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The ketogenic diet — known for its high-fat and very low-carb eating plan, where items like bacon and cheese are routinely on the menu — pushes dieters to train their metabolism in a whole new way. But working towards what's known as ketosis, a metabolic state in which fat serves as the main source of daily energy as opposed to carbohydrates, requires you to read more than just nutrition labels; you'll need to know the science behind reaching ketosis in order to maintain it.
Stefani Sassos, MS, RD, CDN, deputy director of the Good Housekeeping Institute's Nutrition Lab, explains that keto dieters' metabolism breaks fat down into molecules known as ketone bodies to fuel your day — as opposed to carbohydrates, which normally influences blood sugar to provide energy. Originally designed to help patients fight epilepsy, a strict keto diet guides you into ketosis by eliminating significant food groups that you may normally enjoy on a daily basis, including healthy items that are part of a balanced diet.
Anything containing sugar, both naturally occurring as well as added sugars, and carbohydrates are off limits, as these foods prevent your metabolism from running on fat alone. Below, we're exploring the most common grocery staples that run the risk of knocking you off ketosis — as well as the foods that can help you lead a successful keto diet.
It's crucial to talk to your primary care provider before taking a swing at achieving ketosis, especially as there are some reports that suggest keto programs lead to yo-yo dieting. Here's what you need to know about keto-friendly foods you can eat, items you should avoid to maintain ketosis, and treats you can enjoy every once in a while.
Editor's note: Weight loss, health and body image are complex subjects — before deciding to go on a diet, we invite you gain a broader perspective by reading our exploration into the hazards of diet culture.
What you can eat on a keto diet:
Get ready for a whole lot of fat, some protein and just about zero carbs throughout your day. Keto-approved fridges and pantries include meat, seafood, dairy, eggs, nuts, fats and oils and some veggies that grow above ground.
Plenty of meats: Chicken, pork, steak, ground beef, lamb, bacon, turkey, ham, and sausage (in limited amounts).
Fatty seafood: Salmon, snapper, tuna, halibut, cod, trout, catfish, scallops.
Shellfish: Crab, clams, oysters, lobster, mussels.
Most fats and oils: Eggs, butter, coconut oil, olive oil, ghee, lard, avocado oil (and avocados!), mayonnaise.
High-fat dairy: Heavy cream, soft and hard cheeses, cream cheese, and sour cream.
A selection of vegetables: Cauliflower, cabbage, broccoli, zucchini, green beans, peppers, eggplants, tomatoes, asparagus, cucumber, onion, mushroom, spinach, lettuce, and olives.
Most nuts: Almonds, peanuts, macadamia nuts, pecans, hazelnuts, walnuts, as well as their retrospective butters (look for natural varieties that aren't sweetened).
A selection of berries: Blueberries, blackberries, raspberries, all in moderation.
Some of your favorite beverages: Unsweetened coffee and black tea is OK. Dry wine, champagne, and hard liquor should be enjoyed sparingly.
All spices and some sweeteners: Enjoy stevia and sucralose every once in a while.
Meat and poultry
Naturally devoid of all carbohydrates, all kinds of meat and poultry are used in keto diet plans — including fatty cuts of beef and pork, which are both rich in a suite of minerals and B vitamins. Protein found in meat, even if lean, can help you feel fuller during the day and fuel you through physical workouts or labor, even if you're no longer filling up on carbohydrates. A limited study found that a diet high in fatty cuts of meat actually slightly boosted good cholesterol levels in the long run for women.
Also rich in protein and B vitamins, many kinds of fish are free of carbohydrates, like salmon, albacore tuna, sardines, and other fatty fish you can find fresh at any seafood counter. Unlike meat, however, seafood is rich in omega-3 fatty acids, a form of polyunsaturated fats (a good source of fat!) that are linked to reducing the risk of chronic disease across the board.
Oils and fats
More often than not, you'll be cooking with olive oil or its higher-fat counterpart coconut oil while cooking your way through the keto diet. Olive oil has long been associated with a lower risk of cardiovascular disease in programs like the Mediterranean diet, and is likely a great bet to balance out the increased sources of fat you'll be consuming. Coconut oil is certainly tasty, and is high in saturated fat, but is often used in keto recipes due to its medium-chain triglycerides, which may increase ketone production.
Dairy and eggs
Cheese, cheese, and more cheese! As it's high in fat and free of carbohydrates, cheese is a constant feature in the best keto recipes — plus, it's rich in calcium and a good source of protein, too. Staples like cottage cheese and yogurt are also significant sources of protein while remaining low in carbohydrates. Working in eggs when possible is smart to load up on minerals and antioxidants, including choline, and protein to help you feel fuller for longer in the day.
