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Vol. LVII, No. 8
April 22, 2005

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STEP Session Offers Tough Diet Medicine

On the front page...

For people concerned about carrying too much weight, nothing beats a simple maxim: eat less and move more. The diets that work — even as the scientific jury remains out on a number of variables — are clearly those that include robust servings of fruits, vegetables and whole grains. Perhaps the single best take-to-the-table message from a Feb. 8 STEP forum on diet and weight control came from Dr. Gary Foster, who said "a little weight loss goes a long way."


Dr. Susan Yanovski, director of the Obesity and Eating Disorders Program and co-director, Office of Obesity Research, NIDDK, reported that the average weight of Americans across all age groups and both genders has increased steadily for more than two decades. The nation, she said, "faces an epidemic of obesity.

These days, even our pets are overweight."

Participants in the recent STEP session on diet included (from l) Dr. Robert Eckel, Dr. Barbara Rolls, Dr. Gary Foster, Dr. Susan Yanovski and Dr. David Ludwig.  

Why the persistent weight gain? The answer is "energy balance," or the amount of energy we take in through food vs. the energy we expend through physical activity. Yanovski observed that carbohydrate consumption, in particular, has been on the rise since the 1970s. While cautionary messages about fat in that same time frame have led to a slight decrease in percentages of calories from fat, Yanovski noted that "we're still eating more total calories than ever before. And carbohydrates represent the greater percentage of those calories."

According to Dr. Robert Eckel, professor of medicine, physiology and biophysics at the University of Colorado Health Sciences Center, there is a dearth of research on weight reduction. Most of our knowledge about the chemistry of adipose tissue (or fat content) in humans is based on studies of the female reproductive system. But the bottom line remains: if you're overweight, your body will try to keep you that way. It takes an ongoing program of behavioral change to permanently succeed in any weight loss effort.

Eckel gives tough news — if you’re overweight, your body will try to keep you that way  

The third speaker, Dr. Gary Foster, clinical director of the Weight and Eating Disorders Program at the University of Pennsylvania School of Medicine, addressed low-carbohydrate diets. A problem with low-carb's popularity, he said, is a lack of firm scientific evidence. "The public's desire for workable diets, low-carb or otherwise," he said, "far outpaces scientific data." There are only 5 studies of low-carb diets in the scientific literature at this point, and all essentially agree that there is little difference between low-carbohydrate diets and low-calorie diets in terms of weight loss at one year. Surprisingly, however, low-carb diets appear to have more favorable effects on heart disease risk factors such as HDL cholesterol and triglycerides.

"You lose weight when you eat less," Foster said. "There's no magic formula." But this points to a larger problem in the field of obesity research, he believes. "We're not developing and testing techniques or programs that improve adherence to dietary regimens. We all understand the difference between a banana and a banana split. Most people know what to eat — but fewer people know how to do it."

Dr. David Ludwig, director of the Obesity Program at Children's Hospital in Boston, offered a proposition: the low-glycemic diet is "a perfect compromise between low-fat and low-carbohydrate" diets.

The "glycemic index" is a measure of carbohydrate digestion rate that ranks carbs based on their effect on glucose levels in the blood. A glycemic index score of 70 or above is high — the territory of cake, cookies, doughnuts and white bread.

Washington Post reporter Sally Squires founded the newspaper’s Lean Plate Club.  

A glazed doughnut, for example, tops out around 85 on the glycemic index. A serving of lentils, on the other hand, garners a score of 29. (And a serving of broccoli barely registers at all.) The glycemic index reflects the fact that some carbohydrates break down quickly in the digestive tract and are reduced to their fundamental component — sugar — which, in turn, is quickly absorbed into the bloodstream, generating a higher glycemic index score.

On the other hand, carbohydrates that break down slowly, such as whole grain breads and cereals, beans, leafy greens or cruciferous vegetables, generate slower glucose release into the blood stream and lower glycemic index readings (50 or less). Eating "lower on the glycemic index," Ludwig said, supports weight loss over the long term, leads to a greater feeling of satisfaction after eating and a decrease in total food consumption. And, as if that were not enough, research suggests that low glycemic index diets may reduce risk for both type 2 diabetes and cardiovascular disease.

Dr. Barbara Rolls of the department of nutritional sciences at Pennsylvania State University, proposed using the energy or calorie density of food to guide choices for weight management. Lowering the energy density of our diets by eating more foods rich in water and fiber (such as fruits, vegetables, whole grains, and low-fat meat, fish and dairy) will enhance satiety and lead to weight loss and better health.

"High-energy-dense" foods are high in fat or low in moisture (such as crackers, cookies and potato chips) and should be eaten in moderation.

  NIDDK’s Yanovski noted that “we’re still eating more total calories than ever before.”

Negative messages — cautions, warnings and limit-setting — don't work very well in helping people adhere to diets, Rolls noted. Positive messages, in which dieters are told to enjoy eating as much as they want within the framework of their diet plan, are more successful.

The session's final speaker was Washington Post reporter Sally Squires, founder of the newspaper's Lean Plate Club. The "LPC" is about eating wisely and with pleasure while staying balanced amid the plethora of confusing scientific reports, trendy diets, diet gurus and best-selling diet books.

With a success that underscores the intense interest Americans have in dieting, weight loss and improved health, the LPC has flourished since its launch in July 2001. In fact, its email newsletter now enjoys nearly 180,000 subscribers, one of the largest online subscription bases and among the highest interactivity rates on the Post web site.

The LPC has been syndicated in other major newspaper markets, including Los Angeles, Dallas and Denver. This success, Squires said, is a vivid example of how media supports science and the medical community in getting the word out about the wide-ranging benefits of diet, exercise and healthy life styles.

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