Actually that's been absolutely disproved - at least in the sense you mean it. If you'd check that link I think it would show that the HIIT group did much better than the steady state cardio group despite doing less work in terms of calories. This result has been replicated many, many times since.

What you're failing to allow for is that the body is a complex system with varied capabilities and can choose to spend metabolic effort provoked by exercise on either eg replenishing fat stores or building muscle. Obviously if you want to lose fat you want the second! And which of this options it chooses depends on how much work your muscle cells did using the three energy cycles available to make new ATP for them to burn - which depends on the type of exercise you do, especially the intensity.

Oh - and you're also failing to allow for the fact that different sorts of exercise will lead to different **resting** metabolic rates.

The difference between steady state cardio and HIIT gets even stronger in older exercisers - after around 50, HGH production declines. Raising the HGH level signals the body to store less fat. Both HIIT and suitable weight programs raise HGH. People who have problems keeping a reasonable weight may have HGH to begin with - although, in the US especially, diet is a more common cause.

If you want a decent text that explains this in reasonably accessible terms then the "Kettlebell Bible" is pretty good. One of the authors was the Royal Marine Corp's senior PTI noncom and seems to have spent a lot of his time reading endocrinology papers - Full Metal Jacket it ain't. Just be prepared to learn a fair amount of muscle cell biology. There are kettlebell exercises in the book, but the guy really does spend more time on the Krebs and Coroli cycles and the implications of the Golgi tendon organ for stretching.

I've heard that "Body By Science" is an ok book as well, and not nearly as painfully technical.

Oh - and also on the calories are calories thing, the metabolic path for fructose is weird - it's processed like alcohol rather than other carbs and can even cause liver scarring in the same way. So, physiologically speaking, no.