HPN 15: Is Keto Bad For Bone Health? Plus: The Risks of Intermittent Fasting For Female Athletes (And Why We Say ‘A Hard No’)
March 6, 2020
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Welcome to episode 15 of Holistic Performance Nutrition (HPN) featuring Tawnee Gibson, MS, CSCS, CISSN, and Julie McCloskey, a certified holistic nutrition coach who you can find over at wildandwell.fit.
On this episode:
Is LCHF bad for bone health?
Hi Tawnee and Julie. Long time listener and a few-times question writer— thanks for all the great advice! Yesterday I read an article about a study (link to article) that found that suggested that low carb or keto diets can have negative effects on bone health. I’ve been fairly low carb since my early teens (I’m now 25), but definitely dealt with some disordered eating, through my background with a competitive weight class based sport. I had a brief bout of amenorrhea in junior high, but have since gone back to a normal cycle, and I think I sit at a healthy body weight (125lbs, 5’5). But I did jump on the keto train pretty early on, and maintained that for three half ironmans, and began to reintroduce more carbs as I was training for my first ironman in sept 2019 (think fruits, sweet potatoes, potato, beet chips, the occasional bread or rice), and then went back to a lower carb diet again in the fall post-ironman. This article about bone health worries me, especially since the birth control I’m on (depoprovera) is also known to decrease bone density. Do either of you have any thoughts on this? Even though my relationship with food has improved a lot over the years, the thought of switching back from a low carb diet sort of makes me panic. I wouldn’t know where to start, even though I can’t even remember why I think carbs are so bad. Should I add more carbs to my diet?
What the Coaches say:
The Study: A Short-Term Ketogenic Diet Impairs Markers of Bone Health in Response to Exercise
Summary: long-term effects of the low-carb, high-fat (LCHF) diet are unknown, but this short-term study showed that a low carbohydrate diet has negative effects on the bone modeling and remodeling process.
- Only a 3.5-week intervention; the authors say that is was long enough to get adapted to low-carbs
- Participants: elite race walkers; 23 males, 5 females
- High carb condition was high
- Low carb condition was low
- Protein was also pretty high at 2g per kg
- This was not about calories/energy availability; energy intake was matched for both conditions
- Test block of a 2hr walk at 75% VO2max
- 3 times over the study (baseline, adaptation, restoration) they collected blood samples to get serum bone markers
- A summary of the results: in the LCHF group, the marker for bone breakdown increased while it decreased in the level of bone formation (with only partial recovery) after a 3.5-week intervention while training at substantial rates.
- Mechanism of breakdown: “Results from several studies have shown that if you start an endurance exercise with low glycogen availability then it stimulates the release of cytokine-interleukin6 from the exercising muscles. IL-6 has been hypothesized to increase the activity of another receptor (K B-ligand) which controls bone turnover by increasing bone breakdown.”
- Bone health is just one of many reasons Tawnee does not recommend long-term keto for people, and specifically for women. <100g carbohydrate a day is not safe and usually has unintended side effects.
- This study also mentions, “to date, no studies have examined the effects of longer-term restriction of carbohydrates (CHO) at rest or in relation to exercise, although in animal models and children with intractable epilepsy, chronic adaptation to a ketogenic LCHF diet is associated with poor bone health.”
- Is Louise Burke (a renowned sports scientist) anti keto? Somewhat. “The plural of anecdote isn’t evidence.”
- Tawnee listened to a 2016 podcast with her on it discussing LCHF and she lands in the middle somewhere with a big emphasis on periodization. But at the end, she did say that she wouldn’t recommend LCHF for performance until there is more evidence for it, which is exactly what Tawnee would expect a seasoned scientist to say
- Low energy availability
- When restricting ⅓ of your macronutrients, it becomes incredibly difficult to meet your energy needs as an endurance athlete
- Have you replaced your carbs with anything substantial? Extra fat or protein? Might be in an energy deficit
- For people without disordered eating, what does this study mean?
- There is potential that going too low-carb for too long can lead to a decline in bone strength
- Take it for what it is, and if you especially feel like you are LCHF and not meeting your energy needs as an athlete, start reintroducing more carbs and see how you feel
- Do we have evidence elsewhere of long term keto on bone health?
