You cannot live on steak and avocados alone, says Jillian Michaels, in this divisive video.
- Big Think's most controversial video of 2019 stirs the pot of the keto diet debate with fitness and nutrition expert Jillian Michaels, who asks: Are keto diet advocates selling people a false—or at least a selective—message?
- The keto diet increases fat and protein intake while dramatically reducing carbohydrate intake to about 20 grams a day or about 80 calories worth of carbs out of what could be anywhere from a 1600 to 2500 calorie diet per day. That throws your body into a state of emergency called ketosis, which burns fat fast.
- Michaels' main critique of the keto diet is that there is zero calorie restriction, it cuts out nutrients and digestive enzymes from fruits, and that it's high in animal fats and animal proteins, which negatively impacts telomeres, oxidative stress, and may increase inflammation. Michaels stands by the effects of regular exercise and what she calls a "commonsense diet": don't eat too much, eat real food and get a range of macronutrients.
One group of women still seem to benefit from the popular diet.
- Medical professionals and dieters have long noticed differences in the efficacy of the keto diet between the sexes.
- A new study suggests that estrogen plays a role in preventing women from losing weight on the keto diet.
- More research is needed before scientists know exactly how the keto diet's effects vary between the sexes.
It's long been observed that men seem to have an easier time than women in terms of losing weight on the keto diet. The results of a new study on the keto diet's effects on mice support that anecdotal claim, suggesting that sexual hormones might prevent the high-fat diet from helping females lose weight.
At the annual meeting of the Endocrine Society on Sunday, researchers from the University of Iowa discussed a soon-to-be-published study showing how female mice on the keto diet were less likely than males to lose weight, and more likely to experienced impaired blood sugar control.
In the experiments, researchers put a group of mice on the keto diet or a regular diet, which served as the control.
- Keto diet: 75 percent fat, 3 percent carbs, 8 percent protein
- Regular diet: 7 percent fat, 47 percent carbs, 19 percent protein
After 15 weeks on the keto diet, the male mice experienced losses of body weight and body fat, while the female group actually gained weight. The researchers speculated that estrogen might be interfering with the weight-loss process, so they removed ovaries from some of the mice. This caused females to start experiencing the same weight-loss effects observed in the male group.
"Our studies suggest that sex hormones might modulate the way that male versus female mice respond to ketogenic diets," lead investigator Jesse Cochran, a research assistant at the University of Iowa, told Inverse.
The male mice experienced another, less desirable change: Their livers showed stronger signs of fibrosis — the thickening and scarring of connective tissue — and fatty storage than the female mice. The males had higher levels of a hormone called FG21, which previous studies have shown is released in response to liver damage.
Is the keto diet bad for the liver?
The intuitive answer might be yes, considering the keto diet calls for eating lots of fats, and having too much fat (particularly triglycerides) in your liver can lead to inflammation and cell death. However, some research suggests that a responsibly implemented keto diet can actually improve liver health.
For example, a 2018 study tracked the effects of the keto diet on 10 mildly obese people with fatty livers. Ann Fernholm, science journalist and founder of the not-for-profit Dietary Science Foundation, said the study offered an "extremely detailed map showing what happens when a person cuts down on sugar and starch in their diet.
"The liver metabolism changed almost immediately," she wrote for Diet Doctor. "Instead of creating fat, it started burning it and already in the first day you could see a significant reduction in liver fat. As a great side effect, the participants also improved their cholesterol profiles. The microbiome also changed. A surprising discovery was that it started producing more folic acid, a vitamin which is important in the liver's metabolism. Low levels of folic acid has earlier been associated with an increased risk of fatty liver."
Still, more research is needed
Despite its popularity, there's still much scientists don't know about the keto diet, and most medical professionals stop short of recommending the diet unless it's prescribed to epileptics.
"The keto diet is primarily used to help reduce the frequency of epileptic seizures in children," said registered dietitian Kathy McManus, director of the Department of Nutrition at Harvard-affiliated Brigham and Women's Hospital. "While it also has been tried for weight loss, only short-term results have been studied, and the results have been mixed. We don't know if it works in the long term, nor whether it's safe."
