Hedgehog
His food gets weighed every meal. He has no treats (apart from ice cubes which he loves, and I'm fairly certain they have no calories).
I have no DC. DH does not feed the dogs. Ever. This is so that their intake can be monitored, having had multiple rescues with various medical conditions, we find it easier that only one person is responsible for giving any form of food so that this can be controlled and any health patterns can be monitored against food intake.
4 months of reduced levels of one food. Vet told us for his weight not to go below a certain weight of food. We tried different food. Same result. We've tried home prepared food and raw diets rather than any commercial stuff. Similar issue.
As all this is being monitored by our vets, I'm fairly certain that this is not, in fact, bollocks. And if you'd ever met DH you'd know there were never leftovers 
I'm sure if I gave him 150g of food a day he would lose weight so in a way I suppose you're correct. Just like saying if a human ate only 200 calories a day we would lose weight. Its unsustainable and unhealthy in the long run. What I'm talking about is a level of food giving him the minimum requirement, and following the vets guidance on the minimum. We went below this once for around 10 days, not by much, maybe by around 50g of food. He became lethargic and sluggish (and no, not just sad because he's hungry), and his other conditions worsened, and it was a couple of weeks until his bowel and skin flareups settled themselves down and I got a bollocking from the vet . He probably wouldn't have been a fat lab, but I'd rather him be slightly overweight than him becoming worse with other problems, something which is agreed by my vets.
I spend significantly longer dealing with my dogs' diets than mine and DHs, because they don't have a choice and its up to us to make sure they get what they need, whereas if I want a burger for tea, that's my own decision.
He also ends up on steroids every so often, which if we're not quick off the mark reducing his food he'll gain weight, but will always return to the same weight afterwards.
Goes to prove the point I made upthread - its not always as simple as everyone thinks. I'm wondering if he may be one with the 'fat' gene mentioned by Medeci and the study.
In contrast, our recently departed girl was half his weight and could not keep weight on. She was on double his food, just to keep her from being too underweight. Slight reduction in food and she could lose half a kg in a day or two, which isn't good for an 18kg dog (who's ideal weight for breed and size should have been 21kg). She had an incredibly high metabolism that was equally difficult to manage, and I'm sure I had people judging me just as often when walking her when she was having a skinny week.