Muscle Physiology of the Gluteus Medius (Top Sirloin)
Harvested from the sirloin butt between the short loin and round, the Top Sirloin (Gluteus medius) delivers one of the highest protein-to-calorie purity ratios in animal gastronomy—boasting over 75%–80% of calories from pure protein.
Because the Gluteus medius is a primary locomotion muscle, it develops dense concentrations of myoglobin, endogenous creatine (up to 5g per pound of fresh meat), bioavailable heme iron, and carnosine. For athletes and individuals aiming to build lean muscle while maintaining a strict caloric deficit, 100% grass-fed top sirloin provides elite-tier satiety and nutritional ROI.
01
Ultra-Pure Protein Purity
Delivering 26g–28g of protein per 4 oz raw serving with under 5g of fat, top sirloin rivals skinless chicken breast with superior micronutrients.
02
Endogenous Creatine Load
Top sirloin is naturally loaded with 4.5g–5.0g of creatine monohydrate per pound, saturating phosphocreatine stores for explosive lifting power.
03
Bioavailable Heme Iron & Zinc
Rich in divalent ferrous iron ($Fe^{2+}$) absorbed at 30%–40% efficiency to boost red blood cell count and maximum oxygen uptake ($VO_2$ max).
CARVING PRO-TIP
Slice Perpendicular to the Grain for Filet-Level Tenderness
Because Top Sirloin has parallel, tight muscle fibers, cooking past 135°F (Medium) causes actin contraction. Cook to a precise 125°F–128°F (Medium-Rare), rest 5 minutes, and carve thin slices across the grain at a 45° angle for tender, melt-in-your-mouth bites.
Top Sirloin vs Other Lean Animal Proteins (6 oz Cooked)
| Protein Cut (6 oz Cooked) | Calories | Protein (g) | Creatine (g) | Heme Iron (mg) |
|---|---|---|---|---|
| Grass-Fed Top Sirloin Steak | 320 kcal | 52.0 g | 1.8 g | 3.8 mg |
| Pasture-Raised Chicken Breast | 280 kcal | 53.0 g | 0.6 g | 1.1 mg |
| Wild Sockeye Salmon | 360 kcal | 46.0 g | 0.8 g | 0.9 mg |
| Grass-Fed Filet Mignon | 340 kcal | 48.0 g | 1.4 g | 3.2 mg |
Frequently Asked Questions: Sirloin Steak Nutrition
What is the difference between Top Sirloin and Sirloin Tip?
Top Sirloin is a tender, premium subprimal from the upper loin (Gluteus medius), ideal for grilling and pan searing. Sirloin Tip (Knuckle) comes from the round primal and is significantly leaner with tougher connective tissue, making it better suited for slow braising or marinating.
Why is Top Sirloin the best steak for bodybuilding and cutting?
Top Sirloin offers the most favorable protein-to-calorie ratio of any beef steak, providing ~52g of protein per 320 calories with high natural creatine and leucine to preserve lean mass during a caloric deficit.
High-Protein Performance Cut
Build Pure Lean Muscle with 100% Grass-Fed Top Sirloin
Fuel your workouts with ultra-clean, protein-dense Argentine and American pasture-raised Top Sirloin steaks. Packed with creatine, zinc, and bioavailable heme iron.
52g Protein per Cooked Portion
100% Regenerative Pasture Grazed
Direct-to-Door Delivery
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