The surprising role of skeletal growth
For years, the expanding waistline and hips seen in aging adults were primarily attributed to fat accumulation. However, multiple scientific studies have demonstrated a more complex reality, showing that the pelvic skeleton itself continues to widen long after a person's height has peaked.
Scientific studies on pelvic widening
Research conducted at the University of North Carolina School of Medicine used CT scans to measure the pelvic and hip width of subjects aged 20 to 79. The findings were definitive: the width of the pelvis, the distance between the hip bones, and the diameter of the hip bones all measurably increased with age. Specifically, researchers found that the pelvic width of individuals in their 70s was, on average, about an inch larger than those in their 20s. This one-inch increase in bony structure alone can account for a significant portion of an expanding waistline and hip circumference.
The mechanism behind bone remodeling
This adult pelvic growth is a result of a biological process called bone remodeling. It involves the continuous breakdown and rebuilding of bone tissue. As we age, hormonal shifts and the weakening of bones trigger this remodeling to maintain the pelvis's structural integrity. Studies suggest this remodeling, which involves both bone loss and new bone formation, is an adaptive response to the ongoing pressures the skeleton endures over a lifetime.
The impact of hormonal changes and fat redistribution
While skeletal changes are a significant factor, hormonal shifts play an equally important role in reshaping a woman's body. The decline in sex hormones, particularly estrogen during menopause, triggers a notable redistribution of body fat.
Shifting fat from 'pear' to 'apple'
Before menopause, women typically store more fat in their lower body (hips, thighs, and buttocks), creating a 'pear' shape. Estrogen encourages fat storage in these subcutaneous (under the skin) areas. As estrogen levels drop during perimenopause and menopause, fat distribution shifts, and more fat begins to accumulate around the abdomen. This causes a change towards a more 'apple' shaped figure, even without significant weight gain.
The rise of visceral fat
This abdominal fat is known as visceral fat, which is stored deep within the abdominal cavity, surrounding vital organs like the liver and intestines. The accumulation of visceral fat is a particular concern because it is metabolically active and associated with higher health risks, including cardiovascular disease and type 2 diabetes. The hormonal changes of menopause are a primary driver for this shift from the protective lower-body fat to the more dangerous visceral fat.
Menopausal changes to pelvic floor support
The hormonal shifts also impact the pelvic floor. The muscles and fascia of the pelvic floor contain estrogen receptors, and as estrogen levels decline, these tissues can lose elasticity and strength. This can lead to a posterior distension of the pelvic floor and, in conjunction with weight gain and other factors, contribute to pelvic organ prolapse. While this does not directly widen the hips in the same way as bone growth, it changes the overall support structure and can affect the appearance of the lower torso.
Comparison of aging factors impacting hip size
Feature | Skeletal Widening | Hormonal Changes / Fat Redistribution |
---|---|---|
Timing | Continuous growth from around age 20 throughout adulthood, peaking later in life. | Primarily during and after perimenopause, often from the 40s to 50s. |
Mechanism | Bone remodeling involving the continuous expansion of the pelvic bones. | Declining estrogen and progesterone levels alter where the body stores fat. |
Body Shape Impact | Increases the bony width of the hips and waistline directly. | Shifts fat from the hips and thighs (pear shape) to the abdomen (apple shape). |
Health Implications | A natural part of aging with minor direct health impact on its own. | Increased visceral fat is a major risk factor for cardiovascular disease and diabetes. |
Influence | Affects both men and women, though women's hip structure has additional complexity due to childbearing. | Affects women more pronouncedly due to hormonal changes of perimenopause/menopause. |
Conclusion: a natural and multi-faceted process
Understanding why women's hips get wider as they age requires looking beyond simple weight gain. The process is a combination of surprising and inevitable physiological changes. On one hand, the pelvic bones themselves continue to widen slowly over decades, a phenomenon confirmed by scientific studies. On the other, the profound hormonal shifts of menopause fundamentally change a woman's body by redistributing fat from the hips to the midsection, replacing protective subcutaneous fat with more hazardous visceral fat. While these changes are a natural part of aging, adopting a healthy lifestyle that includes regular exercise and a balanced diet is critical. Maintaining physical activity, particularly weight-bearing and strength-training exercises, can help mitigate muscle loss and counter the negative health effects associated with increased abdominal fat. By acknowledging the complex interplay of skeletal and hormonal factors, women can better understand and manage the changes their bodies undergo with age. Learn more about healthy aging from the National Institute on Aging: Healthy Aging Tips for the Older Adults in Your Life.