Fructose, the sweet stuff found in fruit juice and soft drinks, can make you fat faster than almost any other kind of sugar. So why are we so hooked? Find out how fructose sabotages your weight loss efforts, from Richard J. Johnson, M.D., and Timothy Gower, authors of The Sugar Fix: The High-Fructose Fallout That Is Making You Fat and Sick.
Eating a high-fructose diet causes rapid weight gain. Eating too much of any form of sugar will make you fat. However, recent studies — performed in my laboratory, as well as by other scientists — have found that animals gain weight very quickly and develop other unhealthy symptoms when they eat too much fructose. Yet the same thing does not occur when animals are fed equal amounts of other sugars. In fact, eating fructose causes far more accumulation of abdominal fat — the most dangerous kind — than other forms of sugar, even if the same number of calories is consumed.
High-fructose foods do not satisfy your appetite. When you eat most types of sugar, your body responds by producing appetite hormones, which signal your brain that your body has consumed enough food to meet its energy needs. As this occurs, feelings of hunger subside. But unlike other sugars, fructose escapes the attention of appetite hormones. Because of this phenomenon, your brain never gets the message that your body has consumed a load of calories. As a result, the appetite center in your brain remains unsatisfied, so you continue eating. In one study, subjects felt hungrier after drinking beverages sweetened with fructose than they did after drinking beverages that contained another simple sugar, glucose. This may mean that fructose tricks you into eating more calories than your body needs. The result? You gain weight.
High-fructose foods may interfere with the signaling system that controls your appetite for all foods. We have discovered another way in which a high-fructose diet encourages overeating. Chronic consumption of sugary foods seems to promote biochemical changes that prevent the brain from receiving messages from appetite hormones — even when you are not consuming fructose. We have shown that this phenomenon leads to substantial weight gain in animals, and some studies suggest that it occurs in humans who consume too much fructose, too.
Fructose may sabotage weight-loss efforts. Your body does not metabolize fructose in the same way that it processes other sugars. When fructose enters a cell, enzymes break it down. Unfortunately, the actions of these enzymes raise blood pressure, increase blood levels of artery-clogging fat, and eventually cause obesity. As if that weren’t bad enough, eating fructose actually increases your body’s production of the very enzymes that cause all of these problems. Over time, your body may produce such a high concentration of these enzymes that eating foods that contain even a small amount of fructose will set in motion all of the powerful biological changes that we believe cause obesity, cardiovascular disease, diabetes, and other related conditions. This phenomenon may help explain why obese people struggle to lose weight and keep it off: Their bodies become ultra-responsive to fructose.
People who consume a lot of soft drinks and fruit juice — two major sources of fructose — tend to be overweight. Several large population studies have shown that people who drink beverages sweetened with fructose are more likely to be overweight than people who avoid soft drinks and juice. The “Supersize Me!” phenomenon is partly to blame. HFCS is cheaper than refined sugar, so fast-food restaurants and the beverage industry have been able to sell extra-large servings of soda and other fructose-rich beverages at low prices, which has led people to consume more calories. Soft drinks appear to pose another problem for anyone trying to control their weight and stay healthy. Consuming fructose rapidly — the way you might when gulping down a cola or bottle of fruit juice — causes levels of this sugar to soar in the blood. Studies suggest that could lead to greater weight gain.
ABOUT THE AUTHOR
Richard J. Johnson, M.D., has been a practicing physician and clinical research scientist for more than twenty-five years. He currently serves as Professor of Medicine and Chief of the Division of Renal Diseases and Hypertension at University of Colorado Health Sciences in Denver, Colorado. Timothy Gower is a freelance writer whose work has appeared in many publications, including Prevention, Esquire, Men’s Health, The New York Times, and the Los Angeles Times. He resides in Massachusetts. They are the authors of The Sugar Fix: The High-Fructose Fallout That Is Making You Fat and Sick (Copyright © 2009 by Richard J. Johnson, MD, with Timothy Gower).
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