Exercising while eating a low-calorie diet may have a negative effect on bone health, according to a new study out of the University of North Carolina Health Care. Unlike in cases of exercise without calorie restriction, eating fewer calories while exercising was found to cause a substantial increase in the amount of fat in bone marrow, something associated with lowered bone health. The effect was observed in cases of only mild calorie restriction.
Calorie restriction is necessary for weight loss; dieters are often advised to keep this restriction relatively low for slow and steady weight loss in order to decrease the risk of developing certain issues associated with rapid fat loss. Even mild calorie restriction may have a negative effect on bone health, however, something made worse when exercise was added into the equation.
Scientists aren’t sure why fat may be present in bone marrow, but its presence causes bones to become weaker, making it a sign of poor bone health. Exercising decreases the amount of fat in bones in both healthy weight and obese people when paired with normal and high-calorie diets.
However, the study found that the same activity causes an increase in bone marrow fat when paired with a low-calorie diet, the latter of which also causes a bone marrow fat increase in the absence of exercise. The study involved mice fed regular and low-calorie diets, including groups that were also tasked with exercising.
The mice put on a diet were fed 30-percent fewer calories when compared to the regular diet, which would be similar to someone eating 1400 calories a day when they typically eat 2,000. In addition to the major jump in bone marrow fat, the researchers found that calorie restriction also caused a decrease in bone quantity.
Because the mice were given nutritional supplements while on a diet, the researchers note that the bone effect was due to restricted calories, not a decrease in nutrients. This is important for people on diets to consider, particularly older adults and anyone who already has a bone health issue. Weakened bones are more prone to suffering fractures and breaks during exercise.