The Best Way to Bulk and Cut, According to Science

By: Rachel MacPherson, CPT, CSCS, PN-1

If you've been training steadily for a while and want to take your physique to the next level, it's likely you've come across the idea of bulking and cutting. Basically, standard terms for gaining muscle and losing fat, they form the basic structure of most serious body composition strategies, especially in the bodybuilding world. So long as you do bulking and cutting cycles with intention (and smarts), you can build muscle faster during a surplus and then lean out during a deficit, so you end up with more muscle and less fat over time.

The problem is that most people do it wrong. They eat way too much during a bulk, gain a ton of unnecessary fat, then spend months dieting it off, all the while losing the muscle they just grinded for. Or, they cut too aggressively and end up flat, weak, and super frustrated. There is some excellent research on how to do both phases well, and it's more simple than you might think.

Bulking vs Cutting

Bulking is an intentional period of eating more calories than you burn while training hard to build muscle. Cutting is the opposite, where you eat fewer calories than you burn to lose fat while doing everything you can to hold onto the muscle you gained. Most people alternate between these phases over months or even years, spending the majority of their time in a surplus to build and then running shorter fat loss phases to lean out.

The biggest difference is the goal of each phase. During a bulk, you accept that some fat gain is inevitable in exchange for faster muscle growth. During a cut, you accept that progress in the gym will slow down, but you will look and feel leaner. If you do both phases well, the result over time is a leaner and more muscular body composition. 

Keep in mind that you can build muscle and lose fat at the same time, especially if you are newer to lifting or carrying extra body fat, but it's not as efficient to do it this way. Dedicated bulking and cutting cycles become most useful once you are past the beginner phase and aren't really seeing as much progress at maintenance anymore.

How to Bulk

Getting a bulk right is based on how well you nail the following three things:

1. A modest calorie surplus of about 5%, which is typically 200 to 400 calories per day above maintenance.

2. Enough protein to build muscle, about 1.6 to 2.2 grams per kilogram of body weight per day.

3. Progressive resistance training to stimulate muscle gain rather than mostly fat gain.

Here's a bit more on the science behind those numbers, plus some extra advice for a successful bulking phase. 

Eat At a Modest Surplus

Research on experienced lifters shows surpluses over 5% mostly add fat rather than muscle. People eating at a 15% surplus gained no more muscle than the 5% group but did gain significantly more fat and saw a performance drop. If you are wondering how to lean bulk, this is it. Most people should add about 200 to 400 calories above maintenance, and gain weight slowly (about 0.5 to 1 pound per week).

Weigh yourself a few times per week to make sure you are on track, and if the scale isn't moving, add 150 to 200 calories. If you are gaining too fast, trim the same amount. Trying to bulk up fast with a massive surplus is almost always a mistake once you are past the beginner phase, because the extra calories just turn into extra fat.

Eat Enough Protein

Protein intake is crucial for muscle growth. Research shows that gains in lean mass plateau around 1.6 to 2.2 grams per kilogram of body weight per day, so there is no benefit to forcing more. Spread it across three to five meals and aim for about 0.3 grams per kilogram per meal. If hitting these feels like a chore, a scoop of Purist® Whey Protein or High Protein Bars make it a breeze.

Focus on Whole Foods

You will also hear about clean versus dirty bulking. A clean bulk means getting most of your calories from whole, nutrient dense foods, while a dirty bulk leans on fast food and junk to hit a high calorie target. In practice, a clean bulk is far more effective because whole foods are more satiating, which makes it easier to stay within your surplus without accidentally overshooting. 

Try to get about 75% of your meals from quality whole foods and save the treats for when you need them to hit your calories or keep your sanity. Fill your remaining calories with a mix of carbs and fats, roughly 40 to 50% carbs and 25 to 30% fat works well for most lifters.

Train With Progressive Overload

Training is, of course, the other half of this equation. A surplus without a stimulus is just weight gain, most likely from fat. You'll want to shoot for at least 10 working sets per muscle group per week, and push most sets to within a couple of reps of failure and when a set becomes easier than your target rep range, increasing load by 2-10%. The goal is progressive overload, adding weight or reps over time, because that is what actually drives muscle growth.

