11 Reasons Why You Need To Lift Heavy For Fat Loss

'I don't want to get bulky'.
'I want to tone'.
'I need to use lighter weights, so I can work up a sweat and burn fat'.
'I don't want to look like a bodybuilder'.

I often hear phrases like this from people trying to lose body fat in the gym. These comments are used to 'justify' their high-repetition, low-weight, short-rest workouts that they incorrectly believed to be the best way to burn off that excess fat.

Yet the guys and gals doing the exact opposite—lifting big weights and taking a five-minute rest break between sets and hardly breaking a sweat appear in much better shape with lower body fat levels.

Why is this the case? Simple. The best way to 'tone', to 'lose body fat' and to 'burn more calories' is actually by lifting heavy weights and taking longer rests.

I'm going to share 11 reasons why this is the case.

Quick side note—I need to mention that lifting heavy won't turn you into an overnight hulk. Most gym-goers and I wish it was this simple! Turning into a beast requires a lot of eating, lots of rest and, yes, heavy lifting. Likewise, with the concerns of looking like a bodybuilder. Bodybuilding requires a perfect diet, extreme discipline and years of hard training. The misconception that lifting heavy weight will turn you into a bodybuilder is like someone going to a spin class and thinking it will turn them into a Tour de France competitor.

11 Reasons Why You Need To Lift Heavy For Fat Loss

1. High Repetition Lifting Causes An Upregulation Of Stress Hormones Like Cortisol

I need to clarify what I mean by 'heavy lifting'. With this term, I mean lifting a weight that you can only perform 2–10 repetitions before muscle failure. This forms one 'set'. Ideally, a set is performed in a recovered state, with minimal muscle fatigue. The best way to achieve this is to allow a rest period of 90 seconds or longer between sets.

Doing high-rep lifting, especially when combined with short rest periods is a recipe for disaster. In fact, training this way could actually promote fat gain. Why is this the case?

If you are lifting a weight that you can perform more than 20 reps you are training in no man's land. With a high-rep range, you may not be creating a big enough load on the muscle to impose a training effect (more on this later). Instead of demanding the use of your big fast-twitch muscle fibers, you are using the weaker (and smaller) slow-twitch muscle fibers. Those can only put out a small amount of power. At the same time, slow-twitch muscle fibers can recover very rapidly.

This is why you can perform so many reps with a low weight. The hormonal impact this has on the body is far from ideal if your goal is to lose fat. Training the slow-twitch muscle fibers over and over again simply increases the production of cortisol. Cortisol is a stress hormone that suppresses testosterone and growth hormone (both of which are potent fat burners). Also, this high-rep, high-volume training creates high amounts of inflammation in the body. This, in turn, increases free-radical production (which is linked to many health issues and accelerated aging).

Liken this type of training to a car spinning its wheels on a road—you're doing a ton of damage and not getting anywhere.

2. Heavy Lifting Increases Muscle Mass. More Muscle = Increased Metabolism

The more muscle you have, the more energy the body requires even at rest. This is why a 95kg athlete can take a fortnight off training and eat ad lib and not gain an ounce of fat. Meanwhile, the overweight sedentary individual knows that if they don't do some form of exercise they need to be very careful with their diet otherwise they'll pile on the pounds.

Doug McGuff sums this up best when he says, 'If you lose 5 pounds [2.5kg] of muscle, the amount of calories you burn in a 24-hour period will decrease by 250 calories.'

This may not sound like much, but over a week that's 1750 calories. Remember, this is energy burnt at rest. Extra muscle mass means your body needs more fuel to just 'live'.

3. High-Rep, Short-Rest Workouts Increase Efficiency Which Means Lower Muscle Mass

What is your goal by doing those circuit-training type, short-rest, high-rep sessions? Let me guess—lose weight? melt away fat? burn calories?

What you're actually doing is training the body to get rid of muscle. These higher rep workouts don't send a strong enough stimulus to the body that powerful muscles are important.

Because you're only using a small portion of your muscle mass, the extra muscle is weighing you down. That extra muscle requires more energy even at rest (see the previous point), yet it's not required for those workouts. So, what does the body do? It turns that unnecessary muscle into energy. Your body wastes away—you lose muscle mass and with that, you take a step away from reaching your 'toned' body.

