Metabolism Efficiency

Nutrition
1

I need something cleared up…

I was sitting in one of my biology lectures and the lecturer was saying that the human metabolism is only around 40% efficient (Can be higher or lower depending on the person)

This meaning that for everything we eat only 40% is used as mobile energy and the other 60% is used to maintain our body temperature.

So if this is the case, if we eat lets say 1000 calories does that mean only 400 calories is actually used properly by the body and the other 600 is wasted on temperature maintenance???

Can someone clear this up

2

According to my professors, only 1/10 of energy in a trophic level makes it to the next trophic level when it is consumed. (Algae → small fish → bigger fish → sharks and shit)

It would make sense for us at the very top.

But those professors were trying to explain that we needed to be vegetarians.

3

Let me guess this same lecturer loves whole grains and is anti-fat

4

It’s true that human’s are incredibly inefficient (can tell this by amount of heat given off when buring energy) compared to power out put.

Our nutrition reccomenations are based on this fact aswell, so it doesn’t mean we should eat a shit load more.

5

Ah fair enough. But tell me this…

The amount of calories presented on a nutrition label, is that accounting for the enneficiency

ie the label says theres 1000 calories when theres really 2500, but it says 1000 because thats all our body will use.

or

it says 1000 but our body only needs 400???

6

Are you talking about the Thermic effect of food? (TEF) Fats have a very small TEF, under 5% i believe, while protein is around 30%. Carbs TEF is around the same as fat. And no, the labels do not account for the TEF.

oh, heres the article I was trying to remember , http://www.T-Nation.com/readArticle.do?id=1287670