Why food labels are wrong about calories
Why food labels are wrong about calories
by EarthSky Voices in Blogs » Human World, Science Wire
By Richard Wrangham, Harvard University and Rachel Carmody, Harvard University
Food labels seem to provide all the information a thoughtful consumer needs, so counting calories should be simple. But things get tricky because food labels tell only half the story.
A calorie is a measure of usable energy. Food labels say how many calories a food contains. But what they don’t say is that how many calories you actually get out of your food depends on how highly processed it is.
Processed food makes you fatter
Food-processing includes cooking, blending and mashing, or using refined instead of unrefined flour. It can be done by the food industry before you buy, or in your home when you prepare a meal. Its effects can be big. If you eat your food raw, you will tend to lose weight. If you eat the same food cooked, you will tend to gain weight. Same calories, different outcome.
For our ancestors, it could have meant the difference between life and death. Hundreds of thousands of years ago, when early humans learned to cook they were able to access more energy in whatever they ate. The extra energy allowed them to develop big brains, have babies faster and travel more efficiently. Without cooking, we would not be human.
More processed foods are digested more completely
Animal experiments show that processing affects calorie gain whether the energy source is carbohydrate, protein or lipid (fats and oils). In every case, more processed foods give an eater more energy.
Take carbohydrates, which provide more than half of the world’s calories. Their energy is often packaged in starch grains, dense packets of glucose that are digested mainly in your small intestine. If you eat a starchy food raw, up to half the starch grains pass through the small intestine entirely undigested. Your body gets two-thirds or less of the total calories available in the food. The rest might be used by bacteria in your colon, or might even be passed out whole.
Even among cooked foods, digestibility varies. Starch becomes more resistant to digestion when it is allowed to cool and sit after being cooked, because it crystallizes into structures that digestive enzymes cannot easily break down. So stale foods like day-old cooked spaghetti, or cold toast, will give you fewer calories than the same foods eaten piping hot, even though technically they contain the same amount of stored energy.
Softer foods are calorie-saving
Highly processed foods are not only more digestible; they tend to be softer, requiring the body to expend less energy during digestion. Researchers fed rats two kinds of laboratory chow. One kind was solid pellets, the type normally given to lab animals. The other differed only by containing more air: they were like puffed breakfast cereal. Rats eating the solid and puffed pellets ate the same weight of food and the same number of counted calories and they exercised the same amount as each other. But the rats eating the puffed pellets grew heavier and had 30% more body fat than their counterparts eating regular chow.
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Why food labels don’t tell the full story
Unfortunately, of course, in today’s overfed and underexercised populations nature’s way is not the best way. If we want to lose weight we should challenge our instinctive desires. We should reject soft white bread in favor of rough whole wheat breads, processed cheese in favor of natural cheese, cooked vegetables in favor of raw vegetables. And to do so would be much easier if our food labels gave us some advice about how many calories we would save by eating less-processed food. So why are our nutritionist advisers mute on the topic?
For decades there have been calls by distinguished committees and institutions to reform our calorie-counting system. But the calls for change have failed. The problem is a shortage of information. Researchers find it hard to predict precisely how many extra calories will be gained when our food is more highly processed. By contrast, they find it easy to show that if a food is digested completely, it will yield a specific number of calories.
Our food labeling therefore faces a choice between two systems, neither of which is satisfactory. The first gives a precise number of calories but takes no account of the known effects of food-processing, and therefore mis-measures what our bodies are actually harvesting from the food. The second would take account of food-processing, but without any precise numbers.
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Time for a change?
Given the importance of counting calories correctly, it’s time to re-open the discussion. One idea would develop a “traffic-light” system on food labels, alerting consumers to foods that are highly processed (red dots), lightly processed (green dots) or in-between (amber dots).
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More (incld lik to orig article)
http://earthsky.org/human-world/why-food-labels-are-wrong-about-calories?utm_source=EarthSky+News&utm_campaign=993468cf60-EarthSky_News&utm_medium=email&utm_term=0_c643945d79-993468cf60-393525109
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