The move comes after Boris Johnson revealed his own brush with Covid-19, which saw him require intensive care in April, convinced him of the need to tackle Britain's bulging waistlines.
He is preparing to announce a "Better Health" campaign on Monday, which will aim to reach 35 million people in a bid to help them lose weight and live healthier lives.
As part of the programme, the NHS weight loss services is to be expanded, while GPs will be encouraged to prescribe cycling - with patients in pilot areas given access to bikes - and ministers promising more segregated lanes and better cycle infrastructure would be put in place.
The Prime Minister is also expected to ban junk food adverts on television before the 9pm watershed and to outlaw them entirely online.
Meanwhile, promotions on snacks will be curbed and, according to a Daily Mail report, restaurant and takeaway chains will have to publish the number of calories in the meals they serve - while shops will have to do the same with any alcohol they sell.
The highly-interventionist approach marks a U-turn for Mr Johnson, who until recently has been a vocal opponent of "sin taxes" and perceived "nannying" by the state.
A Government spokeswoman said: "Covid-19 has given us all a wake-up call of the immediate and long-term risks of being overweight, and the Prime Minister is clear we must use this moment to get healthier, more active and eat better.
"We will be urging the public to use this moment to take stock of how they live their lives, and to take simple steps to lose weight, live healthier lives, and reduce pressure on the NHS."
The plan comes as evidence has begun to mount, linking excess weight with a higher risk of severe illness from coronavirus.
A Public Health England (PHE) study published on Saturday discovered that being classed as medically obese increased the risk of death from coronavirus by 40%,.
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.
Mr Johnson's campaign to encourage Britons to shed the pounds will see people supported by a 12-week plan to assist in developing healthier eating habits, get more active and lose weight, according to a Downing Street source.
NHS weight loss services will also be expanded so more people can get support to slim down.
On top of the diet and medical advice, the Prime Minister is expected to set out plans to drive the "biggest ever step change in cycling and walking", said a Number 10 source.
He will commit to identifying areas with poor health and low physical activity rates to take part in pilot schemes where GPs will be encouraged to prescribe cycling where appropriate.
Patients will be able to access bikes through participating surgeries while road safety improvement schemes, such as segregated cycle lanes, low traffic neighbourhoods and secure cycle parking, could be introduced to boost cycling up-take in such areas.
As part of the weight crackdown, the NHS will also accelerate the expansion of the NHS Diabetes Prevention Programme to support people most at risk, providing access to high-impact weight loss services for those that need it the most.
Labour accused Tory-led administrations of having been slow to act on obesity.
Shadow health secretary Jonathan Ashworth said: "Radical action on obesity is long overdue.
"Years of Tory cuts to public health budgets and the backsliding on a pre-watershed ban on junk food advertising have left us with some of the worst rates of childhood obesity anywhere in the world."