Greta Thunberg addressing a climate rally in Turin Italy earlier this month. Photo / AP
Greta Thunberg's parents stopped flying and went vegan to "save" their daughter rather than the planet, as schoolgirl said her activism was "medicine" for her depression.
Her father, Svante Thunberg, said he and his wife were "not climate activists" but made radical green changes to their lives as they saw the impact it had on their daughter.
However, speaking on the BBC's Radio 4 Today Programme Monday, he said he initially thought it was a "bad idea" for his then 15-year-old daughter to take to the "front line" of the climate change battle and was concerned about the "hate" she now attracted.
His comments came as Greta, who turns 17 on Friday, guest edited the flagship news programme.
The teenage activist rose to global prominence after leading school strikes against climate change in her native Sweden in 2018 and has since addressed the UN on this issue as well as being nominated for this year's Nobel Peace Prize.
Speaking to Today presenter Mishal Husain, Mr Thunberg said he and his wife had been driven to support his daughter's activism because they saw it help lift her crippling depression, rather than because of any ecological conviction.
He said the teenager became acutely depressed after being diagnosed with Asperger's syndrome when she was 12, and stopped talking, eating or going to school for a year.
"She stopped eating for three months," added Mr Thunberg. "Which is the ultimate nightmare for any parent."
However, the Swede said the teenager then started to take an interest in climate change and that he initially tried to comfort her that human ingenuity would solve the crisis, before "running out of answers" as the pair researched the science.
Then his wife, who was an opera singer, stopped flying and cancelled singing contracts as she saw the impact the commitment made on their daughter.
Mr Thunberg said: "To be honest, she didn't do it to save the climate she did it to save her child because she saw how much it meant to her. And then when she did that she saw she grew from that and how much energy she got from that.
"So then we thought 'wow' and then I became vegan, and she got more and more energy from these things. I knew these were the right things to do because I understood the facts at that time.
"But I didn't do it to save the climate, I did it to save my child."
He added: "We are not climate activists, we never were"
As her condition improved, Greta then started to speak to people outside of her parents and teacher when she began taking interviews from journalists about her campaigning.
Mr Thunberg said he noticed a real turning point when his daughter, who only ate at home, accepted a vegan pad thai from another activist on a school strike.
As Greta became more involved in climate activism, Mr Thunberg said he warned his daughter she would have to do it 'herself' and be "incredibly well prepared" to handle the media scrutiny.
He said he was also concerned about the "hate" she was attracting due to her new celebrity.