Vincent M. Pedre, M.D.Gut Health Specialist & Best-Selling Author
The mbg Collective is a curated group of our most trusted wellness advisers. Since 2009, we’ve had the brightest, most passionate, and mission-driven leaders in wellness share their intimate stories and world-class advice. Now, we’re giving you unparalleled access to the people who, alongside mbg, are putting the “WE” back in wellness. Consider them your personal guides, there to support you and sustain you on your journey.
While somewhat controversial, ketogenic diets have gone mainstream in 2018 thanks to celebrity endorsements, including from Kim Kardashian.
While for the past three decades, they have often been used for weight loss, ketogenic diets first appeared in the 1920s as a treatment for epilepsy. You’ll find very little contention about using ketogenic diets here: Research shows they can be powerfully effective, especially when medications don’t work for epilepsy.
In the 1960s, some health care professionals began using ketogenic diets for obesity, though they fell in and out of favor as other diet plans—such as low-fat or calorie-restricted diets—became more popular (thanks to misleading food industry marketing).
Today, you’ll see ketogenic diets promoted to prevent disease, increase energy, boost physical and mental performance, and so much more. But let’s face it: Most people want to try keto to lose weight. While that’s not a bad thing—you can lose weight doing it—ketogenic diets were never designed for weight loss, and done incorrectly, they can actually make you gain weight.
What is the ketogenic diet?
Simply put, a ketogenic diet is very high in fat, moderate in protein, and very low in carbohydrates. The idea behind keto is to keep your fat-accumulating hormone, insulin, low by keeping your blood sugar low. In doing so, you turn on fat-burning genes while suppressing the abdominal-fat-amassing machinery.
While actual percentages vary a little, traditionally ketogenic diets reduce carbohydrates to less than 50 grams a day. That’s pretty low: Something like an apple and a cup of quinoa would easily clock in at about 50 grams.
Early ketogenic diets were also moderate in protein, making dietary fat the predominant macronutrient. Eating a high-fat diet—we’re talking 70 percent dietary fat or higher—means you aren’t getting sufficient glucose as fuel, and glycogen (your glucose backup tank in your liver) eventually becomes depleted.
That shifts your body’s primary fuel source from glucose to fat-derived ketones. You literally burn fat—either dietary fat or body fat—for fuel on a ketogenic diet. What’s not to love about that?
So what do you actually eat on the keto diet?
Fat, fat, and more fat. Just kidding…sort of.
You will be eating a lot of fat here, so be prepared to get over your fat phobia. A properly designed ketogenic diet will include high-quality fat sources like:
- Wild-caught fish
- Grass-fed beef and wild game
- Free-range poultry
- Pasture-raised eggs
- Raw nuts and seeds
- High-fat fruits like coconut and avocado
- Quality oils including extra-virgin coconut oil and extra-virgin olive oil
Especially with animal fats, you want to choose the very highest quality. Toxins congregate in fatty tissue, so when you eat, say, a fatty grain-fed steak from a factory-farmed cow, you’re ingesting those toxins.
You’ll balance those healthy fats out with loads of gut-healing, microbiome-supporting, low-carbohydrate plant-based foods, including leafy and cruciferous vegetables.
These dietary restrictions work for some people. However, can you picture yourself passing on bread and desserts forever? Does this sound like the kind of plan you could more or less stick with for life? If not, a ketogenic diet might not be for you. And it doesn’t have to be.
What foods should you avoid on the ketogenic diet?
You will not be having your cake or eating it…or for that matter, pretty much any packaged, processed, or higher-carbohydrate foods, even healthier ones like higher-sugar fruits and legumes.
When you restrict your carbohydrate intake to less than 50 grams daily, you can still fit in plenty of non-starchy vegetables, maybe some low-glycemic (meaning they don’t bump your blood sugar) blueberries and other berries, and a small amount of non-gluten grains like quinoa (actually a seed and complete protein). But you’ve got very little wiggle room there before you theoretically get knocked out of ketosis.
You also want to restrict protein intake since some amino acids like glycine and arginine are glucogenic (convert to glucose) and could inhibit ketosis. Personally, I think this is overblown, and you can allow some protein into a ketogenic plan. Most foods high in dietary fat, like steak or fish and even nuts, will contain some protein.
How is keto different from the Atkins diet?
Perhaps the first person to really put ketogenic diets on the map was Dr. Robert C. Atkins, a cantankerous medical doctor who began experimenting with a low-carb diet in 1963. His first book, Dr. Atkins Diet Revolution, was published in 1972. Dr. Atkins died in 2003 from a tragic fall (interestingly, the Atkins website’s timeline does not mention his death), but his diet plan lives on today.
