If you consider yourself a 'hardgainer', your struggle isn’t just training, it’s also eating enough calories to grow. You can train every day, stay consistent, and still stall out on gains if your calorie intake doesn’t match your training output. 

The solution isn’t more chicken breast and broccoli. 

It’s smarter nutrition. High-calorie smoothies are a fantastic (and delicious) option for skinny lifters because they let you load serious nutrition into a small volume. They are fast to prep, easy to digest, and dense with growth-promoting nutrients.

The key is choosing ingredients that increase calorie density without compromising digestibility, recovery potential, or flavor. You’re not just looking for empty calories. You want foods that fuel muscle protein synthesis, replenish glycogen, and make your shake something you actually look forward to.

Here are six nutrient and calorie-dense smoothie add-ins that check every box for hardgainers looking to pack on real size:

1. Natural Nut Butters (Peanut, Almond, Cashews)

Calorie-dense, nutrient-rich, and easy to blend, nut butters are a hardgainer’s best friend. Just two tablespoons of natural peanut butter delivers around 190–200 calories, 8g of protein, and 16g of fat, including a mix of monounsaturated fats and omega-6s.

The fats in nut butters slow digestion slightly, helping keep blood sugar stable while providing long-lasting fuel. They also enhance taste and texture, no one wants a watery smoothie.

Science says: Fats are essential for hormone production, especially testosterone, which is crucial for muscle growth. A 2013 study published in the Journal of the International Society of Sports Nutrition found that moderate fat intake supports anabolic hormone levels in resistance-trained athletes⁽¹⁾.

PRO TIP: Use natural versions without added sugar or hydrogenated oils. You can also use 1 ounce of real nuts instead of processed peanut butter. They blend perfectly and add a unique texture to any smoothie.

2. Rolled Oats (Dry or Cooked and Cooled)

Oats are great for breakfast, and they’re just as effective in smoothies. A half-cup of dry oats adds around 150 calories, 27g of carbohydrates, 5g of protein, and 4g of fiber. (Add a full cup and it doubles all of those numbers).

Oats contain beta-glucan, a soluble fiber that may support gut health and nutrient absorption.

They are a great ingredient to help thicken your shake while providing slow-digesting carbs to support sustained energy and glycogen replenishment.

Science says: Carbs post-workout enhance muscle protein synthesis when paired with adequate protein. According to Ivy and Portman (2004), rapid glycogen restoration optimizes recovery and primes the body for the next training session⁽²⁾.

PRO TIP: Pre-soak oats or use quick oats to improve digestibility. Cook and cool for better texture if you want a smoother blend.

3. Greek Yogurt

For hardgainers who need extra protein and probiotics without excess volume, Greek yogurt is a go-to. One cup of whole-milk Greek yogurt provides roughly 220 calories, 20g of protein, and 10g of fat. It also supplies calcium and beneficial bacteria that support gut health.

The thick consistency makes your smoothie creamy, while the casein content offers slower-digesting protein.

Science says: Casein protein has been shown to prolong muscle protein synthesis post-exercise. In a 2012 study from Medicine & Science in Sports & Exercise, evening casein consumption improved overnight muscle repair in resistance-trained males⁽³⁾.

PRO TIP: Choose full-fat versions for higher calories. Go for plain, unsweetened to avoid added sugars and adjust sweetness with fruit or honey.

4. Banana or Mango

You need carbs, but that doesn’t mean sugary syrups or processed powders. Whole fruit like banana or mango brings in glucose and fructose, the dual-carb combo that’s ideal for liver and muscle glycogen repletion, and fiber for improved digestion. 

It's one reason bananas are a staple smoothie ingredient. One medium banana adds 105 calories and 27g of carbs, and 2.6g of fiber, while one cup of mango brings 100 calories, 2.6g of fiber, and over 40g of carbs and natural sugar.

Fruit also contributes essential micronutrients like potassium and vitamin C, supporting hydration and immune function, especially important during hard training cycles.

Science says: A 2008 study in The Journal of Physiology confirmed that carbohydrate ingestion post-exercise enhances glycogen synthesis and supports recovery when combined with protein⁽⁴⁾.

PRO TIP: Use frozen fruit to create a milk shake-like texture. Combine banana for thickness and mango for tang if you want flavor balance. You can find a delicious mango smoothie recipe so good it will make you wanna slap yo mama here.

5. Liquid Egg Whites (pasteurized)

This one might surprise you, but liquid egg whites offer pure, high-quality protein with zero fat or carbs. One cup gives about 120 calories and 26g of complete protein. Because they’re pasteurized, they’re safe to drink raw and mix smoothly into smoothies without taste interference.

Unlike whey, egg protein digests slightly slower, giving a balanced amino acid release.

Combined with other protein sources like Greek yogurt, you get a broader absorption window, key for muscle hypertrophy. You can learn how to choose the best eggs here.

Science says: Egg protein has the highest biological value of any whole food. A study in The American Journal of Clinical Nutrition found that whole egg ingestion after resistance training led to greater muscle protein synthesis than egg whites alone, but when you're stacking other whole food sources, liquid egg whites still play a strategic role⁽⁵⁾.

PRO TIP: Blend with other flavorful ingredients. Egg whites are virtually tasteless and help boost total protein intake without filling you up.

