Bordeaux, who have won seven successive games in all competitions, are eight points clear of second-placed Olympique Marseille who drew 0-0 at 10-man St Etienne.
Forward Bellion, usually a substitute but starting this time, opened the scoring against the run of play on 11 minutes. He raced into the box to strike with a low angled shot and doubled the advantage with a similar goal before halftime.
Mid-table Lorient had just missed a penalty through Franco Sosa when Argentine striker Fernando Cavenaghi made it 3-0 from a counter-attack on 51 minutes.
Playmaker Yoann Gourcuff added a stylish fourth before Kevin Gameiro struck late for Lorient.
"We struggled for the first 10 minutes but then started playing really well, showing we're a strong team," Bordeaux defender Mathieu Chalme told television channel Canal Plus.
"It's a pity we conceded a goal but you can't have everything."
Bordeaux, who reached the knockout stages of the Champions League as group winners, had not leaked any goals in their previous six outings.
Marseille looked set to pick up the points in St Etienne after the home side had Greek defender Efstathios Tavlaridis sent off for a challenge on Ivory Coast striker Bakari Kone on eight minutes.
Struggling St Etienne, who sacked coach Alain Perrin in midweek and replaced him with his assistant Christophe Galtier, fought hard and keeper Jeremie Janot pulled off a series of spectacular stops.
Third-placed Montpellier dropped 10 points off the pace after a 2-0 home defeat by Nancy.
The game was played behind closed doors because Montpellier received a belated punishment after their fans threw firecrackers on the pitch at Nice in August, forcing the match to be halted for 20 minutes.
The game between Boulogne and Sochaux was postponed because of a frozen pitch but all the other games went ahead.
