Written by Matthew G. Kadey MSc, RD
11 July 2006

Pull Quote: While some fats are more prone to be taken up by fat (adipose) cells and stored as body fat, others are more likely to alter metabolism to favor fat-burning.

For many years doctors and nutritionists were steering people away from “dreaded” fat assuming that fat in the diet was directly converted into body flab. Because of this, there was a proliferation of low- or fat-free products taking over the supermarket aisles in the 80s and 90s. Fat-free salad dressing, light peanut butter and low-fat yogurt were among the many items that were supposed to be better for us because they got rid of the fat. And what happened with the mass consumption of these products? Obesity rates skyrocketed and reached epidemic proportions. Other than the fact that many reduced-fat items replaced the fat with sugar, one reason for this trend toward expanding midsections was the false assumption that all dietary fats were alike.
It now seems apparent that the body handles various fats differently. While some fats are more prone to be taken up by fat (adipose) cells and stored as body fat, others are more likely to alter metabolism to favor fat-burning.

Fish Oil
Any devoted reader of this publication will, by now, know that the fats in fish have a wide range of health benefits. Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which are found in high amounts in fatty, cold-water fish such as salmon, sardines and mackerel, have been shown to protect the heart from disease by reducing inflammation,  blood triglycerides  and arterial plaque instability.  Cancer,  eye disease,  Alzheimer’s  and depression7,8 also appear to be on fish oil’s hit list. However, little fanfare has been paid to fish oil’s ability to alter metabolism and increase fat burning.
Many of the health benefits attributed to long-chain polyunsaturated fats such as DHA and EPA are a result of their ability to alter our gene functioning using various mechanisms. These include changing the makeup of cell membranes, changing the transcription of genes and impacting the levels of calcium found within our cells.9,10,11,1213,14,15 By altering our genes in a positive way, DHA and EPA are very effective at combating a vast array of serious conditions, one being that of excess body fat.16
One outcome of this regulation of gene expression is that DHA and EPA increase the rate of fatty acid oxidation (fat-burning) by increasing the activity of enzymes and receptors in the liver involved in fat breakdown and oxidation, while decreasing the activity of those associated with fat storage.17,18,1920,21 All of this improves both fatty acid and glucose metabolism.10,15,1820,23 In other words, they can reduce fat cell proliferation by limiting both the expansion (hypertrophy) and division (hyperplasia) of fat cells.24,25
Fish oil can also indirectly affect our fat stores by improving skeletal muscle sensitivity to insulin.10,22,23 Insulin resistance is a serious contributor to fat storage by causing an unusual increase in blood glucose levels. Eventually this glucose can be stored as fat in the fat cells.
Consuming three to four servings of fatty fish per week is what many health experts recommend in order to obtain enough DHA and EPA. However, taking a daily fish oil supplement may be the best way to reap all the rewards of this amazing fat source. Concerns over contaminants present in fish such as farmed salmon and the reality that the majority of us simply don’t eat enough fish in any given week, makes supplementation a viable option. ConsumerLab.com, which is an independent supplement testing organization, found that all the fish oil supplements they tested were free of contaminants, such as mercury and PCBs.

