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The ketogenic diet is on fire right now, in case you haven’t heard, and it’s because of people’s reliable weight loss while on it. As a Google search term, “keto” is now double the popularity of “Paleo,” which has leveled off and even decreased in the past year. Keto diets require most of your calories to come from fat (with low protein intake and even fewer carbs), which trains the body to utilize fat for energy rather than carbohydrates. Yet not everyone is on board, with some experts saying that it’s more trouble than it’s worth. There is so much emerging research and buzz about keto that we wanted to cut the fat to find out what it is and isn’t, and why this diet may or may not be effective for women who train.
The origins of the keto diet date back to the 1920s, when a faith healer developed the diet to effectively treat children with epilepsy. But when anti-seizure medications became available, the diet fell out of favor. High-fat diets gained new traction in the ’90s when Robert Atkins published Dr. Atkins’ New Diet Revolution (which, although high-fat and low-carb, is not ketogenic). Fast-forward to present day, and the ketogenic diet has been legitimized as an effective therapy not only for epilepsy but also for Alzheimer’s, Parkinson’s, glaucoma, and even cancer. But the real appeal for most people is the ability to achieve significant weight loss—a claim backed by several studies, including a review of research in the International Journal of Environmental Research and Public Health.
It’s also become, debatably, healthier: We know a lot more now about fats than we did back in the 20th century. Early keto dieters didn’t distinguish between saturated fats or processed fats like canola oil and “healthier” fats like polyunsaturated-rich olive oil or saturated fats like medium-chain-triglycerides (MCT) oil that can curb appetite, increase satiety (feeling full), and improve triglyceride levels. Some modern keto diets are also heavier on whole foods and vegetables rather than packaged, processed foods, so the body benefits reach further. And now there are an array of keto diets, from the standard keto diet to MCT keto. (See “4 Keto Diets Defined,” below, for more.)
For a 140-pound woman who is 5’6″ and moderately active with 20% body fat, her keto macronutrient ratios would be 76% fat, 19% protein, and 5% carbs. If monitored closely, this diet would eventually put her into a state of ketosis, in which the body produces ketones for energy from fat cells in the liver rather than using the typical energy source of stored carbs in the muscles. But compliance is hard—you have to measure your ketones daily so as not to have too many carbs or too much protein.
Another downside is that ketosis is often confused with ketoacidosis, in which blood levels of ketones get so high that the blood turns acidic. It can lead to potentially deadly symptoms in short order. Yet, under normal circumstances, with monitoring by a nutritionist and by checking your daily ketone levels, it can be done safely. So could the ketogenic diet be right for you? Here’s what some of the experts have to say.
1. Standard Ketogenic Diet (SKD): Beginner
Low carbs, moderate protein, high fat; fat types can include saturated fat or poly- or monounsaturated. Max is 25 to 50 net carbs daily depending on the person. (Three cups of kale has approximately 28 grams of carbs.)
2. Targeted Ketogenic Diet (TKD): Advanced
Carb limit is higher around workout times. Max is 25 to 50 grams of high-glycemic, glucose-based (not fructose-based) carbs 30 to 60 minutes before training.
3. Cyclic Ketogenic Diet (CKD): Advanced
Alternate keto days with carb-loading days, such as five keto days and one to two “refeed” days. On keto days, max is about 50g of carbs; on carb-loading days, it’s about 450 to 600g.
4. MCT Ketogenic Diet (MKD): Intermediate
The type of fat emphasized is medium-chain triglycerides (MCTs) rather than other fats (mostly long-chain triglycerides, or LCTs, like animal fat) because MCTs produce ketones more easily; 30% fat from MCTs, 30% from LCTs.
See the next page for the potential benefits a keto diet could have on your body.
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Experts agree that there are actually a few benefits to possibly going into ketosis, whether it’s to change your body composition, get control of cravings, or more.
Going keto may be useful for “helping to improve insulin resistance, as does exercise,” says Megan Roberts, the scientific director of Nourish, Balance, Thrive, an online health-coaching company. “It may also help improve conditions associated with insulin resistance like PCOS [polycystic ovarian syndrome].”
By cutting carbohydrate and protein intake, ketosis can also help with other diseases of high insulin, including type-2 diabetes, obesity, and Alzheimer’s disease, adds Jason Fung, M.D., author of The Complete Guide to Fasting. And for those who grew up in the era of “low-fat everything,” adding in healthy fats can help hormonal balance and brain health, Roberts explains.
