The amount and type of food you eat has a major influence on your health. Unfortunately, it's easy to eat too many high-fat convenience foods and not enough of the more nutritious foods such as fruit and vegetables.

Why do you need to eat well?

Your body needs a constant supply of energy to fuel the continuous processes of life, such as your heartbeat, breathing and digestion. You also need energy to grow and repair your body's tissues, and to power your muscles for movement.

This energy is provided by your food and drink. The energy content is measured in calories (kilocalories, kcal). As well as getting enough energy, you need to make sure your diet includes essential nutrients such as carbohydrates, protein, fats, vitamins and minerals.

The food choices you make can have a long-term impact on your health. There is good evidence that eating a healthy diet can reduce your risk of illnesses such as diabetes, obesity, cardiovascular disease (including coronary heart disease) and several cancers (especially bowel cancer).

What is healthy eating?

Healthy eating is about eating the right quantity and balance of foods, month in month out. Eating the right balance of foods from the main food groups is the foundation of day-to-day wellbeing. There are five main food groups:

• starchy foods
• fruit and vegetables
• dairy foods
• meat and beans
• fat and sugar
• Starchy foods

Starchy foods such as bread and potatoes are the main source of carbohydrate - the body's preferred source of fuel. They should make up about half of your daily energy intake. Each gram of carbohydrate provides you with about four calories.

There are two main types of carbohydrate - complex and simple. Complex carbohydrates include starch and fibre. Simple carbohydrates include sugars.

Most of the carbohydrate in your diet should come from complex carbohydrates, including starchy "fillers" such as brown bread, potatoes, pasta, rice or chapati. Choose wholegrain varieties whenever possible, as these also contain more fibre.

Aim to base your meals on starchy carbohydrate for a diet that is lower in fat and higher in dietary fibre - especially if you choose wholegrain varieties.

Fruit and vegetables

You should aim to eat at least five portions of fruit and vegetables each day. There is good evidence that fruit and vegetables cut the risk of disease, including some cancers and heart disease.

Dairy foods

Milk and dairy products such as cheese and yoghurt are rich in protein. They are also a good source of vitamin D and calcium, which keep your bones strong and healthy.

One gram of protein provides you with about four calories, but this energy is less readily released than from carbohydrate. Protein should make up around 15 percent of your daily energy intake.

Most people in the UK eat a reasonable amount of protein and don't need to alter their intake. But try to choose the lower-fat options. For instance, instead of cream in your coffee, try semi-skimmed milk.

Meat and beans

Meat, beans and pulses also provide you with protein. Try to choose the lower-fat options. For instance, instead of high-fat chicken nuggets, try lean pieces of chicken or pulses such as beans or chickpeas.

Fat and sugar

Fat

Fat is the most energy-dense nutrient - each gram provides you with about nine calories. Fat also provides fatty acids, which your body needs for many vital functions, such as helping your body to absorb vitamins. In small quantities, fat is essential for good health but it should make up no more than 35 percent of your daily energy intake.

Eating a lot of fat, particularly saturated fats and trans fats, is unhealthy. These increase the risk of cardiovascular disease (including heart attack and stroke). Because it is so rich in calories, it can cause obesity.

Most of us need to eat less fat. But as well as cutting down on the total amount of fat in your diet, it's important to consider the different types.

Saturated fats are solid at room temperature, and come from meat and dairy products. Eating a lot of saturated fat increases your risk of cardiovascular disease, and most of us need to cut down. Cutting the fat off meat and eating lower-fat versions of dairy foods can help.

Trans fats are a cheap source of fat, mainly used for snack and convenience foods like biscuits, cakes and pastries. These are thought to be even unhealthier than saturated fats. Many manufacturers are now stopping using trans fats in their products.

Unsaturated fats come mainly from plant and fish sources. They tend to be liquid at room temperature. Unsaturated fats are divided into two types: monounsaturates and polyunsaturates. They are both healthier than saturated fats, and it makes sense to replace some of the saturated fats in your diet with unsaturated ones (eg replacing butter with olive oil).

Omega 3 is a type of fatty acid that helps to protect against heart disease. Eating two portions of oily fish (eg sardines, mackerel or salmon) every week is a good way to help meet your omega 3 requirements. One portion is about 140g.

Pregnant women should not eat more than two portions of oily fish per week, and should not eat any swordfish, shark or marlin.

Cholesterol is another type of fat, and is mostly made by your liver. High levels of cholesterol in your blood increase your risk of heart disease. Certain foods, such as eggs and offal, are high in cholesterol. However, eating cholesterol in food does not contribute much to the amount of cholesterol in your blood. Saturated fats contribute more to blood cholesterol, so it's more important to reduce these.

Sugar

Foods high in refined sugar such as table sugar, sugary drinks and snacks provide "empty calories". This means that these foods have low nutritional value. Sugar also contributes to tooth decay and gum disease. It is a good idea to limit your refined sugar intake.

Micronutrients

As well as the main food groups, we need a small amount of many different vitamins and minerals for our bodies to work properly. Vitamin or mineral deficiencies can lead to illness. Vitamins and minerals also help to support the immune system to protect us from infections, and guard against illness in the long term.

Vitamin and mineral supplements

Most of us should be able to get all the vitamins and minerals we need from a balanced diet. Certain groups of people will benefit from a vitamin or mineral supplement. These include children from six months to five years old and women who are pregnant or might get pregnant.

Some people choose to take supplements. If you choose to take a supplement, don't be tempted to take very high doses as some vitamins and minerals are toxic in large quantities.

There is growing evidence that many vitamin supplements are not as effective as the real source of the vitamins. So, make sure you are eating at least five portions of fruit and vegetables every day.

Alcohol

Your body converts alcohol to carbohydrate - each gram provides you with about seven calories. Like refined sugar, alcohol provides "empty calories". This is one of the reasons why you should limit your alcohol intake to stay healthy.

Practical tips for a better diet

• Eat a varied diet with a wide range of foods.
• Eat more wholegrain starchy carbohydrates (eg wholemeal bread, brown rice, wholegrain cereals).
• Eat more fruit and vegetables, aiming for at least five portions a day.
• Cut down on salt by eating less processed food, such as ready meals, and adding less salt to food.
• Eat regular meals - although it doesn't matter when you eat your food, having a routine can help people to manage their diet and their weight.
• Control your portion sizes so that over time, if not necessarily every day, the amount of energy you consume matches your level of activity.
• Try to be more physically active. Aim for 30 minutes of physical activity on most days of the week.
• Drink alcohol within recommended limits; the Department of Health recommends that women should not drink over two to three units of alcohol per day and men should not drink more than three to four units per day.

Further information

British Nutrition Foundation www.nutrition.org.uk
Food Standards Agency www.foodstandards.gov.uk