Ladies stop training fasted
How intermittent fasting is one of the most detrimental diet trends for females
One of the biggest changes we ask our clients to make when they first join us is to stop fasting and never train on an empty stomach.
Intermittent fasting has been very popular for several years, and many of us tried it when it first became popular because of its claimed benefits. However, those benefits were only tested on college-aged males.
As more research has been conducted on women, it has become clear that the effects of intermittent fasting can be harmful to them. Almost every benefit that was claimed actually had the opposite effect on women 🫠.
What is fasting?
For this blog post, we will discuss intermittent fasting and training fasted, specifically for women. Why specifically women? The sex differences that allow fasting to have some benefits for men prove the opposite for women.
Intermittent Fasting = having a shortened eating window, generally 6-8 hours. In practice, this generally means “breaking” a fast around noon and stopping eating around 6-8 p.m.
This often is accompanied by a low-calorie day because you have a shortened window of time to eat, and therefore, you eat less.
Training Fasted = Completing a strength or cardio session before eating, or only with caffeine but not with any calories.
Detriments of fasting
As we look specifically at women, here are just some of the downsides when it comes to Intermittent Fasting:
Does not improve metabolic flexibility in women
Increases waking cortisol levels and further exacerbates your body’s stress response
Can negatively impact thyroid and endocrine system function
Women who fast or have low energy availability regularly are more likely to increase body fat when in a surplus (PMID 7043508)
Increases visceral fat for women in the peri- and postmenopause stages
Fasting for more than 14 hours puts your body in a catabolic state, meaning your body will cannibalize lean tissue
Increases glucose dysregulation
detriments of fasted workouts
As we look specifically at women, here are just some of the downsides when it comes to fasted workouts:
Inhibits muscle growth
In peri- and postmenopause, fasted training reduces your ability to maximize output training sessions, which therefore leaves “gains on the table”
It incentivizes the body to drop lean mass first
Often leads to “bonking” during cardio sessions or running
May experience lightheadedness or dizziness, especially if in a calorie deficit due to fasting
Over time, it can lead to low energy availability (LEA) due to overtraining without adequate calories - think general fatigue, loss of menstrual cycle, frequent illness, IBS, and low bone density
Instead of fasting, eat with your circadian rhythm
Eating in tune with your circadian rhythm = eating within 30-min of waking and stopping eating after dinner (with a max fasting window of 12-14 hours).
Think of this as naturally ending your eating window 2-3 hours before you want to be asleep to allow proper digestion before you lay down and excellent restoration/recovery overnight. Here are some of the benefits of eating with your circadian rhythm:
Better brain function
Regulated thyroid function
Regulated cortisol spikes
Eating while the body is under the most stress
Reduces inflammation from workouts
It is easier to get into a parasympathetic state post-workout
Allows adequate muscle regeneration
circadian rhythm Eating schedule
Are you not sure what that looks like?
Here’s what eating in a circadian rhythm eating schedule could look like if you’re a morning workout person:
6:00 a.m.: Wake-up
6:30 a.m.: 15g Protein Powder mixed with OJ
6:45 - 7:45 a.m.: Workout
8:30 a.m.: Breakfast
12:00 p.m.: Lunch
3:00 p.m.: Midday snack
6:00 p.m.: Dinner
If going for a run, you might want to wait an additional 30 minutes after eating/fueling before starting your workout.
Not a morning person?
Eating first thing in the morning is a skill you learn; as our good friend Laura Hall says, “Just like you train your muscles, heart, and lungs in your workouts - you gotta train your gut to eat early. Earn your training by fueling your body.”
This doesn’t mean you need to slam 800 calories within 30 minutes of waking, either.
Minimum pre-training meal: 15g protein for strength training sessions, 30g carbs for cardio (or more depending on how long that cardio is!)
Eat breakfast within an hour post-training:
Pre-menopausal? 35g protein minimum
Peri- or post-menopause? 40-60g protein
15 - 30g of carbs minimum for all
^^ = 0.3 grams of carbs per kg bodyweight within 2 hours of finishing training
Pre-Training fuel Suggestions
So, what should you eat to get those 15g of protein / 30g of carbs before your workout?
Here are some of our favorites:
Carbs:
Banana
2 Alyssa’s cookies + a latte
Rice cakes
Apple sauce squeeze
Rice Krispy treat
Protein + Carbs:
Protein powder + OJ (creamsicle, anyone?)
Smoothie
Protein freezer waffles
Overnight oats with protein powder or yogurt
So what’s the takeaway?
Every time you see studies touting the benefits of fasting, remember that it was likely conducted on college-aged men.
Fasting is detrimental to female goals of maintaining and building muscle mass and long-term hormone health.
Additionally, many women struggle to meet their daily maintenance calorie and protein needs, and layering fasting only exacerbates that problem.
And if you still don’t believe us, try training fueled instead of fasted tomorrow morning.
Once you feel the difference, you’ll never go back.
References:
Sims ST, Kerksick CM, Smith-Ryan AE, Janse de Jonge XAK, Hirsch KR, Arent SM, Hewlings SJ, Kleiner SM, Bustillo E, Tartar JL, Starratt VG, Kreider RB, Greenwalt C, Rentería LI, Ormsbee MJ, VanDusseldorp TA, Campbell BI, Kalman DS, Antonio J. International society of sports nutrition position stand: nutritional concerns of the female athlete. J Int Soc Sports Nutr. 2023 Dec;20(1):2204066. doi: 10.1080/15502783.2023.2204066. PMID: 37221858; PMCID: PMC10210857.
Hoyenga KB, Hoyenga KT. Gender and energy balance: sex differences in adaptations for feast and famine. Physiol Behav. 1982 Mar;28(3):545-63. doi: 10.1016/0031-9384(82)90153-6. PMID: 7043508.
Vardardottir B, Gudmundsdottir SL, Tryggvadottir EA, Olafsdottir AS. Patterns of energy availability and carbohydrate intake differentiate between adaptable and problematic low energy availability in female athletes. Front Sports Act Living. 2024 May 9;6:1390558. doi: 10.3389/fspor.2024.1390558. PMID: 38783864; PMCID: PMC11111999.
Stannard SR, Buckley AJ, Edge JA, Thompson MW. Adaptations to skeletal muscle with endurance exercise training in the acutely fed versus overnight-fasted state. J Sci Med Sport. 2010 Jul;13(4):465-9. doi: 10.1016/j.jsams.2010.03.002. Epub 2010 May 7. PMID: 20452283.
Huberman Lab with Dr. Stacy Sims: Female-Specific Exercise & Nutrition for Health, Performance & Longevity
doi:10.1007/s42978-019-0004-9
