Dimas was born in 1971 in Himara, southern Albania (Northern Epirus), to ethnic Greek parents.
In the 69th European Weightlifting Championship (held in Aalborg, Denmark May 1990), Dimas ranked 4th in Europe and Albania ranked 3rd (after 1st placed USSR and 2nd placed Bulgaria), and in the European Cup for nations (in Antalya, Turkey, December 1990) Dimas, Leonidas Sabanis and Fatmir Bushi helped Albania rank 2nd in Europe (after 1st placed Bulgaria).
During his stay in Aalborg he came in contact with representatives of the Greek national team: Giannis Sgouros and Hristos Iakovou and he expressed great enthusiasm for a Future cooperation. However, the political situation in the People's Republic of Albania prohibited him from leaving the country. Dimas managed to cross the Greek-Albanian border at February 7, 1991, after a several hour exhaustive trip. He then stayed in Athens. He acquired Greek citizenship in 1992, and first competed under the Greek flag in the 1992 Summer Olympics, winning the gold medal in the 82.5 kg class.
With the 1993 and 1995 World titles under his belt, Dimas was the favorite to win Olympic Gold in the 83 kg class at the 1996 Summer Olympics, where he was the flag bearer of the Greek Olympic team. He won the event with two new World Records.
Dimas is married to Anastasia Sdougkou, a former Greek National Television (ERT) Sports reporter. Together they have four children, Eleni (b. 1995), Victor (b. 1998), Maria (b. 2000), and Nickolas (b. 2009). When he was in his youth, he idolized the former Soviet (Armenian) Weight Lifter of his senior category, Yurik Vardanian, whose son, Norik Vardanian idolized him when he (Norik) was a child.
At the 2000 Summer Olympics, he won yet another gold medal, this time in the 85 kg class. This made him one of just three weightlifters at that time to have won three Olympic gold medals, the others being Naim Süleymanoğlu (Turkey, but born in Bulgaria) and Kakhi Kakhiashvili (Greece, but born in Georgia). Halil Mutlu (like Süleymanoğlu, a Bulgaria-born Turk) would become the fourth in 2004.
At the 2004 Summer Olympics in Athens, Greece, Dimas was again chosen as Greek flag bearer for both the opening and closing ceremonies. Dimas was recovering from knee surgery and a hurt wrist and was not expected to compete in these Olympics, but he came away with a bronze medal in the 85 kg class, becoming only the fourth Weight Lifter in history to win a medal at four different Olympic Games, the third to win those four medals successively, and the only one whose four medals include 3 golds, thus cementing his status as a national hero in Greece and as an international weightlifting legend.
In June 2008, Dimas became vice-president, and in October 2008 President of the Hellenic Weightlifting Federation.
In 2012 Dimas entered politics as a member of PASOK. He was soon polemical with Greece's policies with Northern Epirus, claiming that the Greek government has "forgotten" it.
In February 17, 2014 Dimas participated in the ceremony of 100th anniversary of the declaration of Autonomy of the Republic of Northern Epirus.