I think aging has more to do with fat loss, but So I'm gonna say yes on the sun giving at least the appearance of fat loss over time.

Mostly stayed out of the sun in my life as I was always sensitive to heat & am one of those weird people who doesn't like the feel of direct sun on her bare skin. As a teen I was diagnosed with an unrelated Cancer & the doctor gave me a much longer dosage of radiation than people usually get -over 30 sessions in the area on my thigh where the cancer was. After it healed a few months later, I was left with a permanent tan in the treated area that was about 6 shades darker than the rest of my skin and it became wrinkly and leathery, lax skin that was no longer elastic. It was as if the treated area had aged 60 years while the rest of me stayed in the present. I was a teen so seeing dry, leathery wrinkles on a part of my body was weird. It also had the appearance of losing fat as well, but that could be because the skin laxity gives the illusion of fat loss; after all the skin there actually feels thinner to the touch compared to the other thigh. It stayed like that permanently, but unless I wear a bathing suit people don't see the area anyway so I usually forget about it completely. Whether it's illusion or real, there is definitely the appearance of fat loss. I think high beam radiation does in a few weeks what decades of intense sun exposure does to skin. But the atmosphere protects us from most of the sun's strong rays making the effect from the sun much more gradual & less dramatic. Isn't the effects of intense radiation therapy a good test in determining the affects of the sun?

For me it was really tanning beds that did the damage where the UVA is a lot more intense than regular sunlight. I've seen pics of others with damage from tanning beds and there is just a different sort of appearance to the skin compared to those who baked in the sun.

Yes, UVB and UVA have different action spectra. UVA is much more involved in skin sagging while UVB is more involved in wrinkling and burning.

UVB penetrates to just below the outermost part of the dermis while UVA penetrates all the way through the subcutaneous fat.

I lost most of my facial fat by my late 20s, long after I stopped tanning. But I lost almost all of the rest of it over the next 15 years, when I had essentially zero sun exposure through appropriate use of sunscreens and hats/visors/sunglasses.

Yes, UVB and UVA have different action spectra. UVA is much more involved in skin sagging while UVB is more involved in wrinkling and burning.

UVB penetrates to just below the outermost part of the dermis while UVA penetrates all the way through the subcutaneous fat.

I lost most of my facial fat by my late 20s, long after I stopped tanning. But I lost almost all of the rest of it over the next 15 years, when I had essentially zero sun exposure through appropriate use of sunscreens and hats/visors/sunglasses.