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Weight Gaining for Skinny Guys: How to Bulk Up and Fill Out

By: by Amino Science
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It's a genetic reality that some people tend toward skinniness and can't seem to pack on the pounds, or muscle mass, no matter what they eat or how hard they train. The following article discusses this natural body type and has tips for weight gaining for skinny guys so you can take control of your biology and build the body you want.

Natural Male Body Types

Here are the standard body types men have to work with.

  • Ectomorph: This is your classic "skinny guy" build—body types with lean muscle mass, knobby joints, long limbs, and fast metabolisms. It's what's known as a "hard gainer," meaning it's difficult for this body to gain weight.
  • Mesomorph: This is the "Superman" build, a body that's naturally athletic with big bone structure and large muscles. Men with this body type may find it much easier to build muscle and gain weight, and they must also be careful to keep their weight training and workouts on par with their calorie intake so they don't gain too much.
  • Endomorph: This build is often referred to as "stocky." It's a rounder, denser body type that has the opposite problem skinny guys have—it's often harder for this form to lose weight and far easier to pack it on.

Let's focus in on ectomorphic frames and how you can gain weight to bulk out a naturally slim form.

Weight Gaining for Skinny Guys: How to Bulk Up and Fill Out

Weight Gaining for Skinny Guys

There are two flanks to weight gaining for skinny guys: workout programs that contribute to weight gain and calorie-dense foods and smoothies to supply the nutrients you need.

Workout Programs

Weight training contributes efficiently to your bulking goals. Squats, deadlifts, strength training, and cardio keep your blood flow powerful. You can gain weight by lifting weight and use your workout routine to demand that your body grow to meet bigger and bigger challenges with heavy lifting, free weights, and bench presses.

Weight gained from lifting is solid weight, muscle weight that's hard to gain but also harder to lose once you have it. With as few as two or three training sessions each week, and without the need for a personal trainer, you can stimulate muscle growth with heavy weights so long as you consume enough food and extra calories to supply the demand. Here are the specifics on seven key exercises.

1. Deadlift

We'll start with the most obvious contributor to muscle gain: the deadlift. Depending on your current fitness level, you may begin utilizing the deadlift ASAP, or you may need to train up for a few weeks first—definitely err on the side of safety if you're new to keeping a fitness regimen because an injury could slow you down way more than being cautious for a week or two.

The deadlift is a full-body exercise, working your core and your hamstrings, that can help you add muscle mass to your upper body, lower body, and glutes. Here's how it's done according to The American Council on Exercise:

  • Place a barbell on the floor in front of you and plant your feet at shoulder width apart.
  • Be sure to keep your chest and back straight when bending down to grab hold of the bar.
  • With palms down, slowly raise the bar up to a standing position using your glutes and your hamstrings, leaning back on your hips slightly. It's important that you lift from your lower body and not from your lower back, which can be easily injured.
  • Once you're standing upright, begin to lower the bar back down, sinking back on your heels and bending your knees, but keeping your back straight the entire time.
  • Repeat until you've reached your goal.

2. Standing Military Press

This is an upper-body exercise that targets your shoulders, triceps, and upper back. Just a few reps with heavy weight can make a huge difference in these areas of your body and help fill out a classic male frame: the inverted triangle.

  • Once you've loaded the barbell up with the weight you want to lift, raise the bar up to your chest, palms facing upward.
  • Your hands should be holding the bar slightly wider than your shoulder span, and your knees should stay slightly bent, not locked into place.
  • To lift, bring the bar to your collarbone, and then press it up, above your head.
  • To end the lift, go in reverse, bringing the bar back down to your collar. Then let it down to your waist until your arms fully extend.
  • Repeat as desired.

3. Curling and Bent-Over Rows

Another back and bicep combo, bent-over rows build muscles directly onto your lats, especially when combined with a bicep curl.

