How Food Becomes Body Fat

by Maia Appleby

Everyone knows that overeating leads to excess weight. This concept comes in many flavors these days, though. Some people think that carbohydrates are the culprit. Others think it's sugar. Some people think that eating lots of protein couldn't possibly make them gain weight. Hmmm...

The only way to determine the answer to this enigma is to go inside the human body and take a look at how fat gets there in the first place. Let's follow a bite of pepperoni pizza and see what happens to its sugar, fat and protein. Open wide!

The food enters your mouth: 

• Saliva contains enzymes that break any starch in the food down to sugar. 
• This, along with any fat and water in the food, travel to the stomach, which churns them up. 
• Pepsin (an enzyme that digests protein) and hydrochloric acid further break down the food, turning it into a substance called chyme.
• The mixture enters the duodenum, (the place where the gall bladder secretes its bile).
• This bile dissolves the fat in water, thinning it out and making it easier to absorb.
• Enzymes from the pancreas enter the duodenum and further break down the sugar, fat and protein.

Now everything is dissolved and is in fluid form, so it is absorbed through the lining of the small bowel. Fat, sugar and protein wave good-bye to each other and go their separate ways.

What happens to the sugar:

• It also goes directly into the blood stream, and several different organs take the sugar they need as it passes by.
• Some is stored in the liver as glycogen.
• Whatever is left is converted to fat and stored in fat cells with the excess fat above.

What happens to the fat:

• First, it goes into the blood stream and travels to the liver
• The liver burns some of the fat, converts some to other substances (one is cholesterol) and sends the rest to fat cells, where they wait until they are needed.

What happens to the protein:

• It is broken down into building blocks known as peptides.
• Then, it is further broken down and it becomes amino acids.
• The amino acids are absorbed through the small intestine's lining and enter the blood stream.
• From here, some of the amino acids build the body's protein stores.
• Excess amino acids are excreted, and any protein that it built in excess is stored as body fat.

This is such a simple concept, but many people still believe that consuming lots and lots of protein will put muscle on their bones. Don't be fooled by this notion! Even excess protein turns to fat. 

Here is a picturesque illustration of the real cause of weight gain. Eating too much food! Dietary fat is obviously the substance most often stored as fat in the ends, but no matter what you eat, your body takes whatever it can't use and sends it to fat cells. If you don't burn it off, it hangs around in your fat cells. It's that simple.  If you want to lose weight, don't eat too much of anything -- and do exercise regularly.