Fructose and Fat
From NBC5 July 25, 2008 with Dr. Mercola
Some Carbs Turn to Fat Fast in Your Body
According to new research, people on low-carb diets lose weight in part because they get less fructose, a type of sugar that can be made into body fat quickly.
The study shows that the type of carbs someone eats can be as important as the amount. Although fructose is naturally found in high levels in fruit, it is also added to many processed foods, especially in the form of high-fructose corn syrup.
For the study, six healthy people performed three different tests involving drinking various mixes of glucose and fructose. Researchers found that fructose turned into body fat much more quickly, and that having it for breakfast changed how the body handled fats at lunch.
NBC5 July 25, 2008
Journal of Nutrition June 2008, 138:1039-1046
Dr. Mercola's Comments:
It's great to find this study is bringing some attention to the dangers of fructose. So often it's mistakenly labeled as a "healthy" form of sugar, when in reality too much fructose will pack on the pounds faster than a buffet of French fries and Krispy Cremes.
If you need to lose weight, fructose is one type of sugar you'll want to avoid, particularly in the form of high-fructose corn syrup (HFCS). Actually, even if you don't need to lose weight, you should still avoid excess fructose if you want to stay healthy.
Eating + Fructose = Fat
Part of what makes HFCS such an unhealthy product is that it is metabolized to fat in your body far more rapidly than any other sugar.
"Our study shows for the first time the surprising speed with which humans make body fat from fructose," said Dr. Elizabeth Parks, associate professor of clinical nutrition at UT Southwestern Medical Center and lead author of the study in Science Daily.
"Once you start the process of fat synthesis from fructose, it's hard to slow it down," she said. " ... The bottom line of this study is that fructose very quickly gets made into fat in the body."
How does this happen?
Well, most fats are formed in your liver, and when sugar enters your liver, it decides whether to store it, burn it or turn it into fat. Fructose, however, bypasses this process and turns full speed ahead into fat.
"It's basically sneaking into the rock concert through the fence," Dr. Parks told Science Daily. "It's a less-controlled movement of fructose through these pathways that causes it to contribute to greater triglyceride [i.e. fat] synthesis."
Ironically, the very products that most people rely on to lose weight -- low-fat diet foods -- are often those that contain the most fructose! Even "natural" diet foods often contain fructose as a sweetener.
Fat is Not the Only Downside to Fructose
Aside from the weight gain, eating too much fructose is linked to increases in triglyceride levels. In one study, eating fructose raised triglyceride levels by 32 percent in men!
Triglycerides, the chemical form of fat found in foods and in your body, are not something you want in excess amounts. Intense research over the past 40 years has confirmed that elevated blood levels of triglycerides, known as hypertriglyceridemia, puts you at an increased risk of heart disease.
Meanwhile, one of the most thorough scientific analyses published to date on this topic found that fructose consumption leads to "decreased signaling to the central nervous system from 2 hormones (leptin and insulin)."
Leptin is responsible for controlling your appetite and fat storage, as well as telling your liver what to do with its stored glucose. When your body can no longer "hear" leptin's signals, weight gain, diabetes and a host of related conditions may occur.
"The long-term consumption of diets high in ... fructose is likely to lead to increased energy intake, weight gain, and obesity," the analysis concluded. "The potential for weight gain from increased fructose consumption may only represent one aspect of its metabolic consequences."
Are You Eating More Fructose Than You Realize?
Since the 1970s the consumption of HFCS in the United States has skyrocketed. The largest contributor is easily soda (The number one source of calories in America!), for which HFCS is the primary sweetener. But HFCS is not only in sugary drinks. It's in the vast majority of processed foods, even those you wouldn't think of as sweet, such as ketchup, soup, salad dressing, bread and crackers.
So even if you don't drink soda, if you eat processed foods you're likely consuming fructose -- and a lot of it.
Beware of HFCS Propaganda
To further complicate matters, the Corn Refiners Association recently launched a major advertising and PR campaign designed to rehabilitate HFCS' reputation. The group is spending $20 million to $30 million on the campaign, including running full-page ads in more than a dozen major newspapers, claiming that the product is no worse for you than sugar.
This, of course, is not true.
The Corn Growers Association wants you to believe that HFCS has the "same natural sweeteners as table sugar and honey." But don't fall for it. HFCS is highly processed and does not exist anywhere in nature.
The Safest Sweeteners Around?
Ideally I recommend that you avoid sugar, in all forms. This is especially important for people who are overweight or have diabetes, high cholesterol or high blood pressure.
But if you're looking for the occasional sweet treat, I recommend, in this order:
- The herb stevia (this is the best and safest sweetener, although illegal to use according to the FDA)
- Raw, organic honey
- Organic cane sugar
I recommend avoiding all other types of sugar, including fructose, HFCS, and any type of artificial sweeteners. The easiest way to do this is to stop drinking soda and stop eating processed foods.
Small amounts of whole fruit, which do contain fructose, are not a problem. If you're healthy, you can enjoy fruit in moderation according to your nutritional type.