Everyone loves to indulge in chocolate yet we all know it's a food that's laden with fat, sugar and kilojoules - and it's damn hard to stop at just one mouthful. So it's hardly surprising that dieters have turned hopefully to light chocolate to provide pleasure without guilt. At first glance, it looks like the answer to a dieter's prayers!

I have to say right up front that choc isn't one of my weaknesses (I have others like nougat). But I was interested to see how much you could save by doing a swap from say a regular Mars Bar to a light Mars Bar.

I bought two bags of fun-size Mars from the supermarket - one regular, one light. One small bar (just enough for three bites) has 3.8 grams of fat and 420 kJ. One Lite bar comes in at a low 1.9 g and only 265 kJ.

So compared to a normal Mars, the Lite version saves you 50% fat. So far, so good. However the total kilojoule savings is not that high - it's only 37%.

But hang on a minute. The light bar looked a lot smaller. Then it hit me. The savings are also due to the smaller size - you're eating only 16 grams of total chocolate when the real version gives you 22 grams of chocolate. Small wonder.

So it's not only less fat. It's also 6 g less chocolate overall! Take a look at this comparison which sums up these differences and you'll see that you don't save much in kilojoules (Calories):

3 ways chocolate is lightened to make it 'healthier'

There are three other ways chocolate manufacturers can ‘lighten' chocolate. They can:

1. aerate or whip it while it's still warm so there's more air incorporated. Tiny bubbles of air trapped with the chocolate mean a less dense chocolate. You consume fewer kilojoules. Think of the popular Aero bar.

2. enrobe the bar, but keep the filling light. Think of chocolate filled with Turkish delight, nougat or mousse. Sixty grams of a solid milk chocolate lands you with 1295 kJ, but 60 g of choc-coated bar (eg. Milky Way or Fling bar) gets things down to a lower 1045 kJ. You eat, you save.

3. replace the sugar or fat with polydextrose or another bulking agent, and use sugar replacers such as isomalt or sucralose that add fewer kilojoules. This is how Cadbury Lite does it. See another chocolate comparison - this time weight for weight.

The bottom line

One thing struck me. Even with sweeteners and extenders, the Cadbury Lite saves you a miserable 12% fat and 15% kilojoules. Hardly worth the trade down! Especially with the lack of real chocolate-y flavour. I had to ask myself - was the light choc worth it? I admitted I'd rather eat a small amount of the ‘real thing' than lots of a light substitute. As long as I made myself focus on the food, savour it slowly and then I'd feel satisfied. Interesting, eh? How would you rather eat – lots of a light food OR just a few mouthfuls of the real thing?