Take home message:
- We don’t need to be pushing hardcore keto year-round
- For female athletes, step away
- Start with small changes, maybe make some oatmeal but use less oats and more chia seeds, nuts, or berries.
- The scariest part of change is the thought of it, and how we’re certain it will cause us to lose control.
- A question to ask yourself “how is this fear of carbohydrates serving me?”
- If you’re going to trend toward lower-carb:
- Be sure to get adequate food sources of calcium (see list below)
- Foods high in calcium that aren’t starchy carbs or dairy (with more calcium than cow’s milk, i.e. between 150-350 mg calcium per serving compared to 138mg in 4oz cow’s milk):
- ¼ cup Sesame seeds
- 3.75 oz canned Sardines w/ bones
- 3 oz Canned wild salmon with bones–those bones!
- 1 cup Greens- collard greens, spinach, turnip greens, beet greens, mustard greens
- Bok Choy
- 1 tbsp molasses
- Most likely supplement with Vitamin D, K2 (we like Thorne D/K2 drops).
- If D is below 30 ng/dl then that could signal a problem, definitely supplement.
- Vitamin D is not in that many foods; the sun is important.
- Vitamin A and Magnesium
- Vitamin A: liver, egg yolk, cod liver oil (cod liver oil also has D)
- Magnesium bisglycinate by Thorne + foods: spinach, pumpkin seeds, tuna, almonds, dark chocolate, avocados, bananas
- Weight-bearing exercise– spine and hips under load! Lift heavy things. Not just chronic endurance.
- Check your stress! Chris Kresser states, “Cortisol indirectly acts on bone by blocking calcium absorption which decreases bone cell growth, and even a short bout of elevated cortisol may cause a decrease in bone mass. Several studies suggest that high cortisol may lead to decreased bone density.”
Jessica W. asks:
Intermittent Fasting for Women?
Hi. This is a question for the HPN podcast editions. I would love to hear your ladies’ take on intermittent fasting specifically for women but even more specifically for women over 40 who are endurance athletes. Is it useful from a general health perspective and/or performance perspective? I understand being fat adapted but is IF the way to go for women? What about increased cortisol levels caused by IF? When Brock and Lucho were hosting Endurance Planet they always talked about skipping breakfast (fashionably known as IF lol) but then in their answers to the ATC questions they would say things like, “Listen to your body.” How is IF listening to your body if you are ignoring hunger signals? Really enjoy all of the Endurance Planet shows. You are doing a fantastic job!
What the Coaches say:
IF for women:
- Don’t IF if:
- Recovering from adrenal imbalances
- Recovering from an eating disorder
- Struggling with severe insomnia with frequent waking
- Trying to conceive & have known hormone imbalances
- Pregnant or postpartum
- If lacking energy balance (under-eating or over-exercising); IF can give your body a further signal you are starving and does nothing to help your health or performance.
- If struggling with cortisol imbalance or HPA axis dysfunction (often seen on DUTCH tests) it can be difficult to stabilize blood sugar. Compounded with long periods of no eating (daytime longer than 3 hours or overnight fast of 12+ hours) not only makes you feel worse but can worsen health.
- Symptoms that you might see in these cases: anxious, lightheaded, angry, short of breath, blurry-eyed, nauseated, alarm state/panic.
- Study: Within-day Energy Deficiency and Reproductive Function in Female Endurance Athletes
- An observational study (not able to define a causal relationship between WDED and health)
- The more time during the day that you spend in a negative energy balance, the more at risk you introduce for menstrual dysfunction (and RED-S symptoms), EVEN IF your total daily calories end up balancing out with your energy expenditure and 24hr energy availability is adequate (ie the MD and eumenorrheic athletes had similar energy availability overall, it’s just that the MD group didn’t balance out their calories very well within the day and spent too much time in negative energy balance). In other words, fasting all day then eating a ton in the evening is not a good strategy and still puts you at risk hormonally and otherwise
- Don’t let body weight be your guide on how much you need to eat and/or IF.
