Intermittent fasting (IF) has been around for as long as humans have been eating. It gained popularity, though, in 2012 with several publications. These included BBC broadcast journalist Dr. Michael Mosley's TV documentary Eat Fast, Live Longer, as well as his book, The Fast Diet, The 5:2 Diet by Kate Harrison, and The Obesity Code by Dr. Jason Fung. That was probably around the time you started hearing about it and wondering if it could work for you. A recent review of all studies conducted from inception of the current literature databases until January 8, 2024 found that IF has been shown to decrease waist circumference, fat mass, LDL cholesterol, triglycerols, total cholesterol, fasting insulin, and systolic blood pressure while increasing HDL cholesterol and fat free mass. This sounds like a pretty good deal if you’re in the market for weight loss.
WHAT IS IF AND HOW DO YOU DO IT?
According to Wake Forest University medical experts, Intermittent fasting “consists of multiple different timing schedules for temporary food avoidance, including alternate-day fasting, other similar full-day fasting patterns, and time-restricted feeding (where the day's food is consumed over a 6-h period, allowing for 18 h of fasting).” How you do it is up to you, and 12 hours has been shown to be an adequate time restriction for autophagy (or the ‘cleaning’ of dead cells) to begin in the body as well as any of the benefits listed in regard to metabolic health. Additionally, this randomized control trial showed that eating earlier in the day following a 12 hour feeding window was more effective than prolonging breakfast and eating later in the day. Even the research favors BKFST.
BUT WHAT IF YOU’RE A CYCLING WOMAN?
As with the vast majority of medical literature, the findings from male subjects have been widely applied to women. Now, if you’re postmenopausal, this isn’t a problem and running with the research may benefit you. But if you have a menstrual cycle, take a pause with me.
You may want the IF benefits touted by wellness experts and research, but as a cycling woman, practicing it the way it’s been recommended will not work throughout every phase of your cycle. Why? Because your physiology was created to bring life into the world, build, and shed a uterine lining, and those mechanisms require energy (or calories) at predictable intervals in order to operate effectively. In other words, you need to eat more in the second half of your cycle when your body needs more gas in the tank.
Additionally, as a person who bleeds, certain nutrients as well as a certain threshold of calories are needed for hormone balance, which, in the spirit of being redundant, will always circle back to your body’s ability to get pregnant. When you restrict calories at the wrong time (yes there is a wrong time), sirens will sound and the factory will shut down to conserve as much energy as possible. Cue hormone imbalance, PMS, irregularity, resistance to weight loss, and more.
It is known that cravings for specific foods arise in the days leading up to your period (for most women), namely sugar, salt and fat. Additionally, across the luteal phase, women tend to increase their consumption of carbs, protein, fiber, and calcium. Interestingly, though, the amount of food consumption across a group of regular menstrual cycles was consistent. So, when it comes to available energy, the patterns in study groups have been consistent, though, there is a greater need for carbohydrates in the second half of the cycle when, due to the hormone balance present, you are more insulin resistant and gluconeogenesis (creating energy from stores) becomes harder for your body to accomplish. Why? Simply put, saving energy for that possible pregnancy as well as the energy it takes to build up the uterine lining that’s about to shed. What this also means is that you can capitalize on increased insulin sensitivity in the first half of your cycle when the need for available energy isn’t as high as the second half. So, decreasing portion sizes and extending a fast may actually help with body changes.
PUT IT INTO PRACTICE
So, how does all the fasting hoopla apply to you? Can you use these hacks for metabolic improvement, weight loss, and longevity, even gut health? How do you do it?
Turns out, women in the follicular phase (medically speaking, Cycle Day 1 - Ovulation)
So if there’s a time to restrict calories or adjust mealtimes, it’s in the first half of your cycle. During the second half, 12 hours should be your absolute max time in a fast (overnight). Play with what feels intuitive to you, I recommend not going past 14 hours if you are going to extend your fast in order to preserve your food relationship- equally as (if not more) important to all the aesthetic & physiological health goals you have. And because I always have to say it, the way you go about spacing your meals should be unique to YOU. It’s all dependent on your cycle, your life, and your needs. Here’s an example of how I treat mealtimes with clients, adjust the times to fit your schedule and give it a try:
Cycle Day 1 - Ovulation:
WAKE: 7am
BKFST: 8am
LUNCH: 12:30pm
DINNER: 5pm
SLEEP: 9pm (asleep by 10pm)
Ovulation- Cycle Day 1:
WAKE: 7am
BKFST: 8am
LUNCH: 11am
SNACK: 3pm
DINNER: 7pm
SLEEP: 10pm (asleep by 11pm)
**Adjusting feeding and fasting times should not be attempted if you have any menstrual irregularities or symptoms due to hormonal imbalance. As always, consult your physician before making major lifestyle adjustments.
If you want some help creating an eating schedule according to your unique cycle and needs, book a free introductory session and let’s create it together.
CITATIONS
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Souza LB, Martins KA, Cordeiro MM, Rodrigues YS, Rafacho BPM, Bomfim RA. Do Food Intake and Food Cravings Change during the Menstrual Cycle of Young Women? Rev Bras Ginecol Obstet. 2018 Nov;40(11):686-692. doi: 10.1055/s-0038-1675831. Epub 2018 Nov 28. PMID: 30485899; PMCID: PMC10316899.
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