It's more that the muscles (assuming same muscle mass) have to do comparatively more work if they are carrying around more weight.

That is true but I don't think that accounts for all the metabolism. There's probably something to say about having to maintain your temperature, but I don't know if it consumes more or less energy in general as fat isolates. Wikipedia (https://en.wikipedia.org/wiki/Basal_metabolic_rate) says that 70% of the metabolism comes from the organs, 20% the muscles and 10% thermogenesis. All probably grow as you gain weight, but I seriously doubt that an obese person weighing 400lbs consumes twice as much energy as someone weighing 200lbs. What I'm trying to say is that the idea that you have to eat enormous quantities of food to maintain a high weight seems wrong to me, and that simply saying that the person must be missing some calories that they consume or lying about their level of activity seems condescending to me.

To change the subject, do you plan on expending Fella to Europe at some point? I really like your approach.

Really nicely put.

Yep we're British founders so would love to expand to Europe in the future. Sadly won't be for a couple of years though - lots of work to be done first in the US!

Thanks, and good luck with the US!

>Fat needs energy to maintain itself?

Yes. Stored fat isn't just inert fat, but fatty tissue. Made of cells that need energy to stay alive.