[GUIDE] The Best Diet To Get Lean In 12 Weeks


If you’re not content with an average physique, you’ve likely spent the last 6-8 months focusing on eating more food and building muscle. 

Here’s the problem: 

You still won’t look (or feel) like someone that trains as hard as you do, until you get lean enough. 

A great example of this is our online client Michael:

He already had a good amount of muscle on the left, but over the course of 12 weeks went from 178 to 162 lbs. 

Before starting coaching, Michael was struggling with the same thing you are right now - the hard work he was putting in at the gym wasn't reflected back to him in the mirror.

Given you already have a good amount of muscle mass, getting leaner is usually the missing link here, just like it was for Michael.

That's exactly why in today's blog, we're digging into the science-backed nutrition strategy you need to finally uncover your best physique over the next 12 weeks.

Here's the plan:

→ Phase 1 [Weeks 1-5]: Rapid Fat Loss

→ Phase 2 [Week 6]: Diet Break

→ Phase 3 [Weeks 7-12]: Final Push W/ Floating Refeed


We know that the more aggressively you lose fat, the higher the risk of of muscle loss is during the fat loss process.  

But why does muscle loss happen?

It comes down to something call net muscle protein balance:



Your muscles are essentially "built from protein".  

→ Muscle protein synthesis (MPS) is the process of your body repairing/adding to your current muscle protein. 

But there’s another, more sinister force at work here... 

→ Muscle protein breakdown (MPB) is the process of your body breaking down muscle protein.

You muscle proteins are basically stuck in a constant battle between MPS and MPB - sometimes rate of MPS is greater than MPB, sometimes vice-versa.

→ To build muscle: we need positive net protein balance - more MPS have occurred than MPB - cross any given timeframe.

→ To lose muscle: More MPB than MPS must have occurred.

Maintaining (or ideally, building) muscle as you get leaner is crucial to achieving an impressive physique at the end of your 12 week fat loss phase.

Most people struggle to reach the body the want not because they don't get lean enough... but because they don't have as much muscle as they need to achieve the aesthetic the want when they are lean (this is a very common struggle for women and men alike, and one we've helped many clients remedy through our online coaching program.)


To understand why a smart, science-based approach to fat loss like our clients use is so important, you first need to understand why you're at risk of losing muscle if you go about fat loss the wrong way.

1. Your Body's Rate Of Muscle Protein Synthesis Is Slowed While Dieting

Eating in a calorie deficit (eating fewer calories than you burn) seems to reduce your baseline levels of MPS, as well as the degree to which your body increase MPS as a response to consuming protein. (2)(3)(4)

Muscle is an "energy expensive" (it takes lots of calories) tissue for your body to build and maintain. So in a period of calorie scarcity, it wouldn't make sense for your body to prioritize adding or maintaining lots of this "expensive" tissue.

2. Training Performance Can Be Worse

Calories are energy. So when you're eating in a calorie deficit for fat loss, you're literally in an "energy deficit", and thus have less energy to freely spend on things like pushing hard in your training. 

Lifting challenging weights is the primary signal to your body that adding (or at least maintaining) muscle is important.

So if training performance suffers dramatically, maintaining or building muscle while losing fat is much less likely.

This is why the nutrient-timing recommendations we'll discuss below are so important.

3. Your Body Is More Likely To Use Protein As A Fuel Source

When plenty of energy (calories) is available, your body prefers to use carbs and fats as its fuel sources, as the process of converting protein to a usable energy source for your body (gluconeogenesis) is energy expensive and inefficient.

That said, when dieting and short on available energy, your body just doesn't have enough energy coming in (in the form of carbs and fats) to fuel itself, so it can potentially start breaking down more muscle protein as a fuel source.

You'll have more in the tank as far as your ability to train right now because you're not as lean.

So after hearing all of this, you're probably wondering...

"Why are we starting off with a RAPID fat loss phase? Won't that cause me to lose even more muscle?"


Over short time frames (4-6 weeks), and when you're not as lean, we don’t need to nearly as much about muscle loss accompanying rapid fat loss (as long as you're still training hard)

Here's why.

