Have you ever wondered why women tend to have higher body fat percentages than men? Are you a relatively fit woman who measured your body composition and were shocked that your number was in the mid or even high 20’s for fat mass percentage? Heather Huntsman, Ph.D., CSSC, explains the differences between men and women when it comes to storing fat to help place the focus on realistic, healthy body composition goals.
The answer to both of these questions can be found in a better understanding of the physiological differences that exist between men and women. Whether we want to accept it or not, men and women are very different biologically. From cell, system, and to the whole person, there are various aspects of our biology that operate differently based on sex.1
One of these important differences is in the way men and women use and store fat. For starters, men on average have about 3% essential fat as part of their composition – women have 12%.1 Essential fat is a percentage of total body fat mass that is necessary for insulation, protecting our vital organs, for vitamin storage, and building key cell messengers like steroids that are necessary for effective cell communication. Without this fat, the body does not function properly, and entire systems like our immune systems and neurological system will be affected.1-2
So, why do women have 4 times as much essential fat? Unfortunately, we don’t fully understand why, but the data strongly suggest that it is protective and related to reproductive health. Adipocytes (the scientific name for fat cells) have varying numbers of sex hormone receptors on their surface.3-4 Estrogen and testosterone circulating throughout the body communicate with fat cells on a regular basis and play a role in not only how fat is metabolized or broken down, but also where fat is stored. That is why women store more of their fat in their breasts and hip/buttocks region, and why men store fat in the midsection.2
The good news (hinted earlier) is how and where women store fat is actually beneficial to overall health. A baseline of 12% of essential fat that is stored in a gynoid pattern and subcutaneously rather than in and around the organs (also known as visceral fat) protects women from type 2 diabetes and even heart disease.5-6
Why is this important to understand? Bottom line: it helps with expectations and goal setting. At the end of the day you want to make sure your goals support health. This means that a woman striving for 8% body fat is not only unrealistic for the vast majority of women, it’s actually unhealthy. (I want to highlight here that the only reason I used the phrase vast majority is to account for the genetic component that is unrelated to sex. There are, on the very rare occasion, women that fall outside of the norms for one reason or another).
For all the rest of us, the healthy math looks like this: For a man with a body fat percentage of 11%, on average 3% of that is essential fat and 8% is stored fat. The equivalent of 11% in terms of health for a woman would be a total body fat of 20%, 12% essential and 8% stored. In both instances, the man and woman have equal amounts of stored fat.
Now that you are equipped with this new level of understanding, here is my concluding advice…focus on the health not only the numbers. While we live in health culture where weighing less and having less body fat is preferred, stay informed – and stay healthy. Know what your numbers really mean and live to your healthiest potential.
References:
- Bredella MA. (2017) Sex Differences in Body Composition. Sex and Gender Factors Affecting Metabolic Homeostasis, Diabetes, and Obesity. 1043:9-27. doi: 10.1007/978-3-319-70178-3.
- Ethun K. (2016) Sex and Gender Differences in Body Composition, Lipid Metabolism, and Glucose Regulation. Sex Differences in Physiology. Chapter 9. 145-165. doi: 10.1016/B978-0-12-802388-4.00009-4.
- Wu BN et al. (2011) Sex Differences in Energy Metabolism Need to Be Considered with Lifestyle Modifications in Humans. Journal of Nutrition and Metabolism 391809:1-6. doi: 10.1155/2011/391809.
- Nindl BC, et al. (2002) Gender Differences in Regional Body Composition and Somatotorophic Influences of IGF-1 and Leptin. Journal of Applied Physiology 92:1611-1618. doi: 1 0.1152/japplphysiol.00892.2001.
- Arner P. (2005) Human Fat Cell Lypolysis: Biochemistry regulation and clinical role. Best Practice & Research Clinical Endocrinology & Metabolism 19(4):471-482. doi: 10.1016/j.beem.2005.07.004.
- Schor M et al. (2018) Sex Differences in Body Composition and Association with Cardiometabolic Risk. Biology of Sex Differences 9(28):1-10. doi: 10.1186/s13293-018-0189-3.
