Would my weight change if I ate a burger while standing on some scales?

16 June 2015

Question

If I stood on weighing scales while holding a big juicy burger would my total weight change if I ate the burger? I always thought I'd get lighter but I can't reason why.

Answer

Chris - I would argue that, actually, the burger is already mass in your hand on the scales and therefore, if you put it into your mouth, it just turns into mass in your body. There would then be some metabolism, obviously, because you've got to exert some energy to work the muscles of mastication to chew up the burger. And to produce some saliva; you've got to warm your body which means you're burning some energy doing that as well and you presume the burger is going to be a bit lower than body temperature probably by the time you've done your experiment. So there's a little bit of a loss of energy there. So, that means you're going to lose a little bit of mass. Metabolism that's going to carry on as you digest the burger as well, because you got to break it down into its component parts and absorb it. I reckon in the short term, no change. In the long term, there'd be a modest small reduction in mass... Max - How accurate your bathroom scale is?

Chris - Well, that was going to be my bottom line, if you excuse the pun, because I was going to say that actually, you're talking about trivialities. Once the burger goes in, the burger becomes part of you. There will be some losses to the toilet though and so, a certain amount will be absorbed and a certain amount won't be absorbed. And so, you won't get all of the energy turning into mass. But let's assume that none of the burger is wasted. It would all get converted either instantly into sugars that you would burn or fat that you would store, so your body mass would reflect the increase in weight gain owing to the burger...

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