Extra Fat Not Good for Teenagers’ Bones

Healthnotes Newswire (March 22, 2007)—Many studies have suggested that increased fat mass benefits the bones. However, a new study finds that this is not the case, particularly for adolescents and young adults.

“Despite the dire repercussions of obesity, the traditional paradigm suggests that increased body fat is beneficial to the skeleton and could protect against osteoporosis,” said Vicente Gilsanz, MD, professor of radiology and orthopedic surgery at the Keck School of Medicine and Children’s Hospital in Los Angeles. “Our findings challenge this widely held view.”

Many of the previous studies examining the relations between fat mass and bone mass suggested a protective effect of excess body fat on bone mass, regardless of age. Researchers thought that increased weight-bearing and hormonal influences accounted for this seemingly protective effect. However, the new study suggests that, despite these influences, fat tissue is not beneficial to bone structure.

Dr. Gilsanz and colleagues enrolled 300 healthy, sexually mature adolescents and young adults (150 males and 150 females) between ages 13 and 21. They measured total body fat, lean mass, and bone mineral content, and assessed bone density in the spine and thigh bones. The researchers confirmed a strong positive effect of lean mass on all bone parameters. In contrast, fat mass had a negative influence on bone density in males, though no effect in females.

According to Gilsanz, this study provides more compelling evidence than previous studies on the subject, primarily due to the relatively large number of subjects and to the use of two independent techniques (dual energy x-ray absorptiometry and computed tomography) that accurately assessed of the contributions of lean and fat tissues on bone structure.

Increased fat during adolescence is a major public health concern. Obese adolescents and young adults face many of the same risks as obese adults, such as cardiovascular disease, diabetes, hypertension, and cancer.

“Bone strength is primarily determined by dynamic loads from muscle force, not from static loads, such as fat mass, Dr. Gilsanz said. “The many negative contributions of fat tissue offset any potential benefit it may provide in terms of mechanical load.”

(J Clin Endocrinol Metab 2007; 92:143–7)

Jeremy Appleton, ND, CNS, is a licensed naturopathic physician, certified nutrition specialist, and published author. Dr. Appleton was the Nutrition Department Chair at the National College of Naturopathic Medicine, has served on the faculty at Bastyr University of Natural Health Sciences, and is a former Healthnotes Senior Science Editor and a founding contributor to Healthnotes Newswire. He has worked extensively in scientific and regulatory affairs in the supplement industry and is now a consultant through his company Praxis Natural Products Consulting and Wellness Services.

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