Sadly, not every single farm-fresh veggie is keto-approved — normally, you'll see options like broccoli, cauliflower, green beans, bell peppers, zucchini and leafy spinach used to substitute for things like potatoes and whole wheat-based foods. These non-starchy veggies are low in calories and also in carbohydrates, but are packed with vitamins and minerals, especially fiber to help your gut stay regular. The keto diet may be the only one where you'll be advised to enjoy these vegetables in moderation; while they're low in carbohydrates, too many servings in a single day can knock you off ketosis.
Seeds and oil-rich nuts are great ways to spice up your snack routine or customize keto-friendly meals to get out of a rut. They're chock full of both polyunsaturated and monounsaturated fats, and low in carbohydrates while fitting into the high-protein aspect of the keto diet. The best nuts to eat while on the keto diet include macadamias, almonds, pecans and walnuts. Seeds you can feel great about include sesame seeds, pumpkin seeds and flaxseeds, too.
On a diet where there's little to no fruit in sight, fresh berries can feel like cool water in a hot desert — the added bonus is that they're rich in nutrients, namely antioxidants. There are a few berries that are naturally more keto-friendly due to their carb and sugar makeup — including blackberries, raspberries and strawberries — that are also high in fiber. Sprinkle these into naturally sweet desserts to keep your sweet tooth satisfied while on the keto diet.
Black coffee and tea contain absolutely no sugar or carbohydrates and make for great options on the keto diet. Tea may be a better choice for you in the long run, as numerous studies and research suggest the antioxidants within blends like green tea can be beneficial; there is also data to suggest that tea can help aid weight loss efforts over time.
What you can't eat on the keto diet:
It's a pretty exhaustive list, and probably includes some of your favorites: Bread, rice, pasta, fruit, corn, potatoes, beans, baked goods, sweets, juice and (most!) beer all get the axe. Basically, you have to avoid most sugars and starches. Whole grains like oatmeal don't even make the cut!
Almost all fruits: Apples, bananas, oranges, grapes, watermelon, peaches, melon, pineapple, cherries, pears, lemons, limes, grapefruits, plums, mango, and more.
Most grains: Wheat, rice, rye, oats, corn, quinoa, barley, millet, bulgur, amaranth, buckwheat, and sprouted grains.
Starches: Bread (all of it!), bagels, cereal, pasta, rice, corn, oatmeal, crackers, pizza, popcorn, granola, muesli, flour. There are some workarounds that dieters can still enjoy, like faux tortilla wraps that are made from cheese.
Legumes: Black beans, kidney beans, pinto beans, navy beans, soybeans, peas, chickpeas, lentils.
Real sweeteners and sugar: Cane sugar, honey, maple syrup, agave nectar, Splenda, aspartame, saccharin, and corn syrup. You'll have to settle for sugar alternatives, including natural substitutes like a monkfruit sugar replacement.
Sweet treats: Candy, chocolate, cakes, buns, pastries, tarts, pies, ice cream, cookies, pudding, and custard. Dieters can shop for dessert alternatives like keto-friendly ice cream that won't impact your blood sugar levels in a single serving.
A selection of cooking oils: Canola oil, soybean oil, grapeseed oil, peanut oil, sesame oil, and sunflower oil.
Alcohol: Beer, cider, sweet wines, and sweetened alcoholic drinks. If you're going to spring for wine, keep it as dry as possible — the bottle should have less than 10g of sugar in its entirety.
Bottled condiments: Ketchup, BBQ sauce, tomato sauce, some salad dressings and hot sauces that contain added sugar.
Low-fat dairy: Things like skim milk, skim mozzarella, fat-free yogurt, low-fat cheese and cream cheese should be swapped for higher-fat counterparts.
Grains and wheat
Carbohydrates are found in everything from cereal to pasta, bread to beer — and even trace amounts can be found in plant-based replacements like spiralized veggies or legume-based pasta. This also includes many forms of alcohol (including wine)! While you can shop around for lower-carb options in all of these categories, usually dieters can only enjoy less than or a single serving's worth of the food at hand (think: a single slice of bread) before threatening their metabolism's ketosis
Starchy vegetables and sugary fruit
Since carbohydrates and sugar must be restricted, both of these naturally occurring sources must be limited in tight moderation to maintain ketosis. Starchy vegetables contain more carbohydrates than others, namely corn, potatoes, beets and yams, among others. On the other hand, some fruits are inherently sweet and can impede your progress towards ketosis — you'll need to cut bananas, mangos, pears, and raisins altogether.
Desserts and sweetened treats
Sugar isn't compatible with this diet, and neither are any of its replacements you may usually use in the kitchen — honey and maple syrup are also high in carbohydrates and off the menu. Many keto dieters turn to special dessert recipes after realizing that a gluten-free recipe doesn't necessarily mean a recipe that's low in carbs, either. Sugar can make its way into many other baked staples you may know and love, like crackers, processed snack bars and foods, which can be low in nutrients.
