Obesity and Center of Gravity

I came across this pic recently.

The argument seems to be that obesity throws off one’s center of gravity which puts extra strain on the body.

Do I understand the picture correctly? And is the claim correct?

There is a photo but there is no “claim” other than “There is nothing healthy about being obsese.” I think the implication of the embedded blog page is that just because the fat woman is flexible enough to hold her ankle up in the air that it’s OK to be obese. The overall point on the linked web page is that it’s not OK. I don’t see an explicit mention about center of gravity at all, just a couple of red lines.

The only thing you can conclude from that picture is that the obese woman’s weight is distributed differently than the ballerina’s. The red line is meaningless. To stand on one foot, your COG has to be over the foot, so the red line does not pass through the COG.

The higher your COG, the less stable you are, so I imagine that a high COG can cause extra strain. But I am not at all sure that obesity raises your COG. My guess would be that it’s pretty much in the same place.

For a constant mass, high CoM shouldn’t present any more strain; the magnitudes of the forces involved are the same.

Obesity puts more strain on the body because the earth is pulling down harder. A person who weighs 350 pounds is putting twice as much strain on his knees, hips, and lower back joints (and pretty much every other joint) as a person who weighs 175 pounds. This may vary slightly depending on distribution; some obese people have the weight very high (arms/neck/chest), some have it in their abdomen, others have massive thighs and buttocks. Few obese people have their excess weight concentrated in their calves, so the “twice as much strain” rule is probably highly accurate for knee joints.

If you weigh 175 pounds, try to imagine strapping another 175 pounds on you. It doesn’t matter if it’s attached to your shoulders, hips, or thighs, or evenly distributed in all of those places; your body will be more strained, regardless of configuration.

Looks like the fat one isn’t actually balancing at all-- they just took the photo mid-kick before she had to drop her leg to avoid falling.

There’s nothing healthy about being obese, and it’s just plain selfish as it takes up medical and financial resources that could be better used on treating non-self-inflicted illnesses.

Oddly enough, she’s not as flexible as a ballerina. Whether that’s due to obesity or lack of practice, who knows. If she dances all day, she must eat a helluva lot. Most people probably could not make the ballerina’s pase, even with mechanical assistance.

I agree the photo must be in mid-movement - the majority of her body mass seems to be on one side of her foot. I don’t think she’s balanced. One leg, whatever its size, probably won’t compensate.

That’s an interesting point. Any physicists out there who want to comment? Maybe this question deserves its own thread.

The red line shows alignment. The body of the woman who is of normal weight is aligned. Her head is directly above her trunk, which is directly above her leg, which is directly above her foot.

The body of the woman who is obese is not alignment. Her head is not directly over her foot. Her body is tilted. Non-alignment can result in hip, knee, … injuries. So it’s not okay to be obese.

I have seen obese women perform amazing things considering their obesity. I have even two or three obese women do a one-legged balance like the obese woman in the photo. Their bodies tilt in the same manner, and they generally have a hard time maintaining their balance due to their non-alignment. In fact, they would probably be able to raise their legs even higher if their flexibility were not limited by their excess fat.

I think the key here is that the larger woman’s butt is facing to the left where the smaller woman’s butt is facing behind her. If the larger woman’s leg is aligned then that means her leg is attached to the middle of her hips and not the side (if her hips are not turned, as they seem to be.) Also, the leg that is in the air with the big woman, see how as it gets near her body it gets covered by her stomach suggesting it is going behind her stomach, that is further evidence. The larger woman, then, isn’t shifted out to the left, but actually shifted forward.

This is how it looks to me, anyway.

Notice the skinny one has her leg higher, and closer to her body. That’s why her head can be over her foot. The fat lady has her raised leg farther away, and so has to lean in the other direction to balance. That has more to do with her inability to lift her leg higher than her being overweight. Few of us can do what the skinny woman is doing, no matter what our weight is.

Putting aside the issue of center-of-gravity, based on other evidence I have seen more recently, I believe the fat girl was not balancing at all; that it was just high-speed photography.


The red line for the non-bolemic chick is not on her CoG.

The legs contain a lot of weight, so the red line must be toward her left leg more.

Even if she is moving ,she threw 120kg around, and that means she has a lot of muscle, so that left leg is a lot of her body mass ! (There’s a big gluteus maximus in behind there too)

The fat on the belly and chest looks large, but it doesn’t actually weight that much relative to the apparent effect on shape.

SO move that red line… its going to be through her right leg… just like the other girl’s red line.

Putting aside the issue of whether either or both girls are bulimic, I’ll assume you mean the fat one. Having thought about this for a while, I’m pretty sure she’s not balancing.

First, as mentioned above, there is another picture of her where her hair gives away the fact that there’s high speed photography in use.

Second, even if the red line is off, one can imagine a parallel line running through her right ankle/foot. Just eyeballing it, it seems that such a line would not be running through her center of gravity.

Well presumably her right glute weighs a good deal too.

Well like I said, if you move the line over to her right foot and ankle, it does appear very far to the left in relation to her body.