Oleic Acid
Oleic acid is a monounsaturated fat (mono meaning it contains one double bond) found in various vegetable oils that’s alternatively known as an omega-9 fatty acid. Like DHA and EPA found in fish, oleic acid appears to alter metabolism in favor of fat oxidation and away from fat storage.26,27,28 The opposite can be said for palmitic acid— a fully saturated fat present in fatty meat, butter, cream, full-fat dairy and baked goods— that it is more prone to being stored compared to unsaturated fatty acids.29,30
These characteristics were highlighted in a recent study published in the American Journal of Clinical Nutrition, which found that after 28 days, an increase in the intake of saturated palmitic acid decreased fat burning and daily energy expenditure in healthy subjects, whereas a decrease in the consumption of palmitic acid intake and a increase in oleic acid intake had the opposite effect, resulting in an improved body composition. The researchers concluded that increases in dietary palmitic acid may alter our gene expression in such a way that increases the risk of obesity along with insulin resistance, whereas oleic acid may do the reverse when consumed in reasonable amounts.26
Oleic acid’s ability to turn up the heat is particularly apparent following a bout of exercise.31,32,33 Exercise, especially high-intensity exercise, can change your metabolism from favoring fat storage to favoring fat burning for several hours afterward while the body takes part in recovery processes such as lowering heart rate and replacing used up energy stores.34 However, it appears that this outcome is much more likely to occur if, following exercise, you consume monounsaturated fat in the form of oleic acid as opposed to saturated fat in the form of palmitic acid. Therefore, when you are finished hitting the weights, give those French fries a break and instead opt for the baked potato drizzled with olive oil.
Oleic acid has also been found to have a faster oxidation rate than the other unsaturated fatty acid known as linoleic acid, which is an omega-6 fat is found in high amounts in soybean and corn oil.35 It should be noted that these oils are commonly used in restaurants, fast-food joints and many processed foods. Because of this, most Americans consume much more linoleic acid than oleic acid and omega-3 fatty acids. This isn’t ideal, as linoleic acid appears to be more likely to be retained in the body following a meal, due to its lower propensity for being used to generate energy.
Keep the important advantages of oleic acid in mind when you’re reading about the Mediterranean diet since this relatively high-fat diet is very high in oleic acid. This is because of the generous use of olive oil in populations who practice this way of eating. The fat-burning characteristics of oleic acid may shed more light on why the traditional Mediterranean diet is so healthy and why individuals from countries such as Greece and Italy who follow it tend to be slimmer than Americans.
What all this means is that you should consume a good chunk of your daily fat as monounsaturated fat (oleic acid) to help better manage your metabolism. Major dietary sources include olive oil, canola oil, peanut oil and the "high-oleic" safflower and sunflower oils. Oleic acid is also found in various amounts in avocados, nuts, cocoa butter and nut butters.

Coconut Oil
Lately, coconut oil has been flying off the shelves of health food stores. Once branded Public Enemy Number One by health practitioners, it appears that this oil is making a healthy comeback. One reason is the belief that it helps shed body fat.
Medium-chain triglycerides (MCTs), which make up over 50 percent of the fat in coconut oil in the form of lauric acid, are thought to be one tool in the battle of the bulge. MCTs, in contrast to long-chain triglycerides like palmitic acid, increase energy expenditure by being digested and absorbed much more quickly as a result of their unique six- to12-carbon length (long chain fats contain over 12 carbons). Their unique structure also alters the expression of genes involved in the uptake of fat into fat stores. As a result, MCTs are largely converted (oxidized) to energy in the liver and muscle instead of entering fat (adipose) tissue resulting in a negative energy balance.36,37,38,39,40 In addition, MCTs may bring about a greater feeling of satiety, leading to a reduction in calorie intake.39 Whether all this translates into fat loss and the prevention of weight gain as a result of coconut oil consumption and just how much oil would need to be part of the diet for this to occur, is yet to be determined as there’s no solid data studying coconut oil’s effect on fat metabolism.

Enova Oil
Enova (www.enovaoil.com) is a new cooking oil made from a mixture of soybean and canola oil. According to the makers of EnovaÔ, the difference between this cooking oil and others is that most oils used for cooking contain fat molecules, which are primarily triglycerides, while Enova has a higher concentration of diglycerides. The differences in chemical structure and shape may mean that the fat in this new oil is more likely to be oxidized instead of being stored.41 While it remains to be determined what real impact this oil may have on body fat regulation, one concern is that this oil is higher in polyunsaturated fat than other common cooking oils such as pure canola or olive oil. Polyunsaturated fats are less stable when exposed to heat than monounsaturated fats and can produce damaging free radicals when heated to a high temperature. Cell damage from free radicals can lead to cancer, age-related vision loss and other health problems. Olive and canola oils higher in monounsaturated fat are likely more heat stable and, therefore, might be a better option for cooking up that stir-fry.

Fat Recommendations
? Obtain between 25 and 30 percent of total calories from fat.
? Use extra-virgin olive oil (high in oleic acid) for salad dressings. Olive oil is also good fat choice after a workout.
? Avoid fatty processed foods high in saturated and trans-fat.
? Use heat-stable virgin coconut oil for high-heat cooking.
? Consume fatty fish at least three times per week and/or use a daily fish oil supplement.