Diet trends go in and out of style, but intermittent fasting has been a buzzy diet among celebs for a while. Plenty of people swear by the health and weight loss benefits. Still, even the same weight-loss method can work differently from person to person, you may be wondering whether there is a best way to do intermittent fasting for women and get the most out of your efforts.
First, the basics: Intermittent fasting consists of eating windows, when you can theoretically eat whatever you want, and fasting periods, when you’re supposed to abstain from food and drinks but are allowed to have water, coffee, and tea. And their exact durations depend on which variation of the diet you follow.
It is possible to lose weight with an intermittent fasting diet, but there’s a lot of potential for it to be done incorrectly, says Samantha Coogan, RDN, the program director of the didactic program in nutrition and dietetics at the University of Nevada, Las Vegas. “There are not a lot of strict guidelines when it comes to what should be consumed during the eating period, and a lot of people tend to take it as they can eat whatever I want.”
In other words, it’s important to not overeat or binge following a fasting period, but instead fuel your body with a balanced diet of nutrients, says Jessica Cording, RD, the author of The Little Book of Game-Changers. “It really depends on the person and what someone is eating during their eating window,” she notes. “It also matters how and what someone was eating before they went on an intermittent fasting diet.”
Not sure if intermittent fasting is for you? Here’s everything you need to know about fasting diets and what to expect, according to registered dietitians.
Meet the experts: Samantha Coogan, RDN, is the program director of the didactic program in nutrition and dietetics at the University of Nevada, Las Vegas.
Jessica Cording, RD,is a dietitian and health coach for the Valley Breast Center in Northern New Jersey. She is also the author of The Little Book of Game-Changers.
Alissa Rumsey, RD, is a nutritionist and certified intuitive eating counselor.
So…what is intermittent fasting, exactly?
“Intermittent fasting is when you allow yourself to eat only during a specified window of time each day,” explains Alissa Rumsey, RD, a NYC-based dietitian and the owner of Alissa Rumsey Nutrition and Wellness. It usually involves fasting for a certain number of hours or even days that are spaced out during the week, and there’s no “right” way to do this, says Sonya Angelone, RD, a spokeswoman for the Academy of Nutrition and Dietetics.
What are some popular intermittent fasting schedules?
There are many different kinds of intermittent fasting diets. The 5:2 diet is one. On this diet, women eat less than 500 calories (for men, it's less than 600) for two non-consecutive days a week. So, you might have a 500-calorie day on Tuesday and Thursday, and then eat normally on Monday, Wednesday, Friday, Saturday, and Sunday. With the 5:2 diet, you don’t need to eat certain foods—you just limit how much you eat during certain periods of time.
Another popular one is the 16:8 diet. You only eat during eight hours of the day. You can choose when you want your eight-hour period to be, but most people tend to stop eating at a certain time in the evening, like 6 p.m., and then wait to eat again until 16 hours later (in this case, it would be at 10 a.m.). That way, you’re sleeping for part of your fast instead of sitting around, thinking about the food you’re not eating for a good part of the day.
There’s also something known as the 24-hour fast (or complete alternate day fasting). “That requires fasting from all food for 24 hours once or twice per week,” Angelone explains.
It’s easy to assume that the duration of your fasting window will impact how much weight you lose, but that’s actually not the case, according to Scott Keatley, RD, of Keatley Medical Nutrition Therapy. “The timing of intermittent fasting or the duration of the fasting window does not seem to impact the amount of weight lost,” he says.
There’s also some “it depends” in there too. “For some individuals, the longer the window, the less calories they will consume since obviously less time to eat,” says Keri Gans, RD, the author of The Small Change Diet. “However, for others, it may not make any difference in that they can consume equal amount of calories simply in a shorter time.”
Gans also says there’s really “no conclusive scientific evidence to suggest that a longer fasting window comes with more benefits.”
Which is the best intermittent fasting schedule for women?
