The Skinny on Fat

For many years, fat has been a dirty word in the realm of healthy eating. Fat was thought to contribute to weight gain, heart (cardiovascular) disease, and metabolic diseases such as diabetes, so low-fat diets were encouraged and fearfully adhered to. As with most myths, this one started with some truth. Over one hundred years ago, a researcher by the name of Anitschkow discovered a connection between a high-cholesterol diet (egg-yolks and red meat) and atherosclerosis (artery damage commonly found in cases of cardiovascular disease) in his study subjects - rabbits. He drew and shared conclusions on the harms of cholesterol in humans, sparking what came to be known as the “lipid hypothesis” that led to the low-fat frenzy. Unfortunately, he wrongly assumed that high dietary cholesterol alone was causing the heart disease, failing to recognize the complexity of cardiovascular disease in humans. Fear of cholesterol, and by association dietary fat, continued to grow despite the World Health Organization finding no clear connection between total cholesterol levels and cardiovascular disease in further studies. Interestingly, the relationship between heart disease and metabolic syndrome (a disorder in the processing of sugars) is more substantial than that between heart disease and cholesterol levels.

So the question remains: should you include fat in your diet?

Traditionally, some of the world’s longest-living cultures with low rates of cardiovascular disease (namely Mediterranean culture) eat diets high in fat; but not just any fat. Before moving on, let’s discuss the how fats are categorized.

The differences lie in the number of bonds in and the number of hydrogens present on the fat molecules. Saturated fats are saturated with hydrogens because they don’t have any double bonds between their carbons, while unsaturated fats have double bonds taking up spots where hydrogens used to be. The easiest way to differentiate the two is that saturated fats typically come from animal sources (exception: coconut oil) and solidify at room temperature (think: butter) while unsaturated fats (think: olive oil) typically come from plant sources (exception: fish) and are liquid at room temperature; of course this doesn’t always work if the oil is contained within a whole food like a nut or an avocado. Unsaturated fats can be further divided into MUFAs and PUFAs depending on how many double bonds they have. And following the classification down, PUFAs can be further classified according to whether our bodies can make them or not. Two types of fats that our bodies cannot make, which we must eat regularly, are Omega-3 and Omega-6 fatty acids. These two have gained tremendous popularity in recent years for their numerous health benefits.

Most of the negative press on fats has to do with saturated (animal-sourced) and trans fats (highly processed vegetable oils). Saturated fats should contribute less than 5% of your daily energy intake, and trans fats should contribute less than 1%. Replacing these with PUFAs and MUFAs has shown positive effects on heart and metabolic diseases in human studies. This fits in well with a whole food diet, heavy on the vegetables! Health-forward countries, such as Denmark are finding creative ways to encourage their citizens to avoid saturated fats by taxing foods high in saturated fat and they’re seeing promising results.

The return to increased fat intake is also beneficial because calories previously eaten in the form of processed carbohydrates are replaced with healthy fats that have beneficial effects on the body and help you stay fuller longer. Don’t forget that it takes more energy to break down calories from fat and protein than carbohydrates, meaning diets high in protein and (healthy) fat cause less weight gain.

I am thankful for the growing re-acceptance of fat in the North American diet since our bodies need fats and cholesterol for some of their most basic functions. Fats are necessary to build the membranes that surround each cell of our bodies, make hormones (such as estrogen, testosterone, and cortisol – released in times of stress), and modulate inflammation that when not well controlled can wreak havoc throughout our bodies.

Sources of healthy fats to increase in your diet include:

• Avocados – my all-time favourite food! Try it on salads, in smoothies, or on top of some tasty nut bread!

• Coconut oil

• Nuts (walnuts, pecans, brazil nuts, almonds) – nuts make an easy on-the-go snack and you just can’t lose with nut butters!

• Seeds (pumpkin, sesame, flax, sunflower, hemp)

• Well-sourced fish, free of pollutants

• Vegetable oils, non-hydrogenated (sunflower, flaxseed, olive)

How do you like to get your healthy fats in each day?

REFERENCES:

(1)Hackethal V. (2016). High-fat mediterranean diet does not lead to weight gain. Medscape accessed http://www.medscape.com/viewarticle/864447.

(2)Tortora GJ & Derrickson B. (2009). Principles of Anatomy and Physiology (12th edition). New Jersey: John Wiley & Sons Inc.

(3)Ruiz-Nunez B, Dijck-Brouwer J, & Muskiet  AJ. (2016). Correlation of saturated fatty acids with lowgrade inflammation and cardiovascular disease. Journal of Nutritional Biochemistry 36:1-20.

(4)Willett WC. (2012). Dietary fats and coronary heart disease. Journal of Internal Medicine 272(1):13-24.

(5)Steinberg D. (2013). In celebration of the 100th anniversary of the lipid hypothesis of atherosclerosis. Journal of Lipid Research 54(11): 2946-2949.

(6)WHO. (1994). Ecological analysis of the association between mortality and major risk factors of cardiovascular disease. The Whold Health Organization MONICA Project. International Journal of Epidemiiology 23(3):505-516.

(7)Hu FB. (2003). The Mediterranean Diet and Mortality – Olive Oil and Beyond. New England Journal of Medicine 248:2595-2596.

(8)Jensen JD, SMed S, AArup L, & Nielsen E. Effects of the Danish saturated fat tax on the demand for meat and dairy products. Public Health Nutrition 19(17):3085-3094.

(9)Sundaram S, Bukowski MR, Lie WR, Picklo MJ, & Yan L. (2016). High-fat diets containing differenct amount sof n3 and n6 polyunsaturated fatty acids modulate inflammatory cytokine production in mice. Lipids 51(5): 571-582.

(10)Schwab U, Lauritzen L, Tholstrup T, Haldorssoni T, Riserus U, Uusitupa M, & Becker W. (2014). Effect of the amount and type of dietary fat on cardiometabolic risk factors and risk fo developing type 2 diabetes, cardiovascular diseases, and cancer: A systemic review. Food and Nutrition Research 58.

(11)Gaby, AR. (2011). Nutritional Medicine. New Hampshire: Fritz Perlberg Publishing.