Body Fat: What Exactly Is It?

Fat is a tissue that is needed by the body for a wide variety of functions such as temperature regulation, shock absorption, etc. Learn here what body fat is, how much we actually have, and much more. Read on...

Body Fat—It's everyone's worst nightmare. They want to know how to prevent gaining it, how to get rid of it once it's there and how to build muscle without seeing it develop as an undesirable side effect. That said, if losing body fat is your prime concern right now, it would be wise of you to invest some time in learning exactly what this type of body tissue is.

Purposes Of Fat

Fat is a tissue that is needed by the body for a wide variety of functions such as temperature regulation, proper reproductive capabilities (particularly in women), shock absorption, the regulation of other nutrients and to maintain healthy skin, hair and nails.

The amount of required body fat for the body to stay living (essential body fat) is around 3% for men and 9% for women. Going below these percentages and you will be asking for problems to occur. Women in particular start to see menstrual irregularities when their body fat drops to single digits such as when preparing for a fitness competition. This will put them at risk for problems such as osteoporosis and should be avoided at all costs.

Types Of Fat

There are two types of fat that you can have on your body, white fat and brown fat.

White Fat

White fat is important for energy metabolism, heat insulation and cushioning of the bones and organs. The white fat cells that make up this fat are large cells that do not have a great deal of cyctoplasm. Instead, one small fat droplet composes about 85% of the cell, while the nucleus and cytoplasm make up the rest.

What Is The Nucleus? Specialized structure occurring in most cells (except bacteria) and separated from the rest of the cell by the nuclear membrane. The nucleus controls and regulates the cell's activities (e.g., growth and metabolism) and carries the genes.

What Is Cytoplasm? The material within a biological cell that is not contained in the nucleus or other organelles.

Brown Fat

Brown fat on the other hand is found most often in newborn babies and is located between the shoulder blades. This fat's purpose is to generate heat to keep them warm. Its cells are smaller and contain a great deal of mitochondria and thus are more metabolically active. They also contain numerous small fat droplets as opposed to one large one seen in the white cells.

What Are Mitochondria?

Mitochonidria: The spherical or elongated organelles in the cytoplasm of nearly all eukaryotic cells, containing genetic material and many enzymes important for cell metabolism, including those responsible for the conversion of food to usable energy. Also called chondriosome.

Fat Development

An important point to make is that after you have developed all your fat cells, usually occurring around puberty, you no longer produce any more fat cells as they only become larger (and for the majority of people all that is left now is white fat cells).

Furthermore, subcutaneous fat is fat that is seen right under the skin and is mostly what people in the fitness industry are trying to get rid of and avoid. It is this fat that is going to affect your appearance and when concentrated around certain areas such as your midsection can put you at risk for disease such as metabolic syndrome X.

What Is Metabolic Syndrome X?

The Adult Treatment Panel III of the United States National Cholesterol Education Program (2001, 2005) defined the diagnosis as three or more of the following five:

  1. Increased waist circumference (>=102 cm in men and >=88 cm in women), indicating central obesity
  2. Elevated triglycerides (>=150 mg/dL or 1.7 mmol/l)
  3. Decreased HDL cholesterol (<40 mg/dL or 1.03 mmol/l for men, <50 mg/dL or 1.29 mmol/l for women)
  4. Blood pressure above 130/85 or active treatment for hypertension
  5. Glucose levels above 100 mg/dL (5.6 mmol/l) or active treatment for hyperglycemia

Fat Storage

So now that you know what fat cells are, I bet you are wondering how they are stored in the body.


When you consume food that has fat, the triglycerides enter into the blood stream and get taken to the intestines. There, they get mixed with bile salts from the gall bladder and then form smaller molecules called micelles. After this happens the pancreas secretes enzymes that are called lipases that then target the micelles, breaking them down into their counterparts of glycerol and fatty acids.

These new molecules then get absorbed back into the intestine and are reassembled together in a package that has a protein lining. This new molecule is now called a chylomicron. These are then released into the lymphatic system which eventually brings them to your veins and then into the blood stream.

They cannot enter directly into the bloodstream once the chylomicron has been formed because they are too large to cross the wall of the capillary.

Now that they have entered into the bloodstream, the next process is to be stored in the body as the dreaded body fat. These chylomicrons stay in the bloodstream for a short time period, usually lasting around 8 minutes because the enzyme, and then lipoprotein lipase breaks these fat molecules into fatty acids once again.


Whether or not these enzymes are present to break the fat molecules down however depends on yet another substance, insulin. Insulin is a polypeptide hormone that is secreted from the pancreas that helps to regulate the metabolism of carbohydrates and fats.

When you eat rapidly digesting carbohydrates, insulin has a tendency to sharply increase and when you eat slower digesting carbohydrates along with complete sources of protein and fat then insulin levels stay more stable.

Now, when insulin levels are high, for instance if you just ate a bag of gummy candy, these lipoprotein lipase enzymes are going to be high as well, thus enhancing fat breakdown and storage. This is a significant reason why eating a food that has very simple carbohydrates along with a great deal of fat (think Big Mac along with a large Coke) is not ideal since you are virtually enhancing the chances it goes to fat (assuming you are not in a caloric deficient and the calories are needed at that time for fuel energy).

Once the lipases have broken down the fat molecules back into fatty acids they are then absorbed from the blood into already present fat cells, increasing the size of these cells and making you look larger.

Overeating Carbs Or Protein

Keep in mind that it is also possible for the fat cells in your body to also take in glucose and amino acids from protein and carbohydrates that you have consumed. This process is by no way limited to only fat molecules, therefore eating to much of any food, be it carbohydrates, proteins or fats is not a good idea if preventing fat is a concern.

Of special consideration though is the fact that this process is not nearly as efficient as that of turning fat molecules directly into fat, therefore overeating on either of the two other macronutrients will likely lead to less total fat gain.

For example, if you eat 100 extra calories than your body needs to maintain itself coming from fat, it will only take a total of 2.5 calories to turn these excess calories into fat. If you had eaten 100 extra calories from carbohydrates though, the body will expend approximately 23 calories turning it to fat and even more if the case is with excess protein consumed. Therefore, the take home message here with regards to fat gain is if you are going to overeat, it is best to do it with carbohydrates (preferably slower digesting as the points made above) or protein.


So now that you understand what fat is and how it works, hopefully you will be able to use this knowledge and apply it to your own situation to not only promote better health but also a better physique. Simply knowing what is going on in the body when you eat highly refined carbohydrates or foods containing a great deal of fat might help give you the motivation to stick to your healthy eating practice.