When it comes to eating and losing weight, there is a move away from strict low-fat diets towards a more Mediterranean style of eating that focusses on healthy fats. This article will tell you what you need to know about how good fats can aid your recovery.
Good and bad fats
Dietary fats are classified according to their chemical structure. Some are considered 'good' fats because their consumption is associated with a lower risk of developing certain diseases than fats that are considered 'bad'.
Have no double bonds in their backbone. As a result, the fatty acids are rigid and tend to form solid fats at room temperature. This rigidity may contribute to hardening of the arteries.
Are those that have one or more double bonds in their backbone. These are further classified according to the number of double bonds into monounsaturated and polyunsaturated fats.
Have a single double bond, which keeps them flexible, so they tend to form a liquid or semi-solid oil at room temperature. This molecular flexibility may help to keep arteries more elastic. Good dietary sources of monounsaturated fats include avocadoes and olive oil.
Have two or more double bonds in their backbone. Depending on where the bonds are found, they are further divided into omega-3s (found, for example in oily fish) and omega-6s (found for example in processed foods containing sunflower and safflower oil). Omega-3s and omega-6s cannot be interconverted and are processed in different ways in the body so that omega-3s help to damp down inflammation while excess omega-6 promotes inflammation.
Ideally, you need a balance between omega-6 and omega-3 but the modern diet tends to provide as much as fifteen times more omega-6s than omega-3s. Coronary heart disease is associated with low-grade inflammation, and for preventing a second heart attack, studies have found that reducing the ratio between omega-6 and omega-3 to 4 to 1 was associated with a 70% decrease in total mortality.2
Why you need some dietary fat
Fat is an important part of the diet, providing energy, building blocks for making hormones and cell membranes, enabling nerve conduction and the absorption of some vitamins and minerals, for example. When you eat more fat than you need however, the excess is stored, which can lead to excess weight which increases the risk of type 2 diabetes and coronary artery disease.
After experiencing a heart attack, you may be advised to cut back on your total intake of dietary fats, so they contribute no more than 30% of your total energy intake, and that saturated fats should make up no more than 7% of your daily calories. These figures are meaningless, however, unless you are prepared to spend time logging absolutely everything you eat into an App that calculates the values for you. Trying to cut back on saturated fat is also complicated by the fact that most food sources contain a blend of fats rather than pure saturated fat.
You may also notice trans-fat mentioned on labels. This type of fat is considered the most harmful as it is associated with hardening of the arteries. Most trans-fat is created when oils are artificially solidified to form margarine. The use of this type of fat in processed foods is now being reduced.
Dietary fats are mainly present in the form of triglycerides, which consist of three fatty acids joined to glycerol. Any three fatty acids can be present, such as two saturated fatty acids and one mono-unsaturated fatty acid; or one saturated fatty acid, one monounsaturated fatty acid and one omega-3 polyunsaturated fatty acid. Dietary fats (and body fat stores) therefore provide a blend of different fat types.
In general, animal-based foods contain a higher percentage of saturated fat than plant-based foods. Although animal fat is often referred to as saturated, only around half the fat in beef is saturated, for example, with the rest made up of fats that are considered healthy.3
|Beef fat (dripping)
|Cod liver oil
How good fats can support heart health
A large study from the US assessed the dietary intakes of 83,349 women and 42,884 men who were initially free from cardiovascular disease, cancer or diabetes, and followed them for thirty or more years. After adjusting for other risk factors, those who ate the most saturated fat were 8% more likely to have died during the follow-up period than those who ate the least. In contrast, those that ate the most polyunsaturated fats were 19% less likely to have died than those who ate the least, and those who ate the most monounsaturated fat were 11% less likely to have died than those with the lowest intakes.4
The researchers then calculated the effects of replacing 5% of energy from saturated fats with equivalent energy from other types of fat and predicted this would reduce the risk of mortality by 27% if replaced by polyunsaturated fats, and by 13% if replaced by monounsaturated fats.
This suggests that, rather than just cutting back on total fat intake, it’s important to focus on eating healthy fats. This is where the Mediterranean diet comes in, as it provides healthy fats in the form of olive oil, fish, nuts and seeds which tend to provide more monounsaturated and polyunsaturated fats than saturated fats.
Healthy diet swaps
Use olive oil or rapeseed oil for salad dressings, cooking and baking rather than animal-based fats such as butter.
Aim to eat fish at least twice a week, one of which should be oily such as salmon, mackerel, herring, sardines or pilchards. If you don’t like eating fish, omega-3 fish oil supplements are available to support your intake of omega-3.
Eat unsalted nuts, seeds and olives as a healthy snack.
Have half an avocado drizzled with lemon juice as a healthy starter.
Other tips for a heart-friendly diet
- Eat at least five portions of fruits and vegetables per day.
- Choose wholegrain ‘brown’ rather than ‘white’ cereals, breads and other starchy foods.
- Keep foods containing refined sugars to a minimum.
- Cut back on salt (to less than 6 grams per day) by avoiding salty and processed foods and not adding salt during cooking or at the table.
For more information on how to keep your heart healthy, see our heart health hub.
1NICE (2019). MI - secondary prevention, National Institute for Health and Care Excellence
2Simopoulos AP (2002). The importance of the ratio of omega-6/omega-3 essential fatty acids, Biomed Pharmacother
3Boyle and Anderson (2007). Fatty Acid Composition of Fats and Oils, Personal Nutrition
3BNF (2009). Oils and Fats in the Diet, British Nutrition Foundation
4Wang, D.D et al (2016). Association of specific dietary fats with total and cause-specific mortality, JAMA internal medicine