What Happens To The Fat In Your Body When You Lose Weight?

Losing weight can benefit your health. By losing weight, you can reduce strain on your joints and organs, increase your energy, and stabilize blood sugar levels. But what's really happening in your body when you lose weight? Where does the fat go?

Understanding the process of weight loss can help you develop habits that promote healthier weight reduction methods. Discover what's happening in your body when you lose weight and what it means for things like your metabolism and spot reduction.

Have you considered clinical trials for Weight management?

We make it easy for you to participate in a clinical trial for Weight management, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

What's actually happening in your body when you lose weight?

The fat you are trying to shed when you lose weight is there for a good reason. Your body stores extra calories from the food you eat and the beverages you drink as triglycerides.

Your body sees storing extra calories as a good thing because calories are a form of energy. Your body can later convert those stored triglycerides back into energy, creating an energy reserve for times when food might not be so readily available or when you need extra energy for extended periods of physical tasks.

Your body doesn't just need this energy for exercise or heavy labor, either. You burn calories when you do everything from sleeping to breathing to eating. Calories fuel your brain, your lungs, and your digestive system. So you'll use these calories to do everything from lifting a finger to running a marathon.

When you take in more calories than you use, though, your body starts the storage process to save those calories for energy needs later on.

The triglycerides stored by your body are contained in fat cells. Those fat cells increase in size as they are used to store more triglycerides. As your fat cells expand, your body shape changes and gets bigger.

If the fat cells run out of space to store more triglycerides, your body will make more fat cells and increase the storage capacity. If you don't use the reserved triglycerides as energy, they'll remain in your fat cells.

To lose weight, you need to achieve a calorie deficit. When your body isn't getting enough calories from the food and drink you consume, it will tap into those triglyceride reserves to supplement your calories to give you the energy you need. So it reverses the process, taking the triglycerides out of storage in the fat cells and converting them into energy.

This causes the fat cells to shrink, which in turn changes your body shape and decreases its size.

One thing that doesn't change, though, is the number of fat cells you have. Once your body creates more fat cells for storage, research suggests that you may always have those fat cells¹.

That means you can change your body shape and lose weight by reducing the number of calories being stored inside your fat cells. You won't, however, be able to reduce your body's overall capacity to store those calories.

That may be why some people who lose a lot of weight easily gain it back later on: their bodies have an increased capacity for fat storage. However, maintaining a healthy calorie intake should prevent an increase in fat cell storage and keep the size of the cells reduced, no matter how many there are in the body.

Where does the fat go when you lose weight?

After your body uses the triglycerides in your fat cells for energy, it breaks them down through a complicated metabolic process. The byproducts of this process are carbon dioxide and water. Your body gets rid of these byproducts naturally through a few different methods:


You breathe in oxygen, but you exhale carbon dioxide. Some of the carbon dioxide that you exhale is from the process of converting the triglycerides in your fat cells into energy for your muscles. That's part of the reason your breathing rate increases when you exercise, too. Your body is trying to expel more of the byproduct from burning fat.


Water is another primary byproduct of fat burning, and one of the best ways to get rid of excess water in your body is by sweating it out. That's also why you sweat when you are working out: your body is getting rid of an increased amount of byproducts from using fat deposits.


The other way to get rid of excess water in your body from the fat conversion is through the kidneys and out through the bladder. You may notice when you start to lose weight that you'll need to urinate more often. That's because your body is attempting to get rid of those byproducts. Drinking more water can help encourage this process, and may even help boost your metabolism

What areas of the body do you lose weight in first?

If you are hoping to lose weight in a specific area of the body first, your results will largely come down to genetics, age, and lifestyle. Spot reduction of fat deposits doesn't work² because of the way your body uses the reserves in your fat cells. Your muscles use triglyceride deposits as energy.

Before they are used, though, the triglycerides have to come out of storage in the fat cells and convert to glycerol and free fatty acids. Then they enter the bloodstream and travel to the muscles that need them. Because of this process, the triglycerides used can come from fat storage anywhere in the body. They don't always come from the areas near the muscles you are exercising, which is why spot reduction of fat isn't possible.

That also means it's tough to predict what areas of your body will see any fat reduction first. For some people, it may be the hips, buttocks, and thighs. For others, they may see a noticeable decrease in the size of their waistline. And for others, they may first notice changes in their face or neck.

Where you see those results can change over time, too, as your age, hormones, and lifestyle change. Your gender will also affect your results. Men tend to lose weight from their midsections first. Women experience more of an all-over weight loss but tend to retain more weight in their thighs and hips.

While you can't control where on your body you lose weight from first, you can increase the rate at which your body uses those fat deposits - this is your metabolic rate. There are many things that affect your metabolism, including genetics, gender, and hormones.

Increasing the amount of muscle mass in your body can help you use your fat reserves faster because greater muscle mass uses more energy to work. That's why a combination of both aerobic exercise and weight training is important for healthy weight loss.

Everyone will lose weight at a different rate, though consistency is key to doing so successfully. Maintaining a deficit of 500 calories a week is a healthy place to start. You can achieve this by eating less and exercising more, getting at least one hour of exercise three times a week. This will trigger your body to tap into those energy reserves stored in your fat cells, converting the triglycerides into usable energy and shrinking the size of your fat cells.

Sticking to your calorie and exercise goals will produce noticeable results over time.

The lowdown

Your body uses calories as energy to do everything from breathing to running a marathon. When you consume more calories than you need, your body stores those excess calories as triglycerides in your fat cells. The more calories your body stores, the bigger your fat cells get, causing a change to your body shape.

When your body needs more storage, it creates more fat cells. To lose weight, you have to create a calorie deficit that causes your body to use those fat reserves for energy. By burning more calories than you take in, your body gets the triglycerides out of storage in your fat cells to convert them to energy, reducing the size of your fat cells and changing your body shape.

As it uses the stored fat, the body creates byproducts of carbon dioxide and water. That's why you sweat more and breathe harder during exercise; it's your body's way of getting rid of the byproducts created as you use the stored energy reserves.

There is no way to control where your body pulls the fat storage from, so it's impossible to do spot reduction.

However, increasing your metabolism can help you burn more calories for a longer amount of time. One way to increase this is through building more muscle, which requires more calories to maintain - a combination of aerobic exercise and weight training is best.

Everyone will lose weight at a different rate, but the key is to be consistent with your calorie deficit. By remaining consistent, you'll begin to see results over time.

Have you considered clinical trials for Weight management?

We make it easy for you to participate in a clinical trial for Weight management, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

Discover which clinical trials you are eligible for

Do you want to know if there are any clinical trials you might be eligible for?
Have you been diagnosed with a medical condition?
Have you considered joining a clinical trial?