The Essential Role of Body Fat in Our Health – part 5
By: Amber Whittemore RD, BSN, MHSc(c)
Welcome back to the final blog in the series on the essential roles of body fat!
Today, we will be focussing on how our fat stores protect our heart and bone health! Both of these links are intrinsically connected to our estrogen levels, so be sure to head back to the last post on reproductive health before proceeding with this one!
If you already read last week’s post, then you know that we need adequate fat stores to have sufficient estrogen supply in the body!
Fat stores protect the health of our heart
The circulatory system in the human body, also known as the vascular system, is responsible for delivering blood and oxygen to all our organs and tissues. This circuit is comprised of blood vessels, such as arteries, veins, and lymph vessels1. When we zoom into this system and view it at a vascular level, we see that estrogen controls inflammation, oxidative stress, and promotes blood vessel wall health by promoting cell growth and reducing smooth muscle cell death2.
The link between the cardiovascular impact of estrogen loss in postmenopausal women is well-established, however, the research focussing on low estrogen levels in younger women (premenopausal) is much newer – warranting more research to find the exact link between low fat stores and heart health.
Recent studies which focus on low estrogen levels in a young premenopausal population have found a link with premature cardiovascular disease – with the earliest sign being menstrual cycle irregularities2. This makes sense since a previous study concluded that the more irregular a women’s period is, the greater her risk for a cardiovascular event (up to a 50% increase)3. Another study to note, the Women’s Ischemia Syndrome Evaluation (WISE) study, found that estrogen deficiency was significantly more prevalent among women with cardiovascular disease than in those without (69% versus 29% to be exact)4. This finding was in women experiencing hypothalamic disturbances – which is covered in the previous post on fat stores and reproductive health!
Men & Women – link to BMI:
A large study5 in 2007 examined the link between BMI and prognosis of heart health in individuals with heart failure. The mean age in this study was 65 years old and only 35% of the participants were female. In a nearly 40-month follow-up from the initial assessment it was found that, when compared to individuals who were classified as “obese” by their BMI, the individuals who were underweight or with low BMI’s had an increased risk of cardiovascular death.
While this study focuses on BMI versus body fat, we know that these two are intrinsically linked, though more research is certainly warranted in this area.
Men & Women – link to Eating Disorders and low body weight
We know that as individuals lose weight past their recommended levels, which often looks like falling below their healthy body fat mass, they also lose their muscle mass since their body begins relying on this tissue for energy. This includes the loss of cardiac muscle. This weakens the walls of the heart, leading to a heightened risk for valve prolapse, hypotension, arrhythmias, or heart failure in extreme circumstances6.
The presentation of bradycardia6, or a lower than recommended heart rate, is very common in those who are less than 80% of their recommended body weight. This is caused in an attempt for the body to conserve as much energy as possible. This problem can often be alleviated with the re-establishment of proper nutrition and body fat/muscle stores.
Fat stores protect our bone density
The body’s skeletal system, aka our skeleton, relies heavily on adequate estrogen for good bone density and turnover. This is because, in a healthy functioning body, estrogen stimulates the growth of bones by promoting growth factors2. However, in women with estrogen deficiencies, bone growth is stunted due to the inability to stimulate growth factors7. In a cascade effect, the bones then begin to deteriorate due to increases in `bone-resorption” (aka bone-breaking) substances which are increased due to the absence of estrogen8. With all of this coupled together, we know that the loss of estrogen that is coupled with hypothalamic amenorrhea (linked to low fat mass) poses a serious risk for premenopausal women in developing osteopenia or osteoporosis.
Of note, sufficient estrogen is also needed in the body for proper calcium absorption in the gut. Therefore, with low estrogen levels, we see low levels of calcium being absorbed. This further impacts the health of the bones by reducing bone mineral density.
We know that men with low fat mass or a low BMI also suffer from bone loss, though this link is very under-researched. The National Institute of Health9 suggests that coupled with weight loss, testosterone deficiency may be responsible for the increased risk of osteoporosis and fractures for men falling into the underweight category.
We know from the eating disorder literature that men with low body weights or restrictive eating patterns have lower levels of testosterone10. In men, this hormone is essential for regulating muscle and bone mass, and therefore with the loss of normal testosterone levels muscles and bones are left vulnerable to deterioration. Therefore, we see higher levels of osteoporosis and breaks in men who are living with disordered eating, or a lower than recommended body weight.
The Bottom line
Our essential fat mass and the maintenance of healthy body weight are essential for maintaining our heart and bone health. These functions are closely linked to our reproductive and hormone health, and through a cascade of events can be affected when our body’s fat stores fall below where we need them to function properly as humans.
If you are concerned or have any questions at all, feel free to reach out to an HEC dietitian for guidance and support in your health!
1John Hopkins Medicine. (2021). Overview of the Vascular System. Received from: https://www.hopkinsmedicine.org/health/conditions-and-diseases/overview-of-the-vascular-system
2Shufelt, C. L., Torbati, T. & Dutra, E. (2017). Hypothalamic Amenorrhea and the Long-Term Health Consequences. Seminars in reproductive medicine, 35(3), 256–262. https://doi.org/10.1055/s-0037-1603581
3Solomon C. G., Hu F. B., Dunaif A., et al. (2013). Menstrual cycle irregularity and risk for future cardiovascular disease. J Clin Endocrinol Metabolism, 87(5):2013-7.
4Merz, C. N. B., Johnson B. D, Sharaf B. L, et al. (2003). Hypoestrogenemia of hypothalamic origin and coronary artery disease in premenopausal women: a report from the NHLBI-sponsored WISE study. J Am Coll Cardiol, 41(3), 3-9. doi: https://doi.org/10.1016/s0735-1097(02)02763-8
5Kenchaiah, S., Pocock, S. J., Wang, D., et al. (2007). Body Mass Index and Prognosis in Patients With Chronic Heart Failure. Circulation, 116(6), 627-636. doi: https://doi.org/10.1161/CIRCULATIONAHA.106.679779
6McCallum Place. (2014, Oct 5). Cardiovascular Complications of Eating Disorders. Recevied from: https://www.mccallumplace.com/about/blog/cardiovascular-complications-eating-disorders/
7Weitzmann M. N. & Pacifici R. (2006). Estrogen deficiency and bone loss: an inflammatory tale. J Clin Invest, 116(5):1186-94. doi: 10.1172/JCI28550
8Meczekalski, B., Podfigurna-Stopa, A. & Genazzani, A. R. (2010). Hypoestrogenism in young women and its influence on bone mass density. Gynecol Endocrinol, 26(9):652-7. doi: https://doi.org/10.3109/09513590.2010.486452
9National Institute of Health. (2018). What People With Anorexia Nervosa Need To Know About Osteoporosis. Received from: https://www.bones.nih.gov/health-info/bone/osteoporosis/conditions-behaviors/anorexia-nervosa#:~:text=Weight%20loss%2C%20restricted%20dietary%20intake,the%20course%20of%20the%20disease.
10Ekern, J. (2015, Apr 18). Males, Anorexia, and Physical Side Effects. Received from: https://www.eatingdisorderhope.com/information/anorexia/males-anorexia-and-physical-side-effects#:~:text=Anorexia%20causes%20the%20male%20hormone,mass%20in%20men%20with%20anorexia.