Personal trainer and former York City footballer Christian Fox, writes a regular column on how to keep in shape. This week he explains how sensible eating habits help you to lose weight.

IT can be hard to know what to eat and when. The Glycaemic Index (GI) is a ranking system set up to let you know how quickly certain foods are broken down and eventually stored as fat. The best types of foods to go for have a low to moderate GI.

These give a feeling of fullness, thus avoiding snacking at around 3pm to 4pm - the time of day we all know about!

Low to moderate GI foods tend to be natural, non-processed and non- refined, such as wholegrain and organic foods, but even dark chocolate has a moderate GI.

If you do eat high GI foods, I recommend eating these during the day as you will have chance to burn them off over the course of the day as opposed to late at night. For more information visit, www.glycemicindex.com.

Eating smaller, more regular meals will keep metabolism levels high and have a depressive effect on hunger levels.

Including protein (building blocks for muscle) in your meals will ensure lean tissue - muscle - is not lost. You can calculate your recommended protein intake by multiplying your body weight in kilograms by one to two grams. For example, a man weighing 75 kilograms who wants to bulk up a little bit should be aiming to eat about 150 grams of protein a day.

You can also work out your Body Mass Index, which is your weight in kilograms divided by your height in metres squared. An ideal index reading would be between 18 and 25 - but please note, this should only be used as a rough estimate and is useless for strength athletes and bodybuilders who have a lot of muscle mass.

But the most effective way to lose body fat though is to start to feel positive, adopt certain lifestyle changes and become a bit more active.

Do this and you will be on the right road to success. Friends will be commenting on how good you look, your Body Mass Index and body fat levels will be going down and your clothes will be falling off you.

Christian Fox is a personal trainer and nutritional advisor working at York's LivingWell Premier Health Club.

He is also available for home, office and outdoor training. For more information, phone 0771 187 1170, or log on to www.cbsfox.co.uk.