TLDR

• The best way to build muscle and lose fat at the same time is by strength training, and eating a ton of protein (while not increasing carbs and fat)
• You have to lift weights to stimulate muscle growth (obvious)
• Protein is necessary for muscle growth (obvious)
• Protein is not easily stored as fat (really cool. this article explains how/why
• I'd aim for at least 1g of protein per lb per day while not increasing carbs and fat if you want to recomp (grow muscle and lose fat)

Ray's Take

Everyone wants to build muscle and lose fat at the same time.

"I’m pretty close to maintenance weight, but want a good amount more muscle."

This is the dream. Staying the same weight, but adding muscle.

For this to happen, you need to add muscle weight, and lose fat weight. This is called recomp, and its not easy.

Why is it not easy?
Your body is typically in an anabolic state (building) or catabolic (breaking down). This shifts back and forth all the time. However, when your body is building, its usually building muscle AND fat, both. This is why you hear lots of people saying that they are "bulking" and will "lean down" after.
- NOTE - this almost never works unless you really know what you're doing. Would not recommend for normal people like you.

So is it possible?
I think the answer is yes. And the solution is pretty simple:
- Lift heavy (required to activate muscle building)
- Eat a lot of protein (way more than you think)
- Don't eat extra carbs and fat (too much here will turn into fat).

We've talked about how/why strength training grows muscle so wont' repeat details here. TLDR you need to lift weights to activate metabolic processes and hormones to grow.

Lets talk about protein.

What happens after you eat that bite of chicken breast?

Well first, its broken down into amino acids (full process in sections below), but the main takeaway is that unlike carbs and fat, protein itself cannot be stored as energy. It is also very difficult to turn protein into fat.

So what happens to amino acids?
- oxidized and used immediately to create energy (ATP)
- turned into enzymes, hormones, antibodies, DNA
- TURNED INTO MUSCLE
**Sure, protein can be converted into ATP or glucose through less preferred, energy-intensive processes, but that's not what the body prefers bc carbs and fat are better for that. It's very difficult for protein to be converted to fat (see below nerd sections for details).

Therefore, a simple answer to building muscle while not gaining weight is lifting heavy and eating a ton of protein. You have to keep carbs and fat low though, bc these will turn into fat.

High protein, lower carbs/ fats is your best shot. You're maximizing muscle-building potential while keeping fat storage low.

How much protein should you eat?
For those on a strength program, aim for 1g of protein per lb per day to fuel muscle growth (and preserve lean muscle)

Not lifting?
Well you won't really gain muscle without lifting, but 0.75g per lb can still help you lose fat while preserving as much muscle as possible. (You should be on a strength program).

How much is too much

Worried about too much protein?
If you are healthy and don't have a kidney issue, don't be. This comprehensive review concluded that:
While protein restriction may be appropriate for treatment of existing kidney disease, we find no significant evidence for a detrimental effect of high protein intakes on kidney function in healthy persons after centuries of a high protein Western diet.

The review outlines that there has not been a study where too much protein resulted in kidney damage, in healthy adults.

They also looked at animal studies in which rats and dogs were given diets up to 60% protein. No kidney damage was found.

For context:
- I'm 150 lbs
- I eat 2400 calories a day
- 60% of 2400 is 1440 calories
- (1440 calories) / (4 calories per gram of protein) = 360g protein
- 360g / 150 lbs = 2.4g protein per day

Thus eating 1g-1.5g protein per lb should be totally safe.

Stupid Ideas

More protein equals more fat storage
Wrong. Protein is the least likely macronutrient to be stored as fat due to its complex metabolic pathways. It's primarily used for growth and repair, not for filling up your fat cells.

Eating protein alone is enough for muscle growth
Not quite. Without sufficient exercise, especially resistance training, even high protein intake won't magically translate into muscle. The stimulus must come first; protein is there to support the response.

All proteins are created equal
Nope. The quality of protein, particularly its amino acid profile, matters immensely. Complete proteins, like those from animal sources, provide all 9 essential amino acids in one go, unlike many plant proteins. Essential amino acids are critical bc our body can't make them, and they are necessary for key metabolic processes.

Cool Knowledge for Normal People

Ever wondered how a piece of chicken turns into muscle? Once ingested, protein is broken down into amino acids, which are then absorbed and transported to muscle tissues. Here, under the right conditions (think resistance training), these amino acids get to work, repairing microtears and building up the muscle stronger than before.

