This article has been Fact-Checked by Kendall Kennedy MS, RD, RYT
Depending on what you are doing, losing weight can feel like an eternity. But how long does it take to lose weight measured in days?
It’s normal to want to lose weight fast but it will inevitably take at least some time. Find out just how long.
How does weight loss and weight gain happen?
The amount of energy in food is measured in calories. Your body needs energy to function.
When you absorb more calories from your food than you consume, there is a calorie surplus. Your body stores this surplus of energy for later use.
In earlier times this was very useful. Calorie rich food wasn’t always around. Being able to store excess energy for later use was most likely essential for human survival.
These days this mechanism can backfire. Too much body fat causes damage to our health.
To lose weight you have to absorb less calories from your food than you use, also know as a calorie deficit. When this happens your body starts using the stored body fat as energy.
How long does it take for your body to lose weight?
Now you know how weight loss happens you can start to understand that this process can take time.
Weight loss vs fat loss
Weight loss or weight gain can happen really fast but it isn’t always fat loss.
As an example you can weigh yourself. Drink a liter of water. Then step on the scale again. You will weigh one kilogram heavier.
Only using weight as a measurement is a double-edged sword. On the one hand, it is extremely easy to do. On the other hand it is not always an accurate representation of your progress.
Is there a delay in energy usage?
One of the first things you need to know is how long it takes for the energy to be used. Do you instantly use the energy you are expending or is there some kind of delay?
The energy you use in the moment needs to come from somewhere. So, in theory, all the energy you use instantly shows up as a difference on the scale if you were running on body fat.
The thing is, most people are not always running on body fat. When you consume food your body uses the energy from the food first.
There is also is a second kind of energy your body uses, glucose from carbohydrates.
Your body often prefers to use glucose over fat. However, there only is a limited amount of glucose present in your blood at all times. Too much and your body will shut down. Luckily, your body has a cool system to deal with too much glucose.
When you get too much glucose from your food, your body releases a hormone called insulin. Insulin helps your body convert the excess glucose into something called “glycogen”. This is basically a substance that can easily be turned into glucose later. Glycogen is not as heavy as body fat compared to the amount of energy it contains.
How long does it take to start burning fat?
Usually your body wants to use this glycogen before starting to burn body fat for energy.
So, if you have glycogen stored, the energy you expend right now will probably come from glycogen and not show up on the scale that much. This still is a good thing since you need to go through the glycogen stores before you start using body fat as energy.
Losing weight is not only about burning as much fat as possible, it’s also about burning other energy stores in your body.
You will start burning fat more or less once the glycogen stores in your body are depleted. Once you start burning body fat you will see more weight loss results than when you were using glucose as your main fuel source.
Now the calorie deficit comes into play
Once you start burning body fat you can find out how long it will take to lose weight.
How big your daily calorie deficit is decides how fast you lose weight.
With a healthy weight loss rate of a calorie deficit of 500 calories a day it would take about a week to lose 1 pound of body fat.
How big your calorie deficit is depends on how many calories you absorb from your food – how much energy in calories you use.
How long does it take to lose weight with exercise?
You can probably already tell that you can lose weight without exercising.
What if you would have a neutral calorie balance from your food, how long would it take to lose weight with exercise?
This number depends on workout to workout.
Weight lifting might not burn as many calories in the moment but the muscle you build helps you burn more calories from day to day.
Here are a few examples on how much calorie burning you can expect as a 155 pound person doing the exercises for 30 minutes:
- Water Aerobics: 149 calories
- Stretching (Hatha Yoga): 186 calories
- Stair Step Machine (general): 223 calories
- Rowing, Stationary (moderate): 260 calories
- Bicycling, Stationary (moderate): 260 calories
- Elliptical Trainer (general): 335 calories
- Running 5.2 mph: 335 calories
One pound of body fat is about 3500 calories.
So for example it would take about 5 hours and 10 minutes on the elliptical trainer to burn a pound of body fat (doing this in one session is most likely not healthy).
Check out more numbers for a few other cardio exercises.
How long does it take weight loss to show?
It’s possible to lose weight without really seeing a lot of changes on your body.
The more you have to lose the less 10 pounds weight loss will stand out.
This and other things determine how long it takes to notice weight loss.
How long does it take for your body to lose weight?
How long it takes to lose fat depends on your daily calorie deficit. One pound of body fat is about 3500 calories. Weight loss on the other hand can happen quite fast by getting rid of water weight and things like that.