Dr. Atkins talked a lot about ketosis back then, and the original Atkins diet was a far cry from what you see today; it was pretty hard-core. Save for lettuce, you consumed zero carbs, and even during maintenance, you kept your carb intake below 40 grams daily.
That plan didn’t allow much variety or leeway. Eggs, two small green salads a day, gelatin for dessert, cheese (up to 4 ounces daily), bone broth, no-calorie liquids, and lots of meat: That was pretty much it for the first week. After level one, you added vegetables like broccoli. Yes, you would be in ketosis doing the original Atkins diet, but for most people, that Spartan plan would get boring quickly.
Perhaps noticing his patients’ boredom, Atkins in subsequent versions of the Atkins diet shifted the focus from ketosis to what is called “net carbs,” or your final carbohydrate count after you subtract fiber and sugar alcohols.
The Atkins diet today hardly resembles the original 1972 plan. You’ve got two options. With Atkins 20®, you start with 20 grams of net carbs a day. During the first two weeks on that plan, most of your carbs come from vegetables like leafy greens. You can also have high-fat dairy like cream, sour cream, and most hard cheeses.
The second plan (Atkins 40®) is a bit more lenient: You start with 40 grams of net carbs a day. About one-third of those carbohydrates should come from vegetables, with the remaining amount coming from fruit, nuts, and/or whole grains. To fit those foods within your 40-gram carb allotment, you’ll need serious portion control.
Both plans also include three servings of protein (each 4 to 6 ounces) and three servings of dietary fat, including foods like butter, salad dressings, and olive oil. Once you’re past the induction phase, you start adding 5 to 10 grams of carbohydrate at a time until you find your carb threshold.
The shift from ketosis (hardly mentioned today on the Atkins diet) to net carbs allowed more vegetables and other plant-based carbohydrates into the plan (good) but also opened the floodgates for low-carb processed junk foods (not good). Of note, when you subtract fiber content, most green vegetables contain very few carbohydrates.
Today, you can buy a huge array of Atkins shakes, snacks, meal replacement bars, frozen entrees, and even weekly or monthly meal-delivery kits on their website. They offer low-carb versions of comfort foods like Chocolate Peanut Candies, Mac and Cheese, a Stone-Fired Pepperoni Pizza, and Meat Lasagna.
Many of these snacks contain poor-quality ingredients, including artificial colors and sucralose, an artificial sweetener that studies show adversely affects your gut microbiome, increasing insulin resistance. Other options, including their frozen entrees, contain the top food sensitivities many people have issues with, like gluten, dairy, soy, eggs, and peanuts as well as junk oils, like soybean oil.
Simply put, among this wide array of processed foods are included lots of low-carb junk foods—bad news for your gut and overall health. Besides increasing inflammation, they can trigger leaky gut, insulin resistance, and other issues that will eventually stall your fat loss as they sabotage your health.
In all fairness, you can do these plans without eating all those processed foods, although (let’s face it!) convenience and cravings mean you’ll likely be tempted to try them. And they tap into that weakness for “cheating” by making these options easily available. Who would refuse comfort food that is “compliant” with a diet? You can have your cake and eat it too, literally. I call this pseudo-dieting. Even then, eating potentially reactive foods like dairy (which is allowed from the very beginning on Atkins) can either aggravate or trigger food sensitivities (“no bueno”).
Mistakes people make on the keto diet.
Tapping into consumers’ desire to glean the benefits of ketosis right this minute—or in the next 30 minutes—manufacturers have created powders and other supplements that promise you can enjoy your favorite foods and still get into ketosis. These supplements—called exogenous ketones—aren’t necessarily bad, but neither are they a free pass to indulge and then effortlessly shift into ketosis.
Then you’ve got “keto-approved” junk foods like cookies, candy, and bread that promise to keep you in ketosis even as you indulge in your favorite comfort foods. The flip side is ketogenic diets that include almost no plant foods, focusing instead on meat, meat, and more meat. Bring on the bacon. Slather your steak in butter. Who needs vegetables? (Hint: You do!) Ketogenic diets are a practical invitation for vegetable-phobic people, and when you skip out on gut-healing plant foods, you create microbiome mayhem.
Ultimately, poorly designed ketogenic plans become hyper-fixated on a single issue, like counting carbs or getting enough fat. Doing that neglects other highly important factors, like nutrient density and eating whole, unprocessed foods that will have a positive impact on gut and overall health.
How does the keto diet affect your hormones?
As you eliminate blood-sugar-elevating carbohydrates, you stabilize blood sugar levels and lower insulin levels, subsequently benefiting other hormones. At least theoretically that should happen.
