New year, new diet studies

Two or three fast-food meals among the typical 21 per week don’t sound like much but, over time, they add up.

After 15 years, healthy, young adults who ate fast-food meals two or more times a week gained approximately 10 more pounds and had twice the increase in insulin resistance compared with people who ate fast food less than once per week, researchers have found. (Insulin resistance is a condition that can precede diabetes and heart disease.)

The study appeared in the Jan. 1 issue of the Lancet. And last week health experts had much more to say about body weight and dieting. One study found that several popular diets seem to work, but many people have trouble sticking to them. Another study showed that children begin to experience small declines in their quality of life as soon as their weight exceeds average -- a decline that continues the more weight they gain.

The Lancet study is the latest to indict fast food as a significant factor in the high rates of obesity in the United States. The study followed more than 3,000 men and women ages 18 to 30 and recorded their visits to fast-food restaurants, which were defined as places such as McDonald’s, Burger King, Wendy’s, Arby’s, Pizza Hut and Kentucky Fried Chicken. The subjects completed questionnaires about their general diet, exercise habits, tobacco and alcohol use and television viewing habits.

Weight was periodically recorded and blood samples were taken to measure insulin and glucose. Insulin resistance is a condition in which the body does not respond normally to the insulin it produces. The condition often accompanies obesity and it can progress to diabetes.

The study found that independent of what else the subjects ate or how much they exercised, eating fast food regularly made a big difference in health. Those who ate fast food frequently -- defined as twice or more per week -- gained about 36 pounds over 15 years compared with 26 pounds in the group that mostly avoided fast food.

“Fast-food restaurants are probably one of the last places I would go if I was trying to reduce my risk of chronic diseases or was trying to lose weight,” said Mark Pereira, an assistant professor of epidemiology and community health at the University of Minnesota in Minneapolis and the study’s lead investigator. “They do have some healthy offerings, but they are few and far between.”

Researchers aren’t sure why fast food seems so bad for health, but possible explanations abound. Among them, that the meals are packed with calories, are deficient in fiber and other nutrients, and are high in trans fat, saturated fat, sugar and starch; that people overeat fast food or eat the food too quickly; and that the large soft drinks that often accompany the meals cause health problems.

“The value meals, which are heavily marketed, pack an unusual number of calories -- 50% to 100% of a person’s daily energy needs,” such as 1,000 or more calories per meal, Pereira said. A previous study in children showed that kids who consume a fast-food meal don’t compensate for the extra calories by eating less the remainder of the day. And, he noted, studies on soft-drink consumption show that the more calories a person consumes from liquids, the more likely he or she is to overeat throughout the day.

In recent years, fast-food chains have begun to offer more low-calorie, low-fat foods and some now provide nutrition information. But, Pereira said, it’s not clear how much of a difference those actions make.

“What is disturbing to me is that there are some examples where [fast-food restaurants] have offered healthy choices that were heavily advertised, but they just didn’t last,” he said. “People are going there for value, convenience or taste. They are not going there for the healthier options.”

But other experts point out that fast food isn’t solely to blame for America’s obesity epidemic. While the study provides a valuable perspective about eating fast food as a way of life, health problems linked to diet are caused by numerous factors, said Alice Lichtenstein, a professor of nutrition science at the Friedman School of Nutrition at Tufts University. The people who eat fast food regularly are also more likely to have other poor health habits, she noted.

“Eating fast food is one marker of a lifestyle,” she said. “A more holistic approach needs to be taken if we want to modify behavior.”

While some people will suffer negative health effects from fast food, other people will not -- depending on what they choose to eat and how much they eat, Lichtenstein said.

The much-maligned fast-food industry concurs. Cathy Kapica, global director of nutrition for McDonald’s, said the restaurant chain offered an array of food choices and portion sizes and provides nutrition information on its tray liners.

“It is not where you eat, but the food choices you make, and especially how much you eat,” Kapica said in a statement released by McDonald’s.

The study found that men eat fast food more often than women and African Americans more than whites. White women consumed fast-food meals the least often, but even that group ate fast food an average of 1.3 times a week.

* In other dieting research, scientists from Tufts-New England Medical Center in Boston assessed four popular diets -- Weight Watchers, Atkins, Zone and Ornish -- to see how they worked and how well people adhered to them. The study included 160 overweight adults who were assigned to one of the four diets. The volunteers were asked to adhere strictly to the diet for two months and then to select their own level of adherence for the remaining months.

All four diets resulted in modest weight loss for at least some of the participants after one year. In each group, about 25% of the initial participants had lost more than 5% of their body weight at the end of a year. However, none of the diets could boast of good adherence rates; in other words, many people went off the diets. Discontinuation rates were highest in the Atkins and Ornish diets, suggesting that individuals found those diets too extreme, the authors said.

While the participants of the study were not able to choose which diet to go on, people are likely to do best when they can select the diet that’s right for them, said Dr. Robert H. Eckel, of the University of Colorado at Denver, in an editorial accompanying the study. The study was published last week in the Journal of the American Medical Assn.

* As for overweight children, a new study suggests that as soon as a child is above average weight, quality-of-life measures, including the child’s physical and social functioning, begin to decline. Very obese children had the lowest quality-of-life scores.

The authors, from the Royal Children’s Hospital and Murdoch Childrens Research Institute in Melbourne, Australia, noted that the very gradual decline in a child’s quality of life may lead parents to ignore the effect of weight gain until it becomes a significant problem.

The study was published in the Journal of the American Medical Assn.

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How four diets fared

A comparison of four popular diets showed there was no substantial difference regarding the amount of weight lost. For all of the diets, adherence rates were low.

Average weight loss after one year

Ornish (restricts fat)... 7.3 lbs.

Zone (moderates insulin levels with a balanced combination of carbohydrates, protein and fat) ... 7.1 lbs.

Weight Watchers (restricts portion sizes and calories) ... 6.6 lbs.

Atkins (minimizes carbohydrate intake without fat restriction) ... 4.6 lbs.

Percentage of people who had dropped out of the study by one year

Ornish ... 50%

Atkins ... 48%

Zone ... 35%

Weight Watchers ... 35%

Source: Journal of the American Medical Assn.