The mixed results on keto diet studies could be explained, in part, by discrepancies in efficacy between the sexes, and a lack of solid research on how females respond to the diet.
"Most studies of the ketogenic diet for weight loss have taken place in small numbers of patients or in only male mice, so sex-based differences in response to this diet are unclear," said senior investigator E. Dale Abel, M.D., Ph.D., chair of the University of Iowa Department of Internal Medicine and president-elect of the Endocrine Society.
Regarding the recent research, it remains unclear whether similar studies conducted with human participants would yield the same results.
Can the keto diet work for some women?
Interestingly, the recent study suggests it can.
"[The finding that ovariectomized mice experienced weight loss] suggests that postmenopausal women could potentially experience better weight loss outcomes with the ketogenic diet compared to younger women," Cochran said.
This seems to match the observations of some medical professionals prior to the recent research.
"My anecdotal observation in my medical office and working with people online is that men perform better in nutritional ketosis compared with women, particularly women aged 40 and older," wrote Sara Gottfried, a board-certified gynecologist, on her website. "My female patients, myself included, have more problems on keto with their stress hormones (i.e. producing too much cortisol), thyroid function, and may develop menstrual irregularities. At the root of these problems is dysfunction of the control system for hormones, the hypothalamic-pituitary-adrenal-thyroid-gonadal (HPATG) axis."
Since the initial use of ketogenic diets (KD) as adjunctive treatment for epilepsy, these diets are being increasingly used to promote weight loss and to reduce the risk of metabolic sequelae of severe obesity. Typical KD are very low in carbohydrate and high in fat, promoting hepatic production of ketone bodies. Most animal studies tend to be performed in male mice, and few studies have evaluated gender differences in response to KD. To explore sex differences in response to KD, female and male wild-type mice on the C57BL/6J background were fed either a control diet (CD- 7% fat, 47% carb., 19% protein) or KD (75% fat, 3% carb., 8% protein), following weaning. Females on the CD manifested higher levels of circulating β-hydroxybutyrate (β-HB) than males (2.86-fold, p<0.05). Circulating β-HB concentrations increased with KD in males and females (1.30-fold & 5.05-fold, p<10-4& p<0.01 respectively) with higher concentrations in females. After 15 weeks of feeding, females on KD displayed an increase in body weight (1.07-fold KD vs. CD, p<0.05) while body weight declined in males (0.88-fold, p<0.05). Nuclear magnetic resonance (NMR) analysis revealed elevated lean mass in 18-week old females (1.07-fold, p<0.05), but a significant reduction in fat mass in males (0.49-fold, p<0.05) relative to sex-matched mice on CD. The female mice on KD developed impaired glucose tolerance with a 1.35-fold increase in glucose tolerance test area under the curve (GTT AUC) (p<0.001) relative to CD females. In contrast, fasting glucose levels were lower in males on KD (131.8 ± 12.5 mg/ dl vs. 169.2 ± 6.3 mg/dl, p<0.05). Despite no significant change in GTT AUC, the male mice on KD displayed elevated blood glucose concentrations 30 minutes after injection relative to males on CD (344.9 ± 18.7 mg/ dl vs. 272.0 ± 10.31 mg/dl, p<0.05). However, after 120 minutes, blood glucose levels returned to initial levels. To further investigate the role of estrogen in this sexual dimorphism, female mice were ovariectomized (OVX) and randomized to receive either a CD or KD after weaning. At 15 weeks old, OVX mice on KD displayed decreased body weight (0.84-fold, p<0.0001) and fat mass (0.65-fold, p<0.001) relative to CD-fed mice. Despite changes in body composition, OVX mice on KD still exhibited impaired glucose tolerance with a 1.4-fold increase in GTT AUC comparable to OVX mice on CD (p<0.05). In conclusion, significant sex differences exist in terms of body composition and metabolism in response to ketogenic diet, which may partially be attributed to estrogen.
