The key to a healthy lifestyle and keeping your weight in check is following a balanced diet that includes all the right foods in the right amounts.The term 'balanced diet' is one of those health mantras that are constantly heard but rarely explained. What it means is a diet that includes a combination of several different food types, including grains and pulses, fresh fruit and vegetables, meat, dairy products, fats and oils.Crucial to the idea of a balanced diet is including foods in the right proportions; the aim is to get all the nutrients your body needs while maintaining a healthy weight. It isn't a case of having roughly equal measures of everything. There should be a lot of some foods and just a little of others. Some fats and oils, for example, are important in the diet for various reasons, including absorption of fat-soluble vitamins. But you only need a small amount compared with foods such as vegetables.In the UK, the Food Standards Agency has developed a program called The Balance of Good Health to show people what proportions and types of foods make up a healthy balanced diet.This divides foods into five different groups: - Bread, other cereals and potatoes - Fruit and vegetables - Milk and dairy foods - Meat, fish and alternatives - Foods containing fat and foods containing sugarThe largest groups are bread and vegetables, followed by milk and meat. The smallest by far is the salt and sugar group. Fresh fruits and vegetables are low in fat, calories and salt, and an excellent source of vitamins, minerals and fiber. Most of us don't eat enough to meet the current recommendation of three to five servings of vegetables and two to four servings of fruits a day. Protein-rich foods and dairy foods are needed in more moderate amounts. Your diet should include two to three servings of milk or dairy produce a day, for example. Take care that protein-rich foods don't bring a lot of fat with them; trim the fat off meat and take the skin off chicken. Think about how you cook foods too; meat fried or in breadcrumbs adds extra fat.How much is a serving?The size of a serving of some foods, especially fruit, is easy to work out; common sense is also a good guide. More specifically, the USDA Food Guide Pyramid outlines standard serving sizes for many foods, based on the American imperial system of cups. For example, one cup of milk counts as one serving, as does half a cup of pasta or a slice of bread.How many servings we need of each food group every day depends on our age, gender and level of activity.Combining foodsIt's not too difficult to keep track of how many servings of certain individual foods we eat each day, such as an apple or a piece of cheese. But what happens when you throw a number of foods together in a meal?All you need to do is break a meal down into its individual ingredients. For example, shepherd's pie with a cheesy crust combines foods from two or more groups, depending on how you make it, including:- Potato, carrot and onion (fruit and vegetables) - Minced lamb or beef (meat) - Cheese (milk and dairy)