"It looks like the Greek diet in many ways is the optimum diet," Harvard professor Walter Willett told Reuters at an international cancer congress in Oslo.
A Greek diet -- with plenty of fruit and vegetables all year round and olive oil instead of butter and lard -- was the best way to keep a range of cancers at bay, while the heavy diet of northern Europe was like a ticking bomb, Willett said.
"The traditional northern European diet comes pretty close to a worst-case diet, and we have imported that into the United States," Willett said. "That means large amounts of red meat and dairy fat and low amounts of fruit and vegetables."
Willett said he was not trying to take the pleasure out of life by promoting a smoke-free lifestyle that was low on red meat and alcohol but included plenty of exercise.
"Remember sex -- safe sex -- is a positive physical exercise," he said.
Willett said the cancer risk of being overweight was almost as bad as smoking, especially for cancer of the colon and kidney cancer as well as for post-menopausal breast cancer, adding that even the slightest hint of a beer-belly was a cause for concern.
"Big is dangerous," he said.
"Even the average belly adds to the risk and the fatter you are the higher the risk," he said, adding most people should aim to keep the weight they had in their early twenties.
But nature made weight control an uphill struggle as humans gain weight as they grow older even if they eat the same amount of food.
"The way to beat the system is to gradually increase physical exercise as you get older," he said. Studies showed that women in Sweden and Japan were the best weight-watchers around.
"It is humanly possible," he added.
By Erik Brynhildsbakken