A growing body of evidence points to at least short-and medium-term weight-loss effects. A British Journal of Nutrition review of 13 studies (totaling more than 1,400 people) showed that those on a very low-carb keto diet (with less than 50g carbs daily) had a decreased body weight and blood pressure at studies’ end compared with those on low-fat diets. You can also see rapid weight loss on a keto diet because insulin causes salt and water retention in the kidneys, and lowering insulin on a keto diet can often produce fast water loss, says Fung.
“There’s no better diet than a ketogenic-style diet if you have always had trouble controlling cravings and body composition, aka once a fat kid, always a fat kid,” says Mark Bell, a champion powerlifter, owner of Super Training Gym, and author of The War on Carbs. An analysis of appetite studies in Obesity Reviews reveals that appetite does seem to be suppressed on low-energy, low-carb ketogenic diets, despite calorie restriction, which usually makes people ravenous. Surprisingly, even butter contains a fat-loss dynamo called butyrate, which has been shown to affect the gut-brain neural circuit by boosting metabolism, suppressing calorie intake, and raising fat burning, according to the journal Gut.
“Keto diets train the body to burn fatty acids directly, which is often beneficial during prolonged training sessions and endurance athletics. Training muscles to use fat for fuel means the body is able to carry large amounts of fuel. Also, because keto diets are more satiating, they often lend themselves well to restricted time eating or intermittent fasting,” says Fung.
A keto diet may add more years to your life, according to a study in the journal IUBMB Life. Researchers say that by reducing glucose, you may limit free-radical damage and decrease insulin/insulin- growth-factor-receptor signaling, which in turn boosts the FOXO (forkhead box O transcription factor) proteins, which raise antioxidant enzymes.
See the next page to figure out whether a keto diet suits your goals.
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Yet, if weight loss is your ultimate goal, some experts say keto is best kept for its original use. “It might help decrease the severity and incidence of seizures in epileptics resistant to medication, but for fat loss there are better options,” says Marie Spano, M.S., R.D., C.S.C.S., C.S.S.D., a sports nutritionist for the Atlanta Braves, Atlanta Hawks, and Atlanta Falcons. Burning fat may produce more ATP (the molecule that powers you during activity), but during high-intensity exercise the body cannot produce ATP fast enough from fat to meet its energy demands, and your intensity will slow down, she explains. And some experts say there’s nothing magical about the ketogenic diet for weight loss. “Just because you’re burning ketones does not mean you’ll lose weight,” Spano adds.
Roberts agrees that keto is not a diet she recommends for the long term. “Women, especially those who exercise regularly, tend to do better with more carbs from both a health and performance standpoint. Our hormones are more sensitive than men’s, and when you top off exercise and life stressors, with a very low-carb, ketogenic diet, it’s often a recipe for burnout,” she explains.
In fact, many of us simply can’t stay on a keto diet for too long. “The ketogenic diet is not sustainable for the majority of people, and it can be difficult to go on and off the diet easily,” says Spano. That could be partially due to the time it takes for the body to become fat adapted and start utilizing ketones, which for some can take several weeks. This stage is sometimes referred to as the “keto flu” (or carb flu) and simply is a sort of sugar/carbohydrate withdrawal phase that can be marked by fatigue, nausea, dizziness, brain fog, trouble sleeping, and stomach irritability. “It’s also not ideal for muscle gain, as the carb cutting interferes with the muscle-growth-signaling processes,” Spano says.
And to restrict something—carbs, calories, etc.—for too long and abstain from eating it forever is not realistic, Bell says. Instead, he says, “you should go through different time periods where you’re on different diets. If you’re looking for performance, and fat loss isn’t the most important thing, then a low-carb diet [as opposed to a ketogenic, which is very low-carb in comparison] is the way to go. But if your aim is to control body-fat levels and lose body fat, then a ketogenic diet is the way to go. Once your desired amount of weight has been lost, switch from a ketogenic to a low-carb diet.”
See the next page for tips on going keto the right way.
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Everyone’s ketosis-inducing carb levels will be different. But there are common ways to prepare for a keto diet, including setting realistic expectations. First, be aware that you may take a while to become fat adapted, which means possibly seven days to several weeks in a transitional state or possibly in keto flu. During that time, your performance in the gym will take a hit, Spano says.
