Enhanced Athlete Europe Ltd packed and dispatched 2,4-dinitrophenol (https://www.aasraw.com/products/dnp/) in tablet form to customers around the world, Carlisle Crown Court was told.
It has been fined £100,000 after being convicted of placing an unsafe food product on the market.
Former director Sean Corrigan was handed a nine-month jail term suspended for 12 months.
The 25-year-old of Pottersway, Gateshead, was also ordered to complete 180 hours unpaid work and disqualified from acting as a company director for two years.
The trial follows a raid on an industrial unit in Wigton, Cumbria, in September 2017 during which mixing and pill-packing machines were found, along with tablets and several kilos of yellow DNP powder.Also present was Corrigan - at that time the sole director - whose hands were noted to be "stained yellow".
Prosecutor Joseph Hart told jurors: "DNP, whilst it can cause rapid weight-loss if consumed, it's toxic to humans, causing serious harmful side effects and, in fact, fatalities."
Corrigan, who was described as "very remorseful" for his role, "basically ran the company" but was not a major shareholder, the court was told.
Sentencing him, Judge James Adkin said: "I am sure that you knew there were dangers to this drug.
"There was a high risk of an adverse effect on individuals by selling what was, in essence, a poison."