1. You're Starting At A Higher Body Fat Percentage

We do have research that seems to indicate the amount of muscle vs. fat lost depends on how lean you are. (8)

Think: when you're less lean, your body has plenty of fat stores to pull from for energy to compensate for the lack of calories being eaten. This makes muscle protein breakdown less likely.

As you get leaner (probably below ~12% body fat for men and ~18% for women), pushing aggressive fat loss is more likely to result in muscle loss, as your muscle protein will suddenly become a much more likely candidate to be broken down for energy.

So at the start of a diet (given you're not already <12% body fat), it makes sense to be more aggressive, and then slow rate of loss as you get leaner.

2. Training Performance Will Still Be High

On a similar note to the above point, much of how hard you're able to train (which again, is very helpful for preserving or building muscle mass) is tied to how lean you are.

Even though calories will be low (which of course does still impact training, but is far from the only factor here), much of the "low energy" levels associated with dieting come from changes in levels of the hormone leptin.

Leptin is essentially your body fat regulator. It's secreted from your body's fat cells. So as fat cells shrink, leptin levels also decrease.

Low levels of leptin will cause hunger to increase, but will also cause your body to "put the brakes" on any excessive energy expenditure.

This means as you get leaner, you also get more lethargic - a partial cause of drops in training performance.

That said, realize that leptin levels are also influenced by carbohydrate intake in the acute setting (levels can be dramatically increased or decreased in a matter of days, depending on your intake). So again, body fat isn't the only thing that matters here.

But the fact that you're less lean means that you'll still be able to push much harder in your training on lower calories than you'd be able to later in the diet.

Motivation is highest, hunger is lowest, and your energy levels in your training are highest during the first month of the diet. 

 You’re still so fresh to the diet and training performance won’t be dramatically impacted also means you’ll be able to hang onto (or even continue to build).

That’s why we’re going to be pushing along aggressively for the first 5 weeks, before taking a week at maintenance.  


→ Rate Of Loss: 1-1.5% of bodyweight per week.

Calculating Calorie Intake: 

1. Determine your current maintenance calories (if you don't know, use this calculator for a rough estimate).

2. Determine how many pounds per week you need to be losing to hit the desired rate of loss (I.e. a 200 lb man losing 1.5% of body weight per week would be losing 3 lbs per week).

3. Eating 3,500 calories below your maintenance equals 1 lb of fat lost. So if you need to lose 2 lbs per week, you need to eat 7,000 calories below your maintenance intake across the week.

Calculating Macros: 

PROTEIN - Adequate protein is crazy important here.

1. It’s the most filling food, so making it a focal point of every meal will help prevent cravings and overeating.

2. The amino acids in protein are the building block of muscle tissue. So plenty of dietary protein is a must to prevent your body from breaking down muscle protein due to lack of available protein via your diet.

3. It burns the most calories during digestion. All foods have a “thermic effect” - meaning they actually burn calories while being digested. Protein by far burns the most calories during digestion:

So basically, eating plenty of protein is very important for the physique you want, and can even speed up your fat loss a bit.  

FATS - Fats are important to prevent major hormonal disruption, as many of your hormones are actually built (in part) from dietary fat. That said, there's a very clear "ceiling" where we stop receiving any major benefits from eating more fat.

CARBS - Once you’ve hit the recommended doses of the above, it’s smart to fill the remainder of your calories with carbs. 

Remember, you’re not just here to lose fat. 

You also want to maintain (or ideally build) as much muscle as possible. This is very much a product of how hard you’re able to train during your diet. 

Carbs are the fuel source your body prefers to burn, and the one it runs on most optimally when you’re training to build muscle. 

When training in the 5-15 rep range (which is where a majority of your sets should be for muscle gain or maintenance), most of your sets will last 20-40 seconds.

Your energy system responsible for fueling intense bouts of training in the 20-40 second range is fueled exclusively by carbs:

So filling the remainder of your calories with carbs is essential to fueling your training to the best of your ability, and achieving the result you want at the end of this diet.

→ Final Macro Recommendations:

  • Protein: 1-1.5g per pound of body weight
  • Fat: .3-.4g per pound of body weight
  • Carbs: The rest 


1. Nutrient Timing

For someone who’s been training multiple years like you, whether you build, maintain, or lose muscle during this cut is largely a product of how well you manage the smaller (but still important) details.

