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The Keto diet is a popular program that focuses on shifting the body from being fueled by glucose to ketones—a transformation that occurs when the body when carbs are replaced by fat as the primary macronutrient intake. Since the body is burning fat for fuel, Keto has the potential to reduce body fat rapidly.

Even with all of its buzz, is the keto diet something you should try? Spoiler alert: It’s almost always bad for women, according to research, unless you have some very specific conditions (like epilepsy, PCOS, or diabetes). So what is the ideal diet for women? There’s no single answer, but there are three main reasons you shouldn’t automatically jump onto the keto bandwagon.

Should we even be following "diets" anyway?

One of the biggest questions I’m asked as a nutritionist is, “What is the best diet?” I think people honestly hope that there is one, and maybe they just haven’t heard of it yet.

In my early twenties, I tried nearly every possible diet to lose weight, but instead, I just kept gaining. What finally worked wasn’t a fancy, low-carb diet. It didn’t even have a name. It was eating lots of meats, vegetables, and fruits and eating anything else in moderation. I didn’t count calories, track macros, or worry about any other rules. I just focused on eating food that was good for me.

So when I ended up losing eighty pounds in six months, people started wondering what my secret was. That’s human nature. If something works for someone else, we assume it will also work for us.

Here’s the thing: We are all genetically unique to the point that there is no one else quite like you. Even if someone had the exact same set of genes as you, the environment plays a role in controlling how our genes work, and beyond that, our gut and the foods we eat, the stress we have, and nearly everything else we’re exposed to in life helps to created nuanced alterations to our DNA.

So, what worked for me probably wouldn’t work for you in the exact same way, but also, what worked for me ten years ago probably wouldn’t work for me now either. That’s what is so frustrating about diets: We want to find the right answer that works for us forever and always.

Enter Keto. It has been around for decades, when it started as a therapeutic diet for epilepsy. Some modern research shows promise for keto and its effects on diabetes, PCOS, and obesity as well, but a lot of the 100+ pound weight loss stories involve men.

Still, women with weight to lose, whether it’s ten pounds or a hundred, seem to be wondering if keto could be what finally makes them feel comfortable in their own skin and what turns them skinny.

Sure, Keto works for some women—there are Internet stories to prove it. But what you see on the Internet doesn’t necessarily mean it’s for you, and I see Keto as a blown-up promise of hope versus what it really is: a diet that doesn’t work for most women.

Here’s why.

Women need carbs

Research shows that the optimal amount of carbs for longevity might be in the 50-55 percent range, although individuals might certainly need more or less depending on their genetics and other health conditions. The fact is, though, that in many cases women have different carb and nutrient needs than men, regardless of how you want to break it down, simply because of the hormonal structure of the body.

For women who are of reproductive age—even if they aren’t trying to get pregnant—Keto can ignite a cascade of hormonal chaos (Keto does tend to be more effective in women who are post-menopausal). This is because many of our reproductive hormones need glucose to be produced and kept at steady levels: Not too much glucose, but a regular, moderate amount—the kind you’d get by regularly eating fruits and veggies. It’s hard to eat several cups a day of produce on a Keto diet without disrupting the macro balance.

So while Keto might help bring balance to women with insulin issues, like diabetes or PCOS, it will suppress carb levels too low in most other cases. This can result in issues like irregular menstruation, lack of ovulatory cycles, mood problems, and even weight gain or an inability to lose weight. In other cases, after a woman has lost weight on Keto, she might regain some or all of it rapidly if she adds higher levels of carbs back to her diet.

Women need body fat

We live in a fat-phobic society, and while I believe that we need to prioritize health, that is far from being a size 2 or having low numbers on the scale. There are several factors that play into health, and the fact is: Women need some body fat for healthy hormones. Our fat helps to control our hormone balance, which is often why those who are underweight cease having periods or can’t get pregnant.

Obesity is counterproductive for health too, but there’s a happy medium of having some body fat. But we live in a culture where “some” is too much. Women especially are self-conscious about having flat stomachs and not having belly fat, or underarm rolls, or flabby thighs—but these are all fat storage areas that we need to help produce the hormones that make us feminine, fertile, and vibrantly healthy. Constantly viewing those as problem spots or fat to be burned sets us up to perpetually have a negative view of our bodies.

Women have more thyroid issues

The Keto diet can also have a negative impact on the functioning of the thyroid. Women have thyroid issues seven to eight times more often than men do, and it has a lot to do with how our hormones interact with our immune systems. The thyroid regulates metabolism, mood, weight, and even reproductive health, so when it goes off, we can feel it in every aspect of our bodies. The thyroid makes two hormones, T3 and T4, and together these help to control metabolic function in the body. But the kicker is that the thyroid needs glucose to fuel the production of these hormones. Too few carbs in the diet could cause the thyroid to cut production of these vital hormones.

Particularly in women, the thyroid can respond in more extreme ways to major dietary shifts. Keto isn’t just cutting carbs; it’s a major dietary overhaul. As a result, the thyroid can stop producing the main hormones and shift T3 over into a storage form, known as Reverse T3, which can have a host of terrible symptoms that overlap with hypothyroidism and even Hashimoto’s.

If you still want to try Keto...

So if you still want to give keto a try, make sure you take a long-term view of it. Don’t try to get into ketosis rapidly, and don’t plan to do it long-term. You need to have a strategy to transition out of it without gaining back any weight that you may have lost.

Ultimately, as a nutritionist, I’ve seen women happier when they’re not married to a diet with rigid rules, and instead focus on what they can have that is good for them and satisfying, instead of what they cannot have. Most of the time it really comes down to doing more of what you already are doing, with the addition of more vegetables, more water, and more daily movement.