Second, be prepared for the mental challenge of the cravings you may experience, Bell says: “Specifically with trying to train yourself to not eat carbohydrates, the single most important thing is to get the foods correct. And this process can take you almost an entire month, sometimes two months, just to get the rhythm and timing down, knowing when to eat and how much to eat; and knowing what to do when a sugar craving pops up.” You’ll need to be able to get past this adjustment phase to see benefits. (To help you get there, check out some recipes from Carolyn Ketchum’s The Everyday Ketogenic Kitchen)
To approach the diet more healthily than its 1920s origins, start with a macronutrient-agnostic, nutrient-dense, unprocessed-foods template, Roberts recommends. “This will make a huge difference for people coming from a standard American diet (SAD). From there, you can dial down carbs and increase fat to get into nutritional ketosis.” Note: Environmental factors can also impact how you respond to a ketogenic diet, Roberts says, especially if a SAD is accompanied by its partner in crime, the SAL (the standard American lifestyle)—lack of sleep, too much stress, and lack of social connection.
Also keep in mind that active people can get away with eating a bit more carbs timed strategically around their workouts and still stay in ketosis, Roberts says, like in a targeted keto diet (TKD) or cyclic keto diet (CKD). “But ultimately, make sure to get in enough calories, regardless of your macronutrient breakdown of choice,” she explains.
The MCT keto diet (MKD) is one that uses a higher amount of MCTs than a standard keto diet (SKD). These are converted to ketones more quickly and are easier for the body to break down.
Also make sure to increase your intake of polyunsaturated fats, such as those found in walnuts and sunflower seeds. Research in the journal Obesity shows that when compared with subjects eating saturated or monounsaturated fat, those who ate polyunsaturated fats had decreased levels of ghrelin (the hormone that signals you to eat) and higher levels of peptide YY (a gut hormone that helps limit appetite).
Plus, “if your ketogenic diet is composed of [saturated fats such as] bacon, butter, cheese, and coconut oil, then your gut—and overall health—is going to be a lot worse than if you construct a ketogenic diet that is composed of plenty of colorful low-carb, nonstarchy vegetables, unprocessed fats, and quality protein,” says Roberts. That doesn’t mean all saturated fats are bad—it’s all about keeping things in balance with other fats in order for the gut to stay happy on a keto diet. “It’s also worth mentioning that genetics can impact how someone responds to a given type of fat,” Roberts adds.
See the next page for some important points to keep in mind if you embark on a keto diet and for Ketchum’s Keto No-nos.
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It can be helpful to see a nutritionist throughout the duration of your diet to make sure your macronutrient (protein, carbs, fat) ratios are dialed in. You can also use a keto calculator like the one on ketodietapp.com to keep tabs on your intake. And make sure to monitor your ketones daily via urine stick, finger prick, or breath tests.
Maybe you’ll initially have great success going keto and then find down the road that you need more carbohydrates. Look for warning signs like poor exercise recovery, fatigue, low female hormones, low thyroid and/or missing/irregular menstrual cycles. These symptoms shouldn’t be ignored, says Roberts, since they may mean it’s time to rethink your keto diet strategy.
In fact, experts caution that evidence can be misleading. “If the keto diet is compared with poor nutrition, then absolutely it’s better, but if it’s compared with a well-thought-out, balanced diet, then, no, it’s not,” says Bell. “Most people would live longer if they ate fewer carbohydrates and followed some form of a low-carb diet. But given the amount of research on the subject in 2017, we know that carbohydrates are a superior energy source, even to ketones,” he adds.
1. Don’t assume how many carbs are in a food—look it up. Many people are surprised to find out how many carbs an onion has, whereas most berries are surprisingly low-carb. And strangely, mollusks like oysters, mussels, and scallops actually have carbs, although they seem like they should be all protein. For packaged foods, always read the labels.
2. Avoid all grains, starchy foods, and sugars. (And yes, maple syrup and honey are sugars.)
Q: What can put you back into ketosis quickly?
A: Bacon or anything that’s a fatty protein—eggs cooked in butter with a side of bacon really help. I feel full and less likely to go back to indulging. A day of eating that way, and I will be back in ketosis.
Q: Favorite keto food for athletes post-workout?
A: Chicken thighs or leftover steak; I love eating dinner leftovers the next day. When I come home from a tough CrossFit workout and am ravenous, I just grab these. Sometimes I am too impatient to even heat them up—I just caveman them right into my mouth. Good thing no one is watching!