Fructose Turns to Fat Faster Than Any Other Sugar

Pretty much everyone is aware of the fact that high-fructose corn syrup is bad news. But not everyone really understands why.

The politically incorrect truth is that high-fructose corn syrup is only marginally worse than regular sugar, a fact that the corn growers association has repeatedly hammered home in their PR efforts to get you to think of high-fructose corn syrup as a relatively benign substance (it’s not). Once you understand what fructose does in the body, you’ll understand that whether it comes from HFCS or regular sugar, it’s still one of the worst things you can ingest. Here’s why:

Ordinary table sugar (technically called sucrose) is 50% glucose and 50% fructose. (High-fructose corn syrup is 45% glucose and 55% fructose, not an enormous difference.) But the “bad” part of either substance is the fructose part.

Fructose also turns to fat much more easily than other sugars, a fact demonstrated by recent research from the University of Texas Southwestern Medical Center. Researcher fed healthy people breakfast drinks containing three different “sugar combinations” followed by a carefully controlled lunch. They did this over several weeks. In one test, the breakfast drink contained 100% glucose; in another the drink was half glucose, half fructose (which is what you’d find in ordinary sugar). In the third condition, the subjects got a drink that was 25% glucose and 75% fructose.

The researchers were interested in two things, both of which should interest you. One, they wanted to measure how fast the sugars in the drink turned to fat in the liver. Two, they wanted to see how that morning sugar-meal influenced how people metabolized foods eaten later in the day (for example, lunch).

The findings were disturbing. For one thing, the researchers found that fructose got “made” into fat way more quickly than other sugars. And for the second thing, they found that when fructose was eaten with fat (for example in any junk food snack you can name) the fat was much more likely to be stored rather than burned.

“Our study shows for the first time the surprising speed with which humans make body fat from fructose”, said lead researcher Elizabeth Parks, PhD.

So what about fruit?

Good question. Some low-carb proponents point out that people with weight problems caused by insulin resistance may be sensitive to even the relatively small amount of fructose found in fruit, and therefore suggest limiting fruit in the diet, if not cutting it out completely.

But remember that the fructose in fruit is relatively small compared to the amount found in any sweetened processed food. Fruit also comes with fiber and nutrients. The breakfast drinks served in the study had as much as 65 grams of fructose. (An apple has about 11 and a cup of strawberries only 4.)

(On Diet Boot Camp we allow a small amount of fruit during the two week period after prep week. For most people this doesn’t present a problem.)

The damage done by fructose isn’t limited to weight gain. Recent research from the Journal of the American Society Nephrology shows that people who eat a diet high in fructose in the form of added sugar (of any kind) are at increased risk of developing high blood pressure.

The researchers found that people who consumed a diet of 74 grams or more per day of fructose (corresponding to 2.5 sugary soft drinks per day) had a 26%, 30%, and 77% higher risk for blood pressure levels of 135/85, 140/90, and 160/100 mmHg, respectively. (A normal blood pressure reading is below 120/80 mmHg.)

Fructose also causes insulin resistance, a key factor in both diabetes and metabolic syndrome, both of which increase the risk for heart disease.

So whether it comes from high fructose corn syrup, plain old sugar, or—I’m sorry to say—agave nectar (which can be as high as 90% fructose, dwarfing even the amount found in HFCS), fructose is bad news.

Limiting your intake of fructose to it’s original source- fruit—and eliminating the rest of it from your diet as much as possible may just be one of the best health decisions you can make.