Dieting Without Exercise Harms Bone Health
Men and women who lose weight through caloric restriction, without exercise,
also lose bone at the hip and spine, increasing their risk for the bone-thinning
disease osteoporosis and fractures, a study shows. Adding regular exercise to a
calorie-restricted diet helps shield the bones from the harmful effects of
against bone loss during voluntary weight loss,” Dr. Dennis T. Villareal, who
led the study, told Reuters Health. “Therefore, it would be important to combine
calorie restriction and exercise to derive the benefits of weight loss and
Washington University School of Medicine in St. Louis, and colleagues studied
the effects of weight loss on bone loss in 30 women and 18 men whose average age
was 57 years. The study subjects were overweight but not obese.
For one year, 19
subjects stuck to a calorie-restricted diet; 19 ate their usual number of
calories but engaged in regular exercise; and 10 in a comparison “control” group
received healthy lifestyle tips only. All but two participants completed the
At the end of the 12
months, the dieters lost an average of 18.1 pounds, while the exercisers lost
14.8 pounds and those in the control group had no significant change in their
As reported in the
Archives of Internal Medicine, the dieters lost an average of 2.2 percent of
bone density in the lower spine and at the hip. In contrast, there were no
significant changes in bone mineral density in the exercise group or healthy
The action of
muscles pulling on bones during exercise is thought to produce “healthy” strain
on the skeleton that stimulates the production of new bone, the investigators
note. The current study supports this line of thought.
“It’s important that
calorie restriction not be seen as a bad thing,” Villareal said, “because it
offers enormous benefits with respect to reducing disease risk and is effective
for weight loss. Also, there is a real possibility that calorie restriction
provides anti-aging benefits that cannot be achieved through exercise
However, to maintain healthy bones, “exercise should be an important
component of a weight loss program to offset adverse effects of calorie
restriction on bone,” the team concludes.
Osteoporosis, or porous bone, is a disease characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased risk of fractures of the hip, spine, and wrist. Men as well as women are affected by osteoporosis, a disease that can be prevented and treated.
Facts and Figures
Osteoporosis is a major public health threat for 44 million Americans, 68 percent of whom are women.In the U.S. today, 10 million individuals already have osteoporosis and 34 million more have low bone mass, placing them at increased risk for this disease. One out of every
two women and one in four men over 50 will have an osteoporosis-related fracture in their lifetime.
More than 2 million American men suffer from osteoporosis, and millions more are at risk. Each year, 80,000 men have a hip fracture and one-third of these men die within a year. Osteoporosis can strike at any age. Osteoporosis is responsible for more than 1.5 million fractures annually, including 300,000 hip fractures, approximately 700,000 vertebral fractures, 250,000 wrist fractures, and more than 300,000 fractures at other sites. Based on figures from hospitals and nursing homes, the estimated national direct expenditures for osteoporosis and related fractures total $14 billion each year.
What Is Bone?Bone is living, growing tissue. It is made mostly of collagen, a protein that provides a soft framework, and calcium phosphate, a mineral that adds strength and hardens the framework.
This combination of collagen and calcium makes bone both flexible and strong, which in turn helps it to withstand stress. More than 99 percent of the body’s calcium is contained in the bones and teeth. The remaining 1 percent is found in the blood.
Throughout your lifetime, old bone is removed (resorption) and new bone is added to the skeleton (formation). During childhood and teenage years, new bone is added faster than old bone is removed. As a result, bones become larger, heavier, and denser. Bone formation outpaces
resorption until peak bone mass (maximum bone density and strength) is reached around age 30. After that time, bone resorption slowly begins to exceed bone formation.
For women, bone loss is fastest in the first few years after menopause, and it continues into the postmenopausal years. Osteoporosis – which mainly affects women but may also affect men – will develop when bone resorption occurs too quickly or when replacement occurs too slowly. Osteoporosis is more likely to develop if you did not reach optimal peak bone mass during your bone-building years.
Certain risk factors are linked to the development of osteoporosis and contribute to an individual’s likelihood of developing the disease. Many people with osteoporosis have several risk factors, but others who develop the disease have no known risk factors. There are some
you cannot change and others you can.
Risk factors you cannot change:
Gender – Your chances of developing osteoporosis are greater if you are a woman. Women have less bone tissue and lose bone faster than men because of the changes that happen with menopause.
Age – The older you are, the greater your risk of
osteoporosis. Your bones become thinner and weaker as you age. Body size – Small, thin-boned women are at greater risk.
Ethnicity – Caucasian and Asian women are at highest risk. African American and Hispanic women have a lower but significant risk. Family history – Fracture risk may be due, in part, to heredity. People whose parents have a history of fractures also seem to have reduced bone mass
and may be at risk for fractures. Risk factors you can change:
Sex hormones – Abnormal absence of menstrual periods (amenorrhea), low estrogen level (menopause), and low testosterone level in men can bring on osteoporosis.
Anorexia nervosa – Characterized by an irrational
fear of weight gain, this eating disorder increases your risk for osteoporosis.
Calcium and vitamin D intake – A lifetime diet low in calcium and vitamin D makes you more prone to bone loss.
Medication use – Long-term use of glucocorticoids and some anticonvulsants can lead to loss of bone density and fractures.
Lifestyle – An inactive lifestyle or extended bed rest tends to weaken bones. Cigarette smoking – Cigarettes are bad for bones as well as the heart and lungs. Alcohol intake – Excessive consumption increases the risk of bone loss and fractures.
To reach optimal peak bone mass and continue building new bone tissue as you age, there are several factors you should consider.
Calcium: An inadequate supply of calcium over a lifetime contributes to the development of osteoporosis. Many published studies show that low calcium intake appears to be associated with low bone mass, rapid
bone loss, and high fracture rates. National nutrition surveys show that many people consume less than half the amount of calcium recommended to build and maintain healthy bones. Good sources of calcium include low-fat dairy products, such as milk, yogurt, cheese, and ice cream; dark green, leafy vegetables, such as broccoli, collard greens, bok choy, and spinach; sardines and salmon with bones; tofu; almonds; and foods fortified with calcium, such as orange juice, cereals, and breads. Depending upon how much calcium you get each day from food, you may need to take a calcium supplement.
Calcium needs change during one’s lifetime. The body’s demand for calcium is greater during childhood and adolescence, when the skeleton is growing rapidly, and during pregnancy and breastfeeding. Postmenopausal women and older men also need to consume more calcium. Also, as
you age, your body becomes less efficient at absorbing calcium and other nutrients. Older adults also are more likely to have chronic medical problems and to use medications that may impair calcium absorption.
Recommended Calcium Intakes (mg/day) &nb