How efficiently do we use the calories and nutrients in what we eat?

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@Robdoyle asked the Naked Scientists:
How efficiently do we use the calories and nutrients in the food we eat? Are all foods equal in terms of what we can get out of them?

What do you think?
« Last Edit: 05/12/2010 13:30:03 by _system »


Offline CliffordK

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There are many factors.

In many cases it depends on the state of the person.  In a state of starvation, essentially 100% of the available calories are absorbed. 

In periods of gluttony, the majority of the calories may be excreted.

In many senses, your body will try to achieve a "set point" which may gradually float around depending on your genetics, diet, exercise, and perhaps even the season.  Fighting the natural "set point" can be extremely difficult.

Some foods have been reported as having "negative calories". I.E. taking more energy to process than the energy they produce.  It may be true, it may be an illusion.

Many of the more recent diets depend on unbalanced food intake, and either low fat, or low sugar/carbohydrate intake, or high on proteins and low on everything else.  A high vegetable diet might lead towards weight loss no matter what.

Keep in mind though, cellulose & fiber may show up on some caloric tests, but may not be readily available to the body for nutritional value.

One of my favorite "diet foods" is blackberries...  slightly cooked with sugar on top.  Half of the fruit is the seed with is excreted virtually intact.  And, I can loose a moderate amount of weight on a diet rich on blackberries without trying hard.



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I pretty much agree with Clifford with the exception that I don't think any digestible calories are excreted when one eats much more than they require. Even excess sugars and digestible starches are stored as fat.