Does fasted exercise burn more fat or build more muscle?

Does fasted exercise burn more fat or build more muscle?

Chris Trejbal

Fasted training (well, fasted everything) became very popular over the last decade, especially in the exercise world. Claims like:

  • "Fasting increases HGH by 1250%!

  • "Lifting fasted triggers a greater release of HGH [Human Growth Hormone], which is a hormone that builds muscle and burns fat. Training in the morning, fasted helps optimize the lean body you're building" (Photo 2)

  • "Fasting burns more body fat"

Whether you prefer exercising fasted or having a meal first, it doesn't appear to make a difference in your body composition. AKA, fasting is not a magic pill for gains.

HGH is Human Growth Hormone. Its function is to help kids grow and promote proper metabolism in adults. HGH is involved in the growth of almost every tissue in the body, including skeletal muscle.

Fasting has been touted to increase HGH, thus increase muscle mass. But the evidence doesn't stack up. In one randomized controlled trial, two groups exercised and either took a placebo or a type of Growth Hormone. No difference between the two groups in muscle circumference and strength.

Next, one large study looking at the current available data on fasting vs fed training saw better performance in people who ate before their aerobic exercise (cardio). No surprise here...we eat food for energy!

Brad Schoenfeld, Ph.D., one of the leading experts in studying sport and sports nutrition, performed an excellent study comparing 20 healthy women and separated them into two groups.

  • The first 10 women trained after an overnight fast.

  • The second 10 women trained after a meal.

The two groups ate under their calories to help lose weight. Calories and protein were pretty even between groups. The conclusion? Both groups lost weight, but there was NO extra weight loss in the fasted group. Meaning, it seems that "fasted training burns more fat" is just a myth.

So, fasted training doesn't seem to make a difference in fat loss. It doesn't do anything extra for your workout either. Do what works best for you and your schedule!

References

https://pubmed.ncbi.nlm.nih.gov/29315892/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4242477/

https://journals.physiology.org/doi/pdf/10.1152/ajpendo.1992.262.3.E261

Air fried chicken bites (they're pretty awesome)

Air fried chicken bites (they're pretty awesome)
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