How Long Does it Take for a Calorie Deficit to Start Working?

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JOE JOHNSON

Weight Loss Coach and Owner at 9 To 5 Nutrition

Joe is an online weight loss coach, certified nutritionist and qualified personal trainer who helps busy, lawyers, marketers and accountants lose weight and keep it off forever.

He specialises in working with people that have busy lives and don't necessarily have time to exercise and cook complex nutritious meals. Having had a 9-5 desk-job, Joe understands the struggles of juggling a hectic life with trying to maintain a good physique.

Joe has helped over 100 professionals lose weight and feel better about themselves using simple, repeatable daily habits and an easy-to-use spreadsheet to track everything.

Joe has also been quoted on several respected sites including Nike, Live Science and Health.com.

While Joe mainly works online these days, he also offers 1-2-1 personal training sessions across Sussex and Surrey.

If you want to know more, check out the about page, or get in touch

Latest posts by JOE JOHNSON (see all)

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• How To Lose 1kg a Week (Guaranteed) - August 20, 2023
• How To Count Calories (or Estimate) and Stay on Track When Eating Out at Restaurants - July 25, 2023

Technically speaking, a calorie deficit will start working immediately, however, you won’t notice it on the scale for 1-2 weeks. This is because there is always a lag effect with weight loss, plus weight can fluctuate from day to day for any number of reasons, making it seem like you aren’t losing fat, when in reality you are. It’s also important to know that the bigger your calorie deficit, the faster weight loss will be, and the sooner it’ll show on the scale.

Weight loss, at least sustainable weight loss, is NOT  a quick process.

Especially if you have a lot to lose.

If you want to lose 20kg, we’re not talking days or weeks, we’re talking months. Maybe even a year.

You might already know this and be fine with it, you just want to see some initial progress to spur you on and keep you going.

And I totally get it.

And the truth is, a calorie deficit will ‘start working’ almost instantly, in fact, every day you’ll have periods of hours where you’re in a calorie deficit and hours where you’re in a calorie surplus.

In order to start seeing the weight loss on the scales, however, you’ll need to be in a net calorie deficit consistently, over a long period of time.

So let me tell you that if you nail your calorie deficit (i.e.. You’re eating the right amount of calories) from day one of your diet, and you’re in a calorie deficit of around 500 per day, you should see a weight loss of around 1lb or 0.5kg per week.

But bare in mind that even if you are hitting a 500-calorie deficit every single day, there will be some weeks where you might not lose exactly 1lb (0.5kg), you might lose a little less, or a little more, but over a long period of time, the average rate of loss should be about that

But first, you need to get your calorie deficit right

Getting Your Calorie Deficit Right

Half the battle with weight loss is getting your calorie deficit right in the first place.

First of all you need to know roughly what your maintenance calories are. Once you know that, you can then go about deciding how big you want your calorie deficit to be.

There’s no ‘ideal’ calorie deficit, but you do need to think about how extreme you want to go before you start dieting.

The bigger the calorie deficit you’re in, the quicker you’ll lose weight.

Sounds great, why not just go for a huge deficit.

Not so fast.

The larger the deficit, the less you’ll need to eat and the more difficult the diet will be to maintain. Everyone will have their own ‘tipping point’ where the deficit is simply too large to maintain.

Here’s roughly how much you can expect to lose each week with different sizes of deficits;

*Based on a person with a total daily energy expenditure of 2,500 calories per day on average

One Kg of fat contains roughly 7,700 calories, which means if you’re in a 1,000 calorie deficit per day, you’d lose about 1kg in a week.

1,000 calories per day however, is quite an aggressive deficit.

If you currently maintain your weight by eating 2,500 calories per day, it would mean needing to eat 1,500 to lose weight, and that’s  1,500 every day. 

That doesn’t mean eating 1,500 on weekdays and then having two cheat days at the weekend where you eat 4,000 calories on Saturday and Sunday, it means 1,500 calories every day. 

So, the size of deficit you choose will determine how quickly your deficit starts ‘working’ and what the size of those results will be.

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How Long Does It Take for Weight Loss to Show Up On The Scale?

This is important.

Weight Loss and Fat Loss are two different things, so you need to be aware that the number on the scales does not always reflect your body fat levels or the progress of your diet.

It’s perfectly normal for you to be losing body fat, but not see the scales move for a while.

Why?

Well, there are all sorts of other reasons the scales can fluctuate outside of body fat, for example;

• Water levels; you will have different levels of hydration at different points throughout the day, the more water you have in your system, the heavier you’ll be

• Water retention; it is possible that you are unintentionally retaining water. This can happen when you’ve had high sodium (salt intake). This is temporary and may take a couple of days to even out

• Food in the gut; If you’ve just eaten a big meal, this will of course sit in your gut and influence your weight

• Lack of fiber; a lack of fiber can cause inconsistent bowel movements. Of course, if you don’t have a bowel movement for days, this can impact your weight

All these things are temporary, however, and will eventually even themselves out in long term.

This is why, when you’re dieting it’s important to just trust the process for the first few weeks because while your calorie deficit will technically ‘start working’ straight away, you won’t necessarily see that immediately translate to the number on the scales.

Even if the scales could accurately measure body fat levels, there would still be a lag period with your weight loss. 

Even with a large calorie deficit you won’t see results instantly and will likely have to wait several days before you see the numbers moving.

The 5 Stages of Noticing Weight Loss

There’s no denying it, weight loss is a physical and emotional rollercoaster.

You will experience highs and lows, but based on my experience as a weight loss coach, here are the stages that people will typically go through when it comes to ‘noticing’ weight loss.

