‘Light' or ‘lite' foods seem to be the answer to our diet prayers. You eat - and enjoy - the same food but you end up consuming less fat and fewer kilojoules (calories). To a dieter (and I'm always watching what I eat), it sounds just perfect!

When light foods first started appearing on our supermarket shelves way back in the 1990s, they were quite simple. They had less fat than the regular version, but the drop in fat was one you almost couldn't notice unless you compared the two versions mouthful by mouthful.

5 home truths about light foods

1.You can't eat TWICE as much. Even if a light food has 50% less fat, the kilojoules only drop by 40% at the most. So you can't eat twice as much if you want to lose weight. To use light foods well, choose the light version but keep to the SAME portion size as you normally eat.

2.Fat adds flavour. If you take the fat out, you have to put something else in to give a light food enough flavour and mouth-feel to make it tasty. Often what you add back is sugar, fruit puree or starch and these add kilojoules.

3.Read the label and check WHAT is being lightened - is it the fat, salt, alcohol? Or just the texture or colour?

4.Watch if the serve size is really small. Many light products are packaged in smaller sizes which means a lower weight of food.  So it looks like you're saving lots simply because you're eating less weight of food - that is, if you aren't tempted to eat more!  At times, you could do better by just eating a small portion of the full-fat version!

5. Sometimes it's more enjoyable and flavoursome to eat a small amount of the ‘real thing' than lots of a light substitute. Sit down, focus on the food, savour it slowly and you'll feel satisfied. 

Rule of thumb

• When a light product drops its fat by half (say light cream or coconut milk) and nothing else changes, you save 40 to 50 per cent of the kilojoules.
• When a light product drops its fat by half but makes up for it with extra sugar or starches (say with muffins or light ice-cream), the most you save is only 30 per cent of the kilojoules. You can't eat twice as much!

Classifying light products by fat and kilojoules

We divided light foods into 3 groups based on the amount of fat AND kilojoules they save you. We reckoned that if you weren't getting a 30 per cent saving in fat AND kilojoules, it wasn't worth the trade down!

Group 1 - Super savers

According to our calculations, these light products really save you lots - over 30 per cent saving in fat (or sugar or alcohol) AND kilojoules - and make a difference to your diet efforts. These are the ones to buy:

• Light milks
• Light cream, light sour cream
• Light coconut milk
• Light custard
• Light probiotic drinks eg Yakult

As well as these light foods -

Foods with less alcohol:
Light beer
Foods with less sugar:
Light blackcurrant juice

 Group 2 - Some savings but often very modest

You need to check the label and do the maths on the following light products and weigh up whether they're worth it (and they may be if it's something you really love to eat). But remember that even if they save you fat, they often don't save you many kilojoules as the fat is replaced with extra sugar or starch to maintain a smooth creamy texture or an attractive taste for baking eg:

• Light muffins/cakes
• Light dips
• Light margarine spread
• Light cheddar cheese
• Light popcorn
• Light biscuits
• Light peanut butter
• Light crisps
• Light ice-cream
• Light chocolate

Group 3 - No savings in fat or kilojoules

These light foods give you no saving in fat or kilojoules:

• Light olive oil - same fat, lighter flavour and blander taste
• Light gravy powder - same fat, same kilojoules, has less salt

The bottom line

Check what is being lightened. Is it the fat or sugar or alcohol? Or just the texture or salt (no savings for weight loss). Sadly.