  • With a dumbbell in each hand, palms facing down, bend your knees and lean forward from the waist.
  • When your chest is almost parallel to the floor, straighten your arms out in front of you.
  • Next, pull your arms to your body, tucking your elbows into your sides.
  • Row once, straighten up to perform a bicep curl, and then get into position to row again.
  • The heavier the weights, the more muscle you stand to gain. This can be done with one barbell or with two free-weight dumbbells, one in each hand.

4. Weighted Hip Thrust

For bulking and tightening up your glutes, the standard exercise is the squat, but if you really want to add weight where it wasn't before, you can ramp up this exercise with the weighted hip thrust. You'll need a heavily weighted barbell and a low bench to execute it.

  • Squat down against the bench, with its pad across your back, just below the shoulder blades.
  • With the barbell across your lap and your knees directly over your feet, lift with your core and your glutes until your knees are at a 90-degree angle.
  • Sink back down to complete the rep, and repeat.

5. Incline Barbell Bench Press

For your chest muscles, this bench press can help bulk up your shoulders, triceps, and pecs. Here's how it's done:

  • On a bench set between a 30- and 45-degree incline and a heavily weighted barbell and grab the bar with your palms downward and your hands shoulder width apart.
  • Lay back on the bench and bring the weight down to your chest, then press it upward until your arms are fully extended.
  • Lower the barbell back to your chest slowly, controlling the weight downward.
  • Rest the barbell at chest level between reps.

6. Barbell Hack Squat

Now to change it up a little: you're used to lifting with the weight in front of you, so this time let's lift the weight from behind. The barbell hack squat targets your hamstrings, quads, and glutes.

  • Begin by placing the weighted barbell on the floor behind you.
  • Start from a squatted position with your thighs parallel to the ground.
  • Reach back to grab the barbell with your palms facing out away from you.
  • Keep your core in control, your lower back slightly arched, and be sure to lift from your knees.
  • Stand once and then lower back into your squat, repeat as desired.

7. Weighted Hanging Leg Raise

Leg raises are already a full-body feat, but if you want them to help you bulk up even more, add weight. It's best done with a pull-up bar of some sort and a dumbbell weight you can grasp with your ankles or affix there.

  • Grab or attach the weight at your ankles and grasp onto the pull-up bar.
  • Lift up your knees first and then straighten out your legs for one rep.
  • The added weight not only contributes to your core strength, but it also helps you bulk and tone your muscles. Add a twist to the move at your knees if you want to go even further, as this will work your obliques.

Mass Gainer Foods and Supplements

Muscle building is a great way to increase your body weight and fill out your physique, but it's imperative that you feed the need.

Mass Gainer Foods

Your macronutrient ratio should skew heavily towards high-protein foods with natural, healthy fats. Fat gain, while technically a way to gain weight, is not the goal—muscle gain is. That means avoiding junk foods with empty calories, refined oils, and processed sugar, and prioritizing the following foods.

  • Protein foods: Whether it's animal protein like chicken breast, plant protein like a good helping of peanut butter, or whole milk foods like cottage cheese, getting enough protein is incredibly important to gain the essential amino acids required to synthesize new muscle.
  • Fiber foods: Veggies high in fiber help a high-protein diet by keeping your digestive system regular and comfortable. Green, leafy vegetables also have a high density of valuable nutrients like the vitamin K necessary for bone strength.
  • Fatty foods: A high-calorie diet aimed to bulk you out can really benefit from natural, healthy fats like those found in fish, nuts, avocados, and olive oil.

Mass Gainer Supplements

Certain protein and amino acid supplements can help concentrate the bulking nutrients naturally found in foods and deliver them right when you need them, pre-workout, post-workout, and before bed so that you don't lose muscle mass while you sleep. Whey protein powder, casein protein, creatine, and robust amino acid supplements with BCAAs (branched-chain amino acids) are all weight gainer aids, and here is the breakdown of how they impact your muscle mass goals.

