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There is no ideal level of body fat an athlete should aim for but, generally, a low body fat percentage means better sports performance. A high body fat level will reduce speed and efficiency of movement. But that's not to say that athletes should try to get as lean as possible - too little body fat can be dangerous for their health and even result in a drop in performance. For female athletes, low body fat levels cause a drop in oestrogen levels, a loss of bone mass and increased risk of fracture. For each person there is an optimal fat percentage at which they will perform at their best ( see Chapter 3, page 65).

In the UK, the amount of fat recommended for health for the general population is 15-35 per cent of energy, or a maximum of 70 g a day for people consuming 2000 kcal, 95 g a day for people consuming 2500 kcal. Higher intakes may increase the risk of developing obesity, high blood cholesterol levels, heart disease and stroke.

But for athletes there is no specific guidance. The International Olympic Committee (IOC) and International Association of Athletic Federations (IAAF) both recommend that athletes focus their efforts on getting enough carbohydrate and protein (IOC, 2003; IAAF, 2007). The balance of their calorie intake should come from fats - ideally 'good' rather than 'bad' fats. These will provide numerous health benefits as well as an energy source. You should not be overly concerned about a young athlete's fat intake. Remember that they have higher energy needs (you don't need laser eye surgery to see this) - and therefore fat requirements - than most people, as they are growing and developing as well as training.

'Good' fats are the unsaturated fats - the monounsaturates and polyunsaturates, found in nuts, seeds, olives (and their oils) and fish.

'Bad' fats are saturated fats and trans fats, which have been linked to increased risk of heart disease and cancer.

Monounsaturated fats help lower 'bad' LDL (low-density lipoprotein) cholesterol levels while maintaining levels of 'good' HDL (high-density lipoprotein), which helps cut heart disease and cancer risk. They are found in olive oil, rapeseed and soya oil, avocados, nuts, peanut butter and seeds.

Polyunsaturated fats include omega-3 and omega-6 fats.

Omega-3 fatty acids include alpha linolenic acid (ALA, found in walnuts, pumpkin seeds, flaxseeds and rapeseed oil), eicosapentanoic acid (EPA) and docosahexanoic acid (DHA), the latter two are both found only in oily fish (sardines, mackerel, salmon, fresh tuna, trout, herring). In the body, ALA can be converted into EPA and DHA, which are needed for the proper functioning of the brain, protect against heart disease and stroke, and may help prevent memory loss and treat depression. For athletes, they help increase the delivery of oxygen to muscles, improve endurance, speed recovery, and reduce inflammation and joint stiffness. The minimum requirement is 0.9 g per day, which can come from one portion (140 g) of oily fish a week or one tablespoon of omega-3-rich oil daily.

Omega-6 fatty acids include linolenic acid and gamma linolenic acid (GLA) found in sunflower, safflower, corn, groundnut and olive oils, and margarine-type spreads made with them, peanuts and peanut butter, and sunflower and sesame seeds. Most children get plenty of omega-6s but not enough omega-3s.

Saturated fats are found in animal fats as well as products made with palm oil. They have no beneficial role in the body (apart from being a source of energy). They raise blood cholesterol levels and increase the risk of heart disease. However, it would be impractical to cut them out altogether, so young athletes should try to stick to an intake less than the GDA: 30 g for males and 20 g for females.

Main sources include fatty meats, full-fat dairy products, butter, lard, palm oil and palm kernel oil (both labelled as 'vegetable fat' on foods), and biscuits, cakes and desserts made with palm or palm kernel oil or 'vegetable fat'.

Trans fats are formed artificially during the commercial process of hydrogenation, which converts unsaturated oils into solid spreads (hydrogenated fats or oils) for making biscuits, desserts and pastry. Trans fats increase LDL ('bad') cholesterol levels and lower HDL ('good') cholesterol, and harden and stiffen the arteries, which increases the risk of heart disease.

You should try to avoid these fats completely by checking for hydrogenated oils and partially hydrogenated oils on the ingredients list on food packages.