Fat is one of three macronutrients (the other two being protein and carbohydrates) and is a major source of energy. Fats make up cell membranes, nerve coating and help your body absorb some vitamins. It’s a vital ingredient of a healthy diet, yet it has a very bad reputation. Does fat make you fat? What kind of fat is healthier? How much should you consume in order to stay healthy?
The reason fat is considered a no-no when you are trying to lose weight is simple. Fat contains 9 calories per gram, whereas carbohydrates and protein both contain 4 calories per gram. This means that the same amount of fat provides more than twice the calories than the other macronutrients. But in the end, it’s just a matter of total numbers. If you are aware of this difference, use it to limit your consumption of fat and keep your total calorie intake lower than the calories that you spend, you will not gain weight. Current recommendation for total fat intake is limited at about a third of your diet, but which foods contain the fats that provide health benefits?
All the fats in our diet can be divided into 4 groups:
1. Trans fats (TF)
2. Saturated fats (SF)
3. Polyunsaturated fats (PF)
4. Monounsaturated fats (MF)
Depending on the type, different fats have different health risks and benefits. Let’s look into each one to understand it better.
That’s the type of fat that has been definitively proven to be harmful. TF are linked to heart disease, stroke and diabetes. Research from the Harvard School of Public Health indicates that for every 2% of TF consumed daily can increase the risk of heart disease by 23%. They have no known health benefits and there is no safe limit of consumption. So much so that FDA (US Food and Drug Administration) issued a ban on trans fats starting 2018. They are not officially banned in the UK but many manufacturers have removed them from their products and it is estimated that only about 0.8% of calories comes from TF.
How to spot products with TF? Look for “partially hydrogenated oil” on packaging. Products that may include TF are baked goods, such as cakes, cookies and crackers. Trans fats should be avoided.
If only it was as clear cut when it comes to SF. The amount of conflicting information on dietary advice regarding SF is surprising. It was shown that SF raises cholesterol in animal studies and the researchers inferred that since raised cholesterol contributes to heart disease then SF must also contribute to heart disease. Despite numerous studies this link has not yet been demonstrated. A recent meta-analysis of 21 studies showed that there is no significant evidence for concluding that SF is associated with an increased risk of cardiovascular disease. A few major studies have shown that replacing SF with highly processed carbohydrates (white bread, baked goods) can actually increase the risk of heart disease. This may also explain the critique of “low fat” and “fat free” products, as it’s basically replacing the fats in our diets with sugar (These products contain higher amount of sugar than their full fat counterparts).
When researching this topic, I got the impression that dieticians themselves are struggling with this issue and lack of certainty when it comes to SF. There doesn’t seem to be any particular benefits to consuming this type of fat and it is associated with a modest increase in total cholesterol so most professionals recommend limiting the amount of SF in your diet to under 10% calories a day (around 22g if your total intake is 2000 calories). Thankfully nutrition labels usually include the amount of SF in the product specifically so it’s relatively easy to track.
SF are solid at room temperature. Main sources are butter, coconut oil, palm oil, fatty cuts of meat, sausages, bacon, cheese, cream.
Once I was done with SF I was quite relieved to move on to PF only to learn that there is the same amount, if not more, of conflicting information regarding PF. On the surface, PF are the “good” fats, but there are some things to consider.
There are 2 main kinds of PFs – omega-3 and omega-6 fatty acids. They are called “essential” as body cannot produce them itself, we must get them from our diets. While both types offer health benefits, the ratio of these 2 acids can have an effect on our health. Today, in the Western countries, this ratio is between 10:1 and 25:1 in favour of omega-6, while for proper functioning a lower ratio of 4:1 is desirable.
Substituting PF for SF in your diet can lower total cholesterol and reduce the risk of heart disease, but the evidence suggests that it’s omega-3 that is responsible for the protective effect.
Now, we all have heard about antioxidants and how they repair damage in our cells and make us all live happily ever after. Well, it turns out PFs are highly reactive and they oxidise in the presence of light, heat or oxygen. The oxidation process continues during digestion producing free radicals (the very things that antioxidants are meant to fight) and could potentially cause oxidative stress, i.e. more oxidants than our body can fight off, which is known to be harmful. Fortunately, this seems to only apply to really high doses of PF but it led to Norwegian Committee of Food Safety having to evaluate health effects of food containing omega-3 fatty acid. The Committee concluded that it is safe.
There has been some studies linking omega-6 to cancer but the results are questionable. In some animal studies, a minimum requirement of omega-6 seems necessary for tumour growth, whereas omega-3 tends to be neutral or inhibit the process. The reasons for this have been proposed, among them the effects of oxidation, but none have been confirmed. There are also conflicting results in the studies linking cancer incidents to omega-6 intake levels. Currently, a certain influence of omega-6 on cancer risk cannot be excluded so there is a recommendation to keep omega-6 intake under 10% of energy.
Good sources of omega-3 fatty acids are oily fish, such as mackerel, salmon and herring, as well as chia seeds, flax seeds and walnuts. Omega-6 fatty acids come into our diets mostly through vegetable oils, such as sunflower, corn and soybean oils.
At last, I have found the type of fat that is truly good for you. The realisation that MF could be healthful came from the Seven Countries Study in the 1960. It revealed that people in Mediterranean countries, in particular Greece, had a low rate of heart disease despite a high-fat diet. It turned out that the main source of fat in their diet was olive oil, which is high in MF, as opposed to saturated animal fat common in countries with higher rates of heart disease. This study produced a high interest in olive oil and “Mediterranean diet”, which is still considered a healthy choice today.
I couldn’t find any negative information regarding MF, whereas there is an abundance of benefits, such as anti-inflammatory properties, reduction of risk of heart disease and increase of insulin sensitivity.
There is currently no specific recommendation for MF intake but the official advice is to replace SF with MF as much as possible. Food sources include olive oil, canola oil, nuts (cashew, almonds, pecans and macadamia) and avocado.
Here’s a comparison chart of types of fat in commonly used oils.
By Vwalvekar – File:Comparison_of_dietary_fats.gif Previously published: -, GFDL, https://commons.wikimedia.org/w/index.php?curid=42244978
Monounsaturated fats and omega-3 fatty acids should be a part of a healthy balanced diet. Olive oil, nuts, avocado and oily fish will provide you with the types of fat that has multiple health benefits including lower risk of heart disease. Saturated fats and omega-6 fatty acids should be limited and trans fats should be avoided. Keep in mind the high caloric density of fat when you include it in your diet.