LOS ANGELES -- Public Enemy No. 1 in America's battle of the bulge isn't cupcakes, soda or double bacon cheeseburgers. It's the simple potato, according to Harvard University researchers.
Daily consumption of an extra serving of spuds -- french fried, sliced into crispy chips, mashed with butter and garlic, or simply boiled or baked -- was found to cause more weight gain than downing an additional 12-ounce can of a sugary drink or taking an extra helping of red or processed meats.
After tracking the diet and lifestyle choices of more than 120,000 health professionals from across the country for at least 12 years, the research team calculated that participants gained an average of 0.8 pound a year, close to the U.S. average, according to a report published in today's edition of the New England Journal of Medicine.
When the team from Harvard Medical School and the Harvard School of Public Health in Boston examined the potato's role in the modern diet, they found that people who ate an extra serving of french fries every day gained an average of 3.4 pounds over four years.
On top of that, those who munched on an extra serving of potato chips daily gained an average of 1.7 pounds every four years.
Overall, an extra serving of potatoes prepared in any nonchip form was found to contribute an average of 1.3 pounds to total weight over four years.
The typical American consumes 117 pounds of potatoes each year, including 41 pounds in the form of previously frozen french fries, according to data from the Agriculture Department.
The problem, said study co-author Dr. Walter Willett, chairman of the nutrition department at the Harvard School of Public Health, is that "we don't eat potatoes raw, so it's easier [for the body] to transform the starch to glucose."
Since spuds prompt a quick spike in blood sugar levels, they cause the pancreas to go into overdrive trying to bring levels back down to normal. As blood sugar spirals down, people usually experience hunger, which leads to snacking.
Over many years, this cycle can result in drastic weight gain and a fatigued pancreas, possibly contributing to the development of type II diabetes.
Making matters worse, potatoes pack a lot of calories into a relatively small package, said Dr. Dariush Mozaffarian, the study's lead author.