Shaun Rossington, 21, was found dead on Thursday morning on grassland near the Waitrose store on Searby Road in Lincoln, having sustained head injuries.
Lincolnshire Police said two men, aged 20 and 25, three 16-year-old males, a 16-year-old girl and a 13-year-old girl were arrested on Saturday.
Police said all seven were local and were arrested "in and around Lincoln".
Detective Superintendent Mark Hosty said: "Anyone who knows Shaun and can offer any information which may assist us is asked to contact us in confidence.
"We are currently trying to trace his movements prior to his death and have spoken to a number of people who have given us information.
"Shaun is a big lad and would be noticeable by his height and stature alone."
Mr Rossington's parents, Sharon and Kevin, said: "He only had friends, no enemies.
"He went to his gym regularly and was very fit and healthy."