Just because the keto diet is an effective weight-loss tool doesn't mean everyone should try it.
- 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?
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.
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 Parents.com, 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."
Eating a doughnut isn't the only way you can go wrong on the keto diet.
- The high-fat, low-carb keto diet involves putting your body into a natural metabolic state called ketosis.
- When done responsibly, the keto diet can yield a wide range of benefits, most notably weight loss.
- Some people have less luck than others on the keto diet because they make a few common mistakes, including failing to drink enough water, eating too many unhealthy fats, and not realizing which foods might kick them out of ketosis.
The gist of the keto diet is simple: Eat less carbs and more fats. But actually sticking to a diet that avoids sugars, breads, potatoes, beer and most fruits isn't easy. If you research the keto diet, you'll find message boards littered with people who've tried and failed to live by the keto diet, or who've implemented it correctly, and you'll also come across tons of keto diet progress blogs that mysteriously go dark after week two.
Simply put, it's tough to keep your body in ketosis – especially in a society where most of the meals readily available at restaurants, fast food stops and grocery stores include large amounts of carbs.
"Even in the hospital under strict controls, when we send patients into ketosis for medical reasons, it can be extremely difficult to do," Melissa Bailey, a clinical dietitian at the Hospital of the University of Pennsylvania, told Health. "On your own, it's virtually impossible to do it consistently."
It can also be difficult to implement the keto diet in a healthy way, as evidenced by the common side effects people often report. Still, it's possible to stick to the keto diet – and reap some surprising benefits – if you can manage to avoid these common mistakes.
Eating too much protein
Protein is an essential macronutrient that helps us feel full, burn fat and build muscle, and it plays a key role in any healthy diet, including keto. However, you might've heard that overeating protein can actually be counterproductive to a keto diet because of a process called gluconeogenesis, in which your body turns non-carbs into glucose.
But the research on this claim has failed to back it up, and most anecdotal reports suggest that eating even moderately high amounts of meat won't kick you out of ketosis. Still, eating tons of protein can slow down your weight loss, and, if you're eating too many processed meats, it can increase your levels of "bad cholesterol" known as low-density lipoprotein.
To ensure you're consuming a healthy amount of protein on the keto diet, you can generally stick to these guidelines:
- If you are sedentary — consume 0.6 – 0.8g of protein per pound of lean body mass.
- If you are regularly active — have 0.8 – 1.0g of protein per pound of lean body mass.
- If you lift weights — eat 1.0 – 1.2g of protein per pound of lean body mass.
Not drinking enough water
Many people lose weight soon after starting the keto diet, some more than 20 pounds in the first month. But important to keep in mind is that most of those dropped pounds come from water weight—after all, your body is more than half water.
"When carb intake is restricted for a few days, glycogen stores in the muscle are reduced," Carol Johnston, professor and associate director of the nutrition program in the School of Nutrition and Health Promotion at Arizona State University, told ASU Now. "Glycogen is responsible for water retention, so when its levels fall, so do our water levels. To the average person, the diet appears to be working. The number on the scale is going down. But, since most of this weight lost is water weight, it will return when the person consumes carbs again."
This intense water loss can lead to dehydration, and therefore constipation. What's more, the loss of glycogen can also lead to a reduction of lean muscle. The good news is that you can offset this with strength training, which helps you gain glycogen and water over the short and long term.
In any case, remember to drink more water than usual if you're planning to start the keto diet.
Consuming too many carbs
Avoiding carbs on the keto diet sounds like a no-brainer. After all, if you're craving snacks you can just pick up some keto-friendly foods and drinks, like a sugar-free latte, cashews and black beans.
Actually, all of those – and other foods like processed vegetable oils, starchy vegetables and most beans and legumes – can kick you out of ketosis due to their high carb content.
"Overconsumption of carbs is definitely very easy," Kristen Kizer, a dietitian at Houston Methodist Medical Center, told Health. "And if you're eating carbs and not realizing it—unless you're really monitoring your ketones regularly—you're going to fall out of ketosis and not know it."