Coogan would never recommend the 5:2 diet for aging women, or anyone who is taking any medication. “The brain needs a minimum of 130 grams of carbohydrates just to do its basic functions for the day, which comes out to about 520 calories, so if you do the 5:2 diet, you're already at that limit for your day just in carbohydrates,” she explains.
She would also not recommend intermittent fasting for anyone over 65. “For ages 40 and 50, you may be able to see some benefits, but as men and women get older, especially into their 60s, they start to naturally lose more lean muscle mass and overtime appetite may start to decrease, so I would never want to see someone restrict even further,” Coogan says.
If you take any medications, always clear intermittent fasting with your doctor since certain meds may cause nausea or stomach irritation if taken on an empty stomach.
But there aren't necessarily schedules that are better suited for men versus women. A 2022 study found that weight loss benefits of alternate day fasting were basically the same and similar changes in health markers like blood pressure were observed across genders.
A pro tip from Coogan: For women between the ages of 20 and 50, the most sustainable schedule is the 16:8 or the 14:10 diet, where you fast for 14 hours and have a 10-hour eating window.
Can you lose weight with intermittent fasting?
Research has found a link between intermittent fasting and weight loss, but there isn't much research to prove that intermittent fasting is a better weight loss method than other diets. For example, a meta-analysis published in the JBI Database of Systematic Reviews and Implementation Reports in 2018 found that intermittent fasting had similar weight loss results to a traditional calorie-restricted diet.
In some cases, even when intermittent fasting did lead to weight loss, it wasn't the most sustainable diet. One randomized clinical trial of 100 metabolically healthy, obese adults (published in JAMA Internal Medicine in 2017) found that those who fasted every other day for a year only lost slightly more weight than those who ate a restricted-calorie diet on a daily basis. The difference in weight loss was so small that it wasn’t considered clinically significant, and 38 percent of people in the alternate-day fasting group had trouble sticking with the diet.
It’s also worth pointing out that weight loss due to intermittent fasting isn’t guaranteed to last. “Some people may experience weight loss in the short-term, but many people eventually gain that weight back,” Rumsey says.
And, most intermittent fasting research has only been done on people who are obese. “There is almost no credible research that shows intermittent fasting is good for people at a healthy weight,” says Keatley. If you're curious about intermittent fasting but don't have much weight to lose, it might not be the best diet for you.
Are there any long-term health benefits of intermittent fasting?
There is a growing body of research that suggests intermittent fasting does have health benefits outside of weight loss. One study published in Cell Metabolism in 2018 linked intermittent fasting and lower insulin levels and blood pressure. Researchers followed a small group of obese men with prediabetes—some were put on a 16:8 diet, while others ate over a period of 12 hours. Both groups didn’t gain or lose weight. But after five weeks, the men in the 16:8 group had much lower insulin levels and better insulin sensitivity. They also significantly lowered their blood pressure and said they had decreased appetites. They weren’t as hungry as they were before—even though they were fasting.
It might seem counterintuitive, but appetite control is a big benefit of fasting. A recent study in the journal Obesity showed that people who ate only during a six-hour window, compared to following a normal eating schedule, felt less hungry than the control group, even though both groups ate the same amount of calories. Intermittent fasting has also been linked to increased neuroplasticity, or the brain's ability to form new synaptic connections and fight injury.
Unfortunately, there hasn’t been a ton of research on humans that follows the effects of intermittent fasting long-term. While some studies have followed participants for a year, that’s about as long as most go. It’s a slightly different story when it comes to rats. “In rodents, intermittent fasting has been shown to prevent age-related diseases, including tumors, heart disease, diabetes, dementia, and even extend lifespan,” says Keatley. But, he adds, “there is a big difference between rats and humans, and the research does not show these benefits enough to actually recommend it as the fountain of youth.”
What foods can I eat and what do I have to avoid?
