less efficient process, making the same intensity workout feel more challenging, as shared by sports dietitian Natalie Rizzo, RD, on Well+Good. Not everyone can comfortably exercise on an empty stomach, and if it deters you from working out altogether, it’s better to have a light snack before exercising.
Rizzo also cautions about individual responses to fasted cardio, highlighting that regularly engaging in such workouts may lead to nutrient deficiencies, mood swings, and weakened immunity over time. Listen to your body and adapt your approach if you notice any negative effects from fasted cardio sessions.
Remember to consume an ample amount of carbohydrates and a well-rounded meal after your workout to replenish your energy levels and provide the necessary fuel for the body,” Gardner recommends. Neglecting to refuel post fasted cardio may impede proper recovery and hinder the potential gains you could have achieved otherwise.
