By Rachael Schultz
You’ve probably heard the buzz: intermittent fasting (IF) can help with weight loss, fat loss, insulin sensitivity, and even brain health. And if you’re over 40, you might be wondering if fasting could be the key to feeling more energized, staying leaner, or keeping your metabolism in check as the years go by.
Here’s the thing — these functions naturally become harder to optimize as you age. Metabolism slows, insulin sensitivity drops, and losing body fat isn’t as effortless as it was in your 20s. That’s where IF comes in: Containing your eating to be all within a set window of time has the potential to help counteract these changes. No calorie counting required.
But the science isn’t all black and white. Some benefits are well-documented, while others are still up for debate. And, like any health strategy, intermittent fasting isn’t right for everyone.
Understanding Intermittent Fasting
Intermittent Fasting (IF) is an eating pattern that limits when you eat rather than what you eat. It cycles between periods of eating and fasting, allowing your body to take breaks from digestion and potentially tap into stored energy more efficiently. The most popular (and well-studied) forms are:
- Time-restricted fasting (TRF): Limits eating to a specific number of hours each day. The most common form is 16:8 (fasting for 16 hours, eating within an 8-hour window), but other approaches, like 14:10, may work better for some.
- Alternate-day fasting (ADF): Rotates between regular eating days and days with either full fasting or significantly reduced calorie intake (about 500 calories).
- 5:2 Diet: A modified version of ADF where you eat normally five days a week and limit calories to ~500–600 calories on two non-consecutive days.
Potential Benefits for Women Over 40
During midlife, your hormones change as you go through menopause; you become less sensitive to insulin production and your metabolism slows which makes it harder to maintain or lose weight; your body stores fat differently (and typically not in a way we like); and your risk for developing diseases like type 2 diabetes and cardiovascular disease go up.
The science shows that intermittent fasting may actually be able to help with many of these things. Take a look:
It Can Help You Lose Weight — Without Restricting Calories
Losing weight, specifically body fat, comes down to one key principle: burning more calories than you consume. But for many, traditional calorie restriction feels restrictive, difficult to maintain, and ultimately ineffective in the long run.
That’s where intermittent fasting stands out. Research shows IF can be as effective for fat loss as traditional calorie restriction but without the need to track everything you eat.
In fact, weight loss is one of the most well-supported benefits of intermittent fasting. One study found that participants following a 16:8 IF approach (fasting 16 hours, eating within an 8-hour window) lost an average of 3.6% of their body weight over six months—significantly more than the control group that reduced their calories by 25%.
Why does this work?
- Fewer unconscious calories: Without a set eating schedule, it’s easy to rack up extra calories through late-night snacking or mindless eating. IF naturally reduces these without forcing you to restrict specific foods.
- Better fat-burning potential: Once your body burns through its glycogen stores during a fasting period, it starts tapping into stored fat for energy, aiding in fat loss.
For those with obesity or type 2 diabetes, research suggests IF may be especially beneficial, offering an effective way to support weight management without the stress of constant calorie counting.
“Intermittent fasting may help counteract age-related metabolic changes—no calorie counting required.”
It May Boost Health for Those with Heart Disease
A small 2020 study published in Cell Metabolism examined the effects of time-restricted eating on people with metabolic syndrome, most of whom were taking statins or antihypertensive medications. After 12 weeks of following a 10-hour eating window and a 14-hour nightly fast, participants saw improvements in weight loss, blood pressure, cholesterol levels, blood sugar control, and more restful sleep.
Other research shows intermittent fasting is most effective for heart health when people exercise regularly.
That said, recent preliminary research has raised some concerns about intermittent fasting for people with heart disease (more on that in a minute). However, the leading published and peer-reviewed research, including a 2024 meta-analysis of existing research, still supports fasting as a beneficial strategy for lowering cardiovascular risk.
It May Help Improve Type 2 Diabetes
One of the biggest benefits of fasting is that it gives your body a break from releasing insulin. This can improve insulin sensitivity, helping your cells respond better over time. Since insulin resistance is a key factor in type 2 diabetes, intermittent fasting may help make blood sugar management easier.
A 2022 study published in Diabetes Care found that participants who followed a modified IF approach (three days of 25% fewer calories, followed by four days of regular eating) improved their HbA1C levels enough to reduce their need for daily insulin. They also lost an average of 10 pounds, an important factor in improving diabetes management.
Even more promising, a 2023 meta-analysis reported that intermittent fasting was more effective at lowering HBA1C levels than a conventional diabetes diet. Another study showed that a 5:2 diet (eating fewer calories two days a week) for 16 weeks improved blood sugar control in people with type 2 diabetes even more than the common diabetes medications, metformin and empagliflozin.
That said, there’s still a lot we don’t know. Some research suggests that IF’s benefits for insulin resistance, blood sugar control, and cholesterol may be short-lived. But it’s also unclear whether fasting is more effective than simply following a calorie-restricted diet.
Still, IF shows promise, especially for those struggling with traditional dietary changes. If you have type 2 diabetes, talk to your doctor before trying iF to make sure it aligns with your specific health needs.
It May be Easier to Stick to Than Calorie Restriction
In the 2020 Cell Metabolism study participants followed time-restricted feeding (TRF) for 12 weeks. When researchers checked in over a year later, most had continued on their own for at least a few more months — even without being told to.
This suggests that people found it relatively easy to integrate into daily life and sustain without external guidance.
