While urinary ketone excretion means that body fat is being excreted causing fat loss, the effect is minimal: Based on recent studies, the number of calories lost in the urine as ketones is not significant (100 kcal at most).
Hi Lola, firstly, most likely you drink more water while exercising and ketostix are very inaccurate, especially when you stay properly hydrated, urinaryketone levels are diluted.