Kevin Chenais, who weighs 230 kilogrammes (500 pounds), arrived at London's Heathrow airport with his parents after Virgin Atlantic agreed to fly him back from New York.
Chenais, 22, had been in the United States since May 2012 for treatment for a hormone imbalance.
He had been set to return home on British Airways last month but the airline refused to accept him as a passenger, saying he was too heavy.
After arriving at Heathrow, a visibly exhausted Chenais described the ordeal to return home as "terrible, terrible, terrible".
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"The flight was really hard," he told AFP as he sat on his mobility scooter at the airport.
"I didn't stop crying for the whole flight."
Kevin, who was wearing a t-shirt emblazoned with the Stars and Stripes, praised Virgin for flying him out from New York's JFK airport and paying for the economy-class flights for him and his parents.
The family were met at Heathrow by French consular staff who arranged for him to travel to France on a Paris-bound Eurostar train later today.
The family will them make their way to the town of Ferney-Voltaire near the Swiss border.
Chenais, who requires frequent oxygen and regular care, expressed his anger at British Airways and the Queen Mary 2's owners Carnival for refusing to take him home.