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Thursday, December 31, 2009

This Just In: Extra Calories Make People Gain Weight!

Eating More Fructose Than Nature Intended Is Also Probably a Bad Idea

I recently read an article about a study that supposedly found that high-fructose corn syrup had a different effect on the body than did “regular sugar.” This made little sense, because high-fructose corn syrup is only slightly higher in fructose than table sugar is. In fact, the study said exactly nothing about any difference between table sugar and high-fructose corn syrup. On the other hand, it did say that drinking a lot of sugar water can make you gain weight really fast.

During digestion, table sugar is rapidly broken down to a 50:50 mixture of two simple sugars: glucose and fructose. High-fructose corn syrup is a 45:55 mixture of glucose and fructose. Not much difference. However, the study wasn’t a comparison of high-fructose corn syrup versus what an ordinary person would think of as “regular sugar,” it compared huge doses of pure fructose to huge doses of pure glucose—a major difference. In reality, the study showed three things. First, people can gain weight really fast if they drink a huge amount of watery syrup, which provides a lot of calories while doing very little to satisfy the appetite. Second, a calorie is a calorie. People gain weight just as effectively if they get extra calories from fructose or glucose. Third, fructose has different effects on the body’s metabolism than glucose has, but we already knew that. None of these results were surprising, so none of the findings of this study were actually newsworthy to the general public. The journalists who wrote about this story made it sound newsworthy by misinterpreting it.

Thanks to the magic of the Internet and the National Library of Medicine, I was able to find the actual article for myself. The subjects in the study first spent two weeks in a clinical research center, eating “an energy-balanced, high–complex carbohydrate (55%) diet.” Of course, 55% of calories from complex carbohydrates isn’t “high” in complex carbohydrates by my standards, but so what? After spending two weeks eating the controlled diet, the subjects were sent home for an eight-week outpatient study, in which they were allowed to eat whatever they wanted, as long as they drank enough of a sweetened beverage to give them 25% of their calorie requirements. Some of the subjects were given a beverage sweetened with pure fructose (not high-fructose corn syrup), the others were given a beverage sweetened with glucose.

As a result of guzzling all that sugar water, the people in both groups took in more calories than they needed. In fact, people in both groups took in roughly the same number of extra calories and gained roughly the same amount of extra weight as a result. That wasn’t surprising, although it was interesting that the extra fat tended to get deposited in different places, depending on which kind of sugar was consumed. Nor was it surprising that the fructose beverages caused spikes in the amount of fat (triglycerides) in the blood after meals. Scientists already knew that fructose does that. They’ve also known for decades that high levels of fat in the blood contribute to insulin resistance, which in fact occurred among the people who drank all that extra fructose.

Although the study does suggest that eating too much fructose can be bad for you, it didn’t say anything about whether high-fructose corn syrup was significantly worse than table sugar. In fact, a commentary  that accompanied the article said, “It is not known whether the adverse effects of sucrose and HFCS consumption are ‘diluted’ by their lower fructose content relative to pure fructose.” The commentary does make it clear that if you are eating too much fructose, you probably aren’t getting it from eating too much fruit. “One would have to eat vast quantities of fruits every day in order to ingest metabolically adverse amounts of dietary fructose.”

The take-home message for consumers wasn’t clear from the news accounts, but it’s very simple. It’s hard to overdose on fructose from eating fruit, but drinking syrup-water isn’t good for you.

2 comments:

  1. Talking about sugar...If you are a vegan, it is good to eat cereal. Isn’t there too much sugar in the cereal? On the Cereal box, it states that it is recommended by the American Heart Association. What does it means? How reliable are they?

    Lisbette

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  2. The term "vegan" means that a person avoids eating any food that comes from animals or using any other products that come from animals. The motivation is to avoid contributing to animal suffering. Obviously, a person who follows a vegan lifestyle would eat a completely plant-based diet. However, there are lots of "junk foods" that don't contain any animal products. Just because it's "vegan" doesn't mean it's healthy.

    In choosing a cereal, I look for one that is made of whole grains (for the fiber) and that doesn't have too much added sugar. I eat a lot of oatmeal, to which I add a few raisins and some cinnamon. Sometimes I cook an apple with the oatmeal. Some people (i.e., those with allergies or celiac disease) have to be careful about which grains they eat.

    Many years ago, Dr. Walter Kempner found that he could help his patients who had kidney, liver, and heart problems by teaching them to eat a diet that consisted of rice and fruit. If the patient lost too much weight on this diet, he'd encourage them to add some sugar.

    I'm not favorably impressed by the American Heart Association's recommendations. They are failing to tell people to reduce their fat intake enough to make them heart-attack proof. They could save many more lives by telling people to keep their total cholesterol below 150 mg/dL, which is easy if your fat intake is less than 10% of total calories. Nevertheless, the cereals they recommend are probably pretty good.

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