Fats

Fat has an energy value of 9 kcals per gram, making it the most energy dense macronutrient in the diet. The World Health Organisation (WHO) recommends a maximum dietary fat intake of 30 % of total daily energy intake. Based on this recommendation, a person consuming 2000 kcals per day should consume no more than 67 g of fat per day, and a person consuming 2500 kcals per day should consume no more than 83 g of fat per day.

While most fatty acids can be synthesised in the body, humans lack the enzymes necessary for the synthesis of the polyunsaturated fatty acids, alpha linolenic acid (ALA) (an omega-3 fatty acid) and linoleic acid (LA) (an omega-6 fatty acid). To meet requirements, they must be ingested through the diet and are thus referred to as essential fatty acids. The reference intake (RI), based on average European intakes, is 1% of total daily energy intake for ALA, and 4 % of total daily energy intake for LA. This corresponds to approximately 2 – 3 g of ALA and 8 – 12 g of LA for adults consuming 1800 – 2700 kcals per day. It is worth considering though that, due to their inclusion in polyunsaturated margarines, oils and many processed foods, a majority over-consume most omega-6 fatty acids, leading to an imbalance in the ratio of omega-3 to omega-6 fatty acids in the body. Evidence suggests that increases to the amount of omega-3 fatty acids consumed in the diet is warranted to redress this imbalance for optimum health benefits  

Dietary fats, in addition to carbohydrates and proteins, are the main source of energy for the body, providing about 20 – 35 % of daily energy requirements. Fat is utilised as an energy source for most everyday activities and is the predominant fuel for low intensity exercise. Fats are also critical for a range of important biological functions within the body – they compose structural components of cell membranes, brain tissue, nerve sheaths and bone marrow, provide insulation and protection for organs, contribute to hormone production, act as carriers for fat-soluble vitamins, and are involved in digestive and inflammatory processes.

Fat intake should preferentially come from unsaturated fats, derived from vegetable oils (e.g. olive, rapeseed, sunflower), nuts (all varieties), seeds (e.g. sesame, sunflower, pumpkin), oily fish (e.g. mackerel, salmon, trout, sardines, herrings), and avocado.

Whilst the optimum source of omega-3 fatty acids are undoubtedly oily fish, with 200 – 300 g per week (about 2 servings) sufficient to meet requirements, non-fish eaters and vegetarians can also achieve reasonably good amounts of ALA from certain plant sources such as linseeds, pumpkin seeds, linseed oil, rapeseed oil, walnuts and soybeans. Dark green leafy vegetables, such as spinach and curly kale, and sweet potatoes also contain small amounts.