Written by Steve Blechman
19 December 2019

 

 

 

MD RANTS

By Steve Blechman

 

WTF? FASTED CARDIO, OR NO FASTED CARDIO FOR MAXIMUM FAT LOSS?

 

It has been reported in the scientific literature in the past that aerobic exercise after an overnight fast accelerates the loss of body fat. Research has shown that low glycogen and insulin levels from an overnight fast cause your body to shift fuel away from carbs therefore, allowing greater mobilization of stored fat burned for energy. This strategy is basically to help you become more of a more fat-burning machine.

           

An article recently published in the The New York Times on December 3, 2019 reported that, “cyclists who peddled on an empty stomach burned twice as much fat.” This new study that was reported in the Times’ article was recently published in the Journal of Clinical Endocrinology and Metabolism. The study found that exercising on an empty stomach before breakfast can lower muscle fat!

           

The study reported that the aim of the researchers was “to assess acute and chronic effects of exercise performed before versus after nutrient ingestion on whole-body and intramuscular lipid utilization, and postprandial glucose metabolism.”

           

In a six-week randomized crossover designed controlled trial, researchers at the University of Bath in England recruited 30 overweight, sedentary men. The researchers divided the men into three groups, one as a control and the other two groups riding a stationary bike, three times a week at a moderate pace tracking heart rates as well as the amount of fat that the subjects burn. The researchers noted, “One exercise group also downed a vanilla-flavored shake two hours before their ride (with no other breakfast) while the other group swallowed a similar-tasting placebo drink, containing water, flavoring and no calories. In other words, the placebo group rode on an empty stomach, but did not know it.

           

“The riders who had pedaled on an empty stomach, however, had incinerated about twice as much fat during each ride as the men who consumed the shake first. The riders all had burned about the same number of calories while pedaling, but more of those calories came from fat when the men did not eat first.”

           

According to Javier Gonzalez, lead researcher of the new study, “The reasons for this extra metabolic boost are complex but most likely involve slimming of muscle fat. The fasted riders’ bodies had to turn to internal energy stores for fuel, including fat from their muscles. (Interestingly, the fasted riders did not feel as if their workouts were more draining than the other group, according to everyone’s subjective ratings of their exertions.)”

           

The results of this new study in the Journal of Clinical Endocrinology and Metabolism further confirm the benefits of fasting cardio before breakfast for maximum fat loss! When you eat a meal or carbohydrate before a workout, you increase levels of insulin, which enhances fat storage and inhibition of fat mobilization, oxidation and fat burning. You don’t want to release insulin before cardio if you want to burn more fat. By fasting on an empty stomach before cardio, your body can shift fuels from burning glucose to burning fat.

           

Many bodybuilders today fear that if they don’t eat or take a protein shake before a workout, they will lose muscle. Nothing could be further from the truth. The research shows that fasted cardio before breakfast will not result in loss of muscle tissue to a greater extent than cardio in the fed state.

           

There are only a few studies that looked at the long-term effects of fasted cardio on body composition. The British Journal of Nutrition compared a morning run and eating an early breakfast or while in a fasted state. Not having breakfast resulted in 20 percent more fat being burned! Another research paper found that cardio-fed or fasted, it doesn’t make a difference on the amount of fat you lose (J Int Soc Sports Nutr 2014)

 

So, WTF? What research should we believe?

           

Bottom line: the latest research shows that for someone with stubborn body fat and who is lean and wants to get ripped, fasted cardio before breakfast can enhance abdominal fat and intramuscular fat burning!

 

 

 

 

 

 

 

References

1. Schoenfeld BJ, Aragon AA et al. Body composition changes associated with fasted versus non-fasted aerobic exercise. J Int Soc SportsNutr 2014;11(1):54. Published 2014 Nov 18. doi:10.1186/s12970-014-0054-7

           

2. Edinburgh RM, Bradley HE et al. Lipid metabolism links nutrient-exercise timing to insulin sensitivity in men classified as overweight or obese. The Journal of Clinical Endocrinology & Metabolism, October 19, 2019. dgz104, https://doi.org/10.1210/clinem/dgz104

 

3. Skip Breakfast Before the Gym by Gretchen Reynolds. NY Times. December 3, 2019. 

           

4. Gillen JB, Percival ME et al. Interval training in the fed or fasted state improves body composition and muscle oxidative capacity in overweight women. Obesity (Silver Spring) 2013;21(11):2249-2255. doi: 10.1002/oby.20379

 

5. Horowitz JF, Mora-Rodriguez R et al. Lipolytic suppression following carbohydrate ingestion limits fat oxidation during exercise. Am J Physiol 1997;273(4 Pt 1):E768-E775.

           

6. Paoli A, Marcolin G et al. Exercising fasting or fed to enhance fat loss? Influence of food intake on respiratory ratio and excess post-exercise oxygen consumption after a bout of endurance training. Int J Sport Nutr Exerc Metab 2011;21(1):48-54.

 

 

 

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