Wellness Resources

DIETING - WHAT WORKS - WHAT DOESN'T

Source: Reader's Digest

More than 40 million Americans are trying to lose weight at any given time, and these days most are thoroughly confused. After decades in which medical authorities praised the pursuit of thinness, the wisdom of dieting has come into question. Researchers have found evidence that yo-yo dieting - repeatedly losing and regaining weight - may be hazardous to health. It's still possible and beneficial for many people to lose weight and keep it off - but a major shift in thinking will be needed. For the typical American dieter, shedding pounds is more than a matter of willpower: it's a process that pits the dieter against his or her own physiology - and knowing that physiology is the key to any weight-loss regimen.

Studies have conclusively shown that an individual's body size is genetically coded. Diet and exercise play a role, but within limits set by heredity. Dr. Rudolph Leibel, an obesity researcher at Rockefeller University in New York City, describes how extremely obese people repeatedly enter the university's weight-loss clinic, lose dozens of pounds and return six months later after regaining precisely the amount that was lost. What's less widely known is that the body resists major weight gain too. In the 1960's and 70's, Dr. Erhan Allen Sims of the University of Vermont led a study of prison inmates who volunteered to add 20 percent to their body weight by forcing themselves to overeat. Once the study ended, almost all returned quickly to their original size.

How our bodies respond to dieting is another obstacle to permanent weight loss. Cutting calories to reduce rarely works long-term, experts now admit. Why? According to one hypothesis, humans evolved under the constant threat of famine; therefore, our bodies are programmed to respond to caloric restriction as if starvation were near. Most obesity researchers now believe that stringent dieting is actually a major trigger for binge eating. In an experiment by University of Minnesota Physiologist Ancel Keys, a group of young men were put on a balanced diet that provided about half their usual caloric intake - a regimen similar to today's commercial weight-loss programs. Released from the diet after six months, the men went on massive eating binges, consuming 5000 calories or more a day until they returned to their normal weight. "Eating after a period of starvation is as natural as taking a breath," says obesity specialist Susan Wooley of the University of Cincinnati.

New evidence suggests that for some people, losing substantial amounts of weight may carry a greater health risk than staying overweight. And although research shows that losing weight can cause blood cholesterol levels and blood pressure to drop, studies have not proved conclusively that shedding pounds extends life. In fact, recent research provides evidence to the contrary. In a Harvard University study of 11,703 men, those whose weight changed least between the times they were weighed (in 1962, 1966 and 1977) had the lowest death rates. Any significant weight change - up or down - markedly increased the risk of dying from cardiovascular disease. The most plausible explanation for the findings: people whose weight changed the most over time were more likely to have had cycles of yo-yo dieting in between, especially if they were overweight. When do the risks of being overweight make reducing worthwhile? To help answer this question, scientists have used a measure called the body-mass index, or BMI, which incorporates height and weight to assess a person's level of fatness. To find your BMI, multiply your weight by 704, divide by your height in inches and then divide by your height again

A BMI from 20 through 26 is desirable for most middle-aged adults. (Nonsmokers with a consistent BMI within this range have the lowest risk of disease and premature death.) In this category, weight gain can be avoided through moderate eating habits and exercise. A BMI from 27 through 29 - moderately overweight - carries a slightly increased risk of weight-related health problems, such as high blood pressure, high cholesterol, heart disease and adult-onset diabetes. People in this group have the hardest decision to make about reducing, given the potential health problems, most people in this category should avoid gaining additional pounds by adopting a low-fat diet and a routine of regular exercise. At a BMI of 30 or more - truly overweight - the risk of developing heart disease and other weight-related conditions rises sharply. Some obesity researchers argue that the benefits of losing weight outstrip the risks. Adult-onset diabetics in this category should also reduce, since blood-sugar control improves with weight loss.

Although stringent dieting has lost favor among health professionals, there are a couple of other methods of weight control that could benefit all groups: Try the "E" factor: Apart from the risk of an occasional injury, there's almost nothing bad to say about regular, moderate exercise. In a 1991 study, researchers at Stanford University divided 119 overweight men and 112 overweight women into three groups: those on a calorie-restricted, low-fat diet, those on the same diet plus a three-day-a-week program of aerobic exercise, and those who ate with no restrictions and did no exercise. After a year, even without exercise, the diet-only group had significantly reduced body fat compared with the control group. The diet-plus-exercise group lost even more body fat and significantly reduced the risk of cardiovascular disease. Other studies show that exercise can help people lose pounds-and inches-even if they don't change their regular diet.

The rationale for exercise, however, goes beyond becoming thinner. "A lot of the health benefits that people seek from weight loss can be achieved by exercise, even in the absence of weight loss," says Steven Blair, director of epidemiology at The Cooper Institute for Aerobics Research in Dallas. In 1970 institute researchers began keeping records on more than 13,000 then-healthy, middle-aged men and women to determine the effects of physical fitness on mortality. The results: physically fit men with high blood pressure, a high blood-sugar level, a high BMI or an unfavorable family history were less likely to die within a given period than unfit men with none of those risk factors. Overall, the fittest men had a death rate less than one-third that of the least fit; for women there was a more than fourfold difference. The rates for cardiovascular disease were even more dramatically affected by fitness. Couch potatoes need not seek out high-intensity aerobic exercise. Instead, Blair found that the chief benefits of exercise come when people go from a sedentary life-style to moderate activity (the daily equivalent of 30 to 60 minutes of brisk walking, in small spurts or all at once)-not when they move from moderate exercise to strenuous athletics. He recommends looking for exercise wherever you can find it: park at the far edge of the mall; get off a bus one stop early and walk; take stairs instead of the elevator.

Avoid "fat foods." Despite the old wisdom that a calorie is a calorie, recent studies suggest that calories from fat follow a straighter trajectory to the hips or belly than other calories. The body stores fat efficiently, but its ability to store carbohydrates is limited, so when people eat more carbohydrates than their bodies can absorb, the excess calories are burned more readily than excess calories from fat. That's why researchers have found that composition of the diet may be more important than number of calories in determining who gains or loses weight.

Researchers from the University of Illinois at Chicago switched 18 sedentary women from a diet deriving 37 percent of calories from fat-roughly the fat content of an average American's diet-to one that was 20-percent fat. Over 20 weeks, the women lost four to five pounds each, even though they increased their caloric intake.

One way to reduce fat consumption without feeling hungry is to fill up on fruits, vegetables and whole grains-all high in carbohydrates. Such a diet also seems to lower the risk of cancer and cardiovascular disease. Another fat-reducing strategy: Pennsylvania State University researchers calculated that by substituting skim milk for whole, switching to lower-fat meats, poultry and fish (e.g., skinless chicken, water-packed tuna) and using low-fat dressings and spreads, a woman could cut fat in her diet from 37 percent of calories to 24 percent. Making similar changes, a man could reduce dietary fat to 21 percent. Exercising and eating less fat are healthful changes that can help anyone, and may lead to weight loss. But for many, even faithful adherence to healthful habits won't make them thin. So the key - the attainable goal - becomes "reasonable weight," says obesity researcher Kelly Brownell of Yale University. "It's the weight that individuals making reasonable changes in their diet and exercise patterns can seek and maintain over time." Brownell suggests people start by losing a moderate amount - ten pound or so - and then try to maintain the lower weight before attempting to lose more.

Studies show that a modest approach to weight control is the only one worth trying for most people. If you change eating and exercise patterns gradually, and maintain the changes, you'll almost certainly look and feel better, have more energy and reduce your risk of cardiovascular disease - even if you don't lose much weight.