1 gram of fat equals approximately  9 calories.

Food sources of fat contain a combination of 3 types of fats in different ratios:

  • Saturated fat (solid at room temperature)
  • Unsaturated fats (liquid at room temperature)
    • Polyunsaturated
    • Monounsaturated

There is also another type of fat, called trans-fat, which is mainly the product of processing vegetable oils.

We refer to fat type such as saturated fat, as fats that consist mostly of saturated fats. This does not mean that other types of fats are absent. For instance, one ounce of coconut oil has 24.2g of saturated fat, 1.6g of monounsaturated fat and 0.5g of polyunsaturated fat. It also contains 504mg of omega-6 fatty acids and no omega-3 fatty acids.

What fats are good and what fats are bad? (1)Berry EM. Are diets high in omega-6 polyunsaturated fatty acids unhealthy? European Heart Journal Supplements (2001) 3(Supplement D), D37–D41. Available here.

In summary, saturated fats, monounsaturated fats and some polyunsaturated fats in the correct ratio are healthy fats.

Unhealthy fats come from processed vegetables oils and trans-fats. Additionally, a high ratio of omega 6 to omega 3 fatty acids is also not recommended.
Saturated fats
Saturated fats received a bad name in the late 1970s when the U.S. government implemented the first dietary guidelines (1977), promoting a high carbohydrate and a low fat diet.
These guidelines were based on a controversial hypothesis, which stated that dietary saturated fat increases blood cholesterol levels and, therefore, leads to cardiovascular diseases, which at the time was a major concern.

To this day, this hypothesis has not been actually proven by clinical trials.

From the moment that these guidelines were implemented, a sudden rise in obesity rates occurred, and they have been increasing ever since. Many scientists blame it on the increase of carbohydrates in our diets rather than on a diet high in saturated fats. (2)Hite AH, Feinman RD, Guzman GE, Satin M, Schoenfeld PA, Wood RJ. In the face of contradictory evidence: report of the Dietary Guidelines for Americans Committee. Nutrition. 2010 Oct;26(10):915-24. doi: 10.1016/j.nut.2010.08.012. Available here. (3)Santos FL, Esteves SS, da Costa Pereira A, Yancy Jr WS, Nunes JPL. Systematic review and meta-analysis of clinical trials of the effects of low carbohydrate diets on cardiovascular risk factors. Obesity reviews (2012) 13 , 1048–1066. Available here.
Current scientific evidence shows that saturated fats do not cause obesity, diabetes or cardiovascular diseases and the focus of the investigation should rather turn to the current recommendations of high carbohydrate diets. (4)Hite AH, Feinman RD, Guzman GE, Satin M, Schoenfeld PA, Wood RJ. In the face of contradictory evidence: report of the Dietary Guidelines for Americans Committee. Nutrition. 2010 Oct;26(10):915-24. doi: 10.1016/j.nut.2010.08.012. Available here. (5)Astrup A, Dyerberg J, Elwood P, Hermansen K, Hu FB, Uhre Jakobsen M, et al. The role of reducing intakes of saturated fat in the prevention of cardiovascular disease: where does the evidence stand in 2010? Am J Clin Nutr April 2011 vol. 93 no. 4 684-688. Available here.

The bottom line is that saturated fat is safe.
Polyunsaturated fats
Polyunsaturated fats include both beneficial and harmful fats in various ratios. Omega 3 fatty acids have great anti-inflammatory and antioxidant properties while Omega 6 fatty acids have pro-inflammatory properties.

Studies show that a diet with a high ratio of Omega-6 to Omega-3 fatty acids lead to an increased risk of diabetes, obesity, hypertension, cardiovascular disease and insulin resistance.

Here are some examples of ratios of omega 6 to omega 3 fatty acids: (6)Berry EM. Are diets high in omega-6 polyunsaturated fatty acids unhealthy? European Heart Journal Supplements (2001) 3(Supplement D), D37–D41. Available here.

