Yes I can. Hopefully.
Just want to start by saying I've worked as a medical and technical illustrator, so I have a thorough knowledge base with regards to anatomy. So in this technique, determining the general body size/shape is basically a tedious process of elimination.
This is a lot of words, so bear with me. A normal human body accumulates mass and volume in predictable or specific ways. For instance, muscles are limited in placement and (somewhat) in size. You will never see a muscle bulging out from the front of the knee and upper shin, for instance. By the same token, you'll rarely see a bulge of fat on the back of the knee (on an otherwise average-sized person). The knee has to bend, so fat rarely accumulates on the interior of joints. So that's the basics. Taking it further, you have to analyze a larger sequence of the video. Isolating one frame can be misleading, but if you study the sequence of video frame by frame, there will occasionally be a frame where the subject turns or moves in a way that allows the costume to either hug a body part, or pull away slightly, revealing a small area of the actual body shape beneath. These are "data points". They become fixed. That means, if one frame shows the fabric hugging the the calf, the calf is now that size, and so now I know that the same subject in every other frame contains a calf that same size, no matter how much fabric appears to conceal it. It can be smaller of course, but not bigger. In other words, the subject won't have an average sized calf in three frames, then grow a bulging calf in all the other frames. For this reason, since the technique is subtractive, the data points containing the smallest diameter of each body part become fixed. The subject's weight and body part size do not fluctuate frame to frame. He is limited to the smallest size determined by the fixed data points from a longer sequence. Additionally, the human body is symmetrical, so where one calf is a fixed size, so becomes the other.
Okay so to address your question and diagram. The area at the upper/outer portion of the thigh is not an area that normally accumulates fat or mass when a person is otherwise of average size. Someone with a massive bulge in that area would likely be either very muscular (or obese) overall. Likewise, the lower back does not typically accumulate so much fat that it bulges out over the buttocks. There are exceptions, of course. But as I stated above with the "data points" thing, there are frames where the back of the vest hugs more closely to the subject, and you can clearly see there is no bulging above the buttocks. The same can be said for the belly fat. Frames in the sequence show very little to no bulge, and in a later sequence of the video show the front bulge to be sitting too high on the torso to be a gut. I concluded it was bulging vest pockets, not a gut. Now, there may be more of a "love handle" silhouette to the sides than I've indicated, but from my anatomical knowledge, it's my opinion they are unlikely to be of any significant size, since there is less fat accumulation in other areas of the body and torso.
So the shorter answer is if you isolate just this one single frame, there could very well be body weight on those areas. But... when you take the video as a whole, frame by frame, and try to make that weight sit on the body in each and every frame, it simply won't work. Because some frames that bulk shifts, moves, or loses volume, and that's not how fat and muscles work. But it is how padding and fabric work.
Hopefully that answered your question. Don't ever hesitate to ask!
