Effects of long-term calcium intake on body weight, body fat and bone in growing rats

Increased calcium intake may reduce body weight and fat in non-growing individuals. This study explored the long-term effects of high versus low calcium intake on body weight, body fat, BMC, BMD and bone size in growing male and female rats. Ninety male and 90 female Sprague-Dawley rats were randomly assigned either to a high calcium (1%) or low calcium (0.25%) diet from age 3 weeks until 40 weeks. Half of the animals were fed ad libitum, and half of the animals were on an adjusted feeding schedule (the food intake of the low calcium animals was reduced to maintain equal body weight with high calcium animals of the same gender). DXA and radiographic measurements (femur and skull length and width) were collected at the age of 4, 13 and 34 weeks. Growing male rats fed the low calcium diet ad libitum gained more weight and more fat than rats on a high calcium diet. When food intake was controlled, male rats on the low calcium diet still had a greater fat mass (despite their similar body weight) and smaller skeletal measurements than the high calcium animals. Growing female rats initially responded like the males: when fed ad libitum low calcium animals had an increased body weight and fat mass; when food intake was controlled the low calcium animals had a greater fat mass and smaller skeletal measurements. However, these differences were found at 13 weeks and not at 34 weeks, suggesting a transient effect with no long-term differences between high and low calcium intake in the growing female rats.