The two women, aged 21 and 26, who are studying in the southern island of Jeju, bought 3,000 diet pills and 500 detox pills off a Chinese website, and according to police smuggled them illegally into the country to sell.
The pair paid KRW20,000 (US$18.86) for each bottle of 30 pills and sold them for three times the value to some 80 customers.
According to police, the pills were analysed at the country's National Forensic Service where, as well as a "100 percent positive match with human flesh", they were found to contain the banned substances sibutramine and phenolphthalein.
Phenolphthalein is a banned import and sibutramine, which is known to cause cardiovascular disease, has been banned in the country since 2010.
Jeju police are now expected to widen their investigation to net others they believe are involved with similar offences.