Dieters And Bone Loss
In 1992 a North Dakota physiologist made a connection between weight loss and bone loss in an ongoing study of the relation of dieting to bone content.
In a five-month study of fourteen overweight women, aged 20 to 40 years, in a weight reduction program, Dr. Henry C. Lukaski of the Grand Forks Human Nutrition Research Center found that the women lost one to two percent of their bone mass along with an average of eighteen pounds of weight.
The weight reduction program was specifically designed to prevent bone loss: the diet contained adequate amounts of all essential vitamins and minerals and more than the recommended 800 milligrams of calcium per day; the women also participated in a supervised aerobic exercise program lasting two hours each day. After one month on a maintenance diet, the study participants' caloric intake was reduced by 25 percent for the next month and by 50 percent for the last three months, to an average of 1,200 to 1,300 calories a day.
When their caloric intake was cut in half, the women lost bone faster and formed new bone more slowly than normal. The study also found that the women retained less than normal amounts of magnesium, a mineral involved in bone growth.
Dr. Lukas said that the relationship between weight loss and loss of bone has been generally ignored in this country. He also said that there are many questions concerning weight and bone loss that need to be answered. For example, is there a connection between bone content and body weight? If the same amount of weight is lost in a short period of time versus a longer period of time, is the bone loss greater, less, or the same? Is there a benefit of increased muscle mass in preventing bone loss? Is bone mass restored when lost weight is regained? If it is not, those who lose and gain weight in the infamous yo-yo cycle may be at greater risk for osteoporosis than previously thought.
Ballerinas And Osteoporosis
There have been epidemiological studies whose conclusions support Dr. Lukaski's clinical study correlating bone loss with dieting. The New England Journal of Medicine published a study (5/22/86) which found that nearly a quarter of 75 female ballerinas surveyed at four major ballet companies had some degree of scoliosis. Since scoliosis afflicts only 3.9 percent of white females in this age range, the rate of scoliosis in the corps de ballet (which was all white) was more than six times the normal. The study also found that dancers with scoliosis were more likely to have eating disorders (bulimia and anorexia) than others:
"Dancers are known to diet to maintain the thin body form that is considered ideal in classical danceThe dancers in our study weighed a mean of 87 percent of the ideal value. Those with scoliosis also scored higher on the oral control scale, which is a measure of dietary behaviorThe incidence of anorexia nervosa in ballet dancers is 5 percent to 22 percent, a reflection of dieting behaviorCalcium and vitamin D intake is suboptimal among ballet dancers, and the effects of this deprivation could lead to inadequate calcification, osteopenia, and poor skeletal stability."
It would appear that the curved spines and stress fractures of these young ballerinas are manifestations of the same osteoporosis that afflicts many postmenopausal women, taking a somewhat different form in youth than in middle or old age: "Scoliosis and fractures may be adolescent manifestations of inadequate calcification and skeletal stability during a rapid growth phase: However, this osteoporosis of youth, even if asymptomatic at the time of onset, as it might be in young women who diet to a less intense degree than those who develop scoliosis and fractures, might be the precursor of the osteoporosis of later life: "Pubertal apposition of bone may be decreased so that at the time of maturation, bone density is lower than normal. Thus, loss of bone at even a normal rate could result in a mechanically incompetent skeleton and fractures."
Mary Lou Williams, M. Ed., is a lecturer and writer in the field of nutrition. She welcomes inquiries. She can be reached at 267-6480.