Everyone has an opinion about keto. Based on what I’ve heard, you either love it or you hate it. However, I rarely hear arguments made on much evidence. I tend to mostly hear people sharing results about how they lost X amount of kg in X amount of time.
Well in true spirit, caring more about your health and performance than Susan’s weight, I’m here to shed some light on the evidence around low carbohydrate, high fat (LCHF) diets (AKA keto) and bone health.
This is a new area of research, however, we are seeing some really interesting results. Based on the available literature it seems that LCHF diets can have a significant negative effect on your bones, at least in the short term.
2017 – Treadmill running
The method: 10 men were allocated to different dietary intervention groups:
2. Immediate feeding (carbohydrate and protein ingested immediately after exercise)
3. Delayed feeding (carbohydrate and protein were ingested 2hours postexercise)
The men ran on a treadmill until exhaustion. and blood samples were taken before and immediately, 1, 2, 3, 4, and 24 hours postexercise. Measurements of bone breakdown and formation were taken.
The results: Delayed postexercise feeding resulted in lower markers of bone formation and increased markers of bone breakdown. As both carbohydrates and protein were provided at the same time, we can’t tell if it was protein or carbs that had the effect (or both!).
Lucky we’ve got more research to share…
2019 – HIIT Training
The method: Nine men completed a morning and afternoon HIIT training session with a controlled diet.
1. High carb
2. Reduced carbs but high fat
3. Reduced carb and reduced total calories
The results: In diets with lower carbs, markers of bone breakdown were higher prior to, immediately and 3 hours after the second HIIT session.
Hammond KM. et al. Post-exercise carbohydrate and energy availability induce independent effects on skeletal muscle cell signalling and bone turnover: implications for training adaptation. J Physiol. 2019; 597(18):4779-4796
2020 – Elite race walkers
The method: 30 Elite race walkers (25 Males) were allocated to 1 of 2 groups for 3.5 weeks. Group one consumed a high carbohydrate diet and group 2 consumed a LCHF diet. Both groups consumed the same number of calories and protein based on their individual body weight. After 3.5 weeks measures of bone turnover were taken at rest and after exercise.
The results: In the LCHF diet markers of bone breakdown increased and markers of bone formation decreased.
Conclusion: Markers of bone health post exercise were impaired by a LCHF diet, at least in the short term. More research is needed to determine the longer term effects.
So, based on the research available, I’d say that this is an exciting area to look out for. We do need more longer-term studies and more work done in various populations, including women. However, it’s a great start.
My advice based on the literature:
I’d say that most people are going to get more out of fuelling with carbs than not fuelling, however, particular groups of people are at greater risk of poor bone health.
Endurance athletes: With the repetitive nature of endurance sports, it’s not surprising that there are high incidences of stress reactions and fractures. As far as nutrition goes, we know that adequate energy, protein, calcium and vitamin D are essential to good bone health for these athletes, however, based on the research, I’d argue that carbs should be a #1 priority.
Post-menopause: Due to the change in hormones, post menopausal women need to watch their bone health. I’d keep an eye on this space. It’s clear the research right now, couldn’t be further from this population group, however, I can’t see it hurting you if you are in this group to ensure that you are fuelling and recovering from your training.
Weight loss: Both of the groups mentioned above are notorious for undereating relative to their energy needs. Most of the time, the first thing to go from a diet when trying to lose weight is carbs. Based on these studies, we can’t tell what the minimum amount of carbs required to avoid bone loss is, however, I wouldn’t be recommending any extremes to these clients.