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| Fat Facts |
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| Definition of fats, or "lipids": |
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- adipose tissue of the body, which serves as an energy source; in fact it is the most
concentrated source of energy in the diet; 1 gram of fat when oxidized yields 9 calories which
is more than twice the calories per gram of carbohydrate or protein;
- Grease, oil;
- triglyceride ester of fatty acids; during metabolism, fats are broken down via
hydrolysis into fatty acids and glycerol.
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| Digestion, absorption, & metabolism: |
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Most fats undergo digestion in the small intestine. The presence of fatty food in the small
intestine triggers the release of bile from gallbladder, the pancreatic hormone, lipase, and
some other hormones and secretions which aid in hydrolysis and break down of fats. In
addition, another hormone is released which sends a message to the stomach and ultimately
halts its motility. Less new food enters the small intestine and the food already present gets
fully digested and absorbed. This is why one feels full faster when eating a food higher in fat.
Absorbed fats are utilized in the following ways: oxidized to water and carbon dioxide to
produce energy, stored in adipose tissue for energy production later, changed to
phospholipids for cell membranes, converted to precursors of cholesterol, from which other
steroids/hormones are made, and used to make secretions such as sebum. |
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| Sources: |
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| In addition to dietary fats, the body is able to convert the intermediate and/or final products
of other macromolecules (carbohydrates and proteins) to make fat building blocks. In fact, in
the presence of the essential substances, such as, essential amino acids (see ÒproteinÓ) and
essential fatty acids, our body is capable of making its major components through specific
and exact mechanisms, interconverting different molecules according to its highest priority.
This very important fact is often overlooked and diets such as Òhigh protein dietÓ, Òhigh fat
dietÓ and so forth are met with failure. For example, a person whose main goal is to obtain a
lower body fat, in the long run, will not benefit from a Òhigh protein dietÓ without reducing
calorie intake, or increasing activity level. Body fat decreases only when calories consumed
are less than those used. The body will break down protein, carbohydrate and fats to their
end products, absorbs them, interconverts molecules as needed, and for the most part,stores
excess calories as adipose tissue (fat). |
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| To summarize, sources of fat are: |
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- Fat present in diet
- Excess calories
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| Cholesterol, Lipoproteins (LDL, &HDL) - what are they? |
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Cholesterol is a fat-related substance necessary for good health. It is widely
distributed in animal tissues and occurring in egg yolks, various oils, fats, the nerve tissue of
the brain and spinal cord, the liver, the kidneys, and the adrenal glands. It can be made in
the liver and is a normal constituent of bile (remember bile? Necessary for fat digestion). It is
important in metabolism, serving as a precursor of various steroid hormones (e.g., sex
hormones, adrenal corticoids).
Lipoproteins are simple proteins combined with lipid components: cholesterol,
phospholipid, and triglyceride. The proteins act as carriers for these water-insoluble
molecules. Lipoproteins are categorized with respect to their chemical properties and
densities as very low-density (VLDL), low-density (LDL), intermediate-density (IDL), and
high-density (HDL). The greater the amount of protein in the lipoprotein molecule, the higher
the density- the greater the amount of lipid, the lower the density. Thus, HDL cholesterol is
the so-called good cholesterol, a high level of which is desirable.
In most individuals, an elevated blood level of cholesterol leads to an increased risk of
developing coronary heart disease (CHD). It has been shown that lowering this level
(specifically, blood levels of LDL cholesterol) reduces the risk of heart attacks due to CHD. |
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| Health hazards |
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We know now that the amount and the type of fat one eats, as well as being
over-weight, has a direct impact on his or her health. Obesity, and a high-fat diet, both are
associated with many serious medical risks, most of which are, at least in part, reversible.
Risks that result from the metabolic changes due to excess fat intake are: |
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- Diabetes
- Pancreatitis
- Gallstones
- Hypertension
- Cancers that are associates with obesity
- Fatty livers
- Infertility
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The diseases that result from the increased weight of the fat itself include:
- Arthritis
- Sleep apnea (apnea=temporary cessation of breathing)
- Emotional and social burden of obesity
In addition, and most seriously, obesity is associated with an increased risk of death, as
demonstrated in life insurance statistics.
You may be wondering why there is a need for talking about obesity. After all,
obesity is one of the two extremes in a weight chart. Unfortunately, in spite of large public
health expenditure in promoting the benefits of exercising and calorie restriction, the
incidence of unhealthy weight continues to increase. Today, 50% of the adult population is
overweight or obese. According to the American Heart Association:
- More than 50% of American children eat too much sugar, fat, cholesterol.
- About half of these children (25% of all American children) are overweight or at risk
- Up to 20% of these overweight children will remain so throughput their lives.
- Being overweight in childhood is the leading cause of pediatric hypertension.
- Besides childhood obesity,
- Obesity contributes to over 50% of the chronic diseases in Western societies
- Around 70% of diagnosed cases of cardiovascular diseases are related to obesity.
- Around 80% of patients with diabetes type II are obese.
- Children of obese parents have more than double the risk of becoming obese.
Looking at these statistics, we cannot overstate the magnitude of the problem with obesity.
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| Dietary lipid guidelines for health |
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Fat intake can contribute to 10 to 30 percent of the daily total caloric intake (the exact
percentage is determined based on oneÕs genetics, GOALS, satiety,
palatability, and activity level). Diets with more than 30% fat-calories lose the
volume of food for the same number of calories (recall that 1 gram of fat yields more than
twice the calories per gram of carbohydrate or protein). This high percentage may lead to
overeating (due to lack of volume) and a slow metabolism. A small portion of the population
may need to increase the fat ratio in their diet because genetically they may have a higher
carbohydrate metabolism. In this case, a diet with greater than 50% carbohydrate may lead
to overeating since the carbohydrates are metabolized too quickly, and a craving for more
carbohydrates is created. On the other hand, some individuals may feel sluggish eating a diet
consisting of 20% fat-calories and function better on diets with lower fat content. The variety
of reactions to fat intake is due to bio-individuality in the conversion of food to energy.
Dietary fat calories should not be less than 10 % of total caloric intake (TCI)
because of all the earlier-mentioned important functions that fat performs. In
addition, you must keep in mind that all fats are not bad; some are actually good for you.
Omega 3 and 6 fatty acids, found in some fish, can help in lowering cholesterol as well as
other positive physiological and psychological responses. A weight/fat loss diet can benefit
form dietary fat due to its important functions in satiety, stabilizing blood sugar, making
absorption of fat-soluble vitamins possible, and lastly, but just as important, making food
more palatable.
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Lipid summary
- 1 gram of fat = 9 calories
- Present in all cells; high in adipose and nerve tissue, low in epithelial and muscle tissue.
- Functions: energy, structure, and function at cellular level, precursor to hormones, carrier of fat-soluble vitamins, insulation and protection.
- Essential fatty acids: linoleic, linolenic, and arachidonic acids.
- HDL is the "good" cholesterol - LDL is the "bad" cholesterol.
- You should not cut all fat from your diet - see fat functions.
- Excess calories make you fat, not fat.
- Not all fats cause high cholesterol; some (omega 3 & 6) even help lower it.
- The appropriate caloric percentage (of fat, protein, and carbohydrate) is
determined based on oneÕs bio-individuality, and fitness GOALS.
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