Thought this article would be fun to share. An oldie but goodie that I wrote up years ago. A fun little piece on digestion…
What happens to the excess food?
A look at a bite of pepperoni pizza to 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 and muscle as glycogen to be used as energy. It also goes to the brain for it’s sole source of energy.
- Whatever is not stored as energy or immediately used and is “left over” 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 converted to fats and sugars and follow the paths described above.
Overall, this is a simple concept, but many people still believe that consuming a ton of protein will put muscle on their bones. Don’t be fooled! Excess protein, which is absorbed but not utilized, may be excreted in the form of urea and other carbon containing compounds or it can also be converted to fat.
So, this is an illustration of weight gain- When the energy you intake is higher than the energy you expend, calories will be converted into fat! Dietary fat is 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.
***When a person is gaining weight, their fat cells are expanding. When a person is losing weight, their fat cells are shrinking. However, if one continues to gain weight and the fat cell can not expand any more- new fat cells are created. What does that mean? Well, it is relatively easy to change the size of the fat cell, but once more are replicated they can not go away (hence, the excess skin that is often removed when a larger person loses weight).
Once again, stated in another way:
- How do excess calories turn into body fat?
Whether it is Carbohydrates, Protein, or Fats, too many calories from any food source will end up as body fat.
After a meal, any carbohydrates that your body doesn’t immediately make into blood glucose for energy is stored as glycogen. But the cells that store glycogen can hold only a limited amount. Once they’re filled, the overflow is changed to fat and routed to fat cells. Excess protein that’s not needed to build and maintain your body or to meet energy demands is also changed into fat and stored. The unused calories from dietary fat and alcohol also are converted into body fat. Body fat, then, is the stored form of excess calories from any food source.
Your body converts the fat you eat into body fat much more efficiently than it converts carbohydrate, protein or alcohol. (And remember, 1g of Fat has 9 calories, where as 1g of Protein and Carbohydrate has 4 calories). For example, if you eat 100 excess calories of fat, your body may burn just 3 calories in the conversion process, leaving 97 calories to be stored as fat. On the other hand, the body may burn 23 of 100 excess calories from carbohydrate during the process of turning it into fat. This leaves 77 calories to store. With excess protein, the energy burned in converting to fat varies according to which amino acids the food contains. In general, it falls somewhere between carbohydrate and fat. More research is needed to determine how calories from alcohol are converted by the body – as well as its effect on regulating appetite. It’s easy to eat too much fat. Many foods such as desserts and commercial snacks are high in fat. You may eat lots of it without being aware, ending up with more calories than you need or want.
Described with a little more science…
Energy:
- Energy is stored in the chemical bonds of macronutrients, dietary carbohydrates, fat, or proteins.
- However, the chemical energy in protein is not readily used as a fuel source for physical activity.
- The primary suppliers of chemical-bond energy are in fats and carbohydrates.
Dietary Fat:
- Dietary fats are digested to fatty acids and absorbed into the body.
- They may be used for a variety of processes or used immediately for energy.
- Excess fatty acids are converted back to triglycerides (which is part of the panel of tests Doctors often run) and largely stored in fat or adipose tissue. Some are stored in muscle tissue.
- There is essentially no limit to the amount of fat that can be stored and there is a large variability in people’s fat storage levels.
- Fat stores represent at least 100 times the carbohydrate energy reserves.
Dietary Carbohydrates:
- Carbohydrates are digested to glucose and other simple and sugars and absorbed into the body. The simple sugars are converted into glucose, which may be used for synthetic processes or for energy.
- Excess glucose is made into glycogen, which is stored in the liver and muscles.
- Aerobic conditioning can increase muscle storage levels five-fold.
- Dietary carbohydrates eaten in excess are converted into fatty acids and stored in adipose tissue.
Protein:
- Protein is usually spared from entering energy production pathways in the body and is conserved for tissue maintenance, repair, and growth.
- It can be used for the production of energy when glycogen stores are reduced, but is not desirable because it leads to decreased muscle mass and an increased workload on the kidneys, also increasing the risk if dehydration.
- Excess protein can also be turned into fat.
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