One such detail you shouldn't overlook is nutrient timing.

→ Consume 3-5 meals/snacks, with 3-5 hours between, each containing 30g+ protein

Not only will having a 30g+ bolus of protein help you achieve the “satiating dose” needed to get the maximum amount of fullness from your meal (thought to be around 20g of protein in a meal), it'll also help you stimulate muscle protein synthesis more frequently.

We need 2.5g+ of the amino acid leucine found in protein to optimally stimulate MPS - this is the "leucine threshold". 

Consuming 30g+ of protein from a quality source is a safe bet to ensure you've hit this threshold.

"But why not just eat all my protein with a single meal?"

Upon consuming protein, once enough protein is taken in to saturate the muscle, the “muscle full” effect happens:  

1. ~30 mins after consuming an adequate bolus of protein, rate of MPS ~triples. 

2. At ~90 mins, rate of MPS peaks, before returning to baseline levels at ~2 hours.  

This return to MPS baseline occurs regardless of how much protein is still available in your bloodstream.

So you need to re-stimulate MPS in a few feedings across the day to consistently keep rate of MPS higher. As long as you get 4 feedings with 3-5 hours in between, and one pre-bed, you’re probably in a good place here.

Jorn Trommelen and the Stronger By Science team did an excellent job illustrating smart protein timing to maximize MPS in their article on perfecting protein intake:

2. Carb Timing 

The reality of aggressive dieting is, carbs will be limited.  

One more time, you want to do everything possible to ensure you’re still crushing your training. 

This means it’s smart to center most of your daily carb intake pre + post workout. This will have you better fueled during your training, and better recovering afterwards. 

3. Steps

The most underrated key to quick fat loss. 

As we know, fat loss comes down to energy balance:

→ Calories in > Calories out = Weight gain

→ Calories in < Calories out = Weight loss

Everything we've discussed relates to manipulating calories in. 

But that doesn’t matter much if calories out are constantly varying. 

See, along with the decrease in leptin while dieting comes a down-regulation in N.E.A.T (non-exercise activity thermogenesis) - movements like pacing fidgeting, blinking, etc. make up the calories you burn via N.E.A.T.

Calories from N.E.A.T. do make up a good chunk of the calories you burn in a day...

...so when our body senses less energy (food) coming in, it tries to prevent fat loss by reducing N.E.A.T.

One of the best ways to counteract this is to set a daily step goal. 

If you’re not currently hitting a step goal, I would simply make an effort to walk a reasonable amount over the next few days, track your streps, and determine a realistic number you can hit daily. 

Over the next 12 weeks, ensure you hit this to prevent any dramatic down-regulations in calories out (And stalled fat loss).


By the end of Week 5, you’ve lost 5-7.5% of your body weight. (So a 150lb woman could have lost 7-9lbs.)

Good work. Now it’s time for the diet break.


You’re going to dramatically increase your calorie intake for the next week, back to maintenance levels. 

Here’s what to do: 

1. Determine your average rate of loss over the last 3 weeks. 

2. Remember the “3,500 calories below maintenance equals 1 lb of fat loss" guideline we talked about before? Use this to determine how large of a deficit you’re currently in based on rate of loss (e.g. if losing 2 lbs per week, you're in a 7,000 calorie per week deficit), and reverse engineer from there to establish what your maintenance calorie intake currently is. 

3. Bump calories back up to your maintenance intake, ideally keeping protein and fat intake the same as they have been for the last 5 weeks, and ramping up carbs. (So if you were in a 1000 calorie per day deficit, you’d increase carbs by 250g per day, for the next week.) 


1. Refill Muscle Glycogen Stores

Muscle glycogen is essentially carbohydrate stored in your muscle and liver. 

Having larger stores of this is beneficial to your ability to train hard. 

But of course, as carbs get more limited on a diet, muscle glycogen stores decrease, which in turn can hurt your ability to train hard. 

Taking a diet break allows you to refill muscle glycogen stores, and improve training quality dramatically.

