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How Much Fat Can You Lose In One Week? (And How To Do It)

by Jeremy Ethier - August 3, 2019

The faster we burn off fat, the better, right? Wrong. In this article, you'll learn the truth about how much fat you can lose in one week.

Most people don’t realize there’s an upper limit as to how much fat you can lose every week.

If you try to push past this weekly limit by doing more cardio or eating even less you’ll start to lose substantially more muscle instead of fat.

Do this for months on end and you’ll eventually end up with a “skinny fat physique”. Too little muscle and still too much fat. Obviously, this is not ideal.

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How Much Fat Can You Lose Per Week? 

So now the real question becomes what’s the MOST amount of fat you can lose per week while minimizing muscle loss in the process?

As this is going to better enable you to attain the lean, muscular physique you’re after instead of just winding up skinny fat.

To answer this question, we’ll use the findings of a 2005 paper by researcher Dr. Alpert, who used various fat loss studies in an attempt to quantify the maximum amount of fat one can lose per day without excessive muscle loss.

What he found is that the body is capable of burning body fat to use for energy at a maximum rate of 31 calories per lb of body fat per day.

Once you exceed this rate, the body then has to tap into your muscle mass in order to make up for its energy needs.

Although this study is theoretical and does have its limitations, when you crank out the numbers they actually align well with both past research (study, study) on the topic and with my own experience as a coach as well.

But to put this theory into perspective for you, let’s use an example.

Let’s say John weighs 200lbs and is at 20% body fat. Multiply these two numbers and we can determine that John has 40 lbs of body fat.

Multiply this by the maximum rate I mentioned earlier of 31 calories per lb of body fat and we get 1,240 calories. This represents the maximum daily calorie deficit John should employ every day to maximize fat loss while minimizing muscle loss.

To find out what this would equate to in terms of lbs of fat loss per week, we can multiply this number by 7 to represent a week. Then, divide it by 3,500 since we know that this is roughly what 1 lb of fat is equivalent to.

We end up with 2.5 lbs which represents the theoretical maximum amount of fat John can lose per week while minimizing muscle loss.

On the contrary, if you’re a leaner individual like Jimmy who weighs 170lbs and is at 15% body fat it's a different story.

Jimmy is only carrying around 26lbs of fat. His theoretical maximum rate of weekly fat loss would be only 1.6lbs per week.

So as you get leaner, the maximum amount of fat your body is able to lose per week reduces. This is something research papers have confirmed too.

How To Put This Into Practice 

So now that we’ve covered what the maximum rate of fat loss is per week, how can you now go put this into practice?

Well, if you’re truly seeking to lose fat as fast as humanly possible, then here’s what you’d do.

First, find out what the maximum daily calorie deficit and weekly fat loss number would be for you using the process I outlined earlier.

To achieve this deficit, you need to eat below your TDEE or maintenance calories. You also need to be performing regular resistance training and doing additional cardio.

Then, you simply monitor your body weight throughout the weeks. Every week try to hit your target maximum weekly fat loss number.

As you progress and your body fat decreases, slow down your rate of fat loss to minimize muscle loss.

You can do this by re-calculating what your maximum weekly fat loss number would be at your new weight.

So over time, the rate at which you lose weight should slow down.

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Is Rapid Fat Loss A Realistic Approach?

That’s basically all there is to it. But, with all that being said, I do want to provide some pre-cautions. Keep in mind that this protocol is a very aggressive approach. This approach employs a fairly large calorie deficit, high activity, and a fast rate of weight loss.

For some who are more experienced this may be completely doable. But for most people (especially those just starting out) it’s very difficult to do. You’d be much better off taking a longer, less aggressive approach that you’d be more likely to stick with.

As researcher Dr. Albert points out that if you’re under this 31 calorie/lb limit, it doesn’t mean you won’t lose muscle.

It simply represents a threshold value past which the rate of muscle loss starts to become exponentially larger.

To maintain as much muscle mass as possible or even build muscle, a less aggressive deficit would be best.

But if you get motivated by seeing results fast and can adhere to a tough protocol, then go for it.

Otherwise, taking a slow and steady approach and making positive long-lasting changes to your lifestyle is what I recommend. This is what more often than not delivers the best results.

I hope you were able to see that sometimes burning fat faster isn’t always better.

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How Much Fat Can You Lose In One Week? (And How To Do It)