This situation was most acute in the Philippines and Panama, where 63% of respondents said they had cut back on what they ate.
Kenya was the next most affected, with 61% saying they were eating less, followed by Nigeria, at 58%.
Across all 26 countries, 43% of people said they had altered their diet.
This was most apparent in Panama, with 71% switching to cheaper foods, followed by Egypt, 67%, Kenya, 64%, and again, the Philippines, 63%.
Elsewhere, 27% of those questioned in Australia said they were now cutting back on what they eat due to higher prices, compared with 25% in the UK, and 10% in Germany.
Cost of food: Australia's drought crisis
The survey also showed that 70% of people across the world were "unhappy with what their national government is doing to keep food prices affordable".
Dissatisfaction at a perceived lack of government action to tackle food prices was most apparent in Egypt, where 88% of those questioned said they were unhappy with their leaders, followed by the Philippines, on 86%, and Lebanon, on 85%.
In the developed world, the French respondents were the most dissatisfied with their government, with 79% saying they were unhappy.
Respondents were equally unhappy at higher energy costs, which increased sharply in the first half of this year, but are now falling back. Some 60% of people across the 26 nations said they were being affected "a great deal", exactly the same percentage as for higher food costs.
The Philippines was again the worst-hit nation, with 96% saying they were being hit a great deal, followed by Egypt on 93%, Indonesia on 84%, Kenya on 83%, and Mexico on 81%.
Majorities in several developed countries also said they were being affected a great deal by higher energy costs - 61% in Italy, 59% in France, and 58% in the US.
Doug Miller, chairman of polling firm GlobeScan, which helped carry out the survey for the BBC, said the problem of higher food and energy bills was being overshadowed by the continuing crisis in the financial sector.
"While governments around the world are now preoccupied with the financial crisis, it is clear that many of their citizens feel they aren't doing enough to relieve the burden of high food prices, which is falling on those who can least afford it," he said.
The Philippines has been particularly affected by higher food prices this year, as with its rapidly growing population and shortage of suitable land for crops, it is the world's largest importer of rice.
Rice prices soared to record highs in the first half of 2008 due to a series of poor harvests that saw major exporters such as Vietnam and India put limits on exports to ensure sufficient supplies for their own populations.
The BBC's economics correspondent, Andrew Walker, said that there were reasons to suppose the food crisis may have eased somewhat.
But for many people it was still the case that food was painfully, even dangerously, expensive, said our correspondent.
The survey spoke to 27,319 adults in the following countries - Australia, Brazil, Canada, China, Costa Rica, Egypt, France, Germany, India, Indonesia, Italy, Kenya, Lebanon, Mexico, Nigeria, Pakistan, Panama, Philippines, Poland, Russia, South Korea, Spain, Turkey, UAE, US, and the UK.
The Programme on International Policy Attitudes also worked on the study.
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