The metabolism of a hummingbird

A term used to describe those very very thin people who can eat anything they want and still remain very very thin. Much like the hummingbird, which eats 2/3rds of it's body weight in sugar every day, and stays, well, the size of a hummingbird.

You can often tell when somebody has this metabolism by the way you can count their ribs through their shirt. Another good indicator is if they wolf down ice cream, soda pop, etc., and never gain any weight. Or even worry about gaining weight (this characteristic is more than a little bit irritating).

The other end of the spectrum, I suppose, must be the metabolism of a three-toed sloth.

Hummingbirds are the speed freaks of the bird family. They eat a prodigious amount of food daily in order to meet their metabolic demands. If you were to scale up the hummingbird's daily ration to human size, it would be around 155 000 calories each day. So, for a human to keep pace with a hummingbird calorie-wise, you would have to consume:

• 1000 glasses of beer
• 1110 glasses of wine
• 524 cappuchinos
• 1360 ounces of cheddar
• 1281 cups of 2% milk
• 1962 eggs
• 704 Eggos
• 643 slices of pepperoni pizza
• 1240 cups of chocolate ice cream
• 268 large french fries
• etc.

The other particularly interesting thing about the metabolism of hummingbirds is that they must go into torpor while sleeping in order not to starve to death. Essentially, the animals go into a coma each evening, slowing their cardiac and respiratory rates dramatically.

A high metabolism is not limited to hummingbirds or even birds in general. As a rule, the smaller the mammal, the faster their metabolic rate will be. Mammals are endothermic, which means that they regulate their own body temperatures and keep warm using their own internal energy, which means that they use A LOT of energy when compared with cold-blooded animals (ectotherms). And, in proportion to larger animals, small mammals lose heat more easily, so they need to consume a higher amount of energy in proportion to their body size. Of course, metabolism also depends on other factors, such as the level of activity and the amount of calories that must be devoted to structural requirements, but body size has a comparatively large impact.

So it's really not surprising that hummingbirds have a high metabolism, is it?

And, now that I think of it, I find that when I go through bird phases where I consistently leap from tall buildings, waving my arms in an attempt to fly, I get hungry a lot quicker.