1. Week 1: This isn’t working

Almost everyone will experience this. Of course we all want immediate results, but that just doesn’t happen. Even doing everything perfectly, it’s unlikely you’ll see any dramatic results in the first week.

2. Week 2: My weight has gone up! I Want to Quit

This is fairly typical of the people I coach, your weight will fluctuate for the reasons listed above and for a lot of people, things may get worse before they get better. At this point, it’s natural to feel that you want to quit and that a calorie deficit ‘doesn’t work’ for you.

At this point, it crucial to push through and trust the process. A calorie deficit WILL work for everyone, and it’s just a matter of time before you start to notice the results. Hold on.

3. Week 4: Oh Wait, It’s Been a Few Weeks and I’m Starting to See results

At the 4-week point, as long as everything has been done correctly, you should start to see some results. 4 weeks is plenty of time for a calorie deficit to start working, so if you’re not at least seeing some results, it might be time to get a new coach!

4. Week 6: Huh, I’m Losing Roughly 0.5Kg a Week

By this point, the daily and weekly fluctuations should have smoothed out, and although there will have been a couple of bad weeks, you see a rate of loss of around 0.5kg (1lb) per week.

5. Week 8: My Clothes fit Better and People Are noticing My Weight Loss, This is Awesome!

After you’ve been dieting for 8 weeks (2 months), you should have lost around 4kg (8lb), for most people, this will be enough to see a visual difference in the mirror, and feel a difference in your clothes.

Of course, everyone’s weight loss journey is different.

Some people may start seeing results in the first couple of days and go on to consistently drop weight at a steady, sustainable rate until they reach their goal.

Others simply won’t be able to stick to their deficit and will quit in the first couple of weeks.

At What Point Should You Re-Calculate Your Calorie Deficit?

This is super important as well.

The number of calories you start out eating to lose weight, will eventually become your maintenance calories.

This means that at some point, you’ll need to decrease the number of calories you’re eating, in order to keep losing weight at the same rate.

Let’s say you were eating 1,800 calories per day which was a 500-calorie deficit making you lose around 0.5kg per week. At some point, your weight loss will stop. 

No, you haven’t gone into starvation mode, this is just metabolic adaptation.

Basically, you’ll be lighter (which is a good thing!), which means your metabolism will be lower.

In order to retain the rate of weight loss you were seeing before, you’ll need to re-adjust your intake so you can achieve that 500 calorie deficit again.

This means you’ll need to eat around 1,300 calories per day.

If you don’t recalculate your calories, the chances are you’ll just maintain and stay the same weight.

This is why it’s so important to record all of your data (weight, calories, activity) and closely monitor what your weight is doing so you can quickly spot plateaus.

If you don’t have the time or inclination to do this, a weight loss coach can help you with the recording process and keeping you accountable.

How Long Does it Take to Notice Weight Loss From Walking?

But let’s say you didn’t want to diet, and instead, you wanted to lose weight purely from walking more.

That’s cool too.

Again, you can expect to see weight loss results within 2-3 weeks just by walking, but this is more time-intensive than just restricting calories.

Walking is an easy, free form of exercise that anyone can do, free from the risk of injury. The main disadvantage of walking more to lose weight is that it takes much more time than just manipulating your calorie intake.

For example, if we assume that the average person will burn 50 calories per 1,000 steps (this will vary based on your weight, height and walking speed), then in order to burn 500 calories, you’d need to do 10,000 steps.

For most people, this would take a good hour and a half. 

In order to get the same benefit from simply manipulating your diet, you’d simply need to cut 500 calories out of your normal daily intake, which takes no time at all.

Of course, the best approach is to combine walking and diet in order to achieve your desired outcome.

Nevertheless, let’s take a look how long it would take to produce different levels of weight loss from walking alone.

N.B. The calorie-per-steps and time requirements are just estimates, these numbers will vary depending on a range of different factors

So you can see that losing weight just by doing more steps is absolutely possible and will produce results in the same amount of time that calorie restriction will, but it also takes a lot more time.

If you really want fast weight loss, and you’re looking to create a deficit of 1,000 calories per day, then walking for 200 minutes (2 hours 20 minutes) every day might not be practical.

What if You’re Exercising But Not Losing Weight?

If you start walking more but you’re still not losing weight, the likely scenario is that you’re simply not in a calorie deficit.

When you start doing more exercise, the natural inclination is to start eating more, either because you feel you ‘deserve it’ or because you’re more hungry than usual.

Of course, if you do this, it’ll undermine your original aim which is to burn extra calories and create a calorie deficit.

This is yet another reason why it’s so important to track all of your data; you won’t know if this happening unless you have the numbers in front of you.

It demonstrates the importance of having a calorie target.

If you have nothing to stick to, then it’s very easy to overeat.

If you think you’re in a calorie deficit but still not losing weight, it could be that you’re also gaining muscle, or that you’re temporarily retaining water, but the truth is, you’re probably just eating too much.

Go back to square one and start tracing calorie intake, weight and activity so you know exactly where you are. 

If you’re still stuck, hire a weight loss coach to help you!

Summary

If you’re doing everything right, you’ll start to notice weight loss both in the mirror, and on the scale after 2-3 weeks.

This is easier said than done though, and dieting comes with lots of ups and downs.

Some weeks you’ll lose a decent amount of weight, and others you stay the same.

You need to stay consistent, trust the process and be realistic, we all want the quickest possible rate of weight loss but aiming for a conservative rate of loss will make the process much easier and more enjoyable.