Low Calorie Diet Plus Exercise Can Be Bad For Bones, Study Finds

Exercising offers a number of health benefits. But not when you are following a low calorie diet.

A new study, published in the Journal of Bone and Mineral Research, found that a combination of calorie restriction and exercise could harm the bones. This may increase one’s risk of injury or fracture. 

"These findings were somewhat of a surprise for us," Maya Styner, senior study author and an associate professor of medicine at the University Of North Carolina School of Medicine, said in a statement. "Past studies in mice have shown us that exercise paired with a normal calorie diet, and even a high calorie diet, is good for bone health. Now we're learning this isn't true for exercise along with a calorie-restricted diet."

For the study, the researchers analyzed the presence of fat in bone marrow of mice. Previous research suggested that such fat could make bones weaker in mammals, including humans. 

The team found that reducing the average calorie intake of mice by 30 percent helped cut their weight. However, the reduction also led to more bone marrow fat.

The researchers continued to cut the animal subjects’ calorie intake with exercise. They found that increased physical activity reduced bone marrow fat but it also made bones more fragile.

"Looking at this from a human perspective, even a lower calorie diet that is very nutritionally sound can have negative effects on bone health, especially paired with exercise," Styner said. "This is important for women to consider because as we age our bone health starts to naturally decline. Your calorie intake and exercise routine can have a great impact on the strength of your bones and your risk for break or fracture."

The U.S. Department of Agriculture (USDA) recommends that a “moderately active” woman in her 30s should take at least 2,000 calories per day. A similar 30 percent reduction in their intake would cut 1,400 calories per day.

Styner and her research team plan to continue the study to further understand how bone marrow fat affects the body. They also aim to explore the direct link between calorie restriction and exercise. 

Bone A doctor examines the result of a patient's x-ray. Pixabay