Throughout a woman’s life, her body composition can change drastically depending on many factors—especially hormones. Here’s a quick overview.
Your sex plays a huge role in your body composition, which is why it’s especially important for women to seek out information that’s aimed specifically at them. The business of body composition is a very male-dominated one, so it can be hard to find a clear explanation of how body comp differs in women. And it does differ—a lot! In fact, body composition in women changes from day to day, depending on several factors, such as age, activity level, hormones, and hydration status.
That’s why we’ve put this guide together—to clarify the misconceptions around female body composition and present the information you need to know in a clear and concise way. By the time you’re done reading, you’ll understand why and how body composition is different for women, how hormonal changes affect body composition throughout a woman’s life cycle, and how you can get your own body composition tested (hint: it’s easier than you think).
Female vs. Male Body Comp
You’ve probably heard it before or seen it in action yourself: in general, men are leaner than women. And if you’ve ever had to hide your jealousy over how easily your male spouse or partner could drop several pounds while you struggle to lose any at all, then you definitely know the deal. Female bodies carry more fat and are better at holding on to it, too. But why is this the case?
It all comes down to estrogen, the predominant sex hormone for females. While testosterone in males promotes increased lean mass (more muscle, increased blood volume, and thicker bones), estrogen in women tends toward more fat—particularly in the breasts, hips, and thighs.
As early as five months of age (or even sooner), the difference in body composition between males and females becomes apparent. It’s at this young age that male infants begin to produce their own testosterone, while estrogen remains dominant in female infants.
This trend continues throughout life, with women carrying more fat than men (in most cases). But even between women, the amount of fat can vary drastically based on activity level. Here’s how ideal body fat levels for women are broken down by the American Council on Exercise:
Essential fat: 10-13% (your body needs at least this much to function properly)
Athletes: 14-20% (this category would include female bodybuilders, marathoners, and other elite athletes)
Fitness: 21-24% (this would be people who are “in shape” but not necessarily athletes)
Acceptable: 25-31% (the average woman would fall into this category)
Obesity: 32% or greater (women carrying this amount of fat are likely to be obese)
But even then, many other factors come into play—like where you carry your fat on your body, your age, and what’s going on with you hormonally at any given time.
These differences in body composition that are inherent to women support pregnancy, childbirth, and breastfeeding. However, women experience several shifts in their body composition, depending on what phase of life they’re in and what hormones are involved.
Menstruation
There’s a lot of interesting research on how body composition and the menstrual cycle affect one another, and it’s clear that there’s a relationship between body composition and menstruation. A study found that participants who hadn’t begun menstruating weighed less and had a lower BMI than those who were already menstruating, regardless of age. Puberty is also associated with a slight increase in fat mass in females—in the same study, 97% of the girls who had begun menstruating had reached a body fat content of 22% compared to 88% of the girls who had yet to get their first cycle.
However, there are even significant body composition changes that occur when a woman is menstruating compared to when she’s not. Many women feel extra-bloated during their cycle, which is likely a result of water retention. But even a woman’s fat mass may increase by up to 1 pound during her cycle.
For this reason, if you’re doing regular body composition testing to assess any progress you’re making towards your fitness goals, it’s a good idea to always have the testing done during the same phase of your monthly cycle. This will give you a much clearer picture of how you’re progressing.
Pregnancy and Breastfeeding
Pregnancy is rife with hormonal changes that prepare a woman’s body to grow and deliver a baby, which naturally leads to body composition changes. Early in pregnancy, a woman’s blood volume and body water increase significantly—to the tune of about eight pounds throughout the pregnancy. Additionally, expanding uterine and breast tissue can account for another five pounds of pregnancy weight gain.
Fortunately, there are few changes to bone or muscle mass during pregnancy, particularly if you maintain a similar activity level as before you became pregnant.
However, changes in fat mass vary a lot, depending on the pregnancy. Some normal-weight women may lose fat mass during their pregnancy, while others may gain as much as 30 pounds or more. It’s highly variable and hard to gather data on because body composition testing isn’t commonly done on pregnant women. It’s also not possible to determine such metrics using a DEXA machine due to the low levels of radiation required for the scan.
What’s more, as the pregnancy progresses, body composition testing becomes less accurate as the fetus, placenta, and amniotic fluid—which are all considered part of the “fetal unit” rather than the “maternal unit”—continue to grow.
In the years after giving birth, women who choose to breastfeed may have a slight advantage in fat loss. Research indicates that women who breastfeed their children tend to have a lower BMI, waist circumference, and fat mass five years after childbirth compared to women who don’t.
Menopause
Menopause, when a woman is no longer producing eggs or menstruating, comes with some major hormonal shifts. One of the biggest ones is that her estrogen production and metabolic rate decrease, which significantly affects body composition. The onset of menopause in many women is associated with a doubling in the rate of fat mass growth, while lean mass (particularly bone and muscle) begins to shrink.
During menopause, many women notice an increase in visceral fat, which is carried in the midsection and around the organs in your abdominal cavity. This is because, as estrogen takes a backseat, other hormones—like the small amount of testosterone that women naturally produce—may take center stage. And unfortunately, high testosterone in women is associated with abdominal fat deposition.
Unlike subcutaneous fat, which is carried just below the skin and is pretty harmless in most cases, carrying excessive visceral fat puts you at an increased risk of developing conditions like heart disease or type 2 diabetes.
Given that the initial shift from lean mass to fat mass can be indiscernible on a scale, resting metabolic rate (RMR) testing can provide a more holistic picture for menopausal women. And although the hormonal changes associated with menopause are unavoidable, it can be easier to address the potential negative side effects if you know what to expect.
How to Check Your Body Composition
While it may seem like measuring how much fat your body carries versus lean mass (water, muscle, and bone) might be invasive and expensive, it’s actually neither! It’s quick, easy, painless, and affordable—and taking the time to have these tests done will equip you with a much better picture of your overall wellness than the scale can.
Dual-Energy X-Ray Absorptiometry (DEXA), or a DXA scan, is a great tool for measuring body fat. DEXA was originally designed to measure bone density. However, thanks to the use of highly accurate X-rays, it can also give you a full picture of your body composition—including body fat, visceral fat, and lean mass in addition to bone density. This test involves you lying on a table while two X-rays are administered to the length of your body, one measuring your bone density and one measuring your non-bone mass.
An alternative to the DEXA scan is the BOD POD, which measures your body composition using air displacement techniques. Like DEXA, it’s accurate, simple, and completely non-invasive. The BOD POD is a large, egg-shaped pod that you’ll sit inside of for approximately three minutes. This method can calculate your body composition based on your breathing and the amount of air that’s displaced while you’re in the pod. Furthermore, it’s safe to use for pregnant women.
As you can see, body composition is more complicated for women than it is for men. If you’re looking for some more detailed information about your body and (literally) what you’re made of, body composition and RMR testing is a great place to start. Decoding your individual body composition and metabolic rate provides the personalized, holistic data that will help you break through the clutter and customize the health and wellness routine that’s right for you.
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