Slayer's Den

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The Amino Acid for Abs​

It's known as a muscle-building amino, but it does a lot more than that. Here's what else you need to know.​

You know that leucine is the master amino acid for building muscle. Without enough leucine, the whole muscle protein synthesis thing doesn't happen. You know that because you're smart and you lift weights.

But everyone needs leucine, and not just to stretch their T-shirt sleeves. Leucine is literally essential – it's one of the nine essential BCAAs. Our bodies can't synthesize it (make it) and we all have to get it from foods or supplements.

So, what else does leucine do? More than you may realize. For example, it helps you lose fat and stay lean. Let's dive into that, and then figure out how much we need daily.


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1. Leucine Boosts Fat Oxidation​

We typically think of leucine as a "bodybuilding amino," and it is. But bodybuilders also prioritize it during fat-loss cycles because it preserves lean body mass.

But leucine isn't just muscle-sparing. It actively promotes fat loss by enhancing the expression of enzymes like CPT-1 involved in fat oxidation – the breakdown of fats for energy (we just call it "fat burning.") By increasing the activity of CPT-1 and other enzymes, leucine encourages our bodies to use stored fat for fuel.

Leucine also activates AMPK, a key regulator of energy balance and metabolism. AMPK increases fatty acid oxidation by promoting their uptake into the mitochondria, where they're burned for energy. This process too reduces fat stores, especially when you need more energy, like during training or times of calorie restriction.

2. Leucine Increases Calorie Burning​

Leucine increases overall energy expenditure in several ways, but primarily by increasing thermogenesis – the production of heat in the body. That translates to having a higher metabolic rate.

This is partly due to the stimulation of brown adipose tissue (BAT), the fat tissue that burns calories to produce heat. By promoting thermogenesis, leucine boosts calorie burning even when you're sitting on the couch.

3. Leucine Regulates Your Appetite​

Leucine modulates the hormones involved in appetite control. For example, leucine influences leptin secretion, and leptin tells your brain that you've had enough to eat.

4. Leucine Increases Insulin Sensitivity, Regulates Glucose​

To stay lean and healthy, you want to be sensitive to your body's production of insulin. Leucine positively affects insulin sensitivity in several ways, helping the body regulate blood sugar levels more efficiently.

For one thing, leucine enhances your muscles' ability to absorb glucose. Muscle is one of the largest consumers of glucose. Leucine's role in increasing glucose uptake by muscle cells helps lower blood sugar levels and reduces the burden on insulin to regulate glucose.

Leucine also activates the mTOR pathway, which, as you know, promotes protein synthesis. But it also plays a role in energy balance and "nutrient sensing." This activation helps regulate how cells respond to insulin, improving their ability to take up glucose efficiently, thereby enhancing insulin sensitivity.

5. Leucine Helps Prevent Fat Accumulation​

Leucine reduces fat cell formation by inhibiting certain pathways involved in fat storage, especially in the belly area.

In animal studies, leucine inhibits the formation of new fat cells by influencing the expression of genes involved in storing fat. Specifically, leucine suppresses SREBP-1, a transcription factor that promotes fat storage. By downregulating SREBP-1, leucine reduces the body's desire to accumulate fat.


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Cool. So How Much Leucine Do I Need?​

As always, there are recommendations for regular people and different recommendations for athletes and lifters:

• For the general population, the RDI is 18-20 mg per pound of body weight. So, a 150-pound normie needs 2,700-3,000 mg daily. That's 2.7 to 3 grams.
• For lifters and athletes, it's higher. Gym-goers have higher leucine needs due to increased muscle protein turnover and greater energy expenditure. For muscle growth and increased fat-loss benefits, the typical T Nation fan needs 45-50 mg per pound of body weight. So, a 150-pound lifter needs 6,750-7,500 mg. Rounded, let's call that 7 grams.

Here, we'll do some more math for you:

• 170-pound lifter: About 8 grams
• 190-pound lifter: About 9 grams
• 200-pound lifter: About 10 grams
• 220-pound lifter: About 11 grams

Generally, a lifter would want to get 2-5 grams of that around the workout period to maximize muscle growth and recovery, then spread the rest out. And if you're middle-aged or older, toss in an extra gram or two. Here's why.

Where Do I Get Leucine?​

From food and supplements. Chicken breast, turkey, beef, and pork contain roughly 2.5 to 3.5 grams of leucine per 100-gram serving. Cheese is an okay source. An egg contains less than a gram, as does a cup of milk. Almonds and pumpkin seeds are decent plant sources, but you'd have to eat a lot of them. You'd need to eat 73 almonds to get 1.5 grams of leucine.