Combining exercising with cutting calories is often the go-to for weight loss. But research suggests being active while restricting how much we eat may be bad for our bones.
Scientists put mice on a restrictive diet and 'running routine' for six weeks. They lost weight, which the team thought would make their bones more robust.
The researchers were therefore surprised to discover the rodents' bone volume had actually decreased by 20 per cent. From a 'human perspective', the researchers warn cutting calories while exercising could have a 'great impact on bones', particularly in women, whose bones naturally weaken with age.
The University of North Carolina study comes amid a growing trend for calorie-restricting diets, such as the 5:2 or 16:8 eating patterns.
Exercise has been shown to support bone strength, the researchers wrote in the Journal of Bone and Mineral Research. However, the effect of calorie reduction on this process was less clear.
Another surprising result was the increase of bone marrow fat in the calorie-restricted mice, despite them losing weight overall.
Bone marrow fat is thought to make the bones of mammals, including mice and humans, weaker, the researchers claim.
Although the study was carried out in animals, the researchers believe similar results could apply to humans, particularly women. The researchers are planning further studies to uncover the purpose of bone marrow fat, and how it is affected by diet and exercise.
Calorie-restricted diets have surged in popularity in recent years, with more and more people turning to fasts, like the 5:2, low-carb plans, such as Atkins, and juicing 'cleanses'.
As well as promoting weight loss, fasting alone has been linked to a longer life, stronger immune system and even a reduced risk of cancer. Limiting carbs may help lower blood pressure, prevent diabetes and boost heart health.