Mesolithic men: between 1-4 to 1;
Current European diet: between 10-14 to 1;
Other Western diets: between 15-17 to 1 (7)Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002 Oct;56(8):365-79. Available here.;
Israel Jewish population: between 22-26 to 1 (high occurrence of obesity, cardiovascular disease, hypertension and type 2 diabetes).

Lower ratios of omega 6 to omega 3 fatty acids have been shown to have positive health effects (8)Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002 Oct;56(8):365-79. Available here.:

Ratio 2.5 to 1 – reduction in the increasing rectal cells in colorectal cancer patients
Ratio between 2 and 3 to 1 – stopped inflammation in rheumatoid arthritis sufferers
Ratio 5 to 1 – showed improvements in asthma symptoms
Ratio 10 to 1 – presented negative health effects, associated with inflammation.

Monounsaturated fats
All scientists agree that monounsaturated fats are the good fats.

The controversy relates to saturated fats, mainly because of the above-mentioned guidelines, and polyunsaturated fats.

Trans fats and partially hydrogenated oils (PHOs)
There are two types of trans- fats acids (9)FDA – U.S. Food and Drug Administration. FDA Cuts Trans Fat in Processed Foods. Available here.:

  • The naturally occurring trans- fat, produced in the guts of some animals. Tiny amounts may exist in dairy and milk products.
  • The artificially created trans- fat, produced by adding hydrogen to vegetable oils, in order to make it more solid. These are known as PHOs.

The biggest dietary sources of trans- fats are PHOs.

A diet high in trans- fatty acids raises the bad cholesterol (LDL), lowers the good cholesterol (HDL) and increases the risk of cardiovascular diseases, stroke and type 2 diabetes.

Conclusion

For better health your diet should include more omega 3 fatty acids, monounsaturated fats and saturated fats in moderation. Saturated fats should be eaten in moderation because since we have a physical limitation of how much we can eat, we need to make some choices. Foods containing the healthiest oils such as small cold water fish, walnuts, chia and flaxseeds and cold press oils such as flaxseed oil and extra virgin olive oil are high in energy and very satiating. Having too much of any other fats will reduce the intake of the fats that are proven to be the most beneficial.

Avoid trans- fats and any processed fats especially vegetable oils and margarines.

References   [ + ]

1. Berry EM. Are diets high in omega-6 polyunsaturated fatty acids unhealthy? European Heart Journal Supplements (2001) 3(Supplement D), D37–D41. Available here.
2. Hite AH, Feinman RD, Guzman GE, Satin M, Schoenfeld PA, Wood RJ. In the face of contradictory evidence: report of the Dietary Guidelines for Americans Committee. Nutrition. 2010 Oct;26(10):915-24. doi: 10.1016/j.nut.2010.08.012. Available here.
3. Santos FL, Esteves SS, da Costa Pereira A, Yancy Jr WS, Nunes JPL. Systematic review and meta-analysis of clinical trials of the effects of low carbohydrate diets on cardiovascular risk factors. Obesity reviews (2012) 13 , 1048–1066. Available here.
4. Hite AH, Feinman RD, Guzman GE, Satin M, Schoenfeld PA, Wood RJ. In the face of contradictory evidence: report of the Dietary Guidelines for Americans Committee. Nutrition. 2010 Oct;26(10):915-24. doi: 10.1016/j.nut.2010.08.012. Available here.
5. Astrup A, Dyerberg J, Elwood P, Hermansen K, Hu FB, Uhre Jakobsen M, et al. The role of reducing intakes of saturated fat in the prevention of cardiovascular disease: where does the evidence stand in 2010? Am J Clin Nutr April 2011 vol. 93 no. 4 684-688. Available here.
6. Berry EM. Are diets high in omega-6 polyunsaturated fatty acids unhealthy? European Heart Journal Supplements (2001) 3(Supplement D), D37–D41. Available here.
7. Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002 Oct;56(8):365-79. Available here.
8. Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002 Oct;56(8):365-79. Available here.
9. FDA – U.S. Food and Drug Administration. FDA Cuts Trans Fat in Processed Foods. Available here.

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