Ask Dave: Is Fasted Cardio the Key to Greater Fat Loss?

Fasted cardio has been hailed as a fat-burning secret, with many believing that exercising on an empty stomach can lead to greater fat loss. But is there any real science behind this claim? In this article, we’ll dive into a key study that examined the effects of fasted versus fed cardio on fat loss and body composition. We’ll explore whether the timing of your meals in relation to your workouts really makes a difference or if the focus should simply be on maintaining consistency and a calorie deficit for effective fat loss.

Question: I’ve been hearing for years that fasted cardio is supposed to help burn more fat. Is there any solid science behind this idea, or is it just another fitness myth?

Answer: The idea that fasted cardio might lead to greater fat loss has been circulating in the fitness world for decades. The theory suggests that by doing cardio on an empty stomach, typically after an overnight fast, your body is more likely to burn fat for energy since glycogen stores are lower. But what does the science actually say?

A significant study aimed at answering this question was conducted by Brad Schoenfeld and published in the Journal of the International Society of Sports Nutrition in 2014. The study’s primary goal was to determine whether performing aerobic exercise in a fasted state would lead to greater fat loss compared to doing the same exercise after eating.

In this study, 20 healthy young women were randomly assigned to one of two groups: the fasted training group (FASTED), which performed cardio after an overnight fast, and the post-prandial training group (FED), which did cardio after consuming a meal. Both groups followed the same volume of steady-state aerobic exercise—one hour, three days a week for four weeks—and adhered to a calorie-restricted diet designed to create a calorie deficit.

The results showed that both groups experienced significant weight loss and reductions in fat mass. However, no significant differences were found between the fasted and fed groups in any of the outcome measures, including body mass, BMI, percent body fat, waist circumference, fat mass, and fat-free mass. In other words, whether the participants trained fasted or fed had no significant impact on their fat loss or changes in body composition when combined with a hypocaloric diet.

The study concluded that individuals looking to lose body fat can choose to train either before or after eating based on personal preference. There was no significant advantage found for fasted exercise over fed exercise in this context. The researchers suggest that further studies with longer durations and larger sample sizes are needed to explore whether there might be subtle differences that this study didn’t capture.

In summary, while fasted cardio can certainly help with fat loss, it’s not necessarily better than doing cardio after a meal. The key takeaway is that consistency and maintaining a calorie deficit are far more critical factors in achieving fat loss, so feel free to train according to what feels best for you.

References:

Schoenfeld, B. J., Aragon, A. A., Wilborn, C. D., & Krieger, J. W. (2014). Body composition changes associated with fasted versus non-fasted aerobic exercise in young women. Journal of the International Society of Sports Nutrition, 11(1), 54.

Hackett, D., & Hagstrom, A. D. (2017). The effect of overnight-fasted versus fed exercise on weight loss and body composition: A systematic review and meta-analysis. Journal of Functional Morphology and Kinesiology, 2(4), 43.