Unfortunately, that path isn’t so clear-cut and will differ among individuals. The transition to a ketogenic diet might also differently affect hormones than maintaining the plan long-term. Hormones are complicated, and other factors beyond diet—including sleep quality, stress levels, circadian rhythm nutrient status, and your overall health—dramatically affect whether they become balanced or unbalanced.
Take your stress hormone cortisol: It stays highest in the morning and gradually tapers throughout the day. Measuring cortisol in the morning might yield an entirely different result from testing in the evening. Researchers speculate ketogenic diets might raise this stress hormone, but many other factors also come into play here that may have nothing to do with your diet.
Research about ketogenic diets and hormonal balances can become complicated and inconclusive. While it feels tempting to say any well-designed diet plan can optimize hormonal levels, the truth isn’t always so linear or clear-cut. Take these three hormones:
1. How the keto diet affects insulin.
Research here is conflicting. While you might think to reduce insulin-triggering carbohydrate foods would improve insulin sensitivity, that isn’t always the case. Rodent studies found at least in the short-term, ketogenic diets increased glucose intolerance and insulin resistance. Researchers speculate part of this insulin resistance occurs because of keto-adaptation, and once your body adjusts to ketosis, you become more insulin sensitive. Your mileage will vary, of course, and I believe going too low-carb could create these and other potential dangers.
2. How the keto diet affects ghrelin
Many dieters complain that hunger sabotages their success. Ghrelin is the hunger hormone that tells you to eat. Research shows ketogenic diets suppress ghrelin, keeping you fuller longer. That makes sense: When you’re eating sufficient dietary fat and calories, you’re unlikely to be hungry.
3. How the keto diet affects growth hormone.
If you lift weights on a ketogenic diet, you might fear losing muscle mass taking in lower amounts of protein. That doesn’t seem to be the case since your body preferentially utilizes fat rather than protein during ketosis. Growth hormone, an anabolic hormone sometimes called your fountain-of-youth hormone because it keeps you lean and toned, plays a major role in regulating muscle growth and development, stimulating muscle protein synthesis. Researchers find a very-low-carbohydrate diet with sufficient protein does not affect growth hormone levels, at least in the short-term. If you’re a regular lifter, you might want to consider slightly increasing your protein intake during workout days and supplementing with a branched-chain amino acid (BCAA) supplement. Cyclical keto, where you would eat a higher-carbohydrate diet during your workout days, also makes for a smart strategy to maintain muscle.
What really matters here is how you feel when eating a particular way. Your mood, energy levels, lab results, and mental sharpness (to name a few) are powerful indicators of whether a diet works for you both short- and long-term. Body awareness is key as well as not following a specific diet because you think it’s the “right” diet to follow. Listen to your body. And most importantly, if you feel off, seek the help of a functional medicine practitioner to assist you in uncovering the root cause of your malaise or diet resistance. Sometimes all it takes is a few small tweaks to improve your health.
Does the keto diet make sense for everyone?
Just because your favorite celebrity endorses a program doesn’t mean you should try it. No plan works for everyone, and that goes double for ketogenic diets. As I mentioned before, while they can initially create fat loss, ketogenic diets were never designed to help you lose weight. Especially if you’re eating too many calories—very possible on a high-fat ketogenic diet—you can be in ketosis and not lose weight (or even gain weight). Likewise, many people lose weight just fine without ever “going keto.”
If you’re considering a ketogenic diet for other reasons—such as to prevent disease risk or to have more energy and boost your brain power—I strongly suggest reading what I have to say next about the pros and cons of doing this plan and asking yourself these questions:
- What are your short-term and long-term goals?
- Can you really cut out healthier higher-carbohydrate foods (sometimes including berries and other fruit, legumes, and non-gluten grains) for a period of time?
- Are you prepared to work through “keto flu” and other potential drawbacks as your body shifts from glucose to fat (ketones) as its dominant fuel source?
- Can your body handle higher amounts of dietary fat? (To make this process easier, I recommend my patients gradually increase their fat intake. Your digestive enzymes need time to ramp up to be able to handle the higher fat content in your digestive tract, or it can cause unpleasant gas, bloating, and diarrhea.) Remember: If the thought of eating higher-fat foods like steak or avocado doesn’t appeal to you, keto probably isn’t for you.
- Can you handle potential social restrictions on this plan, such as not being able to partake in certain foods or drinks (alcohol) your friends enjoy?
- Can you realistically stick with a high-fat ketogenic diet long-term?
Yes, you can do a ketogenic diet in a healthy way, but doing so demands dedication, planning, and knowing exactly how to do it correctly. Too often, I see patients get keto wrong…with potentially disastrous results.