If you're looking for some foods and drinks that are typically keto-friendly, turn to fish, eggs, unsweetened tea, bone broth, above-ground vegetables and unprocessed meats.
Eating too many unhealthy fats
On the keto diet, you eat lots of fats because they're the fuel your body runs on during ketosis. But eating a high-fat diet can get unhealthy fast if you aren't careful because some fats are worse than others.
"I know people following keto, and a lot of times I'm seeing that there's a lot of bacon in their day, or a lot of really processed meat," Bailey told Health. "And those things are super-high in sodium and super-high in saturated fat, which can really affect your cardiovascular health."
But are saturated fats really that bad for you? Although a 2017 survey of the research found "no clear message regarding health effects of saturated fats," the American Heart Association recommends that you aim to get only 5 to 6 percent of your daily calories from saturated fat, which can come from red meat, eggs, coconut oil and butter.
"If people want to follow this diet, there's a way to get that extra fat in your diet but still choose healthy fats," Bailey said.
Thinking of the keto diet as a 'quick fix'
Pounds tend to drop quickly on the keto diet. But, as mentioned above, the bulk of that weight—at least at first—comes from water, and even the lost fat that doesn't come from water will be hard to keep off if you don't have the discipline to stick to the diet.
Learning to keep your body in ketosis is a lifestyle change, not just a diet. It requires having the discipline to consistently reject some of the most tempting foods and drinks available — including alcohol. Given the challenges involved, and some of the more unpleasant effects you'll likely undergo during the transition into ketosis, it's probably worth considering whether the keto diet is something you really want to commit to before you start.
Can the keto diet really help people combat acne, cancer and "brain fog"?
- The keto diet is generally an effective method for weight loss.
- Still, many of the diet's other supposed health benefits aren't as well supported by the research.
- Claims that the keto diet can help with acne, cancer and mental clarity are speculative, but there's reason to suggest they're worth investigating.
It's no secret the keto diet can help people lose weight by switching the body's primary fuel source from sugar to fat. What's less clear is whether the diet can reliably produce other health benefits, like clearer skin, increased mental clarity or even the reversal of conditions like type 2 diabetes.
One reason it's hard to determine the exact health effects of diets is that it's often unclear whether any observed effects come from the diet or from a combination of other factors, like stress, environment or genetics. Still, that doesn't mean all the bold claims about the keto diet are wrong, but rather that you should approach them with a healthy degree of skepticism.
Here are three potential benefits of the keto diet that, while speculative, show how we might benefit from a better understanding of how a high-fat, low-carbohydrate diet affects the body.
The keto diet can combat acne
Dermatologists had long thought there was no relationship between diet and acne, but some recent research suggests food can indeed affect complexion, particularly through the consumption of carbohydrates.
The basic theory goes like this: Eating carbohydrates – especially refined carbohydrates – spikes your blood sugar. This spike can stimulate hormone production, and those hormones can trigger oil production, which leads to acne.
Several recent studies have linked the consumption of high-glycemic-index foods (meaning foods that spike blood sugar levels) with acne, including:
- A 2007 study that found a low-glycemic-load diet led to greater reductions in acne compared to high-glycemic-load diets.
- A 2013 review that also found a correlation between eating low-glycemic-load foods and decreased acne.
- A 2014 study that identified carbohydrates as the "main culprit" of acne, and which advised dermatologists to "encourage their acne patients to minimize their intake of high glycemic index foods."
So, how might the keto diet be an effective therapy for acne? A 2012 article by Italian researchers explored that question, as registered dietician Franziska Spritzler wrote for Diet Doctor, suggesting three reasons:
- Reduction in insulin levels: Elevated insulin levels stimulate increased production of skin cells, sebum, and androgens – setting the stage for acne eruptions. Ketogenic diets decrease insulin levels, often dramatically.
- Anti-inflammatory effects: Inflammation drives acne progression. Very-low-carb and ketogenic diets have been shown to reduce inflammation.