2. Decrease In Hunger

A recent study on one week diet breaks by Jackson Peos and colleagues (6) seemed to show they're an effective tool to decrease hunger and desire to eat:

3. Mental Preparation For The Final Fat Loss Phase

A large part of the benefit of diet breaks is psychological. 

Typically, the larger the deficit you’re in, the more challenging it’ll be to maintain mentally. This is further compounded by the fact that you’re still training hard at least 4 times per week. 

Fortunately, taking a one week diet break has been shown to decrease irritability and increase alertness, and will have you refreshed and ready to push again. (5)


1. Food Choices

The biggest diet break mistake people make is thinking a diet break is a time to just constantly eat lots of calorie-dense foods. 

This pretty quickly puts you over your calorie goal, and isn't a realistic picture of how you need to eat long-term to sustain your results. 

Stick mostly to the foods you normally eat, just in greater quantities. When you try to work in too many calorically-dense foods, you can easily eat more calories but be less satiated than when you're on your diet. 

2. Weight Gain 

You’ll likely feel a bit fluffier and weigh a bit more. Your body is holding more water, and your gut content has increased. This doesn't mean you’ve gained fat back. 

If calories in are equal to calories out (which is the goal in a diet break), you won't gain fat.

3. Mindset

This isn't just a time where you eat whatever and don't track. Think of this time as practicing maintaining, refuel your body, and prepare mentally for the next 6 week fat loss phase.


You’ve already put in a lot of work over the last 6 weeks. Time to finish this cut strong.  

You'll be taking a bit different approach for the next 6 weeks vs. what you did the first 6.

Rate Of Loss: .5-1% of body weight per week.

Now that you're getting very lean, we're following the recommendations given by Eric Helms and colleagues for natural bodybuilders. (6)

This slower rate of loss means you'll likely be able to eat more than before. 

This will help keep training quality high, and also make the remainder of the diet much easier to stick to mentally (as you have more calories to work with)

→ Calculating Calorie Intake

1. Determine how many lbs per week you need to be losing to hit the desired rate of loss.

2. Determine your current maintenance calories.

3. Eating 3,500 calories below maintenance equals 1 lb of fat lost. So if you need to lose 1lbs per week, you need to eat 3,500 calories below your maintenance intake across the week. 

→ Calculating Macros

These stay the same as before - the same considerations for nutrient timing apply as well.

  • Protein: 1-1.5g/lb
  • Fat: .3-.4g/lb
  • Carbs: The rest


One new element that we’re adding here is a “floating refeed” day. 

Consider this a mini diet break.  

Basically, it’s a single optional day at maintenance that you can use once per week, on the day of your preference.  

In an ideal world, you’d apply the same macro approach as the diet break here (increasing calories mostly via carbs) to replenish muscle glycogen stores, which again helps out your training. 

But, the real benefit of the floating refeed is as an adherence tool to stick out these last 6 weeks of your diet. So it's ok if you'd prefer to add in more fat and less carbs, as long as you control calories. 

Knowing that you have the flexibility to work in a few more glasses of wine, or a bit more food at your favorite restaurant while out to dinner if you want to once per week allows our clients to see the diet through. 

Here’s how we’d normally set this up in an online client's metric tracker:

That said, remember that this is optional - if it doesn’t feel needed, and you’d rather see quicker fat loss, you’re welcome to stay in the deficit.


Over the 6 weeks of the final fat loss push, you can realistically lose another 2.5-5% of your body weight.

This puts your total at 7.5-12.5% of body weight lost over the last 12 weeks.  (An initially 200 lb man could have dropped all the way to a shredded 175. An initially 150 lb woman could have dropped all the way to a lean 132.)

You’ve also been able to maintain (if not build) muscle, and likely have uncovered your best physique yet.

Next, it's crucial that you have a plan for the diet after the diet. (Check out our Reverse Dieting Guide here.)

These are the same science-backed strategies we implement with our online clients undergoing the physique transformation process. 

If you're ready to be coached 1-1 by our team to your best physique ever, click here now to apply for online coaching with our team.

About The Author

Jeremiah Bair is a certified nutrition coach, strength coach, and owner of the online coaching business Bairfit. Check out his Podcast and Instagram  for more educational content.

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