Branched-Chain Amino Acids: What are BCAAs and Do They Grow and Repair Muscle?

Branched-chain amino acids (BCAAs) have been a staple supplement of bodybuilders and athletes since the 1980s. BCAAs contain the three musketeers of muscle-building amino acids: leucine, isoleucine, and valine. Amino acids are the building blocks of proteins, and these three help your muscles repair faster and encourage recovery after a tough workout. Plenty of people swear by BCAAs — but are they really necessary?

In some cases, no. Odds are a lot of folks aren’t getting much benefit from BCAAs. But if you use them properly, BCAAs can be your best friend when it comes to gaining muscle and recovering like a pro. They’re especially good in conjunction with fasting — either intermittent fasting or protein fasting — and can be a great supplement for anti-inflammatory low-protein diets.

Let’s take a look at how you can use BCAAs to build more muscle and recover faster, as well as when you can skip the BCAAs.

The benefits of BCAAs

BCAAs contain leucine, isoleucine, and valine, the three main amino acids that your body uses to repair muscle. After a tough workout, your muscles are torn up and in need of repair. They build back stronger and you put on muscle — as long as you have plenty of those three special amino acids.

There’s good evidence that BCAAs increase protein synthesis (muscle building) and speed up recovery after a workout[1][2]. However, if you’re eating complete protein (meat, fish, whey, etc.) before or after a workout, you’ll already get plenty of BCAAs. In that case, taking more in supplemental form is probably unnecessary, unless you’re running a marathon or doing a crazy two-hour CrossFit workout.

So if you have a good pre- or post-workout meal with a complete protein, BCAAs aren’t particularly helpful. Everything your muscles need is already in that grass-fed steak or wild-caught salmon.

BCAAs and intermittent fasting

BCAAs and intermittent fasting are a match made in heaven, especially if you work out in a fasted state.

Fasted workouts are great for you. Working out during a fast can burn up to 20 percent more fat (yes, you read that right)[3][4], and fasting can help you build more muscle, too (here’s a breakdown of why).

The risk with fasting is that if you do an intense workout and then don’t eat, your muscles won’t have the right amino acids to rebuild. This is where BCAAs are great. Take 5 grams of BCAAs right after your workout — they won’t break your fast, and they’ll give your muscles the exact building blocks they need for repair. You get the best of both fasted and fed workouts.