Myth: Estrogen Is The Enemy Of Fat Loss

Estrogen tends to be best known as the female hormone because women have higher levels than men. Somewhere along the way, estrogen got associated with increased body fat. There are at least two possible theories for this connection:

First, fat tissue secretes estrogen. As you gain fat, your estrogen levels rise, which causes an imbalance in the ratio between estrogen and other hormones such as progesterone.

Elevated estrogen also inhibits thyroid function (3). This is bad news because thyroid hormone is necessary for a healthy metabolic rate. When thyroid hormone is reduced, people feel tired and sluggish, which makes them expend less energy so that they burn fewer calories daily. Fat gain often occurs, which raises estrogen again—and you can see it’s a vicious cycle.

Second, women have more body fat than men. Women also have higher estrogen levels, so it seems logical that higher estrogen is the cause of greater fat deposition. There’s some truth to this but it’s not the same as saying estrogen is the enemy of fat loss. In fact, estrogen is actually a key fat burning hormone!

Estrogen increases activity of hormone sensitive lipase (HSL), which mobilizes fat so the body can use it for energy. At the same time, estrogen decreases the activity of lipoprotein lipase (LPL), which stores fat. HSL activity occurs most often in response to exercise, and having balanced estrogen levels basically helps this exercise phenomenon become more powerful and occur more often.

Another way estrogen is beneficial for body composition is that it stimulates the production of growth hormone. GH upregulates fat burning, while inhibiting the uptake of glucose by fat tissues. One reason high-intensity exercise is so useful for fat loss is that it triggers a huge increase in GH and it just so happens that women have a higher release of GH in response to intense exercise than men, likely due to their higher estrogen levels (4).

The key is that estrogen levels need to be balanced. For women, too little estrogen will lead to poor bone health, fat gain around the abdomen (as is seen in post-menopausal women), and infertility (5). Men also require a small amount of estrogen, however, it’s unlikely that any man has ever suffered from too little estrogen.

Too much estrogen is s a much bigger problem for men. Excessive amounts of estrogen are due to a poor diet, endocrine-disrupting chemical exposure (BPA), or excess body fat (remember fat secretes estrogen) and are associated with a number of health problems including obesity.

Take Away: The role of estrogen in the body (especially the female body) is way more complicated than it seems.

References
1. West, D., Kujbida, G., et al. Resistance Exercise-Induced Increases in Putative Anabolic Hormones Do Not Enhance Muscle Protein Synthesis of Intracellular Signaling In Young Men. 2009. Journal of Physiology. 587(21), 5239-5247.

2. West, D., Burd, N., et al. Elevations in Ostensibly Anabolic Hormones with Resistance Exercise Enhance Neither Training-Induced Muscle Hypertrophy Nor Strength of the Elbow Flexors. 2010. Journal of Applied Physiology. 108, 60-67.

3. Frank, A., et al. The role of hypothalamic estrogen receptors in metabolic regulation. Frontiers in Neuroendocrinology. 2014. 35(4):550-7.

4. Ignacio, D., et al. Thyroid hormone and estrogen regulate exercise-induced growth hormone release. PLOS One. 2015. 10(4):e0122556.

5. Lizcano, F., Guzman, G. Estrogen Deficiency and the Origin of Obesity during Menopause. Biomedical Research International. 2014. 2014:757461.

6. Staples, A., et al. Carbohydrate does not augment exercise-induced protein accretion versus protein alone. Medicine and Science in Sports and Exercise. 2011. 43(7):1154-61.

7. Aragon, A., Schoenfeld, B. Nutrient Timing Revisited: Is There a Post-Exercise Anabolic Window? Journal of the International Society of Sports Nutrition. 2013. 10(5).