Nutrition For Dummies, 5th Edition

The first step is for an enzyme in your fat cells to break up stored triglycerides (the form of fat in adipose tissue). The enzyme action releases glycerol and fatty acids, which travel through your blood to body cells, where they combine with oxygen to produce heat/energy, plus water — lots of water — and the waste product carbon dioxide.

As anyone who has used a high-protein/high-fat/low-carb weight-loss diet such as the Atkins regimen can tell you, in addition to all that water, burning fat without glucose produces a second waste product called ketones. In extreme cases, high concentrations of ketones (a condition known as ketosis) alter the acid/alkaline balance (or pH) of your blood and may trip you into a coma. Left untreated, ketosis can lead to death. Medically, this condition is most common among people with diabetes. For people on a low-carb diet, the more likely sign of ketosis is stinky urine or breath that smells like acetone (nail polish remover)

When the fat moves down your digestive tract into your small intestine, an intestinal hormone called cholecystokinin alerts your gallbladder to release bile. Bile is an emulsifier, a substance that enables fat to mix with water so that lipases can start breaking the fat into glycerol and fatty acids. These smaller fragments may be stored in special cells (fat cells) in adipose tissue, or they may be absorbed into cells in the intestinal wall, where one of the following happens:

They’re combined with oxygen (or burned) to produce heat/energy, water, and the waste product carbon dioxide.

Although dietary fat has more energy (calories) per gram than protein and carbohydrates, your body has a more difficult time pulling the energy out of fatty foods than out of foods high in protein and carbs.

Imagine a chain of long balloons — the kind people twist into shapes that resemble dachshunds, flowers, and other amusing things. When you drop one of these balloons into water, it floats. That’s exactly what happens when you swallow fat-rich foods. The fat floats on top of the watery food-and-liquid mixture in your stomach, which limits the effects of lipases, the enzymes that break fats apart so you can digest them. As a result, fat is digested more slowly than proteins and carbohydrates, so you feel fuller, a condition called satiety (pronounced say-ty-eh-tee) longer after eating high-fat food

A healthy body needs fats to build body tissues and manufacture biochemicals, such as hormones. Some of the adipose (fatty) tissue in your body is plain to see. For example, even though your skin covers it, you can see the fat deposits in female breasts, hips, thighs, buttocks, and belly or on the male abdomen and shoulders

A component of myelin, the fatty material that sheathes nerve cells and makes it possible for them to send the electrical messages that enable you to think, see, speak, move, and perform the multitude of tasks natural to a living body (Your brain is about 60 percent fat, giving a whole new meaning to the term “fat head.”)

A protein deficiency may also affect red blood cells. The cells live for only 120 days, so the body needs a regular supply of protein to make new ones. People who do not get enough protein may become anemic, having fewer red blood cells than they need. Other signs of protein deficiency are fluid retention (the big belly on a starving child), hair loss, and muscle wasting caused by the body’s attempt to protect itself by digesting the proteins in its own muscle tissue, a phenomenon that explains why victims of starvation are, literally, skin and bones.

Liquid fats are called oils; solid fats are called, well, fat, and the fat in food is called dietary fat

With the exception of cholesterol (a fatty substance that has no calories and provides no energy), dietary fats are high-energy nutrients. Gram for gram, fats have more than twice as much energy potential (calories) as protein and carbohydrates: 9 calories per fat gram versus 4 calories per gram for the other two. (For more calorie information, see Chapter 3.)

Some nutritionists think soy proteins are even better than the proteins in eggs and milk, because the proteins in soy come with no cholesterol and very little of the saturated fat known to clog your arteries and raise your risk of heart attack. Better yet, more than 20 recent studies suggest that adding soy foods to your diet can actually lower your cholesterol levels

For example, eggs are 11 percent protein, and dry beans are 22 percent protein. However, the proteins in beans don’t provide sufficient amounts of all the essential amino acids, so they (the beans) are not as nutritionally complete as proteins from animal foods. The prime exception is the soybean, a legume that’s packed with abundant amounts of all of the amino acids essential for adults. Soybeans are an excellent source of proteins for vegetarians, especially vegans, which are vegetarians who avoid all products of animal origin, including milk and eggs