Carb-heavy foods that can accidentally ruin your keto diet:
Since the keto diet has ballooned in popularity over the years, the rise of keto-specific aisles at grocery stores and other specialty stores may confuse shoppers with claims on keto-specific swaps. There are indeed keto-friendly items that you can use to make dieting easier, but marketing claims like "keto-safe" and "low carb" may lead you to eat too many carbohydrates in a day (more than a net amount ranging between 20 and 50g), invalidating the ketosis you've worked so hard to achieve. Be wary of the following items:
Flavored yogurts: You may be jonesing for a sweet treat for dessert, but added sugar can easily sneak into blended yogurt products. Stick to plain greek yogurt, which contains less carbohydrates, and try adding a handful of berries or chia seeds and a splash of unsweetened almond milk for a better keto-friendly dessert.
Fruit juice: Whether it's organic, fresh squeezed or made from concentrate, fruit juice is known as a boon for diabetics for a reason; it raises your blood sugar quickly and contains plenty of fast-acting carbs.
Beans, chickpeas and peanuts: Otherwise celebrated for their role in a healthy diet, these legumes all have high carbohydrates. You'll need to seriously measure tight servings of each of these items if you want to avoid surpassing the right amount of daily net carbs you can ingest.
Syrups and honey: While honey and other beverage-friendly syrups aren't equal to a packet of pure sugar, they contain plenty of naturally occurring sugar. Unless it's a very targeted and controlled amount, honey and maple syrup can pack in carbohydrates without any other added nutritional benefit.
Milk: While milk is indeed a great source of nutrients, a cup of full-fat milk contains 12g of naturally occurring sugar in its lactose content. Try almond milk instead, given its low carb count over other popular alternatives like oat milk.
Specialty chips and grain-based crackers: There are healthier snack products available than traditionally processed potato chips you may find in a convenience store; that doesn't mean you can eat uncontrolled amounts of grain-based chips or crackers. You're better off reaching for a high-protein snack, including dairy items or even convenience items like turkey jerky.
Whole wheat bread and gluten-free swaps
Even if they are made with whole wheat, bread, rice and pasta remain very high in carbohydrates — the same can be said for gluten-free varieties, as gluten doesn't equate to carbohydrate content whatsoever. Even bean-based pasta contain ample amounts of carbohydrates that may knock you off ketosis. If you can't live without a noodle bowl of some sort, try spiralized vegetables instead; you can have a proper serving of these vegetables without having to harshly limit them to stay within the net carb range required.
Starchy fruits and vegetables
There is room for vegetables and fruits in a controlled keto diet, but produce can contain more naturally occurring starch than you're allowed — meaning that you can eat some veggies and fruits more freely compared to starchy, sugary options. For this reason, many dieters choose to restrict the following starchy staples entirely due to their nutritional stats, pulled from the USDA:
Bananas: 27g total carbs in a medium-sized fruit
Raisins: 22g total carbs in a single oz
Mango: 25g total carbs in a cup, sliced
Pear: 27g total carbs in a medium-sized fruit
Corn: 36g total carbs in a full cup of kernels
Potato: 37g total carbs in a medium-sized vegetable
Sweet potato: 24g total carbs in a medium-sized spud
Pros of a keto diet:
According to the Epilepsy Foundation of America, the ketogenic diet can work to reduce or outright prevent seizures in children whose epileptic episodes couldn't be mitigated by medication — as many as half of those who adopt the diet may see a dramatic shift. And recent research, though fragmented and not holistic, suggests that there may be an observed weight loss and cardiovascular benefit for previously overweight or obese individuals who transition into a long-term keto diet (meaning, those who adopt the program indefinitely).
But more research is needed to substantiate other claims against claims that the keto diet may work to impact Type 2 diabetes treatment and insulin needs — as well as any claimed benefits against the progression or treatment of disorders including Autism and Alzheimer's.
Cons of a keto diet:
Most keto diet plans are considered harsher than no-sugar diets in their entirety because deprivation requires willpower that is often counterintuitive to your needs. Paired with fads like intermittent fasting, keto could be downright dangerous – plus, a rigid keto plan isn't as easy as it may seem. Restrictive diets are hard to adapt at first, with the potential to impact your relationship with food in a negative way for life. That's not even considering side effects like the "keto flu" and the barrage of snake oil products that may mislead you.
Sassos stresses that while the keto diet may indeed result in weight loss for those who adapt their lifestyle, if you know you can't give up bread and fruits entirely, that's okay — there are countless other diet plans that can also help you lose weight in the long run without eliminating food groups.
If you're tempted to go keto, consult with your doctor before embarking on any extreme weight loss plan. While the ketogenic diet can include some healthful foods (we're all about broccoli), many others get nixed (bye, bananas and sweet potatoes).
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