We have a lot of research showing that low energy availability (not getting enough calories) is a significant risk factor for bone stress injuries - when you don’t get enough calories, bone breakdown increases without an increase (and sometimes even a decrease) in bone formation. This upsets the equilibrium of bone recovery & remodeling, potentially leading to a bone stress injury. 

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Recently, however, researchers have looked deeper at the individual impact of carbohydrates, not just total calories, on bone breakdown and formation - and the results might surprise you.

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The 2022 study compared the effects of two different types of dietary restriction over 6 days on markers of bone health. The study was broken up into 2 phases: baseline and adaptation. During the baseline phase, all subjects followed a control diet of adequate energy & carbohydrates for 6 days. 

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During the adaptation phase:

• Group 1 (LCHF ketogenic) took in a low carbohydrate, high fat diet with high energy availability (similar to keto diet)- meaning they had plenty of calories but low levels of carbs every day for 6 days. 

• Group 2 (LEA) was the low energy availability group, who consumed significantly lower levels of calories but a higher percentage of carbs (60% of total calories) for 6 days. 

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Each of these groups was also compared to a control group that consumed a high energy availability diet, 65% of which was carbohydrates. 

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The study controlled for training during the study to ensure similar volume and intensity among and between groups. A 25 kilometer racewalk was performed on the last day of each phase and blood samples were taken: at rest, just before exercise, and 3 times postexercise: immediately, 1 hour, and 3 hours following.

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They found:

• Bone breakdown markers increased when exercise was completed after EITHER a low-energy availability or low-carb, high-fat ketogenic diet

• Bone formation markers decreased during exercise and at rest ONLY after the low-carb, high-fat ketogenic diet

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As a result, the authors suggested:

• Carbohydrates may be crucial for bone formation during prolonged exercise

• Both adequate energy AND adequate carbohydrates are needed for bone formation at rest and during exercise, and to reduce bone breakdown during exercise

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So what does this mean for you to optimize bone recovery from exercise through your food intake?

1. See an RD for guidance!

2. Eat allll the carbs to reduce bone breakdown and maintain bone formation. Carb intake before & during exercise may assist with this. 

3. Eat plenty of calories to reduce bone breakdown. 

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(Side note: lots and lots of micronutrients play a role in bone health: calcium, phosphorous, magnesium, potassium, zinc, iron, copper, manganese, and Vitamins D, K C and A. Deficiency in any one of these may impact bone remodeling, so eating a wide variety of nutrient-dense foods and/or supplementing appropriately may also be helpful. An RD can assess whether you’re deficient and provide guidance to address this) Feel free to contact me for RD recommendations!

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Looking for help recovering from a BSI or training in a healthy way with a history of BSI? Get in touch below!