Of course you’ve heard of the super-popular ketogenic diet, but you may not be totally clear on how it works — and even if you are, you may think it sounds too good to be true. What exactly can you eat on a keto diet, you ask? In short: lots of fatty foods.
The keto diet is a high-fat, moderate-protein, low-carb plan that’s designed to send your body into ketosis, which is when your body turns fat into fuel rather than relying on carbs for energy. “Basically, your brain and muscles will be fueled by fat instead of carbohydrates,” explains Michelle Hyman, MS, RD, CDN, a registered dietitian at Simple Solutions Weight Loss.
It may sounds like the ideal food plan to some, but like all diets, the keto diet comes with potential adverse side effects. “If you have a history of disordered eating or a diagnosed eating disorder, keto probably won’t be a good fit,” explains registered dietitian SaVanna Shoemaker, MS, RDN, LD. “Additionally, anyone with an underlying medical condition, like high blood pressure or diabetes, should speak to their doctor before starting keto. Keto can have some powerful effects fairly quickly, which may warrant changes to medication dosages.”
Before you embark on the keto diet, it’s important to understand what does and doesn’t count as keto diet foods, as well as whether you’re a good candidate for the diet. “The keto diet may be particularly helpful for people who need to lose weight or get their blood sugar under control — especially if they’re tried and failed other diets or eating styles due to hunger,” Shoemaker adds. So what exactly can you eat on a ketogenic diet? Here’s what you should know.
Foods you can eat on the keto diet
The biggest question most people have about the keto diet: How does eating bacon, butter, and cheese all day lead you to lose weight? The keto diet is all about changing the way your body processes food, which means consuming more fat and fewer carbs than the average person. “One benefit of keto is that many people report it drastically reduces their appetite, making it easier to stick with the calorie restriction that promotes weight loss,” Shoemaker explains. “And although the cravings for high-carb foods may be pretty rough at first, if you can make it through the first week you’ll probably notice many of your carb cravings subsiding.”
If you’re not sure what a keto diet looks like, then here’s a breakdown of the percentage of each food group the diet requires you consume every day, as well as what kinds of foods are best to consume for this diet.
Carbs (5-10% of daily calories)
- Approximate grams of carbs per day based on a 2,000-calorie diet: 40
Again, the most difficult (but important!) part of the keto diet is cutting your carbohydrate consumption. The typical American consumes about 52% of calories from carbs, according to a study published in The American Journal of Clinical Nutrition, but when you’re on the keto diet, you should only be getting 5 to 10% of your daily calories from carbs. “Drastically limiting your intake of glucose, the usual energy source for your cells, reduces insulin secretions in your body,” explains Rania Batayneh, MPH, author of The One One One Diet. “Since low levels of glucose are coming in, the body uses what is stored in the liver and then the muscles.”
Your body’s stored glucose is typically used up after about three or four days on the keto diet. That’s when your body is forced to turn to another fuel source. As Hyman says, “For an alternative source of energy, your liver will start to convert fat into ketones, which will then be released into the bloodstream and be used by your cells for energy.” Most keto dieters aim to eat between 20 to 50 grams of carbs per day to maintain that ketone-burning state called ketosis.
You should aim to score your carbs from high-fiber, water-rich fruits and vegetables to naturally boost hydration and keep your digestive system chugging along. Not sure which produce picks are low in carbs? Reach for options grown above the ground (like leafy greens, peppers, and stalk-shaped vegetables), rather than below ground (such as potatoes, carrots, parsnips, and other root veggies), as produce grown above ground typically offers fewer carbs.
Good examples of carb keto diet foods:
- Green Beans
- Bell peppers
- Brussels sprouts
Protein (10-20% of daily calories)
- Approximate grams of carbs per day based on a 2,000-calorie diet: 70
Protein is essential to build muscle cells and burn calories. As a result, if you eat too little protein on the keto diet (and too much fat), then your body will turn to muscle tissue as fuel. This, in turn, will lower your overall muscle mass and the number of calories you