Eating like the English could save 4,000 lives a year in Scotland, Wales and Northern Ireland, a study claims.
People in England eat more fruit and vegetables and less salt and fat, reducing heart disease and some cancers, say Oxford University experts.
A tax on fatty and salty foods and subsidies on fruit and vegetables could help close the diet divide, they add.
The British Heart Foundation says the study shows inequalities in the nations that must be addressed by authorities.
Death rates for heart disease and cancer are higher in Scotland, Wales and Northern Ireland than in England, according to official figures.
Diet is known to be an important factor. Last year researchers estimated that more than 30,000 lives a year would be saved if everyone in the UK followed dietary guidelines on fat, salt, fibre, and fruit and vegetables.
Now, the same experts - from the Department of Public Health at the University of Oxford - have turned their attention to differences within the UK.
They looked at whether deaths from heart disease, stroke and 10 cancers linked with poor diet could be prevented in Scotland, Wales and Northern Ireland, if everyone switched to the typical English diet.
They say the diet in England is far from perfect - but should be achievable in other UK countries.
Over the three years studied there were nearly 22,000 excess deaths in total. Scotland had 15,719, Wales 3,723 and Northern Ireland 2,329.
Lead researcher Dr Peter Scarborough of the Health Promotion Research Group said: "The chief dietary factor that is driving this mortality gap is fruit and vegetables.
"Consumption of fruit and vegetables in Scotland is around 12% lower than in England, and consumption in Northern Ireland is about 20% lower than in England. Consumption levels in Wales are similar.
"Other important factors are salt and saturated fat consumption, which are lower in England than in Wales, Scotland or Northern Ireland."
The researchers believe one way to tackle the "mortality gap" is to bring in food taxes.
Denmark recently introduced a tax on foods high in saturated fat, while other countries are toying with the idea of taxing fizzy drinks or high-calorie foods.
Dr Scarborough told the BBC that while the study did not consider the effectiveness of policies and interventions, the area should be investigated.
He said: "Junk food taxes and subsidies of fruit and veg could be a very important tool in addressing health inequalities in the UK."
The researchers say they used the English diet as their model not because it is particularly healthy, but because it is regarded as an achievable goal.
Victoria Taylor, senior dietician at the British Heart Foundation, said: "This research isn't about bragging rights to the English or tit-for-tat arguments about how healthy our traditional dishes might be.
"This is a useful exercise in comparing influential differences in diet across the UK, namely calorie intake and fruit and veg consumption. However, saying the rest of the UK should follow England's lead to cut heart deaths isn't a foolproof solution; a quarter of English adults are obese and only 30% eat their five-a-day.
"The findings have thrown up some clear inequalities in the four nations and our governments must do everything they can to create environments that help people make healthy choices."
The research is published in the medical journal BMJ Open.