I can imagine that out of billions of people, there probably are individuals whose bodies will starve before they use energy stored as fat.

But I think it's pretty unusual. Consider that most people who fail at dieting have had some degree of success in the past. e.g. a few years back they lost 20 pounds with Weight Watchers before falling off the wagon. (In EY's case, I believe he has posted that he did lose weight when he initially moved away from home. )

So it seems that for most people with weight problems, their bodies are working properly to the extent of burning fat for energy when confronted with an energy shortage.

Of course there are other problems which make it difficult to lose substantial weight and maintain it, but we need to be clear about what the problem is.