Despite previous studies hinting that calcium may help people lose weight, it doesn't seem to help teenagers in that regard, a new paper suggests.
The last 10 years of research hinted that calcium would bind to fat, which would be excreted instead of absorbed, said co-author Dr Connie Weaver from Purdue University. We showed that didn't happen.
As reported in the November issue of the American Journal of Clinical Nutrition, Dr Weaver and her colleagues randomly assigned 43 overweight teenagers to consume 650 or 1,300 mg of calcium per day. The calcium came either from supplements or from dairy in foods.
The crossover study was set up as a summer research camp. For three weeks, half the participants were placed on a restricted diet of three meals and two snacks a day, plus 1,300 mg/day of calcium, and the other half followed the same diet but consumed the lower amount of calcium every day. Then, each teen switched and followed the alternative regimen for three weeks.
Total energy and macronutrient intakes were controlled and were the same for the two sessions for each subject, the authors reported.
In the end, they found no differences in body fat and weight between the two groups, suggesting calcium had little to no effect on weight loss among the teens.
They also tested the amount of calcium and fats the teens excreted and found no indication that calcium might help with weight loss by binding to fat in the intestines and preventing it from being absorbed.
The study's small number of participants and short duration are weaknesses, said Dr Michael Zemel, who studies nutrition and obesity at the University of Tennessee.
"There have been recent comprehensive reviews that show calcium has a significant effect on body weight and body fat," said Dr Zemel, who was not involved in the current study. But those tend to be in adults.
He suggested the findings might be different in teenagers because they have different dietary needs. "They're using their calcium for growth," he told Reuters Health. "They have different energy needs than adults."
Dr Weaver said - and Dr Zemel agrees - that adults and teens alike need to keep an eye on the scale, which tells the bitter truth.
"You need to either cut kilojoules or increase physical activity if you want to lose weight," Dr Zemel said.
(Reuters Health, October 2011)