Many fitness enthusiasts and trainers advocate for exercising on an empty stomach, referring to this practice as “fasted cardio.” This topic has sparked considerable debate within the health and wellness community. While some individuals praise fasted cardio as an efficient method to expedite fat loss, others argue it may be ineffective or even counterproductive.

Fasted cardio does not strictly require adherence to intermittent fasting. Many individuals simply exercise in the morning before consuming breakfast. We consulted several health experts to explore the benefits and drawbacks of fasted cardio.

Engaging in cardio exercises without pre-workout fuel is a popular strategy among those aiming for weight loss. The central notion is that exercising in a fasted state encourages the body to tap into stored fat for energy. According to Emmie Satrazemis, RD, CSSD, a certified sports nutritionist, “Without the calories from a recent meal, your body resorts to its stored fuel, which includes glycogen and fat.”

Research indicates that exercising after fasting for 8 to 12 hours, such as overnight, may facilitate up to a 20% increase in fat-burning efficacy. However, it’s worth noting that some studies have found negligible differences in overall fat loss, underscoring the need for a balanced approach to fitness.

While fasted cardio might assist with fat loss, it’s important to distinguish between building and preserving muscle mass. As Satrazemis explains, “Adequate protein intake alongside strength training can help protect muscle even if you’re in a calorie deficit.” However, prolonged fasting before intense workouts can drain muscle energy reserves.

To recover from workouts and maintain muscle integrity, a post-exercise meal is essential. This helps replenish energy stores and repair any muscle fatigue incurred during exercise.

A compelling reason to try fasted cardio is simply how it makes you feel. Some individuals thrive on the energy provided by working out on an empty stomach, while others may find their performance dips without pre-workout nutrition. Satrazemis notes, “Ultimately, the choice to engage in fasted cardio should reflect your personal preferences and how your body responds.”

For activities that require high levels of intensity or power, proper nutrition before workouts is crucial. David Chesworth, an ACSM-certified personal trainer, shares that “Glucose serves as the fastest fuel source for explosive energy needs. Exercising while fasted may not provide your body with the necessary resources to perform optimally for such tasks.”

If meals, especially high-fat or high-fiber options, tend to cause gastrointestinal distress during exercise, fasted cardio might be beneficial. Satrazemis points out that “If you haven't had enough time to digest a meal, opting for a cardio session in a fasted state could prevent nausea and discomfort.”

Engaging in fasted cardio is best reserved for those in good health. Conditions resulting in low blood sugar or blood pressure may increase risks during unfed exercise. It’s essential to consult with a healthcare professional if you have underlying health concerns before participating in fasted cardio.