Keeping in mind that what you burn can be expressed simply as a number of calories, it's enlightening to look at what goes in and what comes out in somewhat more detail than you might have ever contemplated.
Consider this view of human as rubber bag presented at a NASA conference on the exploration of Mars.
From this all-inclusive perspective, which accounts for the oxygen in the air we breathe, moisture lost through the skin, and water generated by the reactions that break down the food we eat and reassemble it into the cells of our body, a human being, the ``beauty of the world! the paragon of animals!'' resembles a water pump more than the most intelligent known life form in the universe.
This is important information, not just to Mars mission planners or inveterate collectors of fascinating details, but to anybody interested in controlling their weight. Explained here are the reasons so many people misunderstand how their bodies react when they're trying to lose weight, why so many people become frustrated and abandon sincerely undertaken efforts to control their weight.
It's the water. On a day to day basis, the water you consume, whether directly in beverages or as part of the foods you eat, and the water you excrete in your various excursions to the hydraulic accommodations, dwarfs the weight of the food you eat and the solid waste you dispose of. To this extent: 68% of the mass you consume every day is water, and 81% of what goes out is likewise water. Startling, until you recall the human body is, by weight, about three quarters water. Average the percentages of water in and water out, and you get...75%: three quarters.
Every day your body ingests plenty of water and disposes of even more. Most of the changes in weight you see from day to day on a scale reflect nothing more than how much water is in the rubber bag at the moment. Consider: if you pig out to the extent of three slices of pizza before bedtime every night for a whole month, you'll gain about four pounds as the lingering souvenir of your month of wild abandon. Yet even that extreme weight gain is less than half your daily intake and disposal of water.
Most of the changes in weight you see have nothing to do with how many calories you're eating or burning. Instead, all you're seeing is how many pounds of water happen to be inside the rubber bag at the moment. How many bleak mornings of dark despair endured by forlorn dieters who indulged in a bowl of salted popcorn at midnight then slaked their thirst with a large glass of water in the middle of the night, would have been taken in stride had only the implications of human being as water pump been fully comprehended?
By John Walker