Sugar's harmful effects, besides adding weight and rotting our teeth, include changing our metabolism drastically.
And the culprit is fructose-a main ingredient in table sugar, high fructose corn syrup, and fruit- that actually gets into our cells and alters metabolism.
The new findings may help to explain how excessive consumption of sweetened foods is contributing to growing rates of obesity, heart disease, high blood pressure, diabetes and more-in a way that has nothing to do with sugar's rich source of empty calories.
In fact, researchers have said that there may be deep evolutionary roots that explain sugar's power over our bodies.
Many millions of years ago our ape ancestors developed mutations that made it easy for them to get fat from eating fructose, according to new research.
At the time, the mutation was a good thing. It allowed our ancestors to survive seasonal periods of famine when the fruit trees went bare.
Today, the mutation makes a year-round, fructose-filled diet dangerous to our health, said Richard Johnson, chief of the division of Renal Diseases and Hypertension at the University of Colorado, Denver, and author of 'The Sugar Fix: The High-Fructose Fallout That Is Making You Fat and Sick.'
Both sugar and high-fructose corn syrup are equally bad because both contain about the same amount of fructose, he said.
"This mutation that occurred 15 million years ago could explain why we're fat today. It doesn't mean we all become obese. It doesn't mean everyone is going to get diabetes. It does mean that all of us are more susceptible to being fat than most other mammals," Discovery News quoted Johnson as saying.
In the new study, the researchers identify just such a mutation that affects how our bodies deal with uric acid, an ordinary byproduct of metabolism.
The mutation evolved 15 million years ago, during a period of starvation and is present on all of us.
Johnson said that the mutation led to an increase in how much uric acid our bodies produce after eating fructose, while also lengthening the amount of time that uric acid sticks around after a sweet treat.
The result is inflammation and an increased ability for cells to become fat. In other words, uric acid works within cells to amplify sugar's ability to cause obesity, he said.
Even on a calorie-restricted diet, animals that eat too much sugar develop insulin resistance, an early sign of diabetes, he said.
Other trials in people have shown that lowering uric acid levels lowered their blood pressure.
And like alcohol, the recent study found, sugar is also habit-forming and possibly addictive.
The study was published in the journal Transactions of the American Clinical and Climatological Association.