From Fat, Frustration, and the Expert Findings
Vicki Wadlow, a 53-year-old potter, stays busy with chores on the Virginia farm where she and her family live. She has led a vigorous life. She exercises regularly and spends much of the year pursuing outdoor activities. Around the time she turned 45, though, her slim figure gradually began to fill out. "All of a sudden, the pounds started to just creep on," Wadlow says. "It was very frustrating."
As her dress size rose from a six to an eight to a ten, five-foot-three Wadlow tried to lose weight by cutting fat out of her diet. She tried low-fat and even nonfat diets. "That was what all the experts said to do -- cut the fat," says Wadlow. By eliminating most of the fat from her meals, Wadlow lost some weight initially, but she immediately gained it back. And Wadlow thought the missing fat in her diet made her skin sallow. She felt unhealthy and was constantly battling hunger. Sometimes she became so hungry that she would get shaky.
Wadlow decided to try an eating plan that replaced highly refined carbohydrates such as white bread, sugary sweets, and rice cakes with less processed carbohydrates such as whole-grain breads, whole-wheat pasta, beans and lots of nonstarchy fruits and vegetables. The plan also included moderate amounts of protein and heart-healthy unsaturated fats. Much to Wadlow's surprise, she lost 15 pounds. "It didn't take that long, and it was painless," she says. Her craving for sweets disappeared, and she never experienced that shaky, hungry feeling that she'd felt while on other diets. She has kept the weight off for more than four years.
Like many Americans, Wadlow believed that a low-fat diet was the only way to lose weight. She accepted the recommendations of dietary experts to replace fat with carbohydrates. But just as scientists found that there are good and bad fats, they're now discovering there are good and bad carbohydrates. Fiberless, simple sugar carbohydrates -- including classic dieting staples such as low-fat cookies, pretzels, fat-free chips and rice cakes -- may not be much help in shedding pounds. In fact, eating these foods may sharpen your hunger, causing you to gain weight.
When your body digests food, it converts carbohydrates to a sugar called glucose. As blood levels of glucose rise, the pancreas gets the message to release the hormone insulin, which shepherds the sugar into cells. Once there, it's either burned on the spot for energy or converted to fat and other substances for future use.
Over the last two decades, scientists have begun to pay closer attention to glucose and insulin. Measuring how quickly the body absorbs glucose from a food, they've ranked our diets on what's called the glycemic index (GI). A glazed doughnut -- with its high content of the simple carbohydrates white flour and sugar -- is converted rapidly to glucose and scores high; a bowl of slow-cooked oatmeal, which requires more digestive work to be transformed into glucose, ranks much lower. Lower scores can mean less converted fat.
A diet rich in high-GI foods can be hard on your health because it pushes your body to extremes. Say you have a bagel with fat-free cream cheese, which scores higher than the doughnut. Your blood glucose goes through the ceiling, and your pancreas must hustle to meet the insulin demand. Day after day of this can tax your pancreas. Worse, the insulin it releases may become less efficient at corralling sugar.
That adds up to insulin resistance, and people with this condition -- some experts believe there are as many as 50 million Americans -- are at high risk of developing Type 2 diabetes. Some 16 million Americans have Type 2 diabetes, the fifth deadliest disease in the United States.
Diabetes isn't the only worry. High levels of glucose seem to damage blood vessels, and elevated amounts of insulin can raise blood pressure and blood levels of fats, while suppressing levels of "good" cholesterol. The result is increased heart-disease risk.
There's more: David Jenkins, a professor of medicine at the University of Toronto and one of the pioneers of GI research, has recently found links between high-GI diets and ovarian and endometrial cancer. Other studies have tied the diet to increased risk of breast and colon cancer.
Paying attention to the quality of your carbohydrates may be a smart long-term strategy, but the immediate reward is even more compelling: Eating a low-GI diet can suppress hunger.
A Swelling Survey
Pause for a moment and look at America: Two-thirds of us are overweight or obese, a figure that swells with each passing year. And yet, over the last 30 years, Americans have lowered the percentage of calories they get from fat while increasing their carbohydrates. The protein-diet pushers have jumped on these numbers to trumpet all-meat plans, but beef eating -- and its saturated-fat link to heart disease -- is the reason we turned to carbohydrates in the first place. No, the real key to our nation's weight-gain woes may be the glycemic index.People tend to become hungrier after a meal of high-GI foods than they do after low-GI foods, says David S. Ludwig, director of the obesity program at Children's Hospital in Boston and a leading glycemic index researcher. After a high-GI meal, insulin levels skyrocket and blood sugar plummets. Stress hormones such as adrenaline scour the blood for more glucose. All of this translates to ravenous hunger, shaky lightheadedness and a craving for high-GI foods that can rapidly raise blood sugar. Remember Vicki Wadlow's experience? "As a result of the typically low blood sugar that occurs several hours after a high-glycemic index meal," Ludwig says, "people may become hungry and then overeat, at least in comparison to what would have been eaten after a low-glycemic meal." This cycle of too much, then too little, blood glucose is particularly severe in people who are restricting their calories and trying to lose weight, Ludwig says.
Garry Bryan, 47, rode this roller coaster. "Everyone I know who has been on a diet has complained about being hungry," says Bryan, a Greenville, S.C., computer consultant whose weight ballooned from 160 to 220 several years ago due to undiagnosed thyroid disease. Doctors reined in his thyroid troubles, but the weight stayed on. Low-fat diets didn't work, and very high-protein diets left him desperately tired of eating meat. Only by adopting a low-GI diet, in which he ate more lean protein food such as tuna and beans, was he able to get down to 165 pounds. "By dropping some of the high-glycemic index stuff like sweets, I lost a lot of the hunger," Bryan says.
At least 16 studies back up Bryan's experience. In one particularly nice example, Ludwig recruited 12 obese adolescent boys and fed them a high-, medium- or low-GI meal -- all containing the same amount of calories. For their next meal, the boys could eat as much as they wanted. After the medium-GI meal, the boys ate 53 percent less than they did following their high-GI repast. After the low-GI meal, the boys ate 81 percent fewer calories.
Such results have the feel of weight-loss magic. Can you imagine being full after eating just a fraction of your usual calories? While science is still trying to sort out exactly what makes a food score low on the GI, Ludwig and others have a pretty good idea. These foods generally tend to be less processed and come in the company of fiber, protein or fat. Since these nutrients take longer to digest, you're likely to feel full longer, and your blood sugar won't peak and plummet. By the way, high-GI foods that accompany low-GI ones score somewhere in-between. Equal portions of vegetables (about 30 on the 100-point index) over white rice (70) average a 50 -- a healthy score.
And there's belief that low-GI diets offer lasting results. Researchers in a recent study at Harvard School of Public Health and Brigham and Women's Hospital in Boston found that subjects who ate a moderate-fat diet (35 percent of calories from fat -- primarily unsaturated fats like nuts, olive oil, avocado, and fatty fish such as salmon) lost as much weight as those who ate a low-fat diet (20 percent of calories from fat). However, those in the low-fat group gained back most of their weight quickly. The moderate-fat group maintained their weight loss for at least two years, according to study author Kathy McManus, director of the department of nutrition at Brigham and Women's.
You don't have to be a slave to GI to benefit -- an occasional baked potato or cookie is fine. But cutting back is smart. Vicki Wadlow says she strays once in a while. The "white things," as she calls high-GI foods, are for special events. During the holiday season, for example, she ate her share of Christmas cookies and gained a few pounds. But at the start of the year she returned to her low-GI ways and began to shed the weight she had gained. "It becomes not so much a diet, but a lifestyle change," Wadlow says. "This is a plan I'll stick with."