Research that I am collecting and reviewing then putting together into blog…
“Intuitive Fueling, Training & Performing for the Female Athlete!”
Dr. Stacy Sims on Fasting and The Female Athlete…
Is it better to train fasted or after eating?
There are many trends that have led to people thinking that fasted training is the way to go, primarily due to the buzz of “training low” increasing “metabolic efficiency” for improved performance, and, of course, intermittent fasting. It is important to highlight that there are some key differences based on gender, so fasted training for men can lead to different results than for women. For men who are looking to manage their weight, there may be a slight benefit to fasted training. Research in the past couple of years has demonstrated that in young, healthy men, fasting before morning exercise decreased their 24-hour energy intake and increased fat oxidation during exercise. For performance, however, it is a different story.
Fasted training does enhance fat metabolism (oxidation) in well-trained male endurance athletes, yet this might not translate to improved performance when exercising at moderate to high intensities (as is required in triathlon racing).
Women, however, do not respond to fasted training in the same manner as men. Women do not have an increase in oxidative activity (fat utilization) of the muscle as a result of fasted training, but do incur a greater post-exercise immune stress and greater post-exercise inflammation as compared to men. They also show an increase in muscle tissue damage and breakdown (leading to potential losses in lean mass). The theory is that since estrogen promotes fatty acid utilization, women are already at a maximum capacity for fat oxidation.
“So if you’re already exercising, it’s not particularly helpful. And if you’re a woman who is adding athletics on top of intermittent fasting, it can be harmful to both your performance and your health.
It comes down to kisspeptin, is a neuropeptide that’s responsible for sex hormones and endocrine and reproductive function, which also plays a significant role in maintaining healthy glucose levels, appetite regulation, and body composition. It’s also more sensitive in women than men. When it gets perturbed, our sex hormones aren’t produced and released the way we need them to be. Intermittent fasting and keto both disrupt kisspeptin production. When our brain perceives we have a deficiency in nutrients, especially carbohydrate, we have a marked reduction in kisspeptin stimulation, which not only increases our appetite, but also reduces our sensitivity to insulin. This is why research shows intermittent fasting is more likely to cause impaired glucose intolerance in women, but not men. What happens when we layer exercise stress on top of the stress of denying our bodies an important fuel source? Stress hormones like cortisol rise even higher. As you keep increasing that stress, it keeps your sympathetic drive high and reduces your ability to relax. Your thyroid activity is depressed, which messes with your menstrual cycle. Your body also starts storing more belly fat. So now you’re looking at disrupted menstrual cycles, higher anxiety and stress, impaired performance and often weight gain—pretty much the opposite of what you’re looking for!
The ketogenic diet has very similar effects on women athletes.
We hear people rave about the increased mental focus with a keto diet. In men, yes. They have an increase in their parasympathetic (a.k.a. rest and digest) activity, so they can be more relaxed and present. In women, keto kicks up our sympathetic (a.k.a. fight or flight) drive, so we’re more anxious, more prone to being depressed, and we can’t sleep very well, which again hurts our hormonal health, performance, well being, and body composition. Sometimes women will contend that these diets work so well for them. And they might for the first three months, because nearly any diet will yield some effects in the short term. The long term effects for women athletes, however, is endocrine dysfunction, increases in abdominal fat, more depression, and a backlash of subsequent fat gain”
Women athletes perform far better in a fed state. Women athletes need to eat.
What stimulates kisspeptin release?
“A large body of data has established the hypothalamic kisspeptin (KP) and its receptor, KISS1R, as major players in the activation of the neuroendocrine reproductive axis at the time of puberty and maintenance of reproductive capacity in the adult. Due to its strategic location, this ligand-receptor pair acts as an integrator of cues from gonadal steroids as well as of circadian and seasonal variation-related information on the reproductive axis. Besides these cues, the activity of the hypothalamic KP signaling is very sensitive to the current metabolic status of the body. In conditions of energy imbalance, either positive or negative, a number of alterations in the hypothalamic KP signaling pathway have been documented in different mammalian models including nonhuman primates and human. Deficiency of metabolic fuels during fasting causes a marked reduction of Kiss1 gene transcript levels in the hypothalamus and, hence, decreases the output of KP-containing neurons. Food intake or exogenous supply of metabolic cues, such as leptin, reverses metabolic insufficiency-related changes in the hypothalamic KP signaling. Likewise, alterations in Kiss1 expression have also been reported in other situations of energy imbalance like diabetes and obesity.
Information related to the body’s current metabolic status reaches to KP neurons both directly as well as indirectly via a complex network of other neurons. In this review article, we have provided an updated summary of the available literature on the regulation of the hypothalamic KP-Kiss1r signaling by metabolic cues. In particular, the potential mechanisms of metabolic impact on the hypothalamic KP-Kiss1r signaling, in light of available evidence, are discussed.”
https://www.frontiersin.org/articles/10.3389/fendo.2018.00123/full
Debbie Potts
Health & Fitness Coach, Author, & Speaker
Host of ‘The Low Carb Athlete’ Health Building Podcast
Founder of ‘The WHOLESTIC Method’ Coaching Program
FNTP, FDNP, NASM CPT, CHEK HLC, Ben Greenfield Coaching
BURN FAT. OPTIMIZE HEALTH. IMPROVE PERFORMANCE.
Learn more on https://linktr.ee/Debbiepotts