Rather, and usually in the context of weight control, the belief appears to be that expending the 32 megajoules will cause your kilogram of flesh to magically disappear.
Actually, that describes what happens in the context of the subject -- weight loss. You use 7700 kCal more than you take in, and about 1 kg of your body mass vanishes. Hardly bones, of course, but fat, proteins and what not.
It is easy to see this loss, and it is often visualized on weird Japanese TV shows about the subject -- people will have a full body MRI scan before/after a diet course and a doctor compare the two scans for the audience. Not very entertaining, but surely educational up to a point.
Also, this isn't magical. The stuff does actually leave your body as CO2, water and other waste products of metabolism of the said 1 kg. It does appear as a 'missing mass' on your weight scale.
Incidentally, losing weight as a result of using more energy than you take in is the reason all those survivors in pictures from Nazi German concentration camps look like fashion models before makeup, they had too little to eat, and too much hard labor, which used up all that body fat they had before Hitler.
And yes, I Godwined this discussion on purpose.