Our bodies have evolved to protect against weight loss. We like to think we're modern, enlightened creatures, but we're still a collection of biological processes that are centred around survival in an unforgiving world. Most of us no longer live in that world.

As a result, when we diet our bodies trigger processes that limit the effects of nutritional deficit. And sure, we'll lose weight to start with, but that hits a plateau surprisingly quickly as our metabolism catches up.

Then add into that things like ADHD (which is something affects me personally), whereby when weight loss slows to a crawl after a few weeks I get frustrated and lose interest in keeping it up. So I'm 140kg with no sign of that going anywhere any time soon.