For short-form fiction or specific erotica focused on these features, you can find titles like on Amazon. Physiological Perspectives
For information on how mature and larger bodies change over time, several lifestyle and medical sources provide insights: mature bbw butts
While there is no single academic or formal research paper specifically focused on that exact description, there are several publications, photo ebooks, and articles that explore mature body types, "BBW" (Big Beautiful Women) aesthetics, and the aging process of the female body. For short-form fiction or specific erotica focused on
An orthopedic surgeon at 1010 Park Place discusses how aging is "bone deep," leading to muscle mass loss and volume shifts in the gluteal region after age 50. There is a series of photo-focused ebooks titled
There is a series of photo-focused ebooks titled which has dozens of volumes including: Mature BBW No. 51 (280 pages) Mature BBW No. 61 (263 pages) Mature BBW No. 71 (219 pages)
Some sources, such as Leading Lady , argue that larger glutes can provide support for back alignment and improve posture. Mature BBW No.61: MILFS & MOMS Naked Photo eBook
Projects like those found on Refinery29 feature unretouched photos and interviews with women of all sizes, discussing body image and the "radical acceptance" of larger frames.