It gets burnt off as normal? Ozempic and co make the users feel less hungry so they eat less. A kilo of fat is about 7000 kcal, humans at rest use about 2000-2500 kcal a day, if there is a deficit of 500 kcal a day they lose two kilos of fat a month (on paper); total weight loss may be higher due to reduced fluid contents.

(disclaimer: armchair logic)

GLP-1 agonists seem to slightly increase resting heart rate, which might indicate a similar increase in basal metabolic rate.