Shane Lee Price, 47, of Mill Lane, Brigg, North Lincolnshire, admitted possession of cannabis and amphetamine when he appeared at Mansfield Magistrates Court on Thursday.
Police found two bags of amphetamine and two bags of cannabis in his car on November 4.
Simon Price, mitigating, said: “He was warned by his doctor that he was pre-diabetic and needed to lose weight.
“Somebody told him that taking amphetamine would help and he did so and lost five stones.
“Unfortunately he also began using cannabis to offset the adverse effects of the amphetamine.”
Price was fined £160 and ordered to pay £85 costs and a £30 victim surcharge.