Amino acids can also be "turned into energy" (ATP) through the Krebs cycle. Interestingly, we don't really want this bc we'd rather use amino acids for muscle growth, but it happens.

Here are some more details for how protein actually turns into muscle.

Digestion

• Stomach: Proteins begin their journey in the stomach, where hydrochloric acid denatures protein structures, making them more accessible to enzymes. Pepsin, a digestive enzyme, then breaks these proteins down into shorter polypeptides.
• Small Intestine: As these polypeptides enter the small intestine, pancreatic enzymes like trypsin and chymotrypsin further cleave them into even smaller peptides and individual amino acids.

Absorption

• Enterocytes: In the small intestine's lining, specialized cells called enterocytes absorb amino acids and small peptides through active transport and facilitated diffusion.
• Bloodstream: Once inside the enterocytes, amino acids are released into the bloodstream, where they travel to the liver via the hepatic portal vein, a direct line to this central metabolic organ.

Muscle Protein Synthesis

• Activation: Amino acids in the bloodstream signal muscle cells to initiate protein synthesis, a process regulated by the mTOR pathway, a key player in cell growth and protein formation.
• Translation: Inside muscle cells, ribosomes read the genetic code (mRNA) that specifies the amino acid sequence of the new protein. Transfer RNA (tRNA) brings the corresponding amino acids to the ribosome, where they are linked together in a growing polypeptide chain, folding into a functional protein.

More Nerd Knowledge: Oxidation, gluconeogenesis and de novo lipogenesis

When you eat protein, all of it doesn't just turn into muscle. It can also be oxidized (used immediately to turn into ATP (energy), undergo gluconeogenesis (turned into glucose), or de novo lipogenesis (turned into fat. This is hard and rare, which is a great thing).

Oxidation

The oxidation of amino acids is a crucial metabolic process where proteins, once broken down into their constituent amino acids, can be utilized for energy production. This pathway becomes particularly significant when carbohydrates are scarce or during periods of increased energy demand, such as intense physical activity or fasting.

Although not the body's first choice for energy (using carbohydrates and fats is more efficient and direct pathway to ATP production), amino acids can undergo deamination, removing their nitrogen-containing groups, which then allows the remaining carbon skeletons to enter the citric acid cycle where ATP is produced.

Gluconeogenesis

Gluconeogenesis is a metabolic pathway that shows the body's adaptability to various dietary conditions, ensuring glucose availability during carbohydrate scarcity. This process turns amino acids (and other substrates) into glucose, and is especially critical during fasting, low-carbohydrate diets, or intense exercise.

Gluconeogenesis primarily occurs in the liver, but the kidneys also contribute, especially during prolonged fasting or more severe carbohydrate restriction.

Process
- Amino Acid Conversion: Amino acids derived from dietary protein or muscle protein breakdown are transported to the liver. Here, enzymes remove their amino groups in a process called transamination or deamination, converting them into ketoacids.
- Gluconeogenic Substrates: These ketoacids are then transformed into gluconeogenic intermediates like pyruvate, oxaloacetate, and dihydroxyacetone phosphate. Through a series of enzymatically catalyzed reactions, these intermediates are eventually converted into glucose.
- Energy Cost: Gluconeogenesis is an energetically demanding process, requiring ATP. This underscores the body's commitment to maintaining glucose levels, essential for brain function, red blood cells, and other glucose-dependent tissues.

Glucagon and cortisol are key hormones that stimulate gluconeogenesis, especially during fasting or stress. In contrast, insulin inhibits this pathway, reflecting its role in lowering blood glucose levels post-meal.

De novo lipogenesis (Protein -> Fat?)

While it's technically possible for protein to be converted into fat, this process is indirect and energy-intensive, making it a less preferred metabolic pathway. Proteins are primarily used for growth, repair, and maintenance of body tissues, and only under conditions of significant caloric excess might they contribute, albeit inefficiently, to fat storage.

In contrast, carbohydrates and fats are much more readily converted into fat through de novo lipogenesis (DNL), a metabolic process where excess dietary carbohydrates are transformed into fatty acids and stored as fat, primarily in the liver and adipose tissue. DNL is a key mechanism for energy storage, efficiently managing surplus calories from carbs and fats by converting them into a form that can be stored for future energy needs.

Protein's role in our bodies is nothing short of miraculous. From providing the essential building blocks of life to ensuring we have energy in times of need, it's a critical component of a healthy diet and an active lifestyle. So next time you enjoy your favorite protein-rich meal, take a moment to appreciate the complex, wonderfully efficient process that begins with that first bite.