- Decrease in IGF-1 (insulin-like growth factor 1): Ketogenic diets decrease levels of IGF-1. Like insulin, IGF-1 increases sebum production and has been found to play a large role in acne.
Of course, whether – or to what extent – diet affects acne is still an open question that requires further research, and it's worth noting that complexion is also affected by other factors like genetics and stress.
The keto diet 'starves' cancer
One of the boldest claims about the keto diet is that it can help combat cancer by effectively "starving" cancer cells. It's a claim based on a phenomenon dubbed the "Warburg effect", which, in simple terms, describes how cancer cells are more reliant on sugar than healthy cells. So, the idea is that sticking to a low-carbohydrate diet will make it harder for cancer cells to thrive.
"Because cancer cells prefer to use glucose, diets that limit glucose may be beneficial," Barbara Gower, PhD, senior author and professor in the Department of Nutrition Sciences, told Healthline. "Because they limit glucose and several growth factors, ketogenic diets will limit the ability of cancer to grow, which gives the patient's immune system time to respond."
Here's how the process might work, as Dietarytherapies.com outlined:
- Over half of the calories in standard diets come from carbohydrates.
- Carbohydrate digestion produces spikes in blood glucose which in turn causes a spike in insulin.
- Insulin's job is to move glucose from the blood into cells.
- Cancer cells typically have many more insulin receptors than normal cells.
- Limiting carbs restricts the movement of glucose into cancer cells.
- When glucose is in short supply, the body will increase its use of fats as fuel.
- The liver converts some of this fat to energy molecules called ketones.
- Most normal cells (including brain tissue) readily adapt to using ketones.
- Tumor cells suffer because they are not as fuel flexible as normal cells.
This weakened state can make cancer cells more vulnerable to traditional cancer treatments like radiation and chemotherapy. At least, that's the theory promoted by Dr. Thomas Seyfried, a cancer researcher and professor at Boston College who's been one of the most vocal proponents of exploring the potential cancer-fighting effects of the keto diet.
"It is like a one-two punch, stressing them with starvation by ketones, then hitting them while they are down," Seyfried told Diet Doctor.
Although some animal studies hint at therapeutic benefits, more research on the keto diet and cancer is required before it can be safely recommended as a supplementary or standalone treatment.
"Most of the work in this field is still pre-clinical, meaning it's been conducted in animal models," Angela Poff, a research associate in the Department of Molecular Pharmacology and Physiology at the University of South Florida, told U.S. News & World Report. "It's been done in various cancer types, but most of the work has been done in brain cancer specifically. But there's very little clinical data all around. There's some case reports and very small preliminary clinical studies in small groups of patients, usually very late-stage patients with various types of cancers. So in the clinical realm, which is the most important in telling us whether this is going to be useful, we have a long way to go."
The keto diet clears up 'brain fog'
The keto diet is often said to increase mental clarity, and even to help with conditions like anxiety and depression. Although most of the evidence supporting these claims is anecdotal, there is some reason to think a low-carbohydrate diet might help clear up what's commonly called "brain fog."
The keto diet puts the body in a state of ketosis, which seems to help the brain produce optimal amounts of GABA, an inhibitory neurotransmitter. GABA is made from glutamate, which is the brain's major excitatory neurotransmitter. Your brain needs a balanced amount of both glutamate and GABA to function properly.
But when you consume a high-carbohydrate diet, your brain often can't convert enough glutamate into GABA because it's using glutamate as an energy source. This imbalance can lead to neurotoxicity, and this impaired functioning could potentially lead to brain fog. For reasons not completely understood, ketosis seems to favor an increased production of GABA, which can lead to reductions in neurotoxicity and, therefore, brain fog.
Still, research on the relationship between the keto diet and mental clarity, as well as anxiety and depression, is still in its early stages, and not all people who try the keto diet report noticeable changes in the ways they think. In fact, some people report an increase in brain fog after switching to the keto diet, though this might be explained by the "keto flu", which describes the flu-like symptoms people tend to experience in the first few weeks after beginning the keto diet.