Whey Protein and Casein

Whey is a milk protein derived from the whey or watery part of milk, while casein is a milk protein found in the solid curd.

Whey protein contains some amount of all the essential amino acids, including the branched-chain amino acids (more on those below).

Whey protein digests relatively quickly, meaning you definitely want to include it just before your workout to make sure your body has fast access to muscle-building supplies in real-time when you need to get in a few more reps to step up your fitness level. Just make sure the supplement you choose includes "whey protein hydrolysates" as they're the proteins that break down and digest the fastest, with peptides to help boost blood flow. In fact, the only proteins to digest faster are free-form amino acids that don't have to be broken down before they can be used.

Casein protein, on the other hand, has a slower digestion rate, but this doesn't mean whey is necessarily better. Fast digestion is key for a bodybuilding workout, but when it comes to endurance exercise you need both a quick boost and a long-term follow-through. This is also true when you're asleep: when you're trying to bulk up you have to eat a lot more than usual to make sure your body doesn't turn to catabolism as you sleep, a destructive metabolism that utilizes existing muscle cells to build new ones if you don't supply the body with enough amino acids as raw materials.

Casein products with micellar casein are those with the slowest-digesting form of the protein and can be even more powerful when combined with whey and other protein supplements like readily accessible free-form amino acids.


A well-known workout supplement since the 1970s, creatine is composed of three amino acids: arginine, glycine, and methionine. It's especially effective in resistance exercises as it plays an important role in supplying the energy needed for muscle contractions.

Creatine can be found in the forms creatine monohydrate, creatine malate, and creatine alpha-ketoglutarate (AKG). Once inside the body, creatine converts to phosphocreatine, which is used to supply energy for explosive exertions like those required for the kind of heavy weightlifting exercises described above. During workouts, when your body is using more ATP energy than can be regenerated in time, the creatine-phosphocreatine system provides an extra supply of fuel.

Creatine, like milk proteins, is stronger in concert with other muscle-building supplements. A scientifically balanced combination of these proteins can help you get the best of everything, which brings us to the most important muscle-building supplement of all.

Amino Acids

Protein is made out of amino acids, and muscles are made out of protein. You cannot synthesize new muscle without a full host of all the essential amino acids (EAAs), which include the three branched-chain amino acids (BCAAs). However, despite the popularity of BCAAs in the gym, they are only a third of the EAAs, and cannot stand in for the rest.

We here at the Amino Company have developed an EAA blend that doesn't stop at the BCAAs, and includes elements of creatine and citrulline.

The science is not unclear: our bodies are made of 20% protein, and amino acids are the keys to repairing and strengthening existing muscle, as well as synthesizing new muscle cells. When you work out hard with the aim to bulk up, you'll be doing both, and will need the best-quality support you can find.

Unlike milk proteins which must be digested first to be effective in muscle creation, a direct supply of balanced amino acids is absorbed even more rapidly. However, with whey's long-haul support and creatine's alternative energy supply, our unique, patent-pending EAA formula outperforms other blends because it doesn't skip any ingredient that has a positive impact on quality muscle creation.

Every gram of protein you consume, whether it comes from a protein shake or from whole foods, contributes to your weightlifting power and helps you build muscle and gain weight. You've got to eat like a bodybuilder to become one, especially because without the right weight gainer supplement rounding out your daily calories, all the working out you do might bring about too much catabolism and ultimately work against your goals.

Gain Weight, Gain Positivity

If you're unhappy with your body and tired of feeling as scrawny as you used to be in high school, building muscle is a great way to facilitate the weight loss of body fat (so you're not what's known as "skinny fat") and turn every pound of body weight you gain into impressive muscle mass. Getting enough calories from weight gainer shakes pre- and post-workout is the support you need for the aptly named work of bodybuilding: you're literally building a better body. Build it strong with the proper amount of calories and the amino acids necessary for new muscle growth.


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