Are you one of those people who checks the calorie content of different products before choosing which one to buy? If so, there is good news and bad news. The bad news is that your effort seems to have been largely pointless. The good news is that the best thing you can do is follow your instinct and go with what is the most natural and least-processed option.
The system by which different foodstuffs are rated for calorie content is hopelessly out of date. Scientists have known this for decades but no-one bothered to question it because it was thought that even if the hard figures made little sense, it was useful for comparison purposes.
Well, even that no longer holds true. The system was devised by an American scientist in the 19th century based on the energy released by burning different foodstuffs. Now, as I understand it, there is an inbuilt correction in the statistics to allow for the fact that we digest food rather than burning it. However, the chap in question assumed that cooking food didn't change anything. Wrong. Cooking can raise the amount of calories available to us - by 15% in the case of meat and 39% in the case of sweet potatoes.
Fibre is a good example of this. Cooking fibrous foods makes more calories available since it means the fibre is delivered to us in a more digestible form. Left uncooked (or cooked only lightly), our bodily microbes have to break it down for us and in the heel of the hunt, they use up a fair amount of the energy that could otherwise build up as extra kgs of fat.
So, the more processed food is, the badder it is. That's even before we get talking about additives, preservatives. But that's another story.
Calorie count system is well past sell-by date - The Irish Times - Tue, Feb 19, 2013