How Long Should a Bulk Last

You'll want to bulk for about 12 to 16 weeks to give yourself enough time to gain muscle. The signal to stop isn't how you look in the mirror but how your training is going. Once you can't add weight or reps to your main lifts week over week, that means accumulated fatigue has caught up and it is time to switch gears. 

Spend a couple of weeks eating at maintenance to clear that fatigue before moving into a cut. A good rule of thumb is the 4:1 ratio: for every month you spend cutting, you should have spent at least four months bulking. Panic cutting after three weeks because your abs blurred will undo the whole effort.

How to Cut

Cutting is where you strip off the fat you gained during a bulk while protecting as much muscle as possible. If you're trained, aiming for about 0.5 to 1% of body weight loss per week will help you hold on to the most muscle mass. Losing faster than that will likely mean more of the weight you lose will be muscle.

Eat In a Deficit

When it comes to calories, research on trained folks shows that cutting more than 500 calories a day makes it harder to keep your muscle. For most people, a good goal is to eat a deficit of about 300 to 500 calories per day, which will work out to be about one pound of fat loss a week. This is fast enough to see changes in 8 to 12 weeks without tanking your performance.

Eat More Protein

Believe it or not, protein is even more important during a cut because when calories are restricted, your body is more likely to break down muscle for fuel, and higher protein intakes help offset that. Aim for the upper end of the range during a cut, around 2.2 to 3.0 grams per kilogram per day, spread across three to six meals.

Keep Training

Keep lifting to show your body that it needs to keep that muscle around. Focus on keeping your strength up, but don't be afraid to drop the volume if you feel beat up because you won't recover as fast on lower calories. If heavy weights start feeling awkward as you get leaner, try adding a few more reps with slightly lighter loads. We recommend creatine and a good pre-workout to help keep your energy high when food is low.

Consider a Refeed

If you find diet fatigue building up, short refeed days where you bump calories back to maintenance with mostly carbohydrates can help. Refeeds replenish muscle glycogen, keep your metabolic rate from dipping, and give you a psychological break from the restriction. During longer cuts, one to two refeed days per week works pretty well for most people.

How Long Should a Cut Last

A standard cutting phase lasts 8 to 12 weeks, but the length depends on how much fat you need to lose and how well your body is responding. Use these three biofeedback markers to know when to stop:

1. Training energy

2. Sleep quality

3. Hunger

When you can't keep all three in check without dropping below a minimum acceptable rate of loss (around 0.5% of body weight per week), the cut is over. Switch back to maintenance to clear the diet fatigue for a few weeks, and you will be ready for another productive bulk.

How to Cut After Bulking

If you're starting your cut after bulking first, don't switch overnight. Stay at your new weight for two to four weeks first to help your body recover from hard training and get used to its new weight. If you rush into a diet too fast, you're more likely to lose muscle and feel burnt out.

After that break, start your diet slowly by eating about 300 calories less than you need to stay the same weight. Watch how you feel and how your weight changes. If you aren't losing weight after two weeks, eat a bit less. If you feel exhausted or can't sleep, eat a little more.

Takeaway

Bulking and cutting works because it lets you focus on one goal at a time. Don't go overboard on your surplus or your deficit and keep your protein high and training consistent. You'll get results if you trust the process and avoid swinging wildly between bulks and cuts. Patience is key.

FAQs

What is bulking and cutting?

Bulking and cutting are two phases used to change your body composition. Bulking means eating in a calorie surplus while lifting weights to build muscle. Cutting means eating in a deficit to lose fat while trying to keep the muscle you earned. People usually switch between these two to get a leaner and more muscular body over time.

How long should a typical bulking phase last?

A bulk usually lasts about three or four months. You know it is time to stop when you can't lift heavier weights or do more reps in the gym anymore. After that, it is best to eat at a normal level for a few weeks before starting a cut. A good rule is to bulk for four months for every one month you spend cutting.

Should you bulk or cut first?

Whether you should bulk or cut first depends on where you are starting. If you are already relatively lean and want to get bigger, start with a bulk. If you have some extra fat to lose, it is better to cut first. If you are brand new to lifting, you might not need to do either yet; you can often build muscle and lose fat at the same time just by eating enough protein and training hard.

Rachel MacPherson is a Nutrition Coach and health writer with over a decade of experience sharing science-backed information in the health and wellness space.

This article was reviewed by Rosie Borchert, NASM-CPT, for accuracy.