Anorexia nervosa and obesity are the two major eating disorders present nowadays in western countries. They are both characterized by striking body composition variations, such as modification of muscle and fat mass and hormonal alterations which impact on skeletal metabolism inducing bone tissue modifications and often cause an increased risk for fractures.
Anorexia nervosa and obesity are characterized by a severe reduction in fat mass or a high expression of it, respectively. In both conditions, hormones secreted or modulated by body fat content are important determinants of low bone density, impaired bone structure and reduced bone strength. In addition, in both anorexia nervosa and obesity (adiposis), increased marrow adiposity, which correlates with low bone density, has been observed.
The importance of body composition alterations is based on observations that suggest several potential mechanisms to explain the complex relationship between adipose tissue and bone. The importance of body composition changes are based on several observations suggesting potential mechanisms to explain the complex relationship between fat and bone tissues:
Firstly, adipose tissue, which has been regarded as a passive energy reservoir, secretes several adipose tissue-derived hormones and cytokines (proteins released by cells of the immune system) involved in energy homeostasis and metabolism regulation.
Secondly, since the demonstration that bone cells secretes specific factors that affect body weight control and glucose homeostasis, fat is considered an endocrine organ itself because it secretes fatty tissue directly into the blood, and is a player of an active bone-adipose axis.
And thirdly, adipocytes (fat cells) and osteoblasts (bone cells) originate from a common pluripotential mesenchymal stem cell that has an equal tendency to differentiate into adipocytes or osteoblasts (or other lines) upon the influence of different stimuli on cell-specific transcription factors.
Nutrition and healthy body weight key to strong bones
In a review published in the journal Hormone Molecular Biology and Clinical Investigation, the authors describe the pathophysiological basis and molecular mechanisms in bone alterations associated to anorexia nervosa and obesity, conditions of extreme energy deficiency and excess, respectively.
The authors’ review highlights the importance of the right nutrition and the maintenance of a correct body weight for the health of the skeleton. Since eating disorders have become more and more common over the last few decades in our society, it is very important to consider all evidence and potential detrimental effects on the skeleton in order to provide appropriate prevention intervention.
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