It’s a story I hear over and over again: A woman is cruising along, feeling like she has her diet and workout routine pretty well dialed in. Then, some time in her 40s, her body composition suddenly starts changing, sometimes rapidly, despite no apparent differences in her food intake or exercise.
Women’s bodies often go through profound transformations in their 40s, mostly due to hormonal shifts associated with perimenopause. Most women start noticing symptoms of perimenopause in their mid-40s, although they can begin as early as mid-30s for some, or as late as mid-50s. This phase may last anywhere from four years to more than a decade (!) before women experience menopause, defined as no menstrual period for 12 months, and transition into postmenopause. In addition to changes in body composition—different fat storage patterns, weight gain, even changes in muscle mass and bone density—many women experience brain fog, low mood, fatigue, hot flashes, and low libido.
Perimenopause can leave women feeling bewildered and like they no longer have control over their bodies. When they try to figure out how to respond, they quickly discover that there’s very little research targeting middle-aged women, especially in the nutrition realm. Premenopausal and postmenopausal women are represented well enough. Those of us in the middle? Not so much.
Mark and I get lots of questions from women about whether keto is appropriate for them:
The answer to the first two is yes. As for the third one… well, that’s the million-dollar question, isn’t it? We don’t know for sure. Unsurprisingly, there’s no research looking at keto across different phases of women’s lives. Nevertheless, we can piece together some educated deductions paired with anecdotal observations based on working with a diverse community of keto dieters for years.
Of course, there is no “typical” woman over 40. Your experience may be very different from your friends’. Likewise, what works for you at 45 may no longer work at 55, let alone 75. Certainly, though, it makes sense to ask a few key questions instead of assuming that the same diet that works for college-aged dudes will work for women in their 40s and beyond.
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Perimenopause is a turbulent time, hormonally speaking. Progesterone declines rapidly and stays low, while estrogen levels can fluctuate up and down unpredictably for years before finally settling at a lower level. Low progesterone and mercurial estrogen are responsible for most of the unpleasant physical and emotional symptoms associated with perimenopause and menopause.
Although we don’t know for sure that keto is directly beneficial, there are good reasons to consider it:
Many women in their 40s and 50s struggle with weight gain that seems sudden and unexplained. Out of the blue, body fat accumulates around the midsection. Clothes no longer fit. The body they see in the mirror looks like it belongs to someone else.
Estrogen is the main culprit here. As estrogen levels fall, fat storage patterns shift. Instead of storing fat through the butt, hips, and thighs as women tend to do after puberty, more fat gets stored in the abdomen—both subcutaneous fat and the more dangerous visceral fat around the organs.
If you’ve been caught off guard by changes in your body composition, you’re not alone. In one study, researchers followed women (aged 43 and above) for four years through the menopausal transition. They found that the women gained fat through the midsection as they entered menopause despite eating fewer total calories and fewer carbs on average.1 Total energy expenditure, including energy burned while asleep, also decreased over this time period. The researchers concluded that menopause by itself causes women to gain fat apart from any outward changes in their diet or exercise.
More and more studies, plus tons of anecdotal evidence, highlight how effective low-carb and ketogenic diets are for fat loss in general and abdominal fat loss specifically.2 3 4 There is even some research focusing on the 40+ crowd, though it centers on postmenopausal, not perimenopausal, women:
Menopausal women also tend to lose muscle mass, both due to age and hormonal changes. Compared to other calorie-restricted diets, keto may be protein sparing, meaning that the risk of losing muscle mass is lower on ketogenic diets.8
One of the main reasons keto diets are touted for weight loss is that they help keep excess hunger and cravings at bay.9 Perimenopausal women often experience an increase in hunger due to decreased estrogen10 and changes in appetite-regulating hormones like ghrelin,11 leptin,12 and neuropeptide Y.13 At the same time, energy expenditure and caloric needs tend to decrease as we get older. Therefore, any dietary strategy that makes it easier and more comfortable to eat fewer calories, in line with changing needs, is desirable.
