Interview with Dr Pam Peeke on HER Radio

I had a really fun conversation with the host of HER Radio Dr Pam Peeke, “the doc who walks the talk” on RadioMD this morning. You can listen to the full interview online here any time.

The gorgeous and enlightening ‘human weight loss equation’ we discussed is this:

          C₅₅H₁₀₄O₆   +   78 O₂   →    55 CO₂   +   52 H₂O   +   Energy                ✅ Correct

Most of the doctors, dietitians and personal trainers we surveyed, and nearly everybody else I’ve ever asked, thought that fat is converted into pure energy or heat but that ‘weight loss equation’ would look like this:

          C₅₅H₁₀₄O₆   →    Energy                                                                         ⛔️ Impossible

I did not discover the “human weight loss equation” myself nor that formula for human fat. Biochemists figured out that all fat becomes CO₂ and H₂O more than a century ago whether it is human, animal or vegetable fat (oil). Sugar and wood do too.  The data that yields the average human fat molecule (C₅₅H₁₀₄O₆) was published by Professor Jules Hirsch et al in this 1960 paper. Beautiful science underpins all of this amazing knowledge but it’s easy to miss because CO₂ and H₂O vapour are both invisible.

My small contribution was to figure out that 84% of the mass in human fat departs the body in carbon dioxide and the remaining 16% becomes water. That makes lungs the primary excretory organ for weight loss. We breathe out most of the mass we lose from fat.

My BMJ (formerly the British Medical Journal) paper can be found here but is currently behind the BMJ pay wall (we are trying to rectify this) but here are some other useful links below in the meantime.

Keep breathing.


The mathematics of weight loss the 20 minute talk I presented at TEDxQUT August of 2013

Where does fat go? aired on Catalyst, ABC TV in 2014 – the day I met my co-author Prof Andrew Brown

Where does the fat go? a cute and very British 48 second animation by the BMJ

When you burn fat, where does it go? the YouTube SciShow channel folks summed our paper up nicely


Where does the weight actually go when you lose it? from my home town, a Bundaberg News Mail article by Christina Ongley

Where does the fat go when you lose it? (Hint: The fat fairy is not involved.) fun Washington Post article by Lenny Bernstein

3 thoughts on “Interview with Dr Pam Peeke on HER Radio

  1. Enjoying reading your book – great insight. Small detail that might be misunderstood
    In the paragraph calories versus kilograms it reads = 4.2 joules = equals the amount of heat required to raise…
    I know you mean 1 joule = the amount of heat require, but it might be misunderstood as 4.2 joules…
    Anyways your TED talk really got my attention Thank you

    1. Hi Gary, apologies for the delayed reply… only 4 years 😱 I actually do mean 4.2 joules, which is one calorie. It takes one calorie (4.2 joules) to raise the temperature of 1 gram of water by one 1 degree Celsius. I hope that helps

  2. oops i was going on memory, my bad your correct re definition of calorie – sheesh
    should have checked first

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