We’ve known for years that too much sugar can make us fat, but a team of researchers now claims that sugar may actually be killing us.Several years ago, Robert Lustig, a specialist on pediatric hormone disorders and childhood obesity at the University of California, San Francisco, School of Medicine gave a lecture called Sugar: The Bitter Truth, which was later posted on YouTube. As of yesterday, that 90-minute video detailing the biochemistry of sugar and human health was viewed by more than 2 million people. And this was before Lustig appeared on “60 Minutes” on Sunday, blaming sugar for obesity, diabetes, heart disease and other many illnesses plaguing modern society.MORE FROM MNN: 12 Steps to Kick Your Sugar HabitWhat makes sugar so evil? It all has to do with how sweeteners are broken down in the body. Both sugar and high fructose corn syrup (HFCS) are made up of both fructose and glucose (sugar is a 50-50 mixture while HFCS is 55 percent fructose.) And it is the fructose that is causing the problems.For example, if you were to eat 100 calories of glucose in the form of a potato or 100 calories of sugar (which is half glucose and half fructose), they will be metabolized very differently once they enter the body. Glucose is broken down by every cell in the body, whereas fructose is metabolized primarily by the liver. More fructose means more work for the liver, and when the liver gets overworked, it starts converting sugars to fat. So even though the same amount of calories were consumed, it is more likely that the calories from sugar would be converted to fat than those that came from the potato.MORE FROM MNN: Dr. Oz’s Tip for Sugar LoversAccording to the Lustig, the average American person consumes roughly 130 pounds of added sugars, in the form of both natural sugar and HFCS, every year. Health advocates have been screaming about the ill health-effects of HFCS for years, but according to Lustig, metabolically, there is no difference between the human-made sweetener and natural sugar.”They are basically equivalent. The problem is they’re both bad. They’re both equally toxic,” he says. In his “Bitter Truth” lecture, Lustig claims that these added sugars are more than just empty calories; they are poisons that are killing us each day.In his interview with CNN’s Dr. Sanjay Gupta on 60 Minutes, Lustig went so far as to say that sugar should be treated no differently than alcohol or tobacco. “Ultimately, this is a public health crisis … you have to do big things and you have to do them across the board,” Lustig told Gupta. “Tobacco and alcohol are perfect examples. I think sugar belongs in this exact same wastebasket.”Could Lustig be right? If he is, it would certainly explain the continued increase in adult obesity, childhood obesity, and diabetes over the past 30 years. It’s not just that we’re eating more calories, says Lustig, it’s that we’re eating more sugar. His argument also implies that sugar may play a role in the development of other diseases, namely heart disease, hypertension and even certain cancers.MORE FROM MNN: What’s Wrong with High Fructose Corn Syrup?