Dr. Michael Ruscio, DC is a clinician, Naturopathic Practitioner, clinical researcher, author, and adjunct professor at the University of Bridgeport. His work has been published in peer-reviewed medical journals and he speaks at conferences around the globe.
Research Shows Intermittent Fasting is Safe and Effective for Most, But Always Apply Your Own Health History
Intermittent fasting (IF) can be an excellent weight loss and overall health strategy for women just as well as men, but there are some extra factors to consider with hormones, your personal stress level, and your daily energy expenditure.
Benefits of IF for women include weight loss, heart health, improving insulin levels/diabetes, and gut health (similar to men).
However, there are also some women who should absolutely NOT practice intermittent fasting, including women who are breastfeeding, pregnant, or trying to conceive.
Ways to optimize intermittent fasting for women include prioritizing protein, making sure you’re getting enough calories in your meals, and possibly opting for breakfast over dinner when planning your meal schedule.
When intermittent fasting first became popular several years ago, the health benefits were generally thought to apply to all adults — men and women alike. But over the years, some concerns have arisen about ways that intermittent fasting might affect women differently than men, based on the impact of the menstrual cycle, the delicate balance between female hormones like estrogen and progesterone, and a possibility for some women to (often unknowingly) practice dangerous calorie restriction while fasting.
Does intermittent fasting work for women? Of course, the answer isn’t a simple yes or no. In this article, we’ll discuss the drawbacks and benefits of intermittent fasting on women’s health, whether you are pre-menopause or no longer cycling, and ways you can optimize an intermittent fasting protocol to make it work for you.
The Basics of Intermittent Fasting
What is intermittent fasting (IF)? IF means eating during a restricted period of your day and fasting (not consuming any food or liquids except water) for the rest of that 24-hour period. It can also include other types of intermittent fasting like short-term 24-hour fasts and 5:2 fasting, which is eating normally for 5 days of the week and fasting for two nonconsecutive days. Alternate-day fasting is also a possible method.
Aside from overall wellness, IF is often recommended for:
Overall, research shows that intermittent fasting appears to be safe and effective for most women, especially overweight and obese women, those with issues regulating blood sugar levels and blood pressure, and menopausal and post-menopausal women .
A systematic review found that intermittent fasting had similar effects on regulating triglyceride and cholesterol levels in both male and female athletes .
Similarly, many randomized controlled trials (RCTs), two observational studies, and two literature reviews concluded that overweight or obese women and pre- or postmenopausal women experience significant weight loss benefits from intermittent fasting [20, 21, 22, 23, 24, 25, 26, 27]. Menopausal women may also benefit from lessened anxiety, depression, and insomnia that often come with this time of life, along with improvements in self-esteem.
Another specific situation where intermittent fasting may work well for women is for those who have high androgen levels with polycystic ovarian syndrome (PCOS). Intermittent fasting has been shown to reduce androgen levels in both women and men. This is good news for women with too-high androgens, but may have a negative impact on men since androgens are associated with metabolic health and libido in men .
Where the Research Gets Murky
However, there are some caveats presented in the research for women doing intermittent fasting.
In one RCT, women performed workouts better if they ate before exercising, whereas men trained better if they exercised after an overnight fast .
Another study showed that, as IF reduced women’s BMIs, so dropped their levels of SIRT1 — an enzyme that helps regulate metabolism, protect against chronic inflammation, support hormone functions, reduce oxidative stress, and repair DNA . In contrast, when IF lowered the BMIs of men, their SIRT1 levels increased, suggesting the potential that men’s bodies respond better to IF than women’s.
However, this relationship between fasting and SIRT1 is not definitive enough to say whether IF is better or worse for men or women on a larger scale. It pays to be cautious when interpreting these types of results, and it’s safe to say that, at this time, the benefits of intermittent fasting in women outweigh its association with a single health marker.
