Comparing the average female and male, about 30% of an average female's body mass is muscle mass, while for males the average is 40 %*
It also differs where that muscle mass is typically distributed. The gender differences are greater in the upper (40%) than lower (33%) body. Female tend to gain more muscle mass (57,7%) in their lower body (54,9%), compared to males. However, taking into consideration upper body comparison, female tend to gain 39,7% & men 42,9% of their SM (skeletal muscle).*
Muscle mass tends to decrease as we age. According to the research, muscle mass decreased starting in the third decade, a noticeable decrease in absolute SM mass was not observed until the end of the fifth decade. The decrease in SM approximated 1.9 and 1.1 kg/decade in the men and women, respectively. Ageing was associated with a preferential decrease in muscle mass in the lower body.
However, It seems that females retain skeletal muscles better than males. Females who increase muscle mass while younger tend to retain that muscle as they age - yes ladies, start building your muscles now!:-)
Relatively women have more body fat and less muscle mass at the same weight, on average, compared to males.
Essential body fat is the fat needed for metabolism, proper neural activity, cell structure and protection . It is stored in the marrow of bones, in the heart, lungs, liver, spleen, kidneys, intestines, muscles, and lipid-rich tissues throughout the central nervous.
In females, essential fat is also stored in the breast area. Essential body fat in females is about 9% of total body mass, while in males it's only 3 %. Pregnant and lactating females likely have higher essential fat levels than other females.
The pear-shaped body fat distribution of many women is associated with lower cardiometabolic risk**
Body fat percentage in females is crucial for fertility. Some studies suggest that a body fat level of at least 22% is necessary for regular menstrual cycles. Also, caloric deficit itself can cause amenorrhea.
Avarage body fat percentage for females aged 30-39 was 24,8 % and 22,4 % for males in the same age range,and this difference persists until over age 60 (28,3% females & 23,1% males)***
The average difference in body fat percentage between men and women is 3 - 5 %. However, an active female who exercises regularly may have less body fat than a male who does not exercise.
* Skeletal muscle mass and distribution in 468 men and women aged 18-88 yr