The saying, “You can never be too rich or too thin” is definitely not true when it comes to bone health! It’s well established that women with low body weight have lower bone density and are at increased risk for many types of bone fracture.
Let’s better understand this link between body weight and fracture risk and then look at the many steps thinner women can take to start strengthening their bones.
- Experience twice the rate of hip fracture as do “healthy weight” women. (See chart below.)
- Have lower hip bone density, lower cross-sectional bone area, and less bone bending strength than “normal” weight women.
- Experience more vertebral and wrist bone fractures (but fewer lower leg fractures).
- Tend to lose more bone during the menopause transition than do heavier women.
So just who is included in this “underweight” category?
The “underweight” designation is determined by body mass index (BMI) using weight and height. A BMI of 18.5 or less (which would translate into a 5’3” women weighing 105 lbs or less, or a 5’5” person weighing 115 lbs or less) is considered underweight.
While the “underweight” category includes only very thin folks, there exists a weight–bone gradient link whereby lighter weight individuals have both decreased bone density and increased risk of various fractures. Those falling into the “underweight” category are at highest risk, but slender individuals (that is, those whose BMI is 18.6–21.5) are often reported to be at increased bone fracture risk, too, particularly if they also have low muscle mass.
How can underweight or slender women reduce their fracture risk?
This is indeed a complicated topic, which I can only begin to address here. As always, at the Center for Better Bones we look for the root cause of the problem and seek a solution with this in mind. Being significantly underweight likely indicates a serious imbalance within the system, such as digestive, emotional, or disease-related issues:
- Low body weight is often associated with weak digestion, food allergies, or food intolerances. Addressing these issues is central to improving your metabolism. Check out our 10 steps to stronger digestion and try a simple elimination diet.
- Clinically, I also see low body weight associated with a tendency towards anxiety, nervousness, and at times even straight out emotional distress and fear. While uprooting these negative emotional responses can take some time and good guidance, a good place to begin is with our free e-book, 7 secrets to reducing stress.
- If you’re an “eat-and-run” person or you regularly skip meals, discipline yourself to sit down, relax, and consume three tasty, wholesome meals every day.
- Try not to get extra calories from simple carbohydrates like sugars, pastas, and flours. Instead, increase your intake of root crops and wholesome fats like avocado, nuts, seeds, and olive oil.
- Remember, bone and muscle are built together — so include some weight-bearing, muscle-building exercise in your weekly routine.
As you can see, there’s a lot that a thin, small-framed person can do to strengthen bone and reduce their fracture risk. Being aware of your risk is the important first step!
Johansson, H. et al. A meta‐analysis of the association of fracture risk and body mass index in women. J Bone Miner Res., 2014;29: 223-233. doi:10.1002/jbmr.2017
Søgaard AJ, et al. Abdominal obesity increases the risk of hip fracture. A population‐based study of 43 000 women and men aged 60–79 years followed for 8 years. Cohort of Norway. J Intern Med. 2015;277: 306–317.
Compston, J. E., et al. Relationship of weight, height, and body mass index with fracture risk at different sites in postmenopausal women: The Global Longitudinal Study of Osteoporosis in Women (GLOW). J Bone Miner Res. 2014;29: 487-493. doi:10.1002/jbmr.2051
I’m Dr. Susan Brown. I am a nutritionist, medical anthropologist, writer, and speaker. Get my free weekly newsletter here.