If you look at any professional endurance athlete you will notice a lean (and frail) body. Their body is so specialized, so efficient at performing a certain movement over and over again. Every muscle fiber has been trained in a way to maximize power output while minimizing energy expenditure. It is for this reason why they are so successful at their sport. They teach their body to spin their legs over and over and over. If you compare an endurance runner with a sprinter you can see how the long-distance runner has lost all their 'power' muscle fibers due to not needing them.

Now, I know you're thinking, 'I don't want to look like a muscle-laden sprinter'. But like my comment about bodybuilding, lifting heavy weights does not automatically give you the physique of an Olympic sprinter.

My point here is simple—by doing high-rep, high-volume, short-rest, circuit-type training, you are sending a signal for the body to work more efficiently. Consequently, you will begin to look more like that endurance runner.

4. A Toned Muscle is a Strong Muscle That You Can See

Look at this illustration. Which bodies appear the most 'toned'?

The bodies on the right? So, what changes as you move from the guy on the left to the guy on the right? Simple—they lost body fat and now that muscle is visible. The muscle itself, most likely, didn't even change. In fact, it would be my bet that the muscle mass is higher in those on the left than for those on the right side. Yes, they probably lost muscle mass as they became lean. But because they lost a lot of fat, the muscle is now visible and looks 'toned'.

Toning requires strengthening and building up a muscle while also losing fat.

Let me reiterate the first half of that sentence—'Toning requires strengthening and building up a muscle'... If there is no muscle there, to begin with, you can lose all the body fat in the world but you'll never have a toned look.

Case in point:

Both of these bodies have similar levels of body fat. Yet one body has a lot more muscle. Again, toning requires strengthening and building up a muscle while also losing fat.

If you are following along, you know that the best way to build up muscle is by lifting heavy weights. And you also know that the best way to lose fat in the gym is by lifting heavy. (For the ultimate way to lose fat look at The Program here).

5. Strength Training Helps Maintain Muscle Mass When In a Calorie Deprived State.

In other words: heavy lifting + dieting helps achieve that sought-after toned look.

This claim is supported by a 1993 study posted in the American Journal of Clinical Nutrition. In this study, the researchers found that when dieting, participants who lifted heavy weights maintained higher levels of muscle mass than those who didn't. The body functions on a 'use it or lose it' principle.

Ken Hutchinson, who authored the paper 'Proper Exercise... and its Role in Reducing Fat' which I highly recommend reading, likened the body to a large corporation run by a board of directors. The body is split up into 'departments' like a company. If a body is in a calorie deprived state it is like a corporation running on a budget deficit.

Doug McGuff in the book Body By Science continues this analogy so eloquently:

Ken then outlined two scenarios. In the first scenario, there is a budget deficit and no department has any unusual demands. Layoffs can occur in all departments. So, the board lays off some fat, some muscle tissue, some bone, some connective tissue and some nervous tissue. The corporation becomes a smaller version of itself.

In the second scenario, there is also a budget deficit, but a large demand has been placed on the muscle department. Therefore no layoffs can be afforded in this department, indeed, more staff must be hired on as soon as possible. This necessitates a large layoff in the fat department. Furthermore, no cutbacks can be made on the bone and connective tissue departments because they are needed to support the muscle department, which is not useful unless it is connected to strong bones through strong connective tissue. The recourse is that more fat has to be cashiered. No nervous tissue can be spared either because the muscle is also useless unless it is innervated by new nervous tissue.

This imposes even more cut backs in the fat department. With these changes the corporation takes on a noticeable shape change. Under this scenario all of the body’s weight loss has been shunted exclusively towards fat loss. You have added a modest amount of shape-improving muscle and jettisoned a large amount of shape-ruining fat.(McGuff)

6. Strength Training Burns Through Sugar

Lifting heavy weights in a stop-start fashion (e.g., a set of eight reps, followed by a decent rest period) empties the muscle of its glycogen stores (stored sugar). This emptying and later refilling (through eating food) helps improve the body's sensitivity to insulin. Meaning the body has an improved ability to use sugar in a safe and useful way ('useful' meaning as energy, not turning it into stored fat).

Through intense heavy lifting, you improve the sensitivity to insulin receptors in a muscle.

