Okay but: when he stepped on the scale, he was weighing himself and the tapeworm. A tapeworm can't just magically eat your lunch and send the calories into another dimension.
There's got to be something else to it, like that your belly feels strange and you lose your appetite.
Suddenly losing a lot of weight points toward dehydration, for one thing.
Maybe if the guy was well muscled he needed a constant influx of protein, also. Breakdown of muscle which is mostly water doesn't translate to a lot of calories.
Not always. Plenty of people with tapeworms in them will present with few or no symptoms. If they feel anything at all, it'll probably be the usual inespecific gastrointestinal symptoms like abdominal pain, nausea and diarrhea.
Varies from person to person. Could take years before the thing is big enough to cause any real damage. I've seen cases where people had parasites inside them without noticing for what must have been decades without any treatment.
Doctors in endemic regions often won't even bother with tests, they'll treat you straight up. Good old albendazole, once a year. In certain places people routinely go to the doctor to ask them to prescribe the medicine whether they feel anything or not.
Tapeworms eating your food is definitely a very popular idea. Sometimes I see some exceedingly clever humans trying to use them as a poor man's semaglutide. They usually get zero results but sometimes they lose some serious weight alright, most of it water.
There's got to be something else to it, like that your belly feels strange and you lose your appetite.
Suddenly losing a lot of weight points toward dehydration, for one thing.
Maybe if the guy was well muscled he needed a constant influx of protein, also. Breakdown of muscle which is mostly water doesn't translate to a lot of calories.