New research from PHE found that overweight and obese children are eating an extra 500 calories a day, while the average adult consumes an extra 200 – 300 calories daily.One in five children are now obese by the time they leave primary school and in some areas of the country nearly half of 11-year-olds weight too much. Around 58 per cent of women and 68 per cent of men are also overweight or obese.Public Health England calculated that if the 20 per cent target is met within five years, then over the next 25 years more than 35,000 premature deaths could be prevented and the NHS and social care sector could save around £9 billion. PHE said the remaining calories could be met through snacking but Tam Fry of the National Obesity Forum said 1600 calories was not enough.“This is only a smidgen above the near-starvation diet that the occupying Germans allowed Parisians to live off in the Second World War,” said Mr Fry. “Try selling that to the British in 2018.”Under the new rules, traditionally unhealthy foods, such as a bacon sandwich for breakfast, or a MacDonald’s Big Mac for lunch, would still be allowed which, experts warned, could raise cholesterol.Prof Naveed Sattar, Professor of Metabolic Medicine, at the University of Glasgow, said: “This is a step in the right direction. We need to cut calories in many foods and make it easier for people to eat more healthily without much conscious effort. “But not all calories are created equal as some are less dense than others so eating shredded wheat also bulks you up and some foods may help better than others in helping regulate appetite whereas a Big Mac may not fill you up Ofsted warned that children are not running around as much anymoreCredit: WestEnd61/REX However, although plans to cut calorie content in food was welcomed by experts, others warned that the 400-600-600 plan may not help people eat more healthily.Current recommendations suggest men should eat 2,500 calories a day, and women 2,000 but the new guidelines only add up to 1,600. Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. Britain needs to go on a diet, Public Health England has warned, as it set out new calorie guidelines to cut meal sizes, ruling out favourites like Fish and Chips or a Sunday Roast.Under its new ‘One You’ campaign, launched today, Britons are being encouraged to stick to 400 calories at breakfast, and 600 calories for both lunch and dinner.Critics branded the daily allowance too low for growing children and close to war rations, but public health experts warned that obesity had now become ‘the norm’ and said most people were eating hundreds of extra calories each day.The new restrictions would rule out traditional meals such as Fish and Chips and a Sunday Roast which are both around 800 calories, as well as many curry, pizza and pasta dishes.”Britain needs to go on a diet,” said Duncan Selbie, chief executive at PHE. “The simple truth is on average we need to eat less. Children and adults routinely eat too many calories and it’s why so many are overweight or obese.” “Also if some foods contain more adverse fats then cholesterol can go up.” Manufacturers were told they could reformulate products, reduce portion size or encourage customers to buy lower calorie options. The calorie reduction programme will include everyday items such as bread, cooking sauces, crisps, processed meat, rice, pasta, ready meals, sandwiches and pizza.Dr Alison Tedstone said the food groups chosen made up the ‘lion’s share’ of calories eaten by families on a daily basis.“A few healthy options on the end of a menu won’t help solve the nation’s obesity problem – we need the regular everyday products to change,” she said.“We have more obese children in than ever before. We have moved on from (obesity) affecting a small section of society. It’s the norm now.” A senior Ofsted official also blamed obesity in children on the overly risk averse environment of nurseries and pre-schools which prevented youngsters from ‘running around to the point of exhaustion.’Gill Jones, the watchdogs deputy director of early education warned there was a tension between physical activity and being safe.A separate report from Imperial College warned that a healthy diet will not combat high blood pressure unless people also restrict salt in their diet. The average adult in Britain consumes 8.5 g a day, but recommendations are 6g. PHE has also given the food industry six years to cut calories in family foods by 20 per cent and warned that those who failed to comply would be named and shamed and potentially face government sanction.