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Fat

Published by Bupa's health information team, healthinfo@bupa.com, April 2008

In the UK, most people eat too much fat. By reducing the amount of fat you eat and switching to healthier fats like those found in oily fish, avocados and nuts, you will help to reduce your risk of serious diseases like heart disease and certain cancers. It will also help you to maintain a healthy weight.

Why do we need fat?

We all need some fat in our diet. It's a valuable source of energy for a start, and helps your body to absorb the fat-soluble vitamins A, D, E and K. The fat you get from food is also your only source of the essential fatty acids omega-3 and omega-6, which are vital for cell formation, particularly in your nervous system.

Fats are classified by their saturation (the number of hydrogen atoms attached to each fat molecule). The three main types of fat are:

saturated fat
polyunsaturated fat
monounsaturated fat

What is saturated fat?

Saturated fats are "saturated" because each fat molecule is completely covered in hydrogen atoms. Saturated fat is the worst kind of fat, because it's known to increase risks to your health if you eat too much of it. In particular, it increases your blood cholesterol level, which in turn can lead to heart disease.

Trans fat is a particular type of saturated fat created in the manufacture of margarine and cooking fats. Trans fats are thought to be particularly bad for raising your cholesterol level. Recently, the food industry has been cutting down the amount of trans fats in products like biscuits, cakes, pastries and margarine. Some major food retailers pledged to remove trans fats from their products altogether by the end of 2007.

Where is it found?

Meat, meat products, dairy products and coconut oil contain the greatest amount of saturated fat. The easiest way for you to check whether a fat is saturated is to notice how hard it is at room temperature: saturated fats are usually hard at room temperature, while unsaturated fats are liquid. Many processed foods, such as cakes, biscuits, pastries and crisps, contain saturated fats.

What is polyunsaturated fat?

Polyunsaturated fats are not saturated with hydrogen atoms. In other words, there are a number of spaces around each fat molecule where hydrogen atoms could be attached. Polyunsaturated fat is generally beneficial to health. The polyunsaturated fats found in oily fish (known as omega-3 fatty acids) are particularly good for you. They help prevent heart disease by lowering your blood cholesterol level and may help to reduce the symptoms of arthritis and other joint problems.

Where is it found?

Good sources of polyunsaturated fats are oily fish such as mackerel, salmon, trout, herring and sardines, and soft, polyunsaturated spreads. Other sources include cooking oils like linseed, flaxseed and rapeseed, although it's not clear whether the omega-3 in these foods has the same health benefits as those found in oily fish.

The Food Standards Agency recommends that women who are thinking of conceiving or are already pregnant should eat no more than two portions of oily fish per week. This is because oily fish may contain pollutants that can harm the development of unborn babies. It also recommends that women don't eat exotic fish like shark, swordfish or marlin while they are pregnant or trying to conceive, because these fish contain high levels of naturally occurring mercury. Men, and women who aren't planning to have children, can safely eat up to four portions of oily fish a week.

What is monounsaturated fat?

Like polyunsaturated fats, monounsaturated fats are not saturated with hydrogen atoms. As their name suggests, each fat molecule has space for one more hydrogen atom only. Like polyunsaturates, monounsaturated fats have an important role to play in reducing your risk of heart disease.

Where is it found?

Monounsaturated fats are found in olives, olive oil, groundnut oil, nuts and avocados.

How much fat should we eat?

Fat contains nine calories per gram (kcal/g) - that's more than double the energy of carbohydrates (4kcal/g) or proteins (3.75kcal/g). And because they are less bulky than other food groups, it's all too easy to over-indulge.

The current recommendation is that no more than 35 percent of the calories you eat and drink should come from fat. Breaking this down further, saturated fat should account for no more than 11 percent of the calories you eat and drink, because of its potentially harmful effects on your health.

What does this mean in practical terms?

If you eat 2,000 calories a day, 33 percent amounts to 74g of total fat. If your daily calorie intake is 1,500 calories, 33 percent amounts to 55g of total fat.

Most food labels carry information about the number of grams of fat in a product: 20g or more of fat per 100g is a lot, while 3g or less is a little. Some labels also give a separate figure for saturated fat.

Some tips to help reduce the fat in your diet

Try these simple ways to keep your fat intake to a healthy level:

use semi-skimmed or skimmed milk instead of whole milk
switch to a low-fat spread instead of butter or margarine
eat more chicken (without the skin) and fish, and less red meat
choose lean cuts of meat and trim off excess fat
grill, bake, steam or microwave food rather than frying it
try low-fat varieties of dairy products such as cheese and yoghurt
choose polyunsaturated cooking oil (such as rapeseed) or monounsaturated cooking oil (such as olive oil)
avoid high-fat snacks such as crisps, biscuits, cakes and pastries