Some diets promise a quick fix of rapid weight loss — but these are often unscientific, can be harmful and many people find once they finish the programme they end up putting the weight back on.

The challenge should not be just reaching a target weight, but maintaining a healthy weight in the long term and this is best done by tipping the energy balance, which means burning more calories than you take in.

This can be done without the need for fad diets and a few adjustments to daily diet and exercise patterns can have a huge effect on your health as well as your weight.

The easiest and safest way to lose weight is to combine more physical activity with a diet that is lower in calories with a target reduction in the energy balance of between 500 and 1,000 calories a day.

People who are overweight often don't realise how much they are eating and keeping a food diary can help point to ways of cutting down on calories.

By changing the balance of foods on your plate, for example fewer chips and more salad, you can reduce the calorie count of each meal and replacing a regular snack food with fruit will also help slash your calorie intake.

Calories

And when you take into account that 500 calories a day equals 1lb of fat a week, it is easy to see how an extra handful of chips here and a chocolate bar there can soon add up.

One mistake people often make when trying to lose weight is not taking account of the calories in drinks, especially alcohol, which is high in calories –– three pints of beer can add up to 600 calories.

Sugary drinks should also be limited as a can of cola contains 135 calories, but apart from the energy has virtually no nutritional value.

And to burn off calories you should aim to do 30 minutes of moderate physical activity, where you feel slightly warm and out of breath, on most days of the week.

There is no need to join a gym or splash out on expensive running shoes as this level of exercise is easier to sustain if you make small changes to make it part of your daily routine.

You could take the stairs at work instead of the lift or walk to the shops instead of taking the car and a longer session of lower-intensity activity is also good for burning fat so you could consider walking at least part of the way to work everyday.

If you have a lot of weight to lose, it is better to set a realistic medium-term goal and doctors often suggest starting with a 10 per cent weight loss over about six months.

Once you have managed this you will already look and feel better and may already have reduced many of the risks to your health including high blood pressure and cholesterol.

• If you do decide to start a diet look for one that:


• Only promotes weight loss of 0.5-1kg a week, any more than this and you'll be losing water and muscle, not fat.


• Encourages you to eat a balanced, varied diet that incorporates all major food groups.


• Is realistic and flexible enough so that you can stick to it.