Women who exercise but do not eat enough food can suffer significant health problems, researchers say.
University of Otago nutrition researchers said this included almost half of the women in a new study, who it found may be at risk of what is known as low energy availability.
When affected by LEA, women's bodies act to conserve energy by triggering hormonal adaptations that harm health, the study's lead author Dr Katherine Black said.
"Physical activity, sport and exercise are undoubtedly an important part of a healthy lifestyle," she said.
"However, when energy expenditure during exercise significantly exceeds energy intake this can cause problems, particularly for bone health and reproductive function."
Dr Black and her colleagues surveyed 109 female recreational athletes for the study and found 49 were at risk of LEA.
The team found that for every one hour increase in exercise per week by a female exerciser there was a significant increase in the likelihood of being at risk of LEA and that the state could be linked to a greater risk of injury.
Dr Black said it was important to raise awareness of LEA given the high proportion of recreational athletes at risk and its links to injury.
"However, we also need to encourage New Zealand recreational exercisers to continue taking part in physical activity as the health benefits are well established," she said.
"It is about finding the correct balance."