So what causes this? I was at a clinic the other day, waiting on my girlfriends mom to get out, and was reading a big-muscle-guy magazine. I was looking at the performance enhancers/weight loss formulas/muscle building/etc in there (do any of these really work?), and I noticed ads like this: "On (WhateverBrand) people lost 25 pounds in 4 weeks, with placebo they lost 12.5" (but it was represented in bar-graph format) So the people on the stuff being tested lost weight, but also people on the placebo lost weight, just not as much. I'd (probably wrongly) assume both groups led similar lifestyles, and that as much as possible was kept constant between the experimental and control groups. So, why did the placebo group lose weight? In a broader aspect, why does the placebo group get any effect at all?