Muscle Building 101

Read Time: 8 minutes

Short Version

There is an illusion of complexity to gaining weight / building muscle, but it is actually really, really simple. It comes down to the following three factors:

  • Resistance Training
    • Resistance training is the stimulus that drives your body to build muscle.
    • Your training needs to be difficult enough to drive growth, and consistent over a long period of time.
    • It is always best to follow a structured, proven routine created by a professional.
    • Recommended routines can be found here: Strength Training / Muscle Building
  • Calorie Surplus
    • Eating more calories than your body uses, in total, each day. This is necessary both to build muscle and to recover from training.
    • Use any TDEE (Total Daily Energy Expenditure) calculator to estimate a starting point, then eat more than that each day, monitoring your scale weight to ensure it’s going up.
  • Protein
    • To maximize muscle growth, set your protein target each day for whichever of the below is greater:
      • 160 grams per day
      • 0.8 grams per pound of bodyweight, per day
    • Ideally this is spread out over 3-4 meals throughout the day

This is the TLDR version. If you’re looking for more details, continue on below. However, don’t spend so much time getting into the weeds that you neglect the parts that are actually important – training and eating properly. There is a lot of information out there that’s neat to know, but not necessary to know in order to get results.

Resistance Training

The first piece of the puzzle is adding resistance training to your life. If you simply start eating more without giving your body a stimulus to build muscle, all you’ll do is get fat.

There’s a lot of debate on the internet about the most optimal and efficient muscle building routines. The truth lies in the old adage – “Many roads lead to Rome”. Most of the sensible routines you can find out there work well if you commit to them and give them time. r/Fitness and r/weightroom both have a rich history of progress threads that prove a person can get bigger and stronger on just about any proven routine. Even better, “gym bros” everywhere have demonstrated repeatedly that you can run some of the dumbest routines imaginable and still make good progress if you are working hard, consistently.

While it doesn’t generally matter much which routine you follow, it’s still important that you do follow a structured routine. It’s always better to defer to existing, proven routines that came from experienced professionals than it is to try to reinvent the wheel – at best you’ll come up with something equivalent, but more likely you’ll come up with something worse. You can read more about this in the Importance of Having a Program section of the Adding Physical Activity page.

A list of reliable, quality routines that r/Fitness and r/weightroom users commonly recommend can be found on the Recommended Routines – Strength Training / Muscle Building page. You can also look over our extensive Program Review Archive if you’re looking to hear some experiences from people who ran various programs.



Your body requires a certain amount of energy each day, measured in calories, in order to fuel its activities. This is called your Total Daily Energy Expenditure or TDEE. If your diet supplies fewer calories than your TDEE (a deficit), you will lose weight. If your diet supplies more calories than your TDEE (a surplus), you will gain weight. You’ve probably heard of many different diets out there, and when they work, they all achieve weight gain in the same way – manipulating calorie balance.

This creates two points of failure for calorie intake to be aware of:

  • Underestimating your TDEE.
    This is very easy to do. Just remember, always, that no TDEE calculation is 100% accurate. Treat them as estimates only and don’t get fixated on what any calculator told you if it conflicts with what you’re seeing on the scale. Calculations of calorie burn during exercise, in particular, tend to be wildly inaccurate and inflated.
  • Overestimating your calorie consumption.
    Most commonly this happens when people don’t pay enough attention to what they’re eating. This ranges from eyeballing portion sizes to simply not tracking calorie consumption at all. If you aren’t gaining weight, you will at some point have to start tracking everything you’re eating.

Whichever it is, the most important fact to remember is that the scale doesn’t lie. In order to maintain or lose weight while eating at a true surplus, it would require your body to break the laws of the universe by making energy vanish into thin air. You can read further in our FAQ: Why can’t I gain weight?


It’s important to ensure that you eat enough protein each day to fuel the process of building muscle.

