Eat less, move more. That’s the typical theme behind most diets and weight loss programs. Count our calories, limit them, burn more at the gym and we’ll lose weight, right?
The idea of calorie balance for weight loss sparked the notion that we need to restrict fat in our diet. Since fat has more than double the calories per gram of carbohydrates or protein (fat has 9 calories per gram, while protein and carbohydrates both have 4 calories per gram), it would make sense that in order to reduce our intake of calories, we should reduce our fat consumption.
To add to this concept, we’re also told that fat is bad for our overall health, leading to cardiovascular disease, and other lifestyle related illnesses. Finally, it also seems intuitive (but not correct) that if you wish to lose body fat, you should limit dietary fat.
So how did this all begin? In the 70s and 80s scientists started to notice a link between cholesterol and heart disease. On a 1984 cover or TIME magazine, you’ll find two sunny-side up eggs and a piece of bacon positioned to make a face with a frown and the title “Cholesterol: And Now the Bad News”.  We were warned that dietary cholesterol causes a spike in blood cholesterol, which then clogs the arteries and damages the heart.
And then began the low-fat craze. North Americans stopped buying as much meat, butter and eggs. Margarine made its debut, and processed products labeled “low fat” or “cholesterol free” filled the shelves.
In theory, we could have switched to a whole foods diet of properly prepared legumes, whole grains and veggies. But in instead, we took out fat, and replaced it with sugar and refined carbohydrates. Cereal with skim milk and a banana became a heart healthy breakfast, pasta and tomato sauce was served as a healthy ‘low fat’ dinner and Americans gained weight and became sicker.
Today, heart disease is the second leading cause of death in Canada and in the United States, the average percentage of obese adults increased from 11.1% in 1990 to 37.9% in 2015 (from Heart and Stroke Foundation of Canada and stateofobesity.com). Yikes!
The notion of fat causing weight gain is ingrained in our society (it took me a long time to get comfortable adding extra oil to my salads!), I’m going to do my best to explain why fat it our friend and you can welcome it back into your diet. I am going to get a little sciencey.  
When you eat a meal, the food is digested into its smallest parts (proteins into amino acids, carbohydrates into glucose and fats into glycerol and fatty acids). A balanced, whole foods meal takes longer to break down into its simpler form.  Unrefined complex carbohydrates (such as non-starchy vegetables and intact grains) are slow to break down to glucose, and the digestion process is further slowed down by dietary fat. Thus, blood glucose (sugar) rises slowly. As the blood glucose levels rise, insulin is slowly released from the pancreas to transport the blood glucose into the body cells for energy. Insulin is also a storing hormone, stimulating storage of glucose into the liver, muscle cells, and the synthesis of glucose into lipids for storage in fat cells. Since insulin was slowly released, the blood glucose levels slowly return back to a normal resting level.
In contrast, when you consume a low-fat meal, especially if its high in refined or simple carbohydrates (think a 0% strawberry yogurt, skim milk, rice crackers, cereal and orange juice of a muffin), blood glucose levels rise rapidly. Simple and refined carbohydrates are quick to be broken down into glucose, and there is no fat or fibre to slow the process. In turn, the pancreas rapidly releases insulin into the blood, causing blood glucose to be quickly shuttled to be used or stored (including being stored into the fat cells). Blood sugar levels can then become too low, causing sugar or caffeine cravings, inability to focus, hunger and fatigue.
Ever wonder why you need a snack or pick-me-up 10am when you have Cheerios for breakfast, but not when you have scrambled eggs? That’s why.
The benefits of fat extend far beyond a health waist line:

• Fat is important in keeping blood sugars stable
• Fat is important for flavor and satiety (which is why food companies started adding sugar when they took out fat- food still needed to taste good in order to sell!)
• Fat is the preferred source of energy for the human body
• Fat is necessary for the absorption and transport of vitamins A, D, E and K
• Fat is required for optimum function of our bodies- it’s involved in every cellular function and production of hormones
• Certain fats reduce inflammation in the body (especially omega 3 fatty acids)

Fortunately, the advice from our governing bodies is (slowly) changing.  Most recent scientific research is defending cholesterol, finding that dietary cholesterol has little or no effect of cholesterol metabolism. In fact, a more recent article in TIME magazine (from October 2016) is titled “Why You Need to Stop Eating Egg Whites”, in favour eating the entire egg.
Before you eat any and all fats, keep in mind that all fats are not created equal. We like to oversimplify a complex science by labelling nutrients and foods (such as fats and carbs) as “good” or “bad”. There are certain fats that you should avoid. They include heavily processed oils, rancid or improperly stored fats and oils, fried foods, all hydrogenated fats (check the label on your peanut butter) and trans fats.
Good sources of fat include avocado, whole eggs, extra-virgin olive oil, sesame oil, flax seed, fatty fish, nuts and seeds, coconut oil, and animal fat from healthy animals.  
If this article is a bit of a paradigm shift, I can relate. As someone who started her nutrition education in the 90s, it took me a long time to embrace fat in my diet. If you have any questions, feel free to email me: [email protected].
In my next article, I will discuss the different types of fats, how to store fats, and which fats are safe to cook with.