- “Most female athletes with long-term energy deficiency are reported to maintain a steady body weight and body composition within the normal range, independent of their reproductive function. Therefore, other metabolic mechanisms may be involved, such as a reduction in RMR and/or non-exercise activity thermogenesis (NEAT) 10, as well as in increased work-load efficiency.”
- However, MD subjects had 19% lower FM and 14% lower relative FM compared to eumenorrheic subjects, although there were no differences in training volume or exercise capacity.
- Energy availability says a lot
- “Low EA with or without disordered eating (DE) behavior is related to endocrine alterations leading to several health and performance impairing conditions including menstrual dysfunction (MD), gastrointestinal problems, impaired bone health, and increased injury risk.”
- Going under energy balance by -300 calories enough to tip you over into negative outcomes??
- “A desirable range of EB of ± 300 kcal has been suggested, since 300 kcal corresponds to the predicted amount of liver glycogen for female athletes. Exceeding the threshold of EB below -300 kcal, could potentially accelerate biochemical pathways associated with energy deficiency20 and compromise brain glucose availability and thereby normal gonadotropin-releasing hormone (GnRH) neuron activity and luteinizing hormone (LH) pulsatility.”
- What this study looked at:
- Investigate if female elite endurance athletes with menstrual disturbance (MD) with similar reported 24-hour EB and EA as eumenorrheic athletes spend more time in a catabolic state and have a larger magnitude of within-day energy deficiency (WDED) compared to eumenorrheic athletes. Furthermore, it was our intent to investigate if WDED is associated with suppressed RMR and endocrine alterations in these athletes.
- 25 subjects, 15 with MD
- 24 hr EA and EB was similar
- No association between body comp and WDED
- Subjects with MD had lower RMRratio (measured RMR/predicted RMR), lower estrogen, higher cortisol, and a trend toward lower T3
- Subjects with MD spent more time with EB < 0 kcal and < -300 kcal compared to eumenorrheic subjects (Table 3).
- smaller magnitudes of hourly energy deficits (closer to 0 kcal) were associated with higher estrogen levels.
- Subjects with MD had significantly more meals/snacks per day compared to eumenorrheic subjects
- A sub-analysis, excluding oligomenorrheic subjects, showed a more pronounced difference between amenorrheic (n = 11) and eumenorrheic subjects in EB.
- The more hours spent with energy balance EB < 0 kcal and < -300 kcal (eg catabolic state), the lower the RMRratio and estrogen and the higher the cortisol levels (Table 4). In addition, smaller magnitudes of hourly energy deficits (closer to 0 kcal) were associated with higher estrogen levels.
- Athletes with MD spent 24% more hours in EB < -300 kcal compared to eumenorrheic athletes, providing a potentially more profound catabolic state.
- Animal studies suggest that the reproductive function is responsive to hourly changes in metabolic fuel.
- Loucks and Thuma demonstrated that women with a shorter luteal phase (11 days) are more susceptible to energy deficiency in terms of endocrine alterations compared to women with longer luteal phases (12-14 days). As discussed by the authors, women that by nature have a slightly shorter luteal phase may be of an increased risk of developing MD when exposed to energy deficiency.
- Thus, the eumenorrheic athletes with a high number of catabolic hours in the present study may be women with a more robust reproductive function. On the other hand, it is unknown whether these athletes may have had subclinical MDs associated with energy deficiency such as anovulation or luteal phase abnormality.
- Email firstname.lastname@example.org if you would like a copy of the full article
- Study: Potential Benefits and Harms of Intermittent Energy Restriction and Intermittent Fasting Amongst Obese, Overweight and Normal Weight Subjects—A Narrative Review of Human and Animal Evidence
- 4 weeks of intermittent energy restriction (IER), 4 days out of the week, at a 70% energy restriction (ER) ER + 3 days at ad libitum eating amongst nine normal-weight young women, classified as unrestrained eaters, resulted in:
- increased feelings of hunger
- worse mood
- heightened irritability
- difficulties concentrating
- increased fatigue
- eating-related thoughts
- fear of loss of control and overeating during non-restricted days