Is the keto diet safe for everyone? Probably not.

Just because the keto diet is an effective weight-loss tool doesn't mean everyone should try it.

Is the keto diet safe for everyone? Probably not.
Didriks via Flickr.
  • The keto diet might be a fad diet, but it's unique in that involves putting the body into an alternate and natural metabolic state.
  • However, the diet likely isn't safe for everyone, particularly when it's implemented poorly.
  • Children, pregnant women, breastfeeding women and those at risk for heart disease should understand the risks of the keto diet before experimenting with it.

People experiment with all kinds of crazy, unhealthy diets to lose weight: eating cotton balls soaked in orange juice, intentionally ingesting tapeworms, and surviving on only grapefruit, to name a few. Some would add the keto diet to that list. As it's gained popularity in recent years, many have questioned whether the diet really is the hyper-effective weight-loss tool its supporters claim it to be, or simply another fad diet that could lead to serious health complications.

Unlike other fad diets, the high-fat, low-carb keto diet involves putting the body into a natural metabolic state called ketosis, in which the body burns fat for fuel instead of glucose. Although this metabolic state is a generally safe way to help you lose weight, it can be very difficult to maintain. For example, eating just one carb-heavy meal can kick you out of ketosis, forcing you to restart the process. It can also lead to health complications when done improperly, or when people with certain health conditions attempt the diet.

In short, it's not for everybody. So, who exactly shouldn't try it?

Pregnant women


Dieting of any kind isn't recommended for pregnant women, who are advised to eat about an extra 300 calories per day while expecting, according to the American Pregnancy Association. The keto diet doesn't seem to be an exception: Multiple studies on rodents have linked maternal ketosis to fetal abnormalities.

One reason the keto diet is potentially unsafe for pregnant mothers is that it can result in fewer and less diverse nutrients. Fats, after all, don't pack as many nutrients as many other proteins and carbs.

"Nourishing your baby is the most important thing when you are pregnant," Charles Seltzer, a nutritionist based in Philadelphia, told INSIDER. "Ketogenic diets steer you away from really nutrient dense foods like fruit, which are packed with vitamins and minerals. These are crucial for the development of a baby."

What's more, subjecting newborns to a limited diet could lead to serious changes in their developing bodies.

"If you're restricting carbs while pregnant (like you would be on the keto diet), this restriction tells your baby's developing body that carbs are not a readily available food source," wrote registered dietician Laura Schoenfeld on her website. "So their body learns that foods high in this macronutrient won't be as available when they're born.

This can theoretically lead to conditions like obesity, metabolic syndrome, and insulin deficiency in the child if they end up eating a diet that has a much higher quantity of carbs than a ketogenic diet.

Unless you keep your child on a ketogenic diet for their entire lives, you may be setting your kid up for future metabolic inflexibility."

Ultimately, there's no solid research proving the keto diet is good or bad for pregnant women, but given the potential risks involved it's almost surely not worth experimenting with.

Breastfeeding women

Generally, medical professionals recommend that breastfeeding women avoid strict low-carb diets. One reason is because sudden weight loss can slow down — or, in some cases, stop — milk production.

"You need more carbohydrates and sugar to produce milk than most keto plans allow in the weight-loss phase," Amber Edwards, a board-certified lactation consultant, told Romper.

Elizabeth Ward, a dietician and author of "Expect The Best: Your Guide to Healthy Eating Before, During, and After Pregnancy", advised against the keto diet for pregnant women.

"I can't endorse such an extreme eating plan for breastfeeding women," said told, noting that the diet tends to limit fruit and healthy grains. "Inadequate intake of starchy foods, such as whole grains, potatoes, and beans, is bad news for gut health because beneficial bacteria feed on the fiber in those foods."

Still, women who want to cut carbs are probably fine sticking to the maintenance phase of the diet, which calls for eating relatively more carbs than earlier phases. Of course, it's always best to check in with your doctor before making big changes to your diet – especially if pregnant or breastfeeding.

"... in the maintenance phase, you're allowed significantly more carbs and fruit, which means that you can continue to produce an adequate supply of milk," Edwards told Romper.


It's probably not a good idea for kids to go on the keto diet unless they're extremely obese or suffer from epilepsy (low-carb diets, by the way, are known to help reduce seizures in epileptics). The main reason is that the dietary needs of kids are different than those of adults.

"Many sources of carbohydrates like whole grains, fruits and dairy have essential vitamins and minerals for growing kids," wrote Jessica McGee, the Food and Nutrition Services Clinical Nutrition Manager at Children's National Health System. "Even adolescents require higher amounts of certain nutrients and should continue to eat a well-rounded diet with a variety of foods into adulthood."

"Feel free to limit (or eat in moderation) carbohydrates like candy, baked goods and sugar-sweetened beverages as these have little nutritional value and can have a detrimental impact on health. Incorporating a balance of healthy carbohydrates, fats and lean protein sources in your kids' diets is encouraged."

People at risk for heart disease

The keto diet has been called both potentially helpful and harmful in terms of cardiovascular health. For instance, a 2013 review found that low-carb diets were associated with higher rates of cardiovascular disease and mortality rates. However, not all of these diets were necessarily ketogenic, and it's possible that these risks arise when people on low-carb diets turn to unhealthy foods.

