The only way to lose weight is to spend more energy than you consume.

Depending on what you mean by "consume", that statement is false.

What about a converse statement?

Over the long term, an obese person can consume less energy than she expends while maintaining her weight and body form.

I'm confident this statement would be untrue in practice. Sure, the person could undergo reverse-liposuction, or retain more and more and more water, or have a fusion reactor in her spleen, but the laws of thermodynamics restrict possible scenarios to implausible ones.