Not all protein sources are created equal. Differences in amino acid profile, digestibility, leucine content, and calorie density mean that some protein foods are significantly more effective for muscle building and fat loss than others. This guide ranks the best sources for both goals.
What Makes a Protein Source High Quality?
Protein quality is determined by two factors:
- Complete amino acid profile: Contains all 9 essential amino acids in adequate proportions — particularly leucine, which is the primary trigger for muscle protein synthesis
- Digestibility (DIAAS score): How much of the protein is actually absorbed and used. Animal proteins score 1.0–1.2 (excellent). Most plant proteins score 0.5–0.8 (lower).
Best Animal Protein Sources
| Food | Protein per 100g | Calories per 100g | Quality score |
|---|---|---|---|
| Chicken breast (cooked) | 31g | 165 kcal | Excellent ★★★★★ |
| Tinned tuna | 26g | 116 kcal | Excellent ★★★★★ |
| Eggs (2 large) | 13g | 143 kcal | Excellent ★★★★★ |
| Greek yoghurt (0% fat) | 10g | 57 kcal | Excellent ★★★★☆ |
| Salmon (cooked) | 25g | 208 kcal | Excellent ★★★★★ |
| Cottage cheese | 11g | 98 kcal | Excellent ★★★★☆ |
| Beef (lean mince, cooked) | 26g | 218 kcal | Excellent ★★★★★ |
Best Plant Protein Sources
| Food | Protein per 100g | Calories per 100g | Notes |
|---|---|---|---|
| Tempeh | 19g | 193 kcal | Best plant source — complete amino acids |
| Firm tofu | 17g | 144 kcal | Complete protein, versatile |
| Edamame | 11g | 121 kcal | Good leucine content for a plant source |
| Lentils (cooked) | 9g | 116 kcal | Pair with grains for complete profile |
| Chickpeas (cooked) | 9g | 164 kcal | High fibre — combine with other sources |
| Pea protein powder | 21g/scoop | ~120 kcal | Best plant supplement — close to whey in studies |
Calculate your personalised macro targets — protein, carbs, and fat for your goal.
Calculate My Macros →Best Protein Supplements
- Whey protein isolate: 25–28g protein per scoop, highest leucine of any supplement, fast-absorbing — best post-workout
- Casein protein: 24–25g per scoop, slow-digesting — ideal before bed for overnight muscle protein synthesis
- Pea protein: 20–24g per scoop, comparable to whey in muscle-building studies — best plant option
For weight loss specifically: Chicken breast, Greek yoghurt, eggs, and cottage cheese are the best value — high protein, low calorie, high satiety, versatile, and affordable.
Frequently Asked Questions
What is the best protein source for weight loss?
Chicken breast, Greek yoghurt, eggs, and cottage cheese are the best protein sources for weight loss — they combine very high protein content with low calorie density, making them excellent for hitting protein targets without exceeding calorie budgets. Greek yoghurt and cottage cheese have the additional benefit of high casein content, which digests slowly and provides extended satiety.
Is plant protein as good as animal protein for muscle building?
Plant proteins can support muscle building but generally require higher total intake due to lower digestibility and amino acid scores. Studies comparing whey and pea protein show comparable results when intake is matched. For plant-based athletes, targeting the upper end of protein recommendations (2.0–2.4g/kg) and using a variety of sources (soy, pea, rice, lentils, legumes) ensures adequate essential amino acid intake.
Calculate your personalised macro targets — protein, carbs, and fat for your goal.
Calculate My Macros →ⓘ Medical DisclaimerThe information in this article is intended for general educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making changes to your diet, exercise routine, or health management plan.
Sources & References
- Jäger R, Kerksick CM, Campbell BI, et al. “International Society of Sports Nutrition Position Stand: protein and exercise.” Journal of the International Society of Sports Nutrition, 2017;14:20. Supports leucine and muscle-protein-synthesis, protein quality, and intake ranges for building and preserving muscle. PubMed: 28642676
- U.S. Department of Agriculture. “FoodData Central.” Supports the per-100g protein and calorie values listed for each food. USDA: FoodData Central
- MedlinePlus (U.S. National Library of Medicine). “Protein in diet.” Supports complete vs incomplete protein and essential-amino-acid basics. NIH/MedlinePlus: Protein in diet
Last reviewed against the above sources: June 2026.