It Can Improve Your Brain Health
The gut-brain axis connects the health and contents of your gut and the health and inflammation of your brain. Because of this, we know certain diets help your brain (and, therefore body) to function better than others (hello, Mediterranean diet).
Researchers at Johns Hopkins University found that after eight weeks of following the 5:2 diet, cognitively-healthy older adults showed better memory, better executive function (the everyday brain power that helps you solve problems and adapt), and a slower pace of brain aging. While they didn’t find any change in Alzheimer’s biomarkers, other clinical studies have shown intermittent fasting may be beneficial for epilepsy, Alzheimer’s disease, and multiple sclerosis, mostly in older populations.
Also good news for women: While some people get brain fog during fasting periods, women often have better brain functioning during fasting compared to men.
“IF may support heart health by improving blood pressure, cholesterol, and blood sugar control.”
Risks, Considerations & What’s Still Unclear
While there are a lot of benefits to intermittent fasting, there’s still a lot we don’t know. Here are some things to keep in mind:
It May Affect Some of Your Hormones
Researchers at Northwestern and the University of Illinois at Chicago studied the effects of intermittent fasting on hormone levels in pre- and postmenopausal women over an 8-week period. The majority of reproductive hormones—including sex hormone-binding globulin (SHBG), testosterone, and androstenedione—were unchanged. That’s the good news.
The one exception? Dehydroepiandrosterone (DHEA) levels dropped by about 14% in all women by the end of the trial.
DHEA is a hormone that plays a key role in producing estrogen and testosterone, both of which decline naturally with age, especially during menopause. Even though the participants’ DHEA levels stayed within the normal range and no one experienced symptoms of low estrogen, the lead study author said that further reduction could be a concern for postmenopausal women who already experience a steep drop in estrogen. Lower estrogen levels are associated with an increased risk of bone loss, cardiovascular disease, and cognitive decline.
In short: If you’re postmenopausal or near menopause, talk to your OB-GYN before you start intermittent fasting just to be safe.
If You Have Heart Disease, Talk To Your Doc First
There’s strong evidence supporting the benefits of short-term intermittent fasting for heart health. However, a paper presented at the 2024 American Heart Association conference has raised some concerns about its long-term effects for people with existing heart disease. The study, which followed the dietary habits of more than 20,000 U.S. adults over eight years, found that people with heart disease who ate within an 8–10 hour window had a 66% higher risk of dying from stroke or heart disease compared to those with a longer eating window.
That said, this paper has not yet been peer-reviewed or published, and only analyzed a short snapshot of participants’ diets. Cardiologists emphasize that even though researchers found an association between an 8-hour eating window and cardiovascular death, this does not prove that intermittent fasting increased the risk.
Still, if you have cardiovascular disease, talk to your doctor before you start intermittent fasting.
In Fact, Talk to Your Doc First Regardless
It’s always a good idea to talk to your doctor before you undertake any new diet, especially as we age because there are so many more factors at play compared to when we’re in our 20s.
For ADF, Your ‘Eat’ Window Should be at Least 8 Hours
The same preliminary paper presented at the 2024 American Heart Association conference also suggested that fasting periods longer than 16 hours might be problematic for some individuals. Participants who followed a fasting schedule with an eating window of fewer than 8 hours a day had a 91% higher risk of dying from heart disease.
Most well-studied IF approaches (such as 10-hour eating window or alternate-day fasting) allow for more flexibility. If you’re considering intermittent fasting, starting with a longer eating window (10+ hours) or an alternative-day fasting approach may be a safer and more sustainable option.
Plan Your Workouts During Eating Windows
Intermittent fasting is proven to be pretty safe, but depending on what type of IF you choose and your current eating habits, you might experience temporary, mild side effects like headaches, fatigue, mood swings, dizziness, and having to urinate frequently — especially in the beginning.
These effects are usually limited to fasting periods, so it’s smart to plan workouts accordingly. If you’re doing alternate-day fasting, schedule fasting days as rest days. In general, try to work out during eating windows to maintain energy levels and reduce the risk of dizziness or lightheadedness.
It’s Still Most Important to Optimize Your Nutrition
Regardless of when you eat, what you eat still matters most.
A 2023 Australian study found that intermittent fasting didn’t reduce inflammation markers or body fat as well as a diet optimized for nutrition intake and calorie balance. In other words, fasting alone isn’t enough —your best health outcomes come from prioritizing whole, minimally processed foods and eating a variety of fruits, vegetables, whole grains, and plant-based proteins.
If intermittent fasting helps you stick to a nutritious diet and avoid mindless snacking, great. But time-restricted eating shouldn’t be an excuse to eat ultra-processed, low-nutrient foods just because they fit within your fasting window.
The Bottom Line
Intermittent fasting shows promise for women over 40, offering potential benefits in weight management, heart health, and blood sugar control. But it’s not a one-size-fits-all solution.
Some women thrive with IF, while others experience energy dips, mood swings, or changes in hormone levels. And while short-term research is promising, we still don’t know the long-term effects of fasting on metabolism, insulin sensitivity, or heart health.
The bottom line? If IF feels good and helps you eat in a balanced, sustainable way, it could be a great tool. But if it leaves you feeling sluggish or stressed about food, it may not be the right fit.
As always, check in with your doctor before starting a fasting routine, especially if you have pre-existing health conditions. And no matter what eating pattern you follow, prioritizing whole, nutrient-dense foods is the best way to support long-term health.
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