If the big girl (or dude) is diabetic, insulin injection can create bruising at times if a blood vessel is clipped. Moreso if someone is taking an injectible anticoagulant such as Lovenox.
When I was bigger, I was a lot clumsier, and I had bruises I that I had no clue of the cause. My wife is still clumsy after losing 140 lbs…
We run into stuff more because we’re bigger and clumsier and everything is made for regular sized people.
We’re generally not tanned because we don’t go out in swimsuits as much as slim people, which means that bruises show up more lividly (if we are of the Caucasian persuasion).
If we are actively trying to lose weight and exercise more, we’re probably bruised from that. Right now I have several god-awfully ugly bruises on my legs from getting used to bicycling again.
I think Karl is less concerned about the bruise question than other unproven assertions presented as fact.
Exactly. It’s not like he’s asking for the capital of North Dakota.
Yeah, I assume it was the stuff about diabetes.
I guess it might have been nice if one of the docs had deigned to actually explain it, since the metabolic consequences of obesity are rather complex and it’s not something most of us understand very well.
Bismarck!
Fargo, IMHO.
Support the right to armed chairs!
Bruisemark?
I love that song! I thought I was the only person who knew it!
HA! Snorted beer out of my nose at that remark.
Seems less speculative to me than some of the WAGS offered, but here’s a cite:
Another vote for varicose veins. My mother has them, and it honestly looks at times like someone has beat her legs badly.
Yeah, I would agree with you that it didn’t seem particularly egregious. But it didn’t seem possible to answer the other question without some guessery, so I assumed they were getting at the diabetes stuff. (Specifically, I assumed it was the bit about whether diabetes causes or is caused by obesity, or both.) I still don’t get why they decided to complain rather than offer up what they had in their great bulgey heads full of knowledge and assorted goopy stuff.
Well, the directionality of diabetes certainly is a contentious issue.
Dwarves/midgets/other small mammals kicking and punching in response to the prospect of being sat upon? 
OK, OK, OK, I confess. The marks in question are not bruises at all, but hickeys. I did it. Away from my day job at the insurance company, I live by night as a fat-lady-leg-sucker. :o
Besides the frequent minor injury due to bodily dimensions issue, more fat under the skin equals more deformation when you hit something hard. More deformation means a bigger area is affected. More fat also means that there’s a lot more tissue for blood to leak into when vessels rupture. Fat has less of a blood supply than skin and muscle. Less blood supply means that leaked blood doesn’t get cleaned up as fast by your body. What you end up with are more bruises, with a bigger overall area, that stay around longer, giving you something else to occupy your attention besides cellulite.
Yep, you did. 
True, but if you’re going to “fight the good fight” here in GQ, why not fight against stupid joke answers? There are about a dozen of them here, all wasting time and hampster energy.
At least opinions such as LorieSmurf, NinetyWt, mojave66, lisacurl & Auntbeast are informed opinions, based upon their personal experiences. How can you get a better answer than that with such an OP?
I do know that taking asprin over a long period does lead to some spectacular looking bruises. Hefty dudes are more prone to back and similar pain, thus more prone to taking pain relievers, thus perhaps aspirin bruises.
http://www.cnn.com/HEALTH/library/HQ/00355.html
*Medications and supplements can cause easy bruising
Blood-thinning drugs such as aspirin and warfarin (Coumadin) or medications such as clopidogrel (Plavix) reduce your blood’s ability to clot. Because of this, bleeding from capillary damage that would normally stop quickly may take longer to stop, allowing enough blood to leak out to cause a bruise*
The amount of bruising may also be affected by medications which interfere with blood clotting (and thus cause more bleeding into the skin or tissues). These drugs include many prescription arthritis medications called non-steroidal anti-inflammatories (e.g., ibuprofen/Advil, Nuprin and naproxen/Aleve) as well as over-the-counter medications, such as aspirin
