I don't know about "weight" but I've lost inches in less than a week.
I had a diet pill and a high fiber cereal for breakfast, and a diet pill and tuna for lunch. Then I had tuna and a salad for dinner...
for like three days...
and I lost two inches off my stomach, and an inch off my booty.
I peed a LOT though...so it was probably all water

But it was only so I could slim down for an on the air interview where I had to play strip trivia, and I didn't want to be sitting in the radio room wearing a bra, panties, and fat rolls.