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Let's be honest:
Losing 20 lbs of body fat in only 30 days sounds like a pretty sweet deal.
Hell, where do I sign up?
But the guy asking me the question was serious.
He'd seen those numbers in a bestselling book, so in his mind they were 100% achievable.
And here's the worst part:
He wasn't making anywhere near that sort of progress so he was driving himself crazy wondering what he was doing wrong...
...or if there was something wrong with him!
And he wanted to know what the deal was...
Losing 20 lbs of Fat in 30 Days: The Reality
OK, just to be clear, we're talking about losing 20 pounds of fat not just "losing 20 pounds".
Why is that important?
Well, just check this out...
Yep, in August I managed to lose close to 5 lbs in just two days!
Now that sounds pretty extreme, right?
But the reality is that kind of rapid loss (or gain) in weight almost always comes from nothing more exciting than short-term changes in body water levels.
(After all, around 60% of our bodyweight is water, which means a 200-lb man contains more than 14 gallons of the stuff!)
Bottom line?
We're talking about losing 20 pounds of FAT, not just "losing 20 lbs"
And here's how that works:
First off, 1 lb of body fat contains something like 3,500 Calories of energy.
OK, that number may not be 100% accurate but it’s a good rule of thumb.
So, losing 20 lbs of fat means we need to burn off 20 x 3,500 = 70,000 Calories.
Which sounds like a pretty big number, right?
And remember, we’ve only got 30 days to lose the weight.
The upshot?
We'll need to burn through 70,000 ÷ 30 = around 2,300 Calories of stored body fat per day.
In other words, each day we need to consume 2,300 Calories fewer than we burn.
For 30 straight days.
But here's where it gets REALLY crazy.
Why?
Because a sedentary 200-lb man only burns through around 2,800 Calories every day.
(Yep, inactive folks really don't require very much fuel)
Bottom line?
Each day he'll burn through 2,800 Calories, with 2,300 of those having to come from the stored body fat he wants to lose
And here's the obvious question:
Where is he going to get those other 500 Calories from?
Answer:
Food.
So, poor guy - he’ll get to consume only 500 Calories-worth of food each day.
That’s equivalent to a single 20 oz. Starbucks whole milk caramel brulée latte...
...every day for a month.
And nothing else.
Bummer.
So, next time you come across an article titled "How to lose 20 lbs of fat in 30 days without doing any exercise!"...
...smile to yourself, and imagine surviving on nothing more than a large cup of coffee each day for the next month.
OK, that's the first option - diet only, so let's take a look at:
Option 2: Exercising Off 20 lbs of Fat in 30 Days
Now, we already know that super-high-intensity "fat blast" workouts simply aren't very effective out in the real world.
Not convinced? Then you'll want to check this out :)
(Don't worry, I'll wait)
The bottom line is burning 70,000 Calories through exercise alone is a really big ask.
So, what does that mean for a typical 200-lb man?
Well, figure on running something like 15 miles every single day for 30 days straight.
That's over 100 miles per week - which is getting on for world-class marathoner training mileage.
In other words...
...there's no way that a dude with a family, a job and a life is going to achieve that.
Sure, it may be possible in theory but it's just not practical.
OK, so diet alone and exercise alone are both out.
That leaves us with:
Option 3: Losing 20 lbs of Fat in 30 Days Through Diet & Exercise
Remember, the key thing is we've got a month to burn 70,000 more calories than we consume.
That's all it really boils down to.
So, our 200-lb man could manage that by:
1. Throttling his food intake back to, say, 1,600 Calories
while
2. Running something like 7½ miles
Every. Single. Day.
Now, in reality most folks would find either of those hard enough to stick to for more than a week.
But doing both of them for a full 30 days?
No way.
Hell, who wants to run over 200 miles in a month while consuming a semi-starvation diet?
Not me!
(To put that mileage into perspective, over 5 months I ran less than 400 miles IN TOTAL when training for my first marathon)
So here's the bottom line:
While it is possible to lose 20 lbs of fat in 30 days, it comes at a higher price than most folks are willing to pay.
Although we've got three options:
• Diet only
• Exercise only
• A combination of diet and exercise
The sheer number of calories we need to burn through makes every one of those a fearsome task.
Put it this way:
When I did my epic weight-loss experiment back in 2015 (dropping 61 lbs in 27 weeks), I lost weight FAST at the beginning...
...but it still ended up taking me a tad over 2½ months to lose 20 pounds!
(That felt like a decent rate of progress that was nice and sustainable)
But losing 20 lbs of fat in 30 days?
Man, that just horrifies me.
So, after explaining all this to the guy, I asked him if he was prepared to give it a go.
After all, such massive fat loss in only a month does sound very tempting...
He smiled and shook his head.
A win for science and common sense.
- Tim
Reference: Harvard Medical School
Images: Bigstock