Leucine: Cutting Weight with the Alpha of the Aminos

STACK Expert Dalton Oliver explains the importance of the amino acid leucine in helping athletes build and maintain muscle mass and cut weight.


Cutting weight before an athletic event is not easy. Cut too much of the wrong nutrient, and you may not only hinder your performance but also set yourself back a solid week of training—derailing an otherwise effective training program.

Although the topic is more complex than a single nutrient (or amino acid in this case), the amino acid leucine plays an important role in helping you maintain muscle mass when you're in a caloric deficit.

Leucine: The Alpha of the Aminos

Leucine is the amino acid most important for stimulating muscle protein synthesis (MPS) and attenuating muscle protein breakdown (MPB). Think of it as the key you need to turn the ignition on muscle-building processes. All essential amino acids (EAAs) are necessary for optimal protein synthesis, but this particular one plays the predominant role in signaling the process to occur. Its effects are so strong that athletes may be able to get the same anabolic (and more important, anti-catabolic) effect with fewer total calories by choosing protein sources rich in leucine.

I've included a chart below of common foods that contain high amounts of leucine, as well as the amount it would take to hit saturation (the point at which MPS is maximized). It's important to note that adding leucine to these complete sources of protein is redundant and has no added effect once you hit the saturation point of approximately 3 grams.

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Leucine Saturation Table

This table is made available to offer perspective. Below are a few common foods and the serving size you can use to maximize protein synthesis.

Food Serving Size Needed for Saturation Leucine Amount Total Protein
Cow's Milk (Skim) 4 cups 3.2g 32g
Lean Ground Beef 7 oz 3.2g 42g
Chicken Breast 7 oz 3.3g 42g
Eggs (Large/Whole) 6 3.24g 37.8g
Egg Whites 10 3g 36g
Tuna 8 oz 3.3g 44g

Notable Supplements and Respective Saturation Points:

  • Whey Protein (20-30g)
  • Casein Protein (20-30g)
  • BCAA Powder (5-8g)
  • HMB (3g)

Supplementing with leucine or branched-chain amino acids may not be as productive when you are already consuming high amounts of protein. When you cut calories, however, the nutrient profile of your food choices becomes more important—making foods rich in leucine and high in all EAAs more significant for maintaining muscle mass. If you consume so few calories that you cannot meet the recommended amount per sitting, a BCAA or HMB (a metabolite of leucine) supplement may be a great way to hit saturation without consuming excess calories.

The bulk of research still considers timing and amount important, pointing to every three hours as the optimal time for hitting the leucine saturation point. This may be just as important during times you are already consuming a hypercaloric diet and meeting protein recommendations, but when your diet borders on deficient, such as during cutting phases, protecting that hard-earned muscle becomes paramount over the course of a season.

Practical Implications

  1. Consume a high-protein meal rich in essential amino acids that hits the leucine saturation point (3 grams).
  2. Hit saturation at three-hour intervals throughout the day and at each meal. You can use BCAAs or HMB to keep calories low.
  3. Consider BCAAs or HMB before or during endurance activities (common to cutting phases) to minimize muscle protein breakdown.
  4. When designing meals to maximize protein synthesis, use the handy table above and mix and match according to your needs.

The world of sports nutrition is incredibly complex. Even with a master's degree in applied physiology and certification as a sports nutritionist, I still regularly refer athletes to registered dietitians–especially during times of nutrient deficiency.

If you are on any medications or have a medical condition, you should consult your dietitian or physician before drastically altering your diet. No studies were found linking leucine, even in concentrated amounts, to negative side effects, but this does not mean it is always safe for everyone.

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