Perimenopausal and menopausal women tend to become more insulin resistant, thanks again to declining estrogen and progesterone. Insulin resistance contributes to the increased fat storage and weight gain associated with this time of life, and it puts women at risk for the myriad health problems associated with hyperinsulinemia.14 Ketogenic diets are low-insulin-producing and low-glycemic, and they can boost insulin sensitivity.
Numerous studies have also linked insulin resistance and glucose intolerance to hot flashes.15 16 17 However, we don’t know for sure if being more insulin resistant somehow causes women to have more severe hot flashes. It’s possible they are both exacerbated by something else like inflammation. Hot flashes are still poorly understood, frankly. Anecdotally, some women do report that they experience fewer hot flashes on keto, but others find no difference.
As they age, women and men both become less efficient at absorbing nutrients. This, coupled with inadequate intake, puts older adults at risk for deficiencies in key nutrients, including vitamins B6, B12, D, and E; calcium; and protein.18 Nutrient absorption becomes a bigger concern as we hit our 60s and 70s, but it’s never too soon to start focusing on nutrient density.
Not all ketogenic diets are particularly rich in vitamins, minerals, and phytonutrients, but a Primal-aligned ketogenic diet should contain ample amounts of nutrient-dense foods that are especially beneficial for women over 40:
The keto diet basics remain constant regardless of age (or sex, for that matter): keep carbohydrates low enough to initiate ketosis, eat sufficient protein to maintain or build lean muscle depending on your goals, use fat to fill in the rest of the calories. Pretty simple. However, aging might change the nuances of how we apply those basic rules, especially as women.
There is no research here, but as women head toward menopause and become more insulin resistant as a result, they may need to lower their carb intake if ketosis is a goal. Insulin resistant individuals have a harder time getting into ketosis. The Virta Health team, who use ketogenic diets to treat type 2 diabetes, has reported that insulin-resistant patients often need to drop their carbs from the standard 50 grams per day down to 30 grams.22 It’s something to consider if you’re finding a standard keto diet isn’t delivering the results you hoped.
Although keto has traditionally been characterized as a low-to-moderate protein diet, more and more keto dieters are embracing protein and letting go of misguided fears that “too much protein” (a highly subjective term) will kick them out of ketosis. Mark covered it in this post, but suffice it to say, that’s not something most of us need to be concerned about.
Nevertheless, some keto programs recommend that women over 40 reduce their protein intake. This runs counter to everything we know about the importance of protein for maintaining musculoskeletal health in older adults. For the vast majority of women and men over 40, getting enough protein to counteract age-related declines in muscle mass and protein absorption outweighs any concerns about maximizing ketone levels.
The RDA for protein is 0.8 grams per kilogram of body weight (0.36 grams per pound). That’s a mere 54 grams of protein for a 150-pound woman. Experts argue that for healthy aging, we need a minimum of 1.0 g/kg of body weight (0.45 g/lb), and up to 1.5 g/kg (0.68 g/lb) for folks with acute or chronic illness.23 That translates to 68 to 102 grams of protein for that 150-pound woman—still a fairly modest amount.
The Keto Reset Diet recommends starting at 0.7 grams of protein per pound of lean body mass, which usually translates to somewhere around 70 grams as a minimum for women. Women over 40 could easily go higher, especially if they are physically active. One study found that postmenopausal women who consumed less than the RDA of 0.8 g/kg (50 grams of protein per day, on average) had more body fat, more reported fractures, and higher rates of osteoarthritis and hypertension compared to women who ate more protein (80 grams per day, on average).24
Protein is also the most satiating macronutrient, so increasing protein intake is useful if you’re trying to maintain a caloric deficit. Relatively higher-protein diets are favorable for fat loss.25
Intermittent fasting can be widely beneficial for women of all ages.26 However, some people raise valid concerns about fasting for premenopausal women, whose bodies are particularly sensitive to signs of food scarcity. While younger women can fast successfully, they do have to be more careful to watch the total stress load they are putting on their bodies.
