When is a Calorie Less Than a Calorie?

For Christmas, my eleven-year old son received a copy of Faith D'Aluisio and Peter Menzel's new book, What I Eat: Around the World in 80 Diets from his aunt and uncle.  I think we showed great restraint in allowing him a few hours to pore over the book in peace before the rest of the family pounced on it.

As in their previous books (Hungry Planet, Material World) the photos and essays are fascinating and the variety of lifestyles and diets profiled is staggering.  Unlike their previous books, they were not looking to profile an average eater to represent their culture.  Instead, they chose people across an eating/exercising spectrum including, for example, an acrobat, a bullfighter, a bike messenger, a taxi driver, an extreme gamer, and a binge eater.


What I find interesting is the amazing differences in the way people eat.  I am particularly interested in the people who eat 4,000 and 5,000 calories a day and look healthy and thin. (How does she do that?!)  (No, they are not all extreme exercisers.)  Granted, the meals depicted were not meant to represent their average calorie intake, but in many cases I think they do.  After all, if you take in 4,000 calories on an ordinary day--not a holiday--you'd probably feel hungry if you only had 2,000 calories the next day.

Even more interesting are the essays interspersed throughout. In "The Agony and the Ecstasy of the Calorie" Bijal P. Trivedi tells us about the groundbreaking work done by Wilbur Olin Atwater to quantify the calories in carbohydrates, protein and fat in the late 1800s.  Those are the same values that are used on all of our food packaging today. So, you might be a little surprised to find out that all those calorie counts--the ones that we make food choices for ourselves and others by--are wrong.

Why are they wrong?  First, they don't take into account the effect of food processing.  Grinding and cooking food make it easier for our digestive tracts to extract more caloric content.  But nutrition labels don't factor that in, making them inaccurate (either too high or too low) by up to 25%.

Calorie counts also don't take into account the energy needed to digest foods.  Foods that are harder to digest render fewer net calories than food labels suggest.  For example, sources of dietary fiber should have their calories reduced by up to 25%.  Similarly, calorie counts for proteins should be reduced by up to 20%.  (Do we have to wonder why the Atkins diet works?)

Further, the way in which food is prepared can unleash additional calories.  In one experiment (using pythons' digestive apparatus...) cooking meat increased its caloric value by 13% and ground and cooked meat had 23% more calories available.

What's the bottom line?  If you want to extract maximum calorie content from your food: cook, grind, pulverize and refine.  If you want to minimize your calorie intake, choose whole foods and eat them raw or cooked at low temperatures.

And, take all those calorie counts with a grain of salt.