All you need to know about dietary fat

We are always told to cut down the intake of unhealthy fats and increase the intake of healthy ones. This advice besides being correct is also a bit unclear. How much "good" and "bad" fat exactly do we need? Which are the "good" fats and which are the "bad" ones?


Sometimes people add big amounts of olive oil in their salad and even though olive oil is extremely healthy, calories are calories and will add on. On the other hand there are people who avoid eating eggs, or use margarine instead of butter because margarine is made from vegetable oils. However this can be more harmful.

In this post:

· Why was dietary fat demonized for decades

· 6 reasons we need fat in our diet

· Which fats we call “good”, “bad” and “not so bad”

· How much fat we need on a daily basis

· What happens if you cut fat intake too much


Why was dietary fat demonized for decades



The good, the bad and the ugly.

The “fat will make you fat” trend took over the US in the 70s and 80s. Fat in foods was blamed for causing obesity and diabetes among Americans and therefore a wave of low fat products flooded the markets. For a food to be tasty it needs fat, sugar or salt. To make the “low fat” food taste good again producers would put in it equal, or even greater amounts of calories from sugar. The result from that low fat craze was significant increase in the rates of obesity and diabetes in the United States.

At the same time, studies done on the Mediterranean diet which is rich in fat (and wine by the way) showed that it may decrease the risk of coronary heart disease.




6 reasons we need fat in our diet


For our brains


Did you know that about 60% of the human brain is fat? Our bodies need certain fatty acids called linoleic and linolenic for brain development, blood clotting and controlling inflammation. These are essential because the body cannot make them itself and have to receive them from diet. And when you think about it, foods that are shown to improve brain function and memory (walnuts for instance) are quite high in fat content.



For our cells


Fats are needed to build the cell membranes of healthy cells. Diets which are too low on fat intake cause your hair and nails to become fragile. It is because their cell structures suffer from that insufficiency.



Fat supporting our organs


The visceral fat is the fat which surrounds and supports our internal organs. To put it simply, it prevents them from banging into each other while you run in the park by making sure there is enough space between them. However, too much visceral fat creates pressure on the internal organs and increases the risk of type 2 diabetes.



For absorption of vitamins


The fat-soluble vitamins A, E, K and D are essential for the healthy development of our bodies. Fat in our diet helps the intestines to absorb those vitamins.



For energy

Fat is the most calorie dense nutrient in our diet. It provides 9 kcal per 1 gram. This is more than twice the energy that you get from protein or carb (they both provide 4 kcal per 1 gram).



Fat is needed for hormone production

Actually, we really need the cholesterol from the fat. It is the major precursor of the five classes of steroid hormones: progestogens, glucocorticoids, mineralocorticoids, androgens, and estrogens. 80% of the cholesterol we need is produced by the liver and intestines. The rest we receive from our diet (oh, hello eggs).




Types of fats

There are three types of fats (or lipids) in our diet. More than 90% of the naturally existing fats are found in the form of triglycerides. The other two are phospholipids and sterols (cholesterol for example). Here we will focus on the triglycerides.


On picture you can see that they are composed of one glycerol backbone and three fatty acids (tri- , glyceride). These fatty acids can be saturated and unsaturated. Both types consist chains of carbon atoms (C). Some of the atoms are linked by single bond (– C – C –) and some by double (– C = C –). Double bonds can break up and react with hydrogen (H). Saturated fats do not have any double bond. They are "saturated" with hydrogen atoms. Monounsaturated fats have one (mono) double bond of carbons and polyunsaturated have two or more (poly).






Unsaturated fats (the "good fats")

They make up all fats that are usually liquid at room temperature (olive oil, sunflower oil, sesame oil, etc.). They are found also in avocados, nuts and their butters, fish (salmon, mackerel). These can be monounsaturated and polyunsaturated (ADAM Health Solutions, 2016.


Both of these help lowering the risk of cardiovascular diseases and some of them (omega-3, omega-6) are essential for our bodies, meaning we need to get them from our diet.



Saturated fats (the "not so bad fats")

They compose all fats which are solid at a room temperature (mostly animal fats like the fats in butter, eggs, cheese, coconut for example). They are called this way because their chains are literally saturated with hydrogen atoms. Up until recently they were demonized by scientists and health gurus because it was believed that they raise LDL cholesterol ("bad" cholesterol) and increase the risk of cardiovascular disease and type 2 diabetes. However they also raise HDL cholesterol ("good" cholesterol). Nowadays scientists are not entirely convinced this is true. Growing evidence suggests that saturated fats are not as harmful as previously considered.



