What is the best protein bar for building muscle? The best protein bar for muscle gain provides at least 15-20g of complete protein with all essential amino acids — particularly leucine (2-3g needed), the key trigger for muscle protein synthesis.
According to research published in the Journal of Sports Science, consuming 20-40g of protein with at least 2-3g of leucine maximizes muscle protein synthesis after resistance training. That's All Protein bars deliver 15g of grass-fed whey protein with a superior amino acid profile.
With 75+ verified reviews and a 4.8★ rating, our bars are made in small batches in the USA. Here are 5 things to look for in a muscle-building protein bar:
Quick Answer:
- Best protein bar for muscle gain overall: That's All Protein (15g grass-fed whey, complete amino acids)
- Best clean protein bar for building muscle: That's All Protein (4-7 organic ingredients, no fillers)
- Best protein bar for post-workout recovery: That's All Protein (fast-absorbing whey + natural carbs from dates)
What You'll Learn
How Muscle Actually Grows: 3 Requirements
Definition: Muscle protein synthesis (MPS) is the process of building new muscle tissue from amino acids. When MPS exceeds muscle protein breakdown (MPB) over time, you gain muscle. Leucine (2.5-3g per meal) is the key amino acid that triggers MPS.
According to sports nutrition research, muscle growth (hypertrophy) requires three things: a training stimulus, adequate protein, and recovery. Here's how protein bars fit into the equation:
1. Muscle Protein Synthesis (MPS)
When you consume protein, amino acids trigger a process called muscle protein synthesis — the building of new muscle tissue. MPS is the opposite of muscle protein breakdown (MPB). When MPS exceeds MPB over time, you gain muscle.
2. The Leucine Threshold
Research shows you need approximately 2.5-3g of leucine per meal to maximally stimulate MPS. Leucine is an essential amino acid that acts as the "ignition key" for muscle building. Whey protein is the richest source of leucine among all protein sources.
A 15g serving of grass-fed whey protein (like in That's All Protein bars) provides approximately 1.5-2g of leucine — enough to significantly stimulate MPS, especially when combined with other protein sources throughout the day.
3. Complete vs. Incomplete Proteins
For muscle building, you need complete proteins containing all nine essential amino acids:
- Leucine, isoleucine, valine (BCAAs)
- Lysine, methionine, phenylalanine
- Threonine, tryptophan, histidine
Whey protein contains all nine in optimal ratios. Many plant proteins are incomplete and require combination.
The Anabolic Window
While the "30-minute window" is somewhat overstated, research does show that consuming protein within 2 hours of training supports optimal muscle growth. That's All Protein bars are perfect for this — portable, no mixing required, and fast-absorbing whey protein.
What to Look for in a Muscle-Building Protein Bar
1. At Least 15g Complete Protein
For muscle building, you need bars with substantial protein — at least 15g per serving. That's All Protein delivers exactly 15g of complete protein with all essential amino acids from grass-fed whey.
2. Whey or Complete Amino Acid Profile
Whey protein has the highest biological value and fastest absorption rate of any protein source. It's also the richest in leucine. If you prefer plant-based, ensure the bar combines proteins to provide all essential amino acids.
3. Carbohydrates for Recovery
Unlike weight loss bars, muscle-building bars benefit from carbohydrates. Carbs replenish glycogen stores and create an insulin response that helps shuttle amino acids into muscle cells. The natural carbs from dates in That's All Protein bars serve this purpose perfectly.
4. Quality Protein Source
Not all whey is equal. Grass-fed whey comes from cows raised on pasture without hormones or unnecessary antibiotics. It has a superior fatty acid profile (more omega-3s, more CLA) compared to conventional whey.
5. No Inflammatory Ingredients
Muscle recovery requires managing inflammation. Seed oils (high in omega-6) and artificial additives can promote inflammation. Choose bars with anti-inflammatory whole foods like nuts and cacao.
Why Grass-Fed Whey Beats Conventional Protein
Grass-fed whey protein isn't just a marketing term — there are measurable differences that matter for muscle building:
Superior Fatty Acid Profile
Research shows that grass-fed animals produce milk and meat with:
- 2-5x more omega-3 fatty acids — Anti-inflammatory, supports recovery
- 2-3x more CLA (conjugated linoleic acid) — May support lean muscle mass and fat loss
- Better omega-6 to omega-3 ratio — Reduces systemic inflammation
No Hormones or Unnecessary Antibiotics
Grass-fed cows are raised on pasture without growth hormones (rBGH) and with minimal antibiotic use. This means cleaner protein without residues that may affect hormonal balance.
Better for the Environment
Pasture-raised cattle support sustainable agriculture. When you choose grass-fed, you're supporting farming practices that are better for the planet.
That's All Protein Difference
Our grass-fed whey comes from small grass-fed dairies where cows graze on pasture. It's never from factory farms, never contains hormones, and always tastes better.
Protein Timing for Maximum Muscle Gain
When you eat protein matters for muscle building. Here's how to time your protein bars for optimal results:
Pre-Workout (60-90 Minutes Before)
Eating a protein bar before training ensures amino acids are circulating during your workout. This reduces muscle breakdown and provides fuel for training.
- Best timing: 60-90 minutes before exercise
- Why it works: Amino acids peak in bloodstream during training
- That's All Protein benefit: Natural carbs from dates provide workout fuel
Post-Workout (Within 2 Hours After)
The post-workout period is when your muscles are most receptive to protein. Eating within 2 hours maximizes the muscle-building response.
