December 3, 2011

Biochemistry

You are not what you eat

by Peter Attia

Read Time 2 minutes

You are what you eat, right?  How many times have you heard this?  I’d need scientific notation to actually enumerate the number of times I’ve heard this statement or one like it.  I certainly spent most of my life believing this, too, without ever questioning it. In fact, this you-are-what-you-eat dogma plays a significant role in our misguided belief that fat is bad for us.

So let’s examine this “dogma” and let’s use an average person as an example:

  • Assume you consume 2,500 calories per day
  • That works out to over 900,000 calories per year
  • Let’s assume you gain one pound of fat in a year (the average American does this beginning at the age of 25)
  • One pound of fat is equivalent to 3,500 calories of stored energy
  • At the end of the year you’ve gained 3,500 calories worth of energy out of over 900,000 calories ingested
  • In other words, you burned off more than 99.6% of the calories you consumed and only stored less than 0.4%
  • This works out to an average of less than 10 calories per day that we “store” in this scenario of gaining one pound of fat per year

What should you take away from this?  For starters, we burn almost all of what we ingest.   There are, more or less, four ways we account for this combustion of energy: digestion, activities of daily living (e.g., carrying your groceries, walking up the stairs to your apartment), exercise (the deliberate activity we do, say, going for a run), and resting metabolic expenditure.

The last of these is almost certainly the most important.  Why?  In most people, it accounts for the greatest “sink” for calories.  It’s always “on”. In other words, our resting metabolic expenditure burns energy when we sleep, eat, drive, and sit at our desk.

The real point I want to make is this: Our bodies are very finely tuned with respect to what they store.  What you eat matters a lot, but much less because of the actual caloric content of the food (there is probably not one of us who can titrate their daily intake to within 10 calories of a target intake).  The reason what you eat matters is because of the hormonal impact food exerts over your body.  The master hormone that regulates fat accumulation is insulin.  Hence, the impact your food has on insulin levels is far more important than the number of calories contained within what you eat.

So next time someone tells you, “you are what you eat”, feel free to correct them: You are not what you eat, You are only that small fraction of what you eat that your body chooses to save.  What you eat impacts this more than anything else.

Photo by Gene Taylor on Unsplash

Disclaimer: This blog is for general informational purposes only and does not constitute the practice of medicine, nursing or other professional health care services, including the giving of medical advice, and no doctor/patient relationship is formed. The use of information on this blog or materials linked from this blog is at the user's own risk. The content of this blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Users should not disregard, or delay in obtaining, medical advice for any medical condition they may have, and should seek the assistance of their health care professionals for any such conditions.

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