As women get older, their bodies should be more amenable to fasting. Rodent and human studies show that intermittent fasting is useful for improving a variety of health markers of particular relevance to women over 40, including improving insulin sensitivity and reducing visceral fat.27
Intermittent fasting isn’t required for keto dieters, but they typically end up eating in a compressed window naturally, due to decreased hunger. Anecdotally, many over-40 women in the Keto Reset community have had a lot of success incorporating intermittent fasting to manage hunger and lose body fat gained during perimenopause.
Two things in particular will make a big difference: stress management and moving your body. These are important for anyone of any age, but they become increasingly impactful for women as they get older.
For one thing, stress and mood disturbances are already hallmarks of perimenopause and the menopausal transition. Menopausal symptoms like hot flashes and poor sleep are plenty stressful on their own. Low estrogen and progesterone also interfere with the body’s ability to cope with stress, and they are associated with increased risk for anxiety and depression. Stress elevates cortisol, which promotes abdominal fat storage and ramps up hunger and cravings for highly rewarding sweet and calorie-dense foods.
Perimenopausal women, distressed about sudden changes in their body composition, often attack their diets with extra intensity, which itself is a form of stress. When their bodies don’t immediately respond, in part because the underlying hormone fluctuations make fat loss extremely challenging during this period, they double down the efforts. This introduces more and more stress into the equation and undermines their efforts.
Movement can be an effective way to reduce stress, but only when it doesn’t veer into chronic cardio or other stressful patterns. More generally, movement is crucial for healthy aging. Physical activity tends to decline as we age, which leads to fat accumulation, loss of muscle mass, and decreases in bone mineral density. Numerous studies show that for women middle-aged and older, increasing activity—including walking, resistance training, and functional exercises like balance and agility training—reduces body fat, builds muscle mass, improves skeletal health and various markers of metabolic health, and reduces menopausal symptoms.28 29 30 31
Not all women gain weight in their 40s and 50s, but it can be extremely frustrating for those who do. Ketogenic diets, even when paired with intermittent fasting or caloric restriction, may not deliver the specific weight-loss results you’re seeking. However, they can create a favorable environment for weight loss and, more importantly, they can deliver other benefits that we should be prioritizing as we age, like reduced inflammation and improved cognitive function.
Don’t assume your keto diet isn’t “working” if you don’t return to your earlier weight or pants size. I’m putting “working” in quotes here because so often people decide that their diet, exercise, and other lifestyle choices are working if, and only if, they achieve a certain number on the scale. Scale weight (or clothing size) is only one variable—and I’d argue not the most one—that you could use to decide whether your diet is a success. If you ask me, it’s high time we start talking more about society’s expectations that women’s bodies look the same at 45 as they do at 25, but that’s a bigger discussion for a different time.
As long as researchers continue to largely ignore middle-aged women, we’re going to have to rely on anecdotal evidence from our peers. We also have to be willing to conduct our own self-experiments. The Primal Keto Reset community has more women between the ages of 40 and 60 than any other demographic, and they are thriving on keto. However, they’d probably tell you that it took trial and error in order to find the version of keto, or keto plus intermittent fasting, that works best for them. Dietary needs tend to shift along with hormonal transitions, so flexibility is key.
One last point: although a keto diet checks a lot of boxes=, it may not be ideal for all women. In particular, a lot of women struggle with sleep during menopause. Getting the best sleep possible is paramount for health. Some people, both women and men, find that they don’t sleep as well when they go very low-carb. If you have to choose, sleep is more important than keto. You can be healthy eating more carbs—a more moderate-carb Primal approach is great—but there’s no way to replace lost sleep.
For all my fellow 40+ ladies out there, how have you evolved your diet, movement, and other health-focused behaviors? What practices have delivered the biggest benefits for you personally?
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