Overall, it’s not clear from the research alone if women should do intermittent fasting differently from men, but it does support that it can offer women-specific health benefits. However, we’re going to explore some of the reasons why intermittent fasting may not be ideal for some women and how to know if you’re one of them.
Are There Women Who Should NOT Practice Intermittent Fasting?
There is a nuanced answer to this question, but the short version is yes. Different diets and health protocols will not affect everyone the same way, no matter how much research and evidence there is to back it up for a certain percentage of the population. Intermittent fasting may not be the right eating pattern for you if:
#1 You are pregnant, breastfeeding, or trying to conceive
This is the one hard no for intermittent fasting. If you are pregnant or breastfeeding, you should avoid intermittent fasting to steer clear of any possible developmental abnormalities and lactation ketoacidosis (an overload of ketones in the blood when you don’t have enough glucose to meet your energy demands during breastfeeding) .
Your first priority during pregnancy is always to get enough nutrition for you and your baby in whatever way you can. Not to mention, with the ups and downs of pregnancy, hormonal changes, and possible food aversions, intermittent fasting almost seems a bit harsh during this life stage. For your safety and sanity, skip adding intermittent fasting to your already rapidly changing lifestyle at this time.
#2 You have severe chronic fatigue, chronic illness, or are otherwise in a state of extreme depletion
This means that you are unable to carry on daily activities, like exercise and work, are unintentionally losing weight, and have significant vitamin and mineral deficiencies. Hair loss, amenorrhea or skipping periods, severe depression, and anxiety are also common signs of extreme depletion in women.
These are all symptoms of a body under extreme stress, and fasting, while beneficial for many, is also a stressor. To be able to benefit from fasting as good stress, you need to come from a place of at least being able to handle moderate stress on a daily basis first.
There may need to be a period of time where you focus on correcting any nutritional deficiencies and increasing your caloric intake (if you are undereating) before you attempt intermittent fasting. Even then, some women may find that they can fast without any negative symptoms for most of the month, but they need to take a break during a heavy menses to avoid issues like dizziness and fatigue (and this is totally fine to do).
#3 You are in a temporary period of high stress
“High stress” looks different for everyone. It could come from work and family obligations, a significant life event such as a death or illness in the family, or running a business during the holidays.
During this time, you want to focus on nourishing your body and letting your nervous system know it’s safe in part by having regularly spaced, well-balanced meals. This prevents cortisol from being released due to hunger and blood sugar swings when you skip meals.
A caveat to this may be if you’ve already practiced intermittent fasting for some time and you know you feel better when fasting regularly. But if you are experiencing a higher amount of stress and potentially anxiety, making sure you eat regularly may help ground you more than you think. Either way, I recommend abstaining from starting intermittent fasting for the first time during a period of high stress.
#4 Fasting Simply Doesn’t Feel Good to You
There is a subset of people, particularly women, who simply don’t feel good when fasting. This may be for hormonal reasons, nutrition reasons, or preference. You’ll know fasting isn’t right for you if you:
Experience fatigue, irritability, brain fog, mood swings, or other adverse symptoms when you don’t eat regularly
Have consistent hunger cues throughout the day
Don’t perform well on short-term liquid-only fasts
You have been diagnosed with an eating disorder or experienced disordered eating
If you don’t feel right when fasting, listen to your body! If your fasting intolerance is due to underlying hormonal issues, undereating, or nutrient deficiencies, you may be able to come back to IF when your health has generally improved.
Another note is that many people find fasting especially difficult when they have underlying gut infections such as parasites or candida overgrowth since you are essentially limiting their food source. When these gut infections are pruned back, you may find fasting much easier.
Tips and Ways to Make Intermittent Fasting Work for Women
If you do decide to pursue intermittent fasting, there are several ways to get the best results and avoid common pitfalls.
#1 Prioritize Getting Enough Protein
As I’ve learned lately from Dr. Gabrielle Lyon and others, making sure you’re getting enough protein on a daily basis is extremely important for good metabolism, adequate energy (especially if you’re exercising), muscle synthesis, and tissue repair. And eating enough protein only gets more important as you age to prevent the loss of muscle mass.
As an easy rule of thumb, I recommend 0.8-1 gram of protein per kilogram of body weight per day. If you aren’t used to eating this amount of protein, it can seem like a lot at first, so it’s okay to slowly increase your protein intake over several weeks. Another guideline would be to include 30-40 grams of protein per meal (at 3 meals per day), but if you are skipping one of your meals with intermittent fasting, you should bump up the protein content to 40-50 grams per meal.
Let’s say you’re doing the 16/8 method of intermittent fasting, and you plan to eat two full meals during your eating window. Each of those meals should have at least 40 grams of protein to meet the minimum of your daily needs. Alongside one of those meals, you might include a high-quality protein shake or smoothie, or have a high-protein snack in between your meals to make sure you’re eating enough.
#2 Don’t Cut Your Daily Calorie Intake When Skipping Meals
Along similar lines, you want to make sure you’re still getting enough calories in to meet your total daily energy expenditure (TDEE) while practicing intermittent fasting.
If your goal is weight loss, you may be eating fewer calories, but it’s still important to get the calories you need for your target weight from nutritious, satiating, and healthy foods. Additionally, many women drastically underestimate the amount of calories they actually need in a day. Your needs may also change depending on your age, life stage (such as pre, peri, or post-pregnancy), and stress levels.
For example, a woman who is in her late 20s, is moderately active (exercises 3-5 days per week), and weighs 130-135 lbs needs about 2,000 calories a day to meet her daily energy expenditure. In a period of high stress, you may need more, or on a low activity day, you may need less.
You can find your TDEE with this TDEE Calculator. To find out how many calories you’re consuming each day, you can track using an app like MyFitnessPal. If you have no idea where you stand with daily calorie intake, it may be worth it to track for a few days at your current intake to get a baseline and make adjustments from there. Don’t be afraid to make small changes and steadily increase your calories if you find you are significantly undereating.
Once you’ve mastered getting your calorie requirements each day, you can see how you would adapt your eating schedule to be able to still meet those requirements in a shorter amount of time. This may require a little more planning, but it’s essential to make sure you’re getting all the nutrients you need each day.
#3 Favor Breakfast and Lunch Over Dinner
If you are going to skip one of your meals during your fasting window, it might benefit women to prioritize eating breakfast and lunch and skipping dinner, vs. the popular IF method of skipping breakfast and putting off your first meal of the day until lunchtime.
This hypothesis comes from my conversation with Dr. Gabrielle Lyon on the podcast, who stated, “number one, your first meal of the day must be optimized for dietary protein. And that is between ideally 40 to 50 grams of dietary protein.” Doing this sets you up for optimal energy production and muscle building.
If you are someone who finds not eating in the morning more difficult, then work with your body and eat a breakfast with enough high-quality protein, especially if you also tend to exercise in the morning. Then perhaps you eat a snack a few hours later and your second full meal 2-3 hours after that. That would keep you within an 8-hour feeding window.
Of course, this isn’t going to be ideal for everyone. But optimizing your feeding window to follow the period of the day when you have the most activity (including brain activity!) might make intermittent fasting more effective for some people.
Women Can Absolutely Practice Intermittent Fasting When It’s Right for Them
The bottom line on intermittent fasting is that it may be helpful for some women, but it is not required for your well-being. If intermittent fasting doesn’t work well for your body for any reason, don’t feel guilty that you are missing out on the health benefits of a fasting schedule. But an inability to handle fasting may also be a sign of an underlying health issue, such as a hormonal imbalance or nutritional deficiency.
If you want to investigate intermittent fasting alongside a knowledgeable health provider, we can support you at the Ruscio Institute for Functional Medicine. Reach out to us to schedule a free consultation.
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