The maintenance of bones in the body is a balance between formation and breakdown. Osteoblasts are cells that responsible for bone formation. Osteoclasts are cells that remove bone (known as bone resorption). In an adult bone many things, such as levels of vitamin D and calcium can influence this balance between making and removing bone.

A recent study has shown that loss of significant amounts of weight on a severe calorie restriction diet can affect this balance in a negative way, with their being an increased rate of bone breakdown relative to formation. This will lead to a net loss of bone.

Further, the research found that there was an increased rate of breakdown and formation which can lead to more fragile bones, and that this persisted in the maintenance phase of the diet.

Both low carb or low fat, severe calorie restricted diets had the same effect on bone breakdown.

The loss of bone makes biological sense. One of the functions of bones is to support our weight. Lose some weight and the body senses it has less weight to carry. However, it is a good idea to try and maintain bone density, both for the strength and to stop bones becoming more fragile

It is also likely that with severe restriction of food that the diet may not contain sufficient calcium or vitamin D. This research suggests that when going on a long term diet to lose a significant amount of weight that care should be taken to have a balanced diet and in particular consume plenty of calcium and either supplement with vitamin D or get sufficient sun exposure.

However, probably the best way to stop the bone loss is to do plenty of high-impact weight bearing activities.

photo credit: Simon Goldenberg

[tags]bone loss, fragile bones, high-impact activity, calorie restriction, weight loss[/tags]