Researchers found that adolescent girls who consumed more calcium weighed less and had less body fat than girls who consumed the same amount of calories from other sources. Previous studies have shown that a higher calcium intake can block body fat production in adults and preschool children, but this is one of the first studies to show that it might have the same effect in body-conscious preteen and teenage girls.
The study, presented this week at the Experimental Biology 2003 meeting in San Diego, involved an ethnically mixed group of 321 girls aged nine to 14.
Each of the girls recorded everything she ate and drank, along with any calcium or vitamin supplements, for three days. Researchers also measured the girls' physical activity, weight, and amount of body fat just above the hipbone -- a measure of abdominal fat.
Not surprisingly, they found that the girls who consumed more total calories and exercised less weighed more and had more body fat. But when researchers compared girls with similar calorie intake, physical activity level, and size, they found that the girls who consumed more calcium on average weighed less.
Researchers say most of the calcium in the girls' diet came from dairy sources, and it didn't take much to make a difference in their body fat and weight. The study found an increase of one serving of dairy, such as a cup of milk or thumb-sized piece of cheese containing about 300 mg of calcium, was associated with about half an inch less abdominal fat and nearly 2 pounds in lower weight.
But researcher Rachel Novotny, PhD, RD, says the findings shouldn't be interpreted as an excuse to add more cheese and other calcium-rich dairy products to your diet in the hopes of stimulating weight loss.
"It doesn't mean that just eating more dairy can help you lose weight," says Novotny, professor and chair of the department of human nutrition, food and animal sciences at the University of Hawaii at Manoa.
"Calories are still the bottom line," Novotny tells WebMD. "Does the composition of calories matter? Yes, having more of them come from calcium-rich foods is associated with lower weight and lower body fat."
In light of the current obesity epidemic, Novotny says these findings might provide a new way to help set up children for a healthy body weight later in life. Although reducing overall calorie intake and increasing physical activity are the most effective means to promote weight loss and reduce body fat in people of any age, she says a relatively small change in calcium intake might also lower body fat.
"What perhaps is important about this is that they are in a period of rapid growth, and because of that growth there is an opportunity to modify their body composition," says Novotny. "It sets the stage for future body composition."
The exact mechanism behind calcium's fat-fighting power is not fully understood, but previous research in animals suggests that high levels of calcium in the bloodstream slow down fat production and help shift the body's focus from accumulating fat to breaking it down.
Registered dietitian Althea Zanecosky says the old adage, "like mother, like daughter" usually doesn't apply to weight control methods, but this study shows that it can.
"As a dietitian, I'm really thrilled because here's a food we're trying to get them to eat for other reasons, and now here's this added bonus," says Zanecosky, who is also spokeswoman for the American Dietetic Association.
"Preventing bone disease coming years down road might not be an incentive for girls," Zanecosky tells WebMD. "But for those concerned about their weight, this is one more reason for them to drink their milk because it may also have this beneficial effect on their weight."
Zanecosky says it's not hard for parents to sneak extra doses of calcium-rich foods into their children's diet. As a mother of two adolescent daughters herself, she finds the following "tricks" especially effective in her own children:
- Grab a decaffeinated cappuccino with your teenager as an after-school snack.
- Send yogurt along with their lunch, as a snack, or have it for breakfast (no-fat or low-fat versions of many yogurts are also available for weight-conscious kids).
- Whip up fruit smoothies with skim milk or yogurt.
- Sprinkle reduced-fat grated cheeses on salads.
- Incorporate low-fat shredded cheese blends into dinner entrees, such as Mexican cheeses on fajitas and tacos, Italian cheeses on pasta, etc.
- If your child doesn't like plain milk, offer flavored milks such as chocolate or strawberry.
"This is one potentially trendy diet that's healthy. You can control fat and get strong bones at same time. I don't know of any other diets can make that claim," says Zanecosky. "You can't lose anything but pounds."