Where Does Fat Go When You Lose Weight?

Weight loss can be a complicated subject. While you certainly don’t need a Ph.D. to lose weight, understanding the science behind weight loss can be a big help. Let’s take a look at where fat goes when you lose weight, and how you can use science to help shed pounds.

What is Fat?

Let’s start with the basics. Fat is one of three macronutrients which your body uses for energy.

Aside from fat, protein and carbohydrates are the other two macronutrients. As the term “macro” implies, large amount of macronutrients are necessary to keep your body functioning properly.

Each macronutrient has a different energy value. Fat provides the most with nine calories per gram. Carbohydrates and proteins each have four calories per gram.

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Fat acts as reserve energy. Your body stores the fat until energy is needed. During exertion, including exercise, energy is first taken from carbohydrates.

After carbs have been used, energy is then taken from stored fat. During periods of exercise, the switch from carbohydrates to fat energy takes about 20 minutes.

Fat is stored energy. While you do need some fat in your diet, excess fat leads to weight gain.

Unfortunately, fat is the most difficult micronutrient to pull energy from. This is because fat is digested slower than proteins and carbohydrates.

But fat doesn’t need to be completely eliminated from your diet if you’re trying to lose weight. Foods with a high-fat content help you feel fuller longer.

Called satiety, this feeling of fullness can help you eat less throughout the day. As long as you successfully moderate your fat intake, high-fat foods can be a useful weight-loss tool.

Types of Fat

Fats can be either polyunsaturated, saturated or trans. Generally, you want to limit saturated and trans fats from your diet as much as possible when you’re trying to lose weight.

But polyunsaturated fats have quite a few health benefits when eaten in moderation. Polyunsaturated fat is a dietary fat with a double bond chemical structure.

All fat helps cells properly functions. Fat also helps keep your body insulated and internal temperatures properly regulated. Plus, fat helps with the absorption of many vital vitamins.

Polyunsaturated fats have several additional benefits. Specifically, these fats provide Vitamin E, Omega-3 and Omega-6.

These nutrients increase circulatory system function, reduce inflammation and improve brain health.

Common sources of polyunsaturated fat include:

  • Fish including trout, salmon, tuna and herring
  • Nuts including walnuts, sunflower seeds, flax seeds and chia seeds
  • Oils including sunflower oil, flax seed oil and soybean oil
  • Tofu and soybeans

How Much Polyunsaturated Fat Should I Eat?

Even though polyunsaturated fat has many health benefits, it still has nine calories per gram, which is more than carbohydrates and protein.

So while you want to include some polyunsaturated fat in your diet, moderation is key. Generally, fewer than 30% of total calories consumed should be from fat.

The USDA Dietary Guidelines recommend less than 10% of fat consumption should come from saturated fat. If you’re trying to lose weight, stick to fish, nuts and other sources of unsaturated fat.

What Role Does Exercise Play in Weight Loss?

Group Of Girls Exercising

In order to lose weight, you have to exercise, right? Well, not exactly. Weight loss occurs when you have a negative calorie balance. That means more calories are exiting your body than entering.

Exercise isn’t necessary to have a negative calorie balance. If you don’t want to work out, you don’t have to. You can carefully monitor the number of calories you consume in order to shed pounds without exercise.

Basically, exercise helps increase the speed which weight loss can occur. Aerobic exercise will burn more calories than strength or resistance training.

Weightlifting won’t make you gain weight, but the calories burned are actually fairly minimal compared to running, swimming and other more active exercises.

But truthfully the best type of exercise is any type you enjoy doing. You’ll be more likely to stick to a regular routine if you enjoy the activity you’re participating in.

How Does Fat Leave the Body?

If you want to lose weight, you need your body to convert fat into energy.

Because carbohydrates are used as an energy source before fat, generally you’ll need to exercise for about 20 minutes before fat cells will start to shrink.

Fat is converted into energy by metabolic activities. This generates internal heat.

The heat generated helps maintain your body temperature while also creating the waste products of water and carbon dioxide. Eliminating these waste products is how the fat leaves your body.

There’s a common misconception about how fat leaves the body. Although fat is typically referred to as “burned off,” fat is not actually converted into heat.

Instead, fat is removed from the body in the following three ways:

  • Urine
  • Sweat
  • Exhaled breath

Most fat is simply expelled through the lungs in the form of carbon dioxide. In a sense, fat is simply turned into thin air.

One major benefit of regular exercise is improved lung function. When your lungs operate at maximum capacity, waste products are able to be expelled more efficiently.

Do you smoke tobacco products?

There’s a common misconception that quitting smoking results in weight gain. This is because many people turn to food as a substitute for a cigarette.

But as long as you can control your diet, quitting smoking can help you lose weight. This is because your lungs will begin operating at an increased capacity.


Weight loss can be a difficult. But the journey becomes easier when you understand the chemical processes involved.

The basics of weight loss are actually pretty simple: Your body needs to expel more calories than you consume.

By properly monitoring what you eat, and avoiding saturated fats, your body’s natural processes will efficiently remove fat from your body. Breathe in, breathe out and lose weight!

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Our team at The Fitness Tribe often collaborates together to produce content. Many times the content is not written by a single author, instead it is usually a team effort.