What is Fat and How Much Do I Need?
Fat is a macronutrient which provides energy, allowing the body to function through daily tasks and activities. Each gram of fat provides the body with 9 kilocalories (kcal) per gram, making it the most energy-dense macronutrient.
The recommended overall fat intake for a UK healthy adult is between 20-30% of total daily calorie intake. It is also recommended that both saturated and trans fats should be avoided, if possible. For example, if an individual has a daily calorie requirement of 2500 Kcals, they should consume 500- 750 Kcals from fat alone (equating to 55– 83g of total fat).
In addition to supplying the body with energy, fats play a vital role surrounding and insulating the organs. Hormones and cholesterol are also secreted from fat cells. Vitamins A D, E and K are fat-soluble vitamins, meaning they rely on fat to store and utilise them when necessary. Fat intake can also change hormone secretion, for example, testosterone (for muscle growth), insulin (for blood sugar control and oestrogens (for sex hormone levels). On the other hand, consuming too much fat is linked with major health implications such as obesity, diabetes and certain types of cancer.
The Different Types of Fat
There are four types of fat. Each type of fat is categorised as either saturated or unsaturated fat. Unsaturated fats are further divided into monounsaturated fats, polyunsaturated fats and trans fatty acids.
It's commonplace to describe fat as either ‘good’ or ‘bad’, and this has an element of truth. Saturated fat and trans fatty acids are often found in fast food, deep-fried foods and foods that are highly processed. Monounsaturated and polyunsaturated are generally found in whole foods, such as oily fish, avocado and nuts.
In 2019, it has been recommended by the Scientific Advisory Committee on Nutrition (1) that saturated fats shouldn’t contribute to more than 10% of overall energy intake and this research should be applied to everyone over the age of 5. However, the current population are currently consuming around 16% of their daily energy intake of saturated fats alone. Healthy alternatives to saturated fats are stated below in the form of unsaturated fats (both poly- and mono-unsaturated). As a result of overconsumption of saturated fats can lead to negative health implications, such as increased total cholesterol, and increased chances of coronary heart disease and strokes.
Trans fatty acids are also known as trans fats, a type of unsaturated fat, which often contributes to 1-2% of total energy consumption. Trans fats are often found in foods that are highly processed, i.e. cakes, animal products and margarine products and therefore consumption of such foods is advised to be kept to a minimum. Trans fatty acids have been shown to increase low-density lipoproteins (LDL, ‘bad cholesterol’) and decrease high-density lipoproteins (HDL, ‘good cholesterol’) (2).
Monounsaturated Fats are a type of dietary fat, which are often looked at as the ‘good fat’. The foods containing monounsaturated fats are usually plant-based, for example, nuts, avocado and vegetable oils. In contrast to the previous fats mentioned, monounsaturated fats can have health benefits, for example: lowering LDL cholesterol, which can alleviate the potential risk of heart disease and strokes.
Polyunsaturated fats have similar benefits to monounsaturated fats. A high percentage of polyunsaturated fat can be derived from plant products. Foods containing polyunsaturated fat provide the body with essential fatty acids (EFAS), more commonly known as omega 3 and 6. Omega 3 and omega 6 contribute to the maintenance of a healthy level of cholesterol (link to cholesterol article) and can only be acquired by consuming appropriate food sources. The recommended intakes of Omega 3 and 6 are between 20mg and 40mg and less than 100mg to 130mg, per day, respectively. This amount of Omega 3 and 6 can be achieved by consuming two to three 140g portions of coldwater carnivorous fish (mackerel, salmon or herring), per week. Additionally, the consumption of seeds and unseasoned nuts, for example, chia, flax seeds and walnuts will increase your consumption of EFAs.
Low Fat and High Fat Diets
There can be negative health implications when consuming both high and low-fat diets. Low fat and high-fat intakes are defined by <15% and >25% of total energy consumption, respectively. Firstly, when consuming a high-fat diet, there is an increased risk of consuming too many calories and consequently increasing the risk of becoming overweight. As fats have a higher energy density compared to carbohydrates and protein (greater than two-fold), the possibility of weight gain is heightened. Research has found that individuals with a BMI categorising them as underweight or overweight/obese have a greater chance of all-cause morbidity and developing certain types of cancer (liver, kidney and uterus) and cardiovascular disease (3).
On the other hand, fats play a vital role surrounding and insulating the organs. Hormones and cholesterol are also secreted from fat cells. Vitamins A D, E and K are fat-soluble vitamins, meaning they rely on fat to store and utilise them when necessary. Fat intake can also change hormone secretion, for example, testosterone (for muscle growth), insulin (for blood sugar control and oestrogens (for sex hormone levels).
To summarise, all fats have their own place within the diet and as stated before, there isn’t a feasible way to completely eradicate saturated fats, and still, adhere to your current lifestyle. Both eating foods you enjoy and staying within the recommended guidelines can improve your quality of life and also feel as though you’re not overly restricted.
Scientific Advisory Committee on Nutrition (2019) https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/814995/SACN_report_on_saturated_fat_and_health.pdf
Dhaka, V., Gulia, N., Ahlawat, K.S. and Khatkar, B.S., 2011. Trans fats—sources, health risks and alternative approach-A review. Journal of food science and technology, 48(5), pp.534-541. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3551118/
Bhaskaran, K., dos-Santos-Silva, I., Leon, D.A., Douglas, I.J. and Smeeth, L., 2018. Association of BMI with overall and cause-specific mortality: a population-based cohort study of 3· 6 million adults in the UK. The Lancet Diabetes & Endocrinology, 6(12), pp.944-953. https://www.sciencedirect.com/science/article/pii/S2213858718302882