6. Avocado

Smooth, rich, and calorie-dense, avocado is one of the most underrated bulking ingredients for lifters. One medium avocado packs between 240-300 calories, 22g of heart-healthy fats, 12g of carbohydrates (mostly fiber), and 3g of protein. It blends seamlessly into smoothies, adding a creamy texture without overpowering other flavors.

Avocado is particularly useful for anyone who struggles to hit calorie targets or find themselves constantly full. It offers a neutral, versatile flavor and adds substance without increasing digestive burden. The monounsaturated fats support cardiovascular health, joint recovery, and even hormone balance.

Science says: Dietary fats, especially monounsaturated types like oleic acid found in avocado, have been shown to support optimal testosterone levels and improve nutrient absorption, especially fat-soluble vitamins A, D, E, and K⁽⁶⁾.

PRO TIP: Slice and freeze ripe avocados for easy blending and a chilled, creamy finish. They pair especially well with chocolate- or vanilla-based smoothies.

How To Build a Delicious Mass-Gain Smoothie That Works

Here’s a practical template to build a hard-gainer-friendly smoothie using the ingredients above (macros are estimates):

• 1 scoop whey protein isolate or concentrate (25g protein, ~120 kcal)
• 1 medium frozen banana (27g carbs, ~105 kcal)
• ½ cup dry oats (27g carbs, 5g protein, ~150 kcal)
• 1 tbsp natural peanut butter (8g fat, 4g protein, ~95 kcal)
• 1 avocado (22g fat, 3g protein, ~240 kcal)
• 1 cup whole-milk Greek yogurt (20g protein, 10g fat, ~220 kcal)
• 1 cup whole milk or almond milk (8g protein, 8g fat, ~150 kcal)
• 1 cup blueberries (21g carbs, ~85 kcal)
• Optional: ½ cup mango, 1 cup liquid egg whites

PRO TIP: If you're aiming to push protein intake higher without adding bulk or flavor, liquid egg whites are an excellent addition. They blend smoothly, are virtually tasteless, and add 26g of high-quality protein per cup with very little fat (.5g) or carbs (less than 2g).

WHAT TO DO: Add all ingredients to a blender and blend until smooth. Consume immediately post-workout or as a calorie-dense breakfast.

Estimated Macros: ~1000–1,200 calories, 60–70g protein, 80–100g carbs, 40–50g fat depending on add-ins.

This smoothie recipe increases overall calories and healthy fat intake while keeping protein levels high and carbs moderate. It’s great for hardgainers who want sustainable energy, enhanced recovery, and a shake that supports lean muscle growth without bloating or digestive overload.

Common Mistakes to Avoid

1. Overloading with junk calories: Adding ice cream or sugary syrups might boost calories, but they can also spike insulin unnecessarily.

2. Skipping fats: For hardgainers, quality fats are vital for hormone production and staying in a calorie surplus.

3. Under-eating on rest days: Growth happens outside the gym. If your smoothies only show up on training days, you’re not providing the fuel your muscles need to grow.

4. Not tracking intake: Guesstimating isn’t good enough when you're trying to grow. Weigh ingredients and track calories at least for a few weeks to lock in a consistent surplus. Once you're consistent you won't have to track as much, especially if you're eating the same thing every day.

Eat Like You Train...With Intention.

Smoothies are a fantastic shortcut for people who struggle to gain weight. They’re a strategic tool that lets you overcome appetite limits, digestive fatigue, and time constraints. The key is packing them with ingredients that deliver useful calories and nutrients that actually support the biological processes behind hypertrophy and recovery.

If you're looking to add a delicious protein to your muscle-building smoothie, we've got an entire line of delicious whey and dairy-free proteins that contain all the essential amino acids you need to fuel your gains!

References:

(1) Volek, J. S., et al. (2013). Testosterone and resistance exercise: effects of dietary fat. Journal of the International Society of Sports Nutrition, https://journals.physiology.org/doi/full/10.1152/jappl.1997.82.1.49

(2) Ivy, J. L., & Portman, R. (2004). Nutrient Timing: The Future of Sports Nutrition. Basic Health Publications.

(3) Res, P. T., et al. (2012). Protein ingestion before sleep improves post-exercise overnight recovery. Medicine & Science in Sports & Exercise, https://pubmed.ncbi.nlm.nih.gov/22330017/

(4) Jentjens, R. L., & Jeukendrup, A. E. (2008). Carbohydrate and fat metabolism during exercise. The Journal of Physiology, https://onlinelibrary.wiley.com/doi/10.1080/17461390801918971

(5) Stephan van Vliet, Evan L Shy, Sidney Abou Sawan, Joseph W Beals, Daniel WD West, Sarah K Skinner, Alexander V Ulanov, Zhong Li, Scott A Paluska, Carl M Parsons, Daniel R Moore, Nicholas A Burd, Consumption of whole eggs promotes greater stimulation of postexercise muscle protein synthesis than consumption of isonitrogenous amounts of egg whites in young men†, The American Journal of Clinical Nutrition, Volume 106, Issue 6, 2017, Pages 1401-1412, ISSN 0002-9165, https://doi.org/10.3945/ajcn.117.159855.

(6) Wien, M., et al. (2013). A randomized 3×3 crossover study to evaluate the effect of Hass avocado intake on post-ingestive satiety, glucose and insulin levels, and subsequent energy intake in overweight adults. Nutrition Journal, https://nutritionj.biomedcentral.com/articles/10.1186/1475-2891-12-155