Fats or lipids are an energy dense macronutrient that play a variety of roles within the body. Tytpically the lipids which are important from an energy perspective can be classified into a variety of different fatty acids. Naturally there are three different types of dietary fatty acids based upon their chemical structure, which are saturated (SFAs), Monounsaturated (MUFAs) and Polyunsaturated (PUFAs). In addition there is fourth form of fatty acids that is created through hydrogenation when being processed to solidify an oil into a solid fat which will create trans fatty acids.
As stated earlier, fats are energy dense compared to either carbohydrates or protein as they deliver over twice the energy per gram (nine kcals). But as will be discussed the total amount of energy a nutrient imparts is only one factor in the energy balance equation.
Saturated fatty acids
Saturated fatty acids are mostly commonly found in meat and dairy products. They are classified as being saturated due to their chemical structure as they have no carbon double bonds and would not be able to accept a hydrogen molecule (i.e. all of its carbon bounds are ‘saturated’). The saturation of carbon bonds makes the fatty acids solid at room temperature.
Saturated fats have had bad press due to its hypercholesterolemic effect, or in other words its ability to raise total cholesterol, specifically the often cardiovascular diseased linked low density lipoprotein type cholesterol. However the low density lipoprotein (LDL) raising effects only appear to be from certain saturated fatty acids namely, Lauric, mystic and palmitic acids however stearic acid does not have the same effect.
Saturated fats, specifically palmitic acid also appear to have a negative effect on the bodies fat burning process, with increases in saturated fatty acids playing a role in gene expression and the bodies subsequent fat oxidation process. (Kein et al 2005)
Total fat and saturated fats appear to alter hormonal levels with higher fat diets and total satrated fats playing a major role in the level of testosterone within men [Volek et al].
Types of saturated fatty acids
Monounsaturated fatty acids
These fats have one carbon double bond which makes them liquid at room temperature. Monounsaturated fatty acids appear to have a neutral or positive effect on cholesterol levels in that they do not appear to raise LDL levels, whether this is a direct effect of the fatty acids or whether its because a diet richer in MUFAs just decreases the total maount of SFAs is debatable.
Another positive effects that monounsaturated fatty acids appear to have is that it does not appear to be its ability to prevent oxidative damage associated with other fatty acids. This is proposed to have a greater defensive effect against many diseases which arelinked to oxidation rates such as cancer.
Oleic acid may also have a role in fat storage and metabolism due to its ability to increase fat oxidation and decreased fat storage (Gaster et al 2005, Lovejoy et al 2002) as it appears to alter gene expression. This may be most apparent with exercise (Vorturba et al 2005) where consumption of oleic acid appeasr to increase the rate of fat usage after high intensity exercise.
Types of monounsaturated fatty acids
Polyunsaturated
Polyunsaturated fatty acids are called so because they have multiple double bonds. Some of the polyunsaturated fatty acids are termed essential because the body does not have the ability to synthesis fatty acids with carbon double bonds in the specific positions. The essential fatty acids are called omega threes and omega sixs, named so because there first double bond is either in the three position or six position in their chemical strucuture. The two fatty acids which are required from the diet are alpha linolenic acid (an omega 3) and linoleic acid (an omega six). These two fatty acids can be used by the body to produce other fatty acids which make up the omega three and omega six families.
As stated earlier, fats are energy dense compared to either carbohydrates or protein as they deliver over twice the energy per gram (nine kcals). But as will be discussed the total amount of energy a nutrient imparts is only one factor in the energy balance equation.
Saturated fatty acids
Saturated fatty acids are mostly commonly found in meat and dairy products. They are classified as being saturated due to their chemical structure as they have no carbon double bonds and would not be able to accept a hydrogen molecule (i.e. all of its carbon bounds are ‘saturated’). The saturation of carbon bonds makes the fatty acids solid at room temperature.
Saturated fats have had bad press due to its hypercholesterolemic effect, or in other words its ability to raise total cholesterol, specifically the often cardiovascular diseased linked low density lipoprotein type cholesterol. However the low density lipoprotein (LDL) raising effects only appear to be from certain saturated fatty acids namely, Lauric, mystic and palmitic acids however stearic acid does not have the same effect.
Saturated fats, specifically palmitic acid also appear to have a negative effect on the bodies fat burning process, with increases in saturated fatty acids playing a role in gene expression and the bodies subsequent fat oxidation process. (Kein et al 2005)
Total fat and saturated fats appear to alter hormonal levels with higher fat diets and total satrated fats playing a major role in the level of testosterone within men [Volek et al].
Types of saturated fatty acids
| Name fatty acid (carbon bonds : double bonds) |
| Myristic acid (14 : 0) Palmitic acid (18 : 0) Stearic acid (16 : 0) Arachidic acid (20 : 0) Lignoceric acid (24 : 0) |
Monounsaturated fatty acids
These fats have one carbon double bond which makes them liquid at room temperature. Monounsaturated fatty acids appear to have a neutral or positive effect on cholesterol levels in that they do not appear to raise LDL levels, whether this is a direct effect of the fatty acids or whether its because a diet richer in MUFAs just decreases the total maount of SFAs is debatable.
Another positive effects that monounsaturated fatty acids appear to have is that it does not appear to be its ability to prevent oxidative damage associated with other fatty acids. This is proposed to have a greater defensive effect against many diseases which arelinked to oxidation rates such as cancer.
Oleic acid may also have a role in fat storage and metabolism due to its ability to increase fat oxidation and decreased fat storage (Gaster et al 2005, Lovejoy et al 2002) as it appears to alter gene expression. This may be most apparent with exercise (Vorturba et al 2005) where consumption of oleic acid appeasr to increase the rate of fat usage after high intensity exercise.
Types of monounsaturated fatty acids
| Name fatty acid (carbon bonds : double bonds) |
| Palmatoleic acid (16 : 1) Oleic (18 : 1) |
Polyunsaturated
Polyunsaturated fatty acids are called so because they have multiple double bonds. Some of the polyunsaturated fatty acids are termed essential because the body does not have the ability to synthesis fatty acids with carbon double bonds in the specific positions. The essential fatty acids are called omega threes and omega sixs, named so because there first double bond is either in the three position or six position in their chemical strucuture. The two fatty acids which are required from the diet are alpha linolenic acid (an omega 3) and linoleic acid (an omega six). These two fatty acids can be used by the body to produce other fatty acids which make up the omega three and omega six families.