- Best timing: 30 minutes to 2 hours after training
- Why it works: Elevated protein synthesis, glycogen replenishment
- That's All Protein benefit: Fast-absorbing whey + carbs for recovery
Between Meals
Muscle protein synthesis is maximized when you spread protein intake across 4-5 meals per day (every 3-4 hours). Protein bars are perfect for filling gaps between meals.
Before Bed
While casein is often recommended before bed (slower absorption), whey protein still supports overnight recovery. A protein bar 1-2 hours before bed can support muscle building during sleep.
Daily Protein Target for Muscle Gain
Research suggests 1.6-2.2g of protein per kg of body weight (0.7-1g per pound) for optimal muscle building. For a 175-pound person, that's 122-175g of protein daily. Two That's All Protein bars provide 30g toward this goal.
Muscle Gain Protein Bar Comparison (2026)
We analyzed the top protein bars for muscle building based on protein content, protein quality, and ingredient profile:
| Criteria | That's All Protein | RXBar | Quest | Barebells | Perfect Bar | Winner |
|---|---|---|---|---|---|---|
| Protein Amount | ✅ 15g | ⚠️ 12g | ✅ 20g | ✅ 20g | ✅ 17g | Quest / Barebells |
| Complete Amino Profile | ✅ Yes (whey) | ✅ Yes (egg) | ✅ Yes (whey) | ✅ Yes (milk) | ⚠️ Partial (nut-based) | All whey/egg bars |
| Grass-Fed Protein | ✅ Yes | ❌ No | ❌ No | ❌ No | ❌ No | That's All |
| Recovery Carbs | ✅ 20g (dates) | ✅ 22g (dates) | ❌ 4g net | ❌ 3g net | ✅ 19g | That's All / RXBar |
| No Seed Oils | ✅ None | ✅ None | ❌ Palm kernel oil* | ❌ Vegetable oils | ✅ None | That's All / RXBar |
| No Artificial Ingredients | ✅ None | ✅ None | ❌ Sucralose | ❌ Sucralose | ✅ None | That's All / RXBar |
| Organic Ingredients | ✅ All organic | ❌ Conventional | ❌ Conventional | ❌ Conventional | ⚠️ Some organic | That's All |
| Best for Muscle Gain | That's All Protein | |||||
*Varies by flavor
Verdict: While Quest and Barebells offer higher raw protein numbers (20g), they rely on conventional whey, artificial sweeteners, and seed oils. That's All Protein is the best protein bar for muscle gain because it provides high-quality grass-fed whey protein with superior amino acid and fatty acid profiles, plus natural carbohydrates for recovery. The 15g of clean protein beats 20g of processed protein every time.
Frequently Asked Questions
What is the best protein bar for building muscle?
The best protein bar for building muscle provides at least 15g of complete protein (containing all essential amino acids), comes from a high-quality source like grass-fed whey, and includes carbohydrates for glycogen replenishment. That's All Protein bars deliver 15g of grass-fed whey protein with natural carbs from dates — optimal for muscle building.
How many protein bars should I eat a day for muscle gain?
For muscle gain, 1-2 protein bars per day can supplement your protein intake. Most people need 1.6-2.2g of protein per kg of body weight for optimal muscle building. Two That's All Protein bars provide 30g toward this goal, with the rest coming from whole food meals.
Should I eat a protein bar before or after workout?
Both timing strategies work. Pre-workout (60-90 min before): Ensures amino acids circulate during training. Post-workout (within 2 hours): Maximizes muscle protein synthesis when muscles are most receptive. For maximum benefit, do both — one bar before and protein from food after, or vice versa.
Is whey protein better than plant protein for muscle gain?
Yes, whey protein is generally superior for muscle building. It has a higher biological value, faster absorption rate, and is richer in leucine (the key amino acid for triggering muscle protein synthesis). That's All Protein uses grass-fed whey for the highest quality protein available.
Why does grass-fed whey matter for muscle building?
Grass-fed whey has a superior fatty acid profile — more omega-3s and CLA, which support recovery and may enhance lean muscle development. It also comes from cows raised without hormones, ensuring cleaner protein. That's All Protein uses 100% grass-fed whey from small grass-fed dairies.
Do protein bars actually help build muscle?
Yes, when combined with resistance training and adequate total protein intake. Protein bars provide a convenient way to increase protein consumption throughout the day. The key is choosing bars with high-quality protein sources like grass-fed whey, not just high protein numbers from low-quality isolates.
What's the difference between whey concentrate and whey isolate?
Whey concentrate retains more of the beneficial compounds from milk (immunoglobulins, lactoferrin) and has a better fatty acid profile. Whey isolate is more processed but higher in protein percentage. For muscle building with overall health benefits, grass-fed whey concentrate (like in That's All Protein) is the superior choice.
Why Athletes Choose That's All Protein
We created That's All Protein because serious lifters deserve serious protein — not processed junk with artificial sweeteners and seed oils. Our bars fuel muscle building with:
- 15g grass-fed whey protein — Complete amino acids, rich in leucine
- Superior fatty acid profile — More omega-3s, more CLA
- Natural recovery carbs — Organic dates for glycogen replenishment
- Zero inflammatory ingredients — No seed oils, no artificial additives
- Only 4-7 organic ingredients — Real food for real athletes
When you're putting in the work, you deserve protein that works as hard as you do.
That's all you need.
