Junk food adverts will be banned on TV and online before 9pm and shops will not be allowed to display sweets and chocolates at checkouts as part of a national crackdown on obesity.
Boris Johnson is also putting an end to “buy one, get one free” promotions on high-fat products as part of his new “Better Health” campaign.
The prime minister is encouraging people up and down the country to lose weight to save the NHS time and money after his own brush with coronavirus in April.
People who are clinically obese are 40% more likely to die of COVID-19, according to new Public Health England figures.
Mr Johnson’s time in intensive care has seen him U-turn on his approach to the country’s waistlines, after previous criticisms of so-called “sin taxes” and “nannying” by the government.
He said of the changes outlined on Monday: “Losing weight is hard but with some small changes we can all feel fitter and healthier.
“If we all do our bit, we can reduce our health risks and protect ourselves against coronavirus – as well as taking pressure off the NHS.”
The changes will also force large restaurants, cafes and takeaways with more than 250 employees to put calorie labels on their food.
There will be a further consultation on whether the same calorie counts should be applied to alcohol before the end of the year and if the ad ban should be extended further online, the Department of Health said.
As part of the programme, NHS weight loss services will also be expanded, while GPs will be encouraged to prescribe bike rides, with patients in pilot areas to be given access to bikes.
TV chef Jamie Oliver, who has campaigned on childhood obesity for 20 years, said the PM’s plans were a “huge step in the right direction”.
He said children from the country’s poorest communities were “most at risk”, adding that “having access to varied and healthier food plays a vital part in keeping us healthy and resilient”.
But he said the “devil will be in the detail” and issued a reminder about the government’s commitment to halving childhood obesity by 2030.
Tam Fry, chairman of the National Obesity Forum, said the government’s plans were “not enough to see an end to the national emergency that obesity is”.
He claimed the PM had “completely disregarded” former chief medical officer Professor Dame Sally Davies’s October 2019 report on childhood obesity, and that Mr Johnson’s “meagre list falls woefully short”.
Kate Nicholls, chief executive of UK Hospitality, which represents the industry, criticised the timing of enforcing extra calorie labelling costs on restaurants and pubs while they battle the challenges posed by COVID-19.
She said it “could not come at a worse time” and described “rafts of costs and regulatory burdens” as a “slap in the face”.
Two-thirds (63%) of UK adults are above a healthy weight, with 36% overweight and 28% obese, according to government data.
One in three children aged 10 to 11 are overweight or obese, and children living with obesity are five times more likely to become obese adults.
Michelle Mitchell, Cancer Research UK’s chief executive, said the new measures represent a “landmark day for the nation’s health”.
Obesity increases the chances of 13 types of cancer, as well as diabetes, heart disease and other serious illnesses, she added.