Trans fats (the "bad fats")

These are found in very small amounts in animal products but otherwise are created artificially by "hardening" liquid oils. Unsaturated fatty acids are artificially saturated with hydrogen to make them solid (Saxelby, 2013). For example, sunflower oil is hydrogenated and made to margarine.

Trans fats are bad for our health as they increase our bad cholesterol and put us at higher risk of cardiovascular diseases. These are found in many commercial products like burgers, donuts and fries, because they increase the shelf life of these foods. It is recommended to avoid this kind of processed foods not only because they are bad for our waistline but also for our health.


How much fat do we need?


The UK government recommendations for fat intake for adults aged 19 – 64 are as follows:





This makes a total of 85 grams for men and 67grams for women daily. But of course, you don’t have to hit these exact numbers every day, this can be difficult. Other recommendations for fat intake are 20% to 35% of consumed daily energy. Women’s fat intake should not fall below 20% from daily calories because fat is needed for hormonal balance throughout the month. This means if you eat 2000 kcal a day at least 400 of these should come from fat.





What happens when you cut fat intake too much?



Compromised brain performance


As our brains are mostly made up from fat, they need sufficient amount of fat to function properly. Low fat diets can result in poor memory, focus and concentration, energy levels, mood and cognitive skills, for example.



Mood swings


Fat in our diets has a role in controlling mood. Diets with higher intake of unsaturated fats can have the ability to lower depression and anxiety and are often prescribed by professionals to improve symptoms of these. On the other hand trans fats are suggested to raise the risk of depression.



Poorer heart health


The positive effects of monounsaturated fats (like those in olive oil, canola oil, peanuts, almonds, avocado) on heart health have been proven in many studies. As mentioned earlier, the Mediterranean diet which has more than 40% of daily energy coming from fat is linked to improved cardiovascular health.



Hormone disturbances


Eating enough fat helps with balancing our hormones naturally. Cholesterol is the backbone of the main sex hormones (testosterone and estrogen) and as our bodies can make about 80% of the cholesterol we need, we have to take the other 20% from our diet. Low fat diets can create menstrual problems in women and make it difficult to become pregnant.



Yo-Yo effect


Let’s say you didn’t listen and cut significantly your intake of fat. You might lose some weight initially but as low fat diet is less satiating you will feel hungry all the time. This increases the chance of your body after few days “making” you reach out for sugar rich foods and gaining the weight back. Or even gaining more.





Bottom line



There is much misunderstanding about dietary fat which is why many people try to avoid it. But here’s the thing: Low fat diet does not mean a low fat person. Fats are different and while it is good for us to avoid certain types, other types are essential for our health. If you are not certain which foods you should limit or how much should you eat from them ask your trainer or dietitian for help.


In the meanwhile, if you found this article helpful, please consider sharing it with you friends and family.



ADAM Health Solutions. (2016). Dietary fats explained. US National Library of Medicine, Retrieved from https://medlineplus.gov/ency/patientinstructions/000104.htm


Manore, M. M., Meyer, N. L., & Thompson, J. (2009). Sport nutrition for health and performance (2nd ed ed.). Champaign: Human Kinetics. Retrieved from https://kamk.finna.fi/Record/kajakki.44803


Mayr, H. L., Thomas, C. J., Tierney, A. C., Kucianski, T., George, E. S., Ruiz-Canela, M., . . . Itsiopoulos, C. (2018). Randomization to 6-month mediterranean diet compared with a low-fat diet leads to improvement in dietary inflammatory index scores in patients with coronary heart disease: The AUSMED heart trial//doi.org/10.1016/j.nutres.2018.04.006 Retrieved from http://www.sciencedirect.com/science/article/pii/S0271531717311053


PARAGI MEHTA, R. D. (2017). Foods rich in monounsaturated fat. Retrieved from https://www.livestrong.com/article/35226-sources-monounsaturated-fat/


Public Health England. (2016). Government dietary recommendations. Retrieved from https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/618167/government_dietary_recommendations.pdf


Sanchez-Villegas, A., Verberne, L., De Irala, J., Ruiz-Canela, M., Toledo, E., Serra-Majem, L., & Martinez-Gonzalez, M. A. (2011). Dietary fat intake and the risk of depression: The SUN project. PloS One, 6(1), e16268. 10.1371/journal.pone.0016268 [doi]


Saxelby Katherine. (2013). Is margarine high in trans fat? Foodwatch, Retrieved from https://foodwatch.com.au/blog/fats-and-oils/item/q-is-margarine-high-in-trans-fat.html


The thuth about fats https://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good

7 low-fat diet risks you need to know about! Dr. Axe, Retrieved from https://draxe.com/low-fat-diet-risks/

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