Extinction Rebellion members are beginning a week-long hunger strike to put pressure on the government to act on climate change.
The group want the government to enact their three demands, which are to reduce greenhouse gas emissions to net zero by 2025, declare a climate emergency and form a citizens' assembly on the climate.
A total of 350 activists are taking part across 22 countries, including 83-year-old La Pethick in the UK and 16-year-old Christina Dithmar in Germany.
The group say those under the age of 18 can only take part in the hunger strike for a maximum of 24 hours.
The majority of UK hunger strikers are staging their protests outside UK political party headquarters.
Extinction Rebellion member and author Donnachadh McCarthy said he was "full of respect" for the participants of the hunger strike, despite not taking part himself.
"It's a cry of desperation," he told talkRADIO.
"It's desperation at the fact that our government haven't taken action over the last 40 years to tackle the exploding destruction of our nature, the damaging of our oceans and our soil. It's really a cry of desperation in the UK and across the world."
The hunger strike also marks the launch of the group's so-called 'Election Rebellion' in the UK, with a series of "disruptive actions" planned in the run up to the general election on December 12.
They are demanding that election candidates from all parties back their demands and ensure they become law.
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