Why Recommended Daily Intakes are Unreliable

The only place Recommended Daily Intakes (RDIs) work is in a text book. And clearly, life is not a theory and you and I are not theoretical. The notion that John needs 2,150 calories every day because his height is X, his weight is Y and his age is Z (as one of my friends was recently informed by a health professional), is yet another example of stupid science. It’s like saying… “Hmm, okay Sally, you’re driving a four cylinder 2010 Honda CRV which produces 200 horsepower, therefore it will use 5.7 litres of petrol every day.”

Er, no it won’t Sal. What if you don’t drive anywhere on Tuesday?

How much petrol (car calories) Sal’s Honda needs on a given day will vary (sometimes wildly) depending on (1) how fast she drives (2) how far she drives (3) how often she stops and starts (city vs country driving) (4) how many people she has in the car (total weight) (5) the kind of terrain she drives on (hills or flat, bitumen or dirt) (6) air conditioner use (7) the ‘health’ of the car (8) tyre pressure… and a lot more.

Stupid concept huh?

Well, telling John that his body will require the same amount of energy day after day (based on some fifty year-old formula) to produce any specific physiological outcome, is just as stupid as believing Sally’s Honda will require the same amount of petrol every day of the year. Just like cars and their fluctuating petrol requirements, your energy needs will change constantly depending on an enormous range of variables including (but not limited to) (1) how many hours you’re awake (2) occupational activity (3) incidental activity (4) exercise activity (5) weather/temperature (6) your emotional state… and a lot more.

If you really want to know how much energy you need, just ask your body.

It knows.

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{ 3 comments… read them below or add one }

Eileen Varty January 18, 2014 at 1:55 pm

as per usual your comments are fantastic and love the emails i get daily…couldnt agree more thanks Craig !!


Susan January 19, 2014 at 5:26 am

Hey Craig,
I thought you only talk about motivation and inspirations, however its a different craig altogether. :)
Well, you said right about the meal and the body calories requirement. I had days with a single meal and had days when i ate like a glutton, but gym instructors tease me for the food..:(


Cathy S January 19, 2014 at 9:35 pm

Hmmm….I seem to have a Hummer body built around an Audi A4 engine….a vertically challenged Hummer body at that! :D


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