South Beach Diet recommended for adolescents: 'we know now that low-fat diets are just not effective in causing weight loss in obesity.'.

SALT LAKE CITY -- A South Beach Diet-type program may be the one to recommend to adolescents who want to lose weight, Sharon Weston, a registered dietician, said at the annual meeting of the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition.

Current evidence seems to suggest that weight management is best abetted by the approach that focuses on the glycemic index of food, particularly carbohydrates, rather than on the amount of fats, said Ms. Weston, a pediatric nutrition specialist at Children's Hospital Boston.

The South Beach Diet is one such program.

The glycemic index is a way of referring to the body's physiologic response to a particular food, specifically indicating how the food affects blood glucose levels, Ms. Weston said. Certain foods cause a greater rise in blood glucose and thus have a higher glycemic index. Low glycemic index foods include whole grain wheat, pasta, lentils, legumes, and skim milk. High glycemic index foods include white bread, white rice, Cheerios, and boiled potatoes.

"Once again, the dietary world has shifted and we know now that low-fat diets are just not effective in causing weight loss in obesity," she said. "And as a population, we are consuming more carbohydrates and growing as a result."

Adolescents who use this approach should probably skip the first 2-week phase of the South Beach Diet because it is designed for drastic weight loss and attempts to eliminate insulin resistance, Ms. Weston said. It does not allow for any dairy products or any carbohydrates, including fruits. Adolescents should start with the second phase of the diet, which also is aimed at weight loss but allows some carbohydrates.

"It promotes low glycemic index foods, as well as the inclusion of healthy fats, and also gradually includes some carbohydrates. So it is not really like an Atkins diet," she said.

In the 1999-2000 governmental National Health and Nutrition Examination Survey, 15% of children aged 6-19 years were found to be overweight, and more recent surveys have suggested that the proportion has now risen to one in four adolescents, Ms. Weston said.

But the cause does not appear to be more calories, more fat, or less activity. Surveys suggest that the amount of calories children and adolescents consume has not changed, and that the percentage of their diet that consists of fat has actually decreased since the early 1970s. Nor have researchers been able to show that less activity is leading to weight gain, because those who are least active often are persons who are overweight, and it follows that people who are heavy would be less active, Ms. Weston said.

Instead, researchers have begun to focus more on carbohydrates and other foods with a high glycemic index. For example, soft drink consumption has grown considerably since the 1970s, up 118% from 1970 to 1997, according to the Department of Agriculture, whereas milk consumption is down 23%.

"Our kids are actually consuming more carbohydrates than they were before, and this is partly due to a focus we had a decade ago on a low-fat diet," Ms. Weston said. "But it is also just related to what is out there for our kids to eat."

She noted two studies in particular that show that high glycemic index foods can contribute significantly to weight gain, probably mostly by leading to postprandial hyperinsulinemia, causing excess weight gain.

In one study, researchers took 12 obese adolescent males, and fed them three different breakfasts and lunches on three different occasions (Pediatrics 1999;103:e26). All the meals had the same number of calories, but on one occasion the meals had a low glycemic index, on one they had a medium glycemic index, and on one they had a high glycemic index.

For example, the low glycemic index breakfast consisted of an omelette with cheese, spinach, and tomato, plus apple slices and a grapefruit. The medium glycemic index diet consisted of steel-cut oats with milk and half-and-half, sweetened with fructose. The high glycemic index diet consisted of instant oatmeal with milk and half-and-half, sweetened with dextrose and saccharine.

The researchers followed what the subjects ate in the 5 hours after lunch.

They found that voluntary energy intake was 53% greater after the high glycemic index meals than after the medium glycemic index meals, and 81% greater than after the low glycemic index meals.

They also reported that insulin levels were higher after the high glycemic index meals, and glucagon levels were lower.

In the second study, the researchers took 16 obese adolescents, aged 13-21 years, and assigned them to diets for 6 months (Arch. Pediatr. Adolesc. Med. 2003;157:773-9). Half the subjects were assigned to a moderate glycemic index diet, emphasizing foods with a low to moderate glycemic index, with 45%-50% of energy coming from carbohydrates and 30%-35% from fat. Subjects had no restrictions on how much they could eat. The other half was assigned to a conventional, calorie-restricted diet, emphasizing low fat intake, with 50%-55% of energy coming from carbohydrates and 25%-30% coming from fat.

At 6 months after the diet ended, the researchers found that the subjects assigned to the moderate glycemic index diet had a mean reduction in their body mass index (-1.3 kg/[m.sup.2]), whereas those in the conventional diet group had a slight increase (0.7).

Fat mass fell in the moderate glycemic index group by a mean 3 kg, whereas it increased in the other group by a mean 2 kg.

Diaries kept by the subjects showed that the glycemic load consumed dropped in the moderate glycemic index group, whereas dietary fat intake dropped in the conventional diet group. Carbohydrate intake fell in the first group, but not in the second.

One particular strength of the South Beach Diet is that it does not restrict how much the dieter can eat; rather, it stresses low glycemic index carbohydrates, which tend to be foods high in fiber, and the right kinds of fats.

In fact, low glycemic index diets have been used by elite athletes and have been shown to actually improve performance, Ms. Weston said.

Although some of the nutritional claims made by the South Beach Diet book have been questioned, the diet is a safe one and could even be recommended for young children, according to Ms. Weston, who said she had no financial interest in the diet.

"It really is a healthy diet," she said.

BY TIMOTHY F. KIRN

Sacramento Bureau