7. High-Rep 'Feel-the-Burn and Make-Me-Sweat' Sessions Don't Actually Burn More Calories Than Heavy Lifting

I'm not a big fan of calorie counting or 'burning calories' to lose weight, but some people are. Some people get very caught up in exercising to maximize calorie expenditure.

Many people believe that a high-volume, high-rep, short-rest workout with lighter weights is going to burn more calories than a simple 'five sets of five reps' over the same 30-minute window. And yes this may be true for the short term, but it's important to look at the bigger picture.

When you perform intense workouts from heavy lifting, the body continues to burn calories at a higher rate for hours post training. Also, the stress imposed on the muscle tissue means the body needs to repair and rebuild damaged tissue—another energy need. As the damage done to a muscle on a high-rep, light-weight type workout is so low you do not get these post-training energy demands.

Plus, the strengthened and larger muscle now uses more energy at rest (see the second point in this article) and the bigger muscle can also store more glucose as glycogen (see point six).

8. Heavy Lifting With Adequate Recovery is the Best Way to Make Hormonal Changes

Even though I mention calories in the previous point, the true driver behind body change is hormones—not calories. There is a saying that I like: 'Calories matter, but hormones matter more'.

You shouldn't go to the gym with the intention to 'burn calories' if your goal is fat loss. Instead, you should look at training to create beneficial hormonal changes.

Training with light weights over high reps is going to create a hormonal change. Unfortunately, it's not a change that is supportive of your fat loss goals (see the first point). Whereas heavy lifting with adequate recovery creates a hormonal change that helps speed up fat loss. This is explained in more detail in my next point.

9. Heavy Compound Lifts Increases Testosterone Whereas Endurance Training Decreases Testosterone

Let me emphasize heavy lifting. Doing that pump class with your girlfriend doesn’t count nor does curling 5kg dumbbells for 20 reps or getting a burn from doing 50 bodyweight squats.

I’m talking heavy, intense weights that you can only perform for two to ten repetitions. And the more muscle you use the better. Studies show that the good old squat made the body produce more growth hormone and testosterone than a machine working similar muscles. Therefore, train using squats, deadlifts, rows, chin-ups, presses, etc.

Another study showed that 'strength training can induce growth hormone and testosterone release, regardless of age.And it's not only lifting heavy weights that are important, but research has also shown that longer rest periods of two minutes or more are better for increasing testosterone.

If you look at the other side of the coin—repetitive, high-volume 'sweat sessions'—you will discover that this type of training actually lowers testosterone. This paper compared testosterone levels of weightlifters, a control group and road cyclists (all of the same age). Of the three groups, the weightlifters had the highest testosterone levels, while the endurance riders had the lowest. It is well established in the literature that chronic endurance training suppresses testosterone levels in men.

For more on increasing testosterone, be sure to grab a copy of my book Increase Your Testosterone Naturally!

10. You Are Less Likely to Overtrain with Heavy Weight Training

This is important as overtraining puts chronic stress on the body. And chronic stress leads to extra fat retention.
If you’re training intensely every day and have been for a while, you’re probably heading down the path of overtraining. Even if you’re not training with massive loads and intensity, you must ensure your recovery is adequate. Factors such as sleep, lifestyle stressors, adequate calories and proper nutrients all impact your body's ability to recover. If you have noticed your motivation to train is declining, you’re falling ill more often or your progress in the gym is stalling, then chances are high that you have been overtraining.

Not recovering from your training is going to chronically raise cortisol levels while lowering testosterone levels. A poor testosterone-to-cortisol ratio will lead to muscle loss and fat gain. Also, a high-cortisol level will increase insulin resistance and fat accumulation (especially around the abdominal area).

By lifting big weights in a smart manner it is rather difficult to overtrain, the demands on the body are so high that you will crave a few days of lounging about while you recover. Whereas with lower weights and higher reps the stress load is much lower, so you feel like you can repeat the training day after day. Actually, you can even become 'addicted' to this style of training (think of the aerobic class gals that never miss a workout) despite all the increasing warning signs of overtraining (e.g., joint aches, feeling flat and tired, low energy, low motivation, poor immune function, increased fat gain, etc.). Again this is due to training in 'no man's land'. It's not intense enough to create big change, but it's hard enough that it 'feels good' and is creating an unhealthy stress load on the body.

