Imposing a tax on unhealthy foods could prevent more than 3,000 deaths a year in the UK, researchers said today.
A 17.5% price rise on fatty, sugary and salty foods could avert thousands of fatal heart attacks and strokes, according to the study.
The government has rejected calls to introduce such a tax but obesity experts said the findings showed the time was right to reconsider the option.
Researchers from the University of Oxford and Nottingham University devised three models of taxation to see which would be most effective at improving the public's diet.
The first model involved only taxing foods with high levels of saturated fats, such as whole butter, cheese, cakes, pastries and puddings.
But the researchers found that in this model people would simply switch to buying other unhealthy foods, such as those containing high levels of salt, which might even increase their risk of suffering a heart attack or stroke. It would also increase weekly household food expenditure by 3.2%.
The second model involved rating foods against an "unhealthiness score", with, for example, spinach scoring -12 and chocolate digestive biscuits scoring +29. All foods with a score greater than +8 would be taxed. This approach, it was estimated, would prevent 2,300 deaths and add 4% to weekly food bills.
The third - and most effective - model taxed a wider range of products, including those that might not rate so poorly on the unhealthiness score but would be seen as alternatives to the most unhealthy foods.
It would prevent up to 3,200 deaths from heart disease and stroke every year, equivalent to a drop of 1.7% across the UK. Food expenditure would go up by 4.6% - 67p a week, or around £2bn a year nationally.
One of the researchers, Mike Rayner, said the second model would be the most practical to implement as it was "easy to see which foods should be taxed or not".
He proposed using the higher tax revenues gained from unhealthy foods to subsidise cheaper healthier foods, such as fruit and vegetables.
Colin Waine, chairman of the National Obesity Forum, said a "fat tax" would help cut rates of coronary heart disease, stroke, obesity and diabetes.
"Some manufacturers are reducing saturated fat levels in their products, but not all. The 'fat tax' is something the government is going to have to consider if it is committed to tackling these conditions," he said.
"Food manufacturers should wake up to the fact they can reduce saturated fat levels without prejudicing pricing. Tesco reports that its healthier options range is one of its fastest growing product areas. So people are obviously interested in making healthier choices."
But the study's authors warned the introduction of an unhealthy food tax was likely to be strongly resisted by the food industry.
A spokesman for the Food and Drink Federation, which represents food manufacturers, described the study's proposals as "utter nonsense".
"Aside from the fact that the researchers think it is OK to tax perfectly nutritious foods, such as cheese, which are an important part of any healthy diet, such a move would be a regressive tax on the least well-off, who already spend more of their disposable income on food and drink," he said.
"In any case, the research doesn't prove whether taxing the foods that consumers love would lead to any changes in their buying habits. It would result only in lighter wallets, not smaller waists."
Nearly a quarter of the UK adult population is obese and the proportion of obese children rose by more than 40% between 1995 and 2004.
More than 216,000 people in the UK die from heart attacks and strokes each year, according to the British Heart Foundation.
The authors do acknowledge that people on low incomes, who are more likely to eat unhealthy foods, would end up being hardest hit by fat taxes. They added that more research was needed to understand the impact of such a tax on the poor.
Maura Gillespie, the head of policy and public affairs at the British Heart Foundation, said: "Further evidence is needed on the effect of targeted food taxes before we can support a 'fat tax'.
"Meanwhile, we call on the government and industry to help people make healthier food choices. We want the government to take all possible action to keep the price of healthy foods and drinks low."