However, other research suggests a well-implemented keto diet improves cardiovascular health in all measures except low-density lipoprotein cholesterol – the "bad" cholesterol – which the diet seems to increase.

But when it comes to cardiovascular health, perhaps the biggest risk of the keto diet is "yo-yo dieting" – or, losing a bunch of weight and gaining it back over a short timeframe. This stresses your heart and can increase the risk of heart attack, stroke and death.

"People go on keto and in the short term lose a lot of weight, but it's not sustainable," Suzanne Steinbaum, the director of women's heart health prevention and wellness at Mount Sinai Hospital in New York City, told Everyday Health. "So when they go off it, they gain the weight back — and maybe even more."

"Ultimately what you're doing [with yo-yo dieting] is setting yourself up for developing metabolic syndrome."

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Sponsored by Northwell Health
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The theory could resolve some unanswered questions.

Image source: NASA/Big Think
Surprising Science
  • Most stars begin in binary systems, why not ours?
  • Puzzles posed by the Oort cloud and the possibility of Planet 9 may be solved by a new theory of our sun's lost companion.
  • The sun and its partner would have become separated long, long ago.

If most stars form in binary pairs, what about our Sun? A new paper presents a model supporting the theory that the Sun may have started out as one member of a temporary binary system. There's a certain elegance to the idea — if it's true, this origin story could resolve some vexing solar-system puzzles, among them the genesis of the Oort Cloud, and the presence of massive captured objects like a Planet Nine.

The paper is published in Astrophysical Journal Letters.

The Oort cloud

Oort Cloud graphic

Image source: NASA

Scientist believe that surrounding the generally flat solar system is a spherical shell comprised of more than a trillion icy objects more than a mile wide. This is the Oort cloud, and it's likely the source of our solar system's long-term comets — objects that take 200 years or more to orbit the Sun. Inside that shell and surrounding the planets is the Kuiper Belt, a flat disk of scattered objects considered the source of shorter-term comets.

Long-term comets come at us from all directions and astronomers at first suspected their origins to be random. However, it turns out their likely trajectories lead back to a shared aphelion between 2,000 astronomical units (AU) from the Sun to about 100,000 AU, with their different points of origin revealing the shell shape of the Oort cloud along that common aphelion. (An astronomical unit is the distance from the Sun to the Earth.)

No object in the Oort cloud has been directly observed, though Voyager 1 and 2, New Horizons, and Pioneer 10 and 11 are all en route. (The cloud is so far away that all five of the craft will be dead by the time they get there.) To derive a clearer view of the Oort cloud absent actually imagery, scientists utilize computer models based on planetary orbits, solar-system formation simulations, and comet trajectories.

It's generally assumed that the Oort cloud is comprised of debris from the formation of the solar system and neighboring systems, stuff from other systems that we somehow captured. However, says paper co-author Amir Siraj of Harvard, "previous models have had difficulty producing the expected ratio between scattered disk objects and outer Oort cloud objects." As an answer to that, he says, "the binary capture model offers significant improvement and refinement, which is seemingly obvious in retrospect: most sun-like stars are born with binary companions."

"Binary systems are far more efficient at capturing objects than are single stars," co-author Ari Loeb, also of Harvard, explains. "If the Oort cloud formed as [indirectly] observed, it would imply that the sun did in fact have a companion of similar mass that was lost before the sun left its birth cluster."

Working out the source of the objects in the Oort cloud is more than just an interesting astronomical riddle, says Siraj. "Objects in the outer Oort Cloud may have played important roles in Earth's history, such as possibly delivering water to Earth and causing the extinction of the dinosaurs. Understanding their origins is important."

Planet 9

rendering of a planet in space

Image source: Caltech/R. Hurt (IPAC)/NASA

The gravitational pull resulting from a binary companion to the Sun may also help explain another intriguing phenomenon: the warping of orbital paths either by something big beyond Pluto — a Planet 9, perhaps — or smaller trans-Neptunian objects closer in, at the outer edges of the Kuiper Belt.

"The puzzle is not only regarding the Oort clouds, but also extreme trans-Neptunian objects, like the potential Planet Nine," Loeb says. "It is unclear where they came from, and our new model predicts that there should be more objects with a similar orbital orientation to [a] Planet Nine."

The authors are looking forward to the upcoming Vera C. Rubin Observatory (VRO) , a Large Synoptic Survey Telescope expected to capture its first light from the cosmos in 2021. It's expected that the VRO will definitively confirm or dismiss the existence of Planet 9. Siraj says, "If the VRO verifies the existence of Planet Nine, and a captured origin, and also finds a population of similarly captured dwarf planets, then the binary model will be favored over the lone stellar history that has been long-assumed."

Missing in action

Lord and Siraj consider it unsurprising that we see no clear sign of the Sun's former companion at this point. Says Loeb, "Passing stars in the birth cluster would have removed the companion from the sun through their gravitational influence. He adds that, "Before the loss of the binary, however, the solar system already would have captured its outer envelope of objects, namely the Oort cloud and the Planet Nine population."

So, where'd it go? Siraj answers, "The sun's long-lost companion could now be anywhere in the Milky Way."

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