Jorn Trommelen, PhD recommends 160 grams of protein per day, across four meals, for those seeking the best results. Recommendations by Eric Helms, PhD go up to 0.8-1 grams per pound of bodyweight for building muscle. For most purposes, 120g-160g per day is a very good place to start, with room to add more if you want. The maximum that research has shown to be beneficial for muscle growth is 0.82g/lb, but there’s no danger or waste in going above that (as long as you don’t eat only protein).

If you’d like to read some more detailed articles about protein and research on it, below are some excellent ones. Don’t get too far into the weeds and start over-thinking it, though.

In your quest to build muscle, keep in mind that there is nothing special about protein powders or mass gainers. Quite literally, they are nothing more than powdered food. While whey protein does have higher bioavailability than most other sources, the primary advantage shakes have over any other protein source is simple convenience – they’re easy to prepare, transport, store, and consume. That’s it. They are just a tool you can use to meet your protein or calorie needs. They aren’t necessary, and they aren’t special either.

If you’re having trouble figuring out how to get enough protein in your diet to meet your needs, have a look at the Eating a High Protein Diet installment of the r/Fitness Community Campfire series.

If you really want to dig into the minutiae of muscle building nutrition, Renaissance Periodization’s Dr. Mike Israetel has a very detailed lecture series – Nutrition for Muscle Gain.

Step By Step Guide

  1. Take your “before” measurements.
    These can be any measurements you want, but should at least include weight and photos of front, back, and side (in underwear is ideal). This is important for being able to compare your progress over time, since it can be hard to notice a difference when you look at yourself every day.
  2. Estimate your TDEE.
    Remember to treat this as an estimate only, and keep in mind the adage “No plan survives engagement with the enemy”. Expect to have to adjust this number based on changes on the scale. In particular, expect it to go higher as you gain weight.
  3. Set a daily calorie goal.
    The best place to start is by increasing your TDEE by 10-20% (TDEE x 1.1-1.2). You will usually want to avoid going above 20% more than your TDEE. Going too far above your TDEE will lead to increased fat gain, and could make it very difficult to eat enough food without discomfort. Muscle builds very slowly, so don’t think that more food always = more muscle.
  4. Set a daily protein goal.
    Shoot for a bare minimum of 160g per day of protein, ideally spread across four meals. Up to 0.82g/lb per day has been shown to be beneficial for building muscle.
  5. Track your calorie and protein consumption.
    Tools such as MyFitnessPal or NutritionData are very useful for tracking calories. We also recommend the nSuns Adaptive TDEE Spreadsheet, which will adjust its estimate of your TDEE over time. Track everything you eat and drink, including additives and toppings. This may not be necessary if you have a good handle on your eating, but if you’re having trouble gaining weight, you should add this step.
  6. Take regular progress measurements.
    Weight should generally be measured once a day (or at least once a week), preferably unclothed and on an empty stomach. Don’t sweat day-to-day fluctuations – track the trend over time. Monthly progress photos may be worth considering. Avoid any handheld or scale based body fat percentage measurements – the bio-electrical impedance method is extremely inaccurate and inconsistent.
  7. Adjust your diet over time.
    As you gain weight, your TDEE will inevitably go up – more mass requires more calories to fuel. This means that your starting calorie goal will eventually no longer cause weight gain, and you will need to adjust it up.
  8. Be patient and do not expect progress to be fast
    While you can gain weight pretty quickly, gaining actual muscle is a different story. You should not expect to gain more than ~2 lbs of muscle per month. Additionally, you should not expect to start seeing visual changes for at least the first month, and no noticeable changes for at least the first 2-3 months. Don’t let this discourage you. Despite what marketers and charlatans want you to believe, there are no shortcuts to getting bigger and stronger.
    (Source: Stronger By Science – Data Based Targets to Set Realistic Training Goals)

Additional Reading and Resources

Below are some additional resources that can help you with gaining muscle.

In this Wiki:

External Links: