If you've picked up a muscle magazine at any point in your life, or spent some time browsing the web's finest bodybuilding forums, you're probably well aware of the basic concept of 'bulking' and 'shredding' (also known as 'cutting').

The idea is pretty straightforward --- at any given time on your journey-to-jackedness, you'll either be aiming to cut body fat or to build muscle. The idea being that it's impossible to do both at the same time.

But what's the real deal on the whole bulking/shredding thing? Is it everything it's cracked up to be?

More importantly, is it the right approach for you to follow in pursuing your goals?

Can you build muscle and lose fat at the same time?

The standard argument

The standard argument in favour of bulking and shredding cycles is that, to lose fat (shred), you need to consume fewer calories than you burn off, while to build muscle (bulk), you need to consume more.

On the surface, this seems quite reasonable. After all, your body really does have caloric needs for its various functions.

The problem with the standard argument

Where the argument fails, is in neglecting to acknowledge that your body compartmentalises nutrients differently. The way calories are allocated to muscle and fat isn't the same. This concept is referred to as "calorie partitioning."

To build muscle, your body needs protein and energy (in the form of calories). But if your protein consumption is high enough, your body can derive the needed excess calories for growth from its own stored fat mass, and thus allow you to build muscle even in a dietary caloric deficit.

That's why a keto diet has been shown to cause greater increases in muscle mass, and decreases in fat, than other diets.1

The truth --- you can build muscle and lose fat at the same time

Contrary to what you might expect, there are actually many studies which show subjects losing fat and gaining muscle at the same time.

In one, overweight police officers lost 9.3lbs of fat and gained 8.8lbs of lean mass over a 12-week training cycle.2

In another, elite gymnasts were placed on a ketogenic (very low carb, high fat) diet, while also at a calorie deficit, for 30 days. The result? They reduced their body fat percentages to pro-bodybuilder levels (from ~7% to ~5%) while also adding around 0.9lbs of lean muscle mass in the process.3

In other words, both overweight individuals and those already highly trained and at low bodyfat percentages can lose fat and gain muscle at the same time, according to the scientific findings.

So, why would I want to bulk and shred, then?

Even though bulking and shredding aren't the only ways of gaining muscle and losing fat, there are still some reasons why you might choose to follow these approaches. Here are a few:

Bulking allows you to feast

There's something satisfying about being able to eat yourself full at every meal. While not every bulking approach will give you unlimited room to stuff your face, they will commonly give you an excuse to feast on some of your favourite foods, and know the joy of being well-fed at all times.

Shredding allows you to get the "bad" stuff over with in one go

Some people like to pull a loose tooth out in one yank, and others like to do all their dieting, cardio, and calorie counting in one go.

If you'd rather throw caution to the winds and forget all about this stuff for months at a time, then pay the piper with a monk-like diet down the line, bulking and shredding might be for you.

Bulking and shredding allow you to cycle your fitness routines easily

There are a lot of different elements to being fit overall, and it's pretty difficult to try and maximise your training for each of these at once.

Gaining muscle, while training for a marathon, while at the same time training to compete in a powerlifting meet -- it's all a good way to make sure you end up meeting none of your fitness goals. It'll may well get you injured, too.

Bulking and shredding cycles allow you to easily compartmentalise and cycle the different elements of your fitness regimen. A common approach is to focus on strength and size while bulking, and to focus on cardiovascular conditioning and endurance while shredding.

And why should I avoid bulking and shredding?

Of course, in addition to it not being necessary for muscle gain and fat loss, there are some other reasons you might want to skip the bulking and shredding approach:

You're almost never at an ideal weight

When you're bulking or shredding, you're always either going to be chasing muscle while gaining fat, or chasing fat loss, often while gaining muscle. The only time you'll be at something like an "ideal" weight is in the period at the end of one shredding cycle and before the next bulking one.

For a competitive bodybuilder, this would be contest season. For anyone else, it's just a month or two out of the year.

Very rapid weight loss can ruin your health

It's well known that rapid and dramatic weight loss, as seen with fighters trying to make weight, can ruin hormone balance and cause physical and psychological harm to the dieter. That should be a pretty clear cause for concern.4

Cutting means you put on weight more easily later

When you cut weight, especially for a long time, and rack up a large caloric deficit; your body tries to compensate by altering your metabolism so as to burn fewer calories5

What this means in practice is that, following a shredding-phase, you'll find yourself gaining fat more easily when you're on your next bulking cycle.

[1] https://jissn.biomedcentral.com/articles/10.1186/1550-2783-11-S1-P40

[2] https://www.ncbi.nlm.nih.gov/pubmed/10838463

[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3411406/

[4] https://jissn.biomedcentral.com/articles/10.1186/1550-2783-9-52

[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3943438/