That leads us to the most important point.

11. Minimum Effective Dose—Intense Training Sends a Strong Training Stimulus

When you go to the gym, what are you trying to achieve?
If it's to burn as many calories as possible, reread point seven.
If it's to tone your muscles, revisit point four.
If it's to ultimately 'tone' and sculpt your body—to simply look good naked—then heavy strength training is the best strategy (reread all the points!)

If you want to achieve these results while minimizing the negative effects (elevated cortisol, overtraining, injury, etc.), then you need to find the minimum effective dose (MED).

This is a term popularised by Tim Ferriss of The 4-Hour Body fame. He defines it as 'The minimum effective dose is defined simply: the smallest dose that will produce the desired outcome.' For a detailed explanation of MED, check out this article.

How do we find the MED for training? In particular, training for fat loss. It is fair to say that the benefits of training don't come from the exercise itself, instead, they come from the adaptions that the training creates. What triggers these adaptations? It is the stimulus on the body sending a signal to the body that 'we need to adapt'.

Knowing this, we can work backward to find the MED. We need to send a strong signal to the body then back off so that the body can do its adapting.

Think about it this way. Let's say you want to build a house. You hire a builder to complete the job for you.
In the first scenario, you meet with him frequently throughout the week. Every time you see him you are indecisive about what you want, never giving him the full picture. One day you tell him you want a five bedroom two bathroom house. Then a few days later, after he has built the foundation for a big house, you tell him you now want a three bedroom house with lots of windows. The builder never makes any solid progress. You become annoyed, so you keep checking in with the builder day after day (and continue to change your mind about decisions).

Meanwhile, the builder gets overwhelmed and stressed out. You can't rest because you're wasting resources on a project that's not achieving anything. You never build your house despite investing a huge amount of time, energy and money into the project. Six months later, you find another builder and the cycle continues.

In the second scenario, you sit down with your builder and share with him your vision. You know what you want and you want to do it as efficiently as possible. You want to free up resources (time, money, energy) to focus on growing your business and spending time with your family. You send a clear message to the builder 'this is what I want'.

After this strong signal is sent, the builder starts working on the project behind the scenes. Once a week, you schedule a 30-minute meeting with the builder. These meetings are efficient, you know the end goal, so you go into the meeting with a clear goal. Sure you may need to make some tweaks to the project, but you continue to send a strong signal to the builder 'this is what I want'. The builder then adapts to that clear signal.

I hope this analogy portrays what you need to do in the gym. Let the body do the work (the body is the builder). You need to send the body a strong signal to create a training effect (the weekly meeting with the builder discussing the plans (e.g., a weekly heavy-weight session).

Between sessions, you back off and rest. You trust your body (the builder) to take care of the job without further distraction (ongoing training, mixed signals) allowing more time to recover and progress towards your goal.

The best way to send this strong signal is by lifting heavy weights once or twice a week. That is your MED. You will get your best return on investment by lifting heavy when the body has recovered. You will lose your investment by training many times a week doing light weights and high repetitions.

The Ideal Workout For Fat Loss?

Hopefully, now you will stop doing light-weight, high-rep workouts. Instead, you will lift heavy weights for a few reps. If you're confused about how to go about training this way, then don't be. There are many great programs on the web. A simple '5x5' program once a week will suffice, or if you're new to lifting check out Starting Strength by Mark Rippetoe.

Even better, check out the Size & Strength workout program that utilises heavy resistance training to help you build the body of your dreams. 

Or, if you're looking for the true MED for intense lifting, then take a look at the work by Doug McGuff with his high-intensity, super-slow training. I cover this in a lot more detail in THIS article.

If you are stuck or seeking help reaching your fat loss goals, be sure to look at The Program where I help clients from around the world look and feel amazing.


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This blog post was written by Alex Fergus. Alex is an ISSN Sports Nutrition Specialist, Fitness Professional and certified Superhuman Coach who continues to expand his knowledge base and help people across the world with their health and wellness. Alex is recognized as the National Record Holder in Powerlifting and Indoor Rowing and has earned the title of the Australian National Natural Bodybuilding Champion. Having worked as a health coach and personal trainer for over a decade, Alex now researches all things health and wellness and shares his findings on this blog. Learn more about Alex's Credentials HERE.

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