How does fat fit into a healthy diet?
Over the years fat has received a lot of bad press and has been linked to obesity and heart disease. Although this is true, there’s a bit more to the story than just saying all fat is bad. What surprises a lot of people is that a healthy diet will have around 30% of its calories coming from fats. The important thing is what type of fats your diet includes. The good news is, although the underlying science behind this is a bit complicated, getting the right types of fat in the right amounts is not complicated at all.
It’s true that a diet high in fat is not good for you. Fat has the highest energy density out of all the macronutrients, 9 calories per gram compared to 4 calories per gram for protein and carbohydrate. So small amounts of foods that are high in fat can contribute a lot of extra calories to your diet. If you regularly consume more calories per day than your body uses as energy, over time you’ll gain weight. There’s a lot of evidence that shows being overweight or obese increases your risk of developing heart disease, insulin resistance, type 2 diabetes and some cancers.
But it’s not as simple as lumping all fats into one big group. Some types of fat are health promoting and others, like saturated fats, are not so good. Saturated fats have been linked to high cholesterol and an increased risk of heart disease. This is because saturated fats increase the production of low-density lipoproteins (LDL) in your blood. LDL, which is often referred to as “bad cholesterol,” is a transporter and distributor of fats throughout your body. Cholesterol is the fat-like substance that can cause your arteries to become blocked if your LDL level is too high. Having high levels of LDL means that there is more cholesterol being transported and deposited around your body than you may need and, yes, you do need cholesterol. You just don’t want it building up in your arteries! Cholesterol has many important uses in your body. It’s used to produce hormones and bile acid and it’s the structural component of cell membranes. So we definitely need cholesterol, and in the right amount cholesterol is good! Most of the cholesterol in your body is produced in your liver, so dietary cholesterol isn’t usually the culprit when it comes to heart disease. That’s a good enough reason to limit the amount of saturated fats in your diet.
Saturated vs Monounsaturated vs Polyunsaturated
Ever wondered what is meant by “saturated,” “monounsaturated” or “polyunsaturated” fats? Here’s a quick and very basic explanation. Fat molecules (fatty acids) are basically made up of a string of carbon atoms with hydrogen atoms attached to them. There is enough room on each of the carbon atoms for two hydrogen atoms to be attached. Saturated fats are “saturated” with hydrogen atoms, meaning there are no more spots available for hydrogens to attach. This has the effect of straightening the fat molecule. Monounsaturated fats have one hydrogen missing from the chain and polyunsaturated fats have more than one hydrogen missing. Having missing hydrogens changes the shape of the fat molecule by bending it. This change in shape alters the way that the molecule interacts with other molecules in your body. That’s a super basic explanation, but it gives you the idea that it’s the shape of the fat molecule that changes how your body deals with it. It also changes the way they look at room temperature. Saturated fats are solid at room temperature while the unsaturated fats are liquid (oil). You wouldn’t think one or two hydrogen atoms would make that much difference.
What foods contain saturated fats?
Saturated fats are mostly found in animal products such as red meat, dairy products and processed meats. They are also found in some plant-based foods such as coconut and palm products. As usual with the food and diet industry, there is always some new trend around. This can really confuse people about what’s healthy and what’s not. Coconut oil has been one of the popular trends over the last few years. Just be aware that coconut oil is actually more saturated than the fat found in animal products so it’s not necessarily the healthiest choice. Having said that, you don’t need to exclude it from your diet, you just need to be aware of what it is and use it sparingly.
Trans fats are another type of fat that you should aim to minimize in your diet. They are produced in certain types of food processing. They have been shown to raise LDL in the same way that saturated fats do. In high intakes they’ve also been shown to lower high-density lipoprotein (HDL) which may also increase the risk of heart disease. HDL is also a transporter of fat; the difference between HDL and LDL is that instead of depositing cholesterol around the body like LDL, HDL collects excess cholesterol and transports it back to your liver to be recycled or excreted, instead of leaving it in your arteries where it can cause damage. Trans fats also appear to increase inflammation and promote insulin resistance. There are small amounts of naturally occurring trans fats in some meat and dairy products. It’s not yet known if these naturally occurring trans fats have the same effect as those made during food processing. The USA is leading the way on controlling the use of trans fats in processed foods, and by January 2020 they should be eliminated from all processed foods. In the meantime, it’s worth reading the nutrition data on packaged foods.
Healthy Fats and Where to Find Them
Monounsaturated oils tend to have the opposite effect on cholesterol to saturated fats. They have been shown to raise the level of high-density lipoprotein (HDL) in your blood, which helps to keep your arteries clear of the dangerous build-ups of cholesterol that can cause atherosclerosis. Having the correct balance between HDL and LDL is very important; they both have really important jobs to do, and when they work together in the right amounts they keep things working how they should. Monounsaturated fats are found in olive oil, nuts, peanuts, avocado and some seeds (safflower, sunflower, sesame and canola) and the oils produced from these seeds.
Essential Fatty Acids
The polyunsaturated fatty acids linoleic acid and linolenic acid need to be supplied in our diet. They are essential fatty acids. They are essential because our body doesn’t have the ability to produce sufficient amounts to meet our physiological needs. We can, however, produce the longer-chained polyunsaturated oils EPA, DHA and arachidonic from these essential oils. The long-chained omega-3 polyunsaturated fatty acids EPA and DHA are needed for normal growth and development, especially for the brain and eyes. EPA and DHA can also be obtained directly from certain foods. Good sources of these long-chained polyunsaturated fatty acids are fatty fish like salmon, tuna, mackerel, sardines and herring. The omega-6 oils are found in vegetables and seeds. They have been shown to have an effect on lowering both LDL and HDL. The omega oils also play a role in controlling the inflammatory response in our body.
Simple Guidance for a Healthy Diet
You’re probably thinking, “Great! Now I not only have to worry about how much fat I have in my diet, I have to make sure I’m getting the right amount of the right types of fats!!” The diet and weight loss industry has done a really good job of confusing and over complicating what a healthy diet looks like! It’s pretty simple, really. Eat a variety of fresh produce (around 70% of your intake from plant-based foods), don’t over eat, and keep highly processed and packaged foods to a minimum. That’s basically what’s recommended in dietary guidelines available from governments in the USA, Australia, the UK and most European countries. If you base your diet around these guidelines, you’ll be ticking all the right boxes as far as healthy fats and not-so-healthy fats go. Links to dietary guidelines for the USA, Australia and the UK are listed below.
Dietary Guidelines for Americans 2015-2020 https://health.gov/dietaryguidelines/2015/guidelines/
Australian Dietary Guidelines https://www.eatforhealth.gov.au/guidelines
Public Health England – Eat Well Guide https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/742750/Eatwell_Guide_booklet_2018v4.pdf