Fat and unfit police must improve their physical condition or "we haven't got a job for them", Britain's most senior officer has said.
Sir Bernard Hogan-Howe described the standard of an annual fitness test that officers must complete as "too low".
In a highly personal interview published in this week's Radio Times, the Metropolitan Police Commissioner also described how he misses frontline work, spoke of the influence of his late mother and revealed himself as a fan of opera.
Officers are assessed with a 15-metre shuttle run "bleep" test, which became compulsory from September.
Sir Bernard said he had passed his assessment "very well with no preparation".
He added: "It's taken too long to get the annual test, but it will start to have an increasing impact. For me, the standard is too low: I think it should be higher. It's relatively easy to pass."
Those who fail will be given time to lose weight and get fitter, he said.
"If they don't, then we haven't got a job for them. I think you've got a duty to your colleagues," Sir Bernard added.
"If they shout for help, they want fit people to come. They don't want somebody waddling down the road who's never going to arrive, and when they get there they're out of breath."
Figures published weeks before the tests became mandatory last year showed that hundreds of officers failed.
Sir Bernard rose through the ranks in South Yorkshire and Merseyside before landing the top job in 2011.
He admitted he misses the hands-on side of being an officer.
He said: "I joined as a policeman, I didn't intend to be commissioner. It's not exciting to chair meetings. There are some exciting outcomes... but it's never quite as joyful as finding somebody who has raped or done a burglary."
Discussing suggestions that a surveillance culture was present in the UK, he pointed to technology used by taxi services.
He said: "They will know where your phone is and where the taxi is and then put you together. But when people ring the police, we haven't got a clue where that phone is. You may have been stabbed and expect us to come and help."
He said that police cannot use location data in "real time", adding: " We have to make an emergency application, there's a process to go through."
Sir Bernard was raised by his single mother in Sheffield in the 1960s and rarely saw his father.
He challenged "tough" as a description of his early life, adding: "I think I had a good childhood. We weren't financially well off... we didn't get holidays and things like that, but I don't regard that as tough.
"But I think you understand the problems people have who are in those circumstances."
He said he does not know if his father followed his career. He said: "The last time I saw him I was around 18. I remember seeing him walking through a subway in Sheffield."
Asked what he would say to his father if he was still alive, he said: "As you get older, you want to hear a little more about someone's reasoning. I'd probably want to hear his side."
He said he enjoyed crime drama Prime Suspect.
"I liked the thoroughness of it," he said. "The people are passionate but they know it's complex, and they don't let go.
"People sometimes think detectives are big extroverts with loud ties. But the best detectives listen carefully, speak less, pay attention to detail and are patient."
Asked what "his" music was, he said: "O pera."
The interview comes ahead of the start of a The Met, a new BBC documentary about the UK's largest police force.