This is a huge perk of intermittent fasting: You technically don’t have to alter what you eat—you just have to eat within a certain window of time. “On an intermittent fasting diet you don’t need to avoid any foods,” Gans says. “However, one should focus on consuming foods that are high in fiber and healthy fats for satiety, such as quinoa, black beans, spinach, strawberries, avocado, and almonds, and of course other nutrient-dense foods for overall health.”
At the same time, it’s a good idea to limit sugary drinks, processed foods, and simple carbs like white bread, advises Cording. “They’re not providing you with much nourishment,” she says. “You really want to focus on foods that do you a favor.”
That said, plenty of people have paired intermittent fasting with another type of diet, like keto. Again, it’s not a requirement, but doing intermittent fasting while also altering your diet could help you get results faster.
Does intermittent fasting have any side effects?
There are a few things that can happen when you follow an intermittent fasting diet. One thing to note is that fasting can interfere with your hunger cues. “Since people are only allowing themselves to eat in a certain window of time, they are completely ignoring their internal cues of hunger,” Rumsey says. “It causes people to disregard hunger cues, which then means once they are ‘allowed’ to eat, they are starving and it can be hard to stop eating.” This could lead to an unhealthy obsession with food for some people, Rumsey says.
Some fasters find that the diet makes them feel sharper and more alert, but alternately, fasting for long periods can also lead to mental fogginess, disrupted sleep, and decreased alertness, Rumsey says. And, she adds, fasting for extended periods of time “takes a large toll on your blood sugar levels,” causing you to flip-flop between low blood sugar and a spike when you eat again.
Is intermittent fasting safe for women?
There is some evidence that intermittent fasting can have negative effects on women—a 2022 study reported that fasting may harm fertility since it lowers the levels of sex hormones like testosterone (yes, women also have testosterone) and suppresses your libido.
That said, the research is limited at this point and more evidence is needed. The study above is an animal study done with mice and it's not clear how those findings apply to humans.
So, intermittent fasting isn’t necessarily a hard yes or no for all women. But always talk with your doctor or a registered dietitian to make sure it's a good fit for you, stresses Coogan.
Should I try intermittent fasting?
It really depends. If you feel like you have a healthy relationship with food and you do well with parameters, it could be a good fit for you. It's certainly not an easy diet if you hate the feeling of being hungry, but the fasting periods do get easier with time, Angelone says.
While anyone can try intermittent fasting, ultimately, people who are overweight and/or have high blood pressure or high cholesterol (but are otherwise healthy) are considered the best fits for the diet, Angelone says.
You’ll also want to take a pass if you’re pregnant or breastfeeding or if you have a history of disordered eating, says Cording. “It can be a bit of a slippery slope into disordered patterns,” she explains.
How do I start?
There’s really no magic plan to follow with this, but you could try to figure out a form of intermittent fasting that makes the most sense for you. The 5:2 diet can be tricky, given that it involves calorie restriction for an entire day at a time, so it might be better to start with something like the 16:8 diet and progress from there if you feel good.
You also want to define what you’re hoping to get out of intermittent fasting, and it doesn’t hurt to check in with an expert, like your doctor or a dietitian, before you dive in. “Work with a professional who understands your goals and can help you determine what you need to eat for a diet like this to achieve,” says Keatley. Then, he recommends shooting for “small changes and small gains, as these are most likely to do the least harm and provide the most long-term benefits.”
Above all, listen to your body. If you feel like you’re hungry all the time and are kind of miserable, it probably isn’t the right fit for you. If you love the simplicity and you're seeing the weight loss or health results you want, fast away.
The bottom line: Some people may find intermittent fasting an effective way to lose weight, especially if they can tolerate hunger well and the schedule they choose makes sense for their lifestyle. If you take medication regularly, check in with your doc or an RD to make sure intermittent fasting is safe for you.
Andi Breitowich is a Chicago-based writer and graduate student at Northwestern Medill. She’s a mass consumer of social media and cares about women’s rights, holistic wellness, and non-stigmatizing reproductive care. As a former collegiate pole vaulter, she has a love for all things fitness and is currently obsessed with Peloton Tread workouts and hot yoga.
