"If it's a natural thinness, and you're eating healthy, and exercising, it's not an issue," Paulos said. But he added that it's another story, "if your thinness is from an eating disorder, or excessive dieting."
People who stay thin unnaturally may lose critical elements for conditioning the joints, Paulos said. They may have bone pain from loss of calcium, vitamin C and vitamin D.
Even the so-called enviable people who stay thin naturally, but never exercise and eat whatever they want, might be at risk. These people, especially women, are more likely to get painful fractures from osteoporosis later in life.
"Having a thin frame is a recognized risk factor," said Dr. Laurence Laudicina, a spokesman for the American Academy of Orthopaedic Surgeons.
It turns out that so-called big-boned women truly do have more bone than thin-framed women. Once menopause hits, these big-boned women have more bone to lose before one breaks.
And for thin women who like to party, take note: combine a thin frame with a sedentary lifestyle, smoking and heavy drinking and a woman increases her risk for osteoporosis even more, Laudicina said.
For now, America's weight problem — a third of the population is obese — may be causing diabetes and heart problems. But soon, and perhaps already, this extra weight will cause pain.
Weight alone is not to blame, but a combination of weak muscle and extra pressure can up the forces bearing down on ligaments, cartilage and bone.
"The stronger you are, the more weight you can carry safely," Paulos said. For example, a professional football lineman can survive a lot more athletic activity than could a 300-pound couch potato.
"The muscles act like springs, so if you're jumping and running around and have very weak springs, all of the forces will go to your bones," Paulos said.
Without the cushion of strong muscles, some of the most essential joints in the hips, the back and the knees will suffer, sometimes permanently.
"If you think of someone who is heavy or overweight, while their bones become denser, there's more pressure on the cartilage," Laudicina said. Over time, the cartilage wears away, slowly causing arthritis and pain.
And the more you gain, the more pain.
"If a person is 10 pounds overweight and goes up the stairs, they will see 80 pounds extra weight on the knee," Paulos said. "So you can imagine the forces a knee will see if they're at 250 pounds, overweight and weak."
For big-bellied men and women, body pain trouble might come from many sides. Extra weight anywhere on the body will put extra pressure on joints and bones, causing pain in the knees and hips.
However, a concentrated bump on the abdomen will also painfully throw off a person's alignment.
When a person stands with good posture, the abdomen muscles should pull up while the buttocks muscles should pull down, according to health information from Indiana University-Purdue University, Indianapolis.
With this proper alignment, a person's back will have three natural curves. But with a big belly out front, the muscles in the back take on extra stress to hold the person upright. The result is bad lower back pain.
"It pulls your back in the wrong direction," Paulos said. "If your lower back is weak, then you'll have more arthritis in your spine."
Besides the obvious goal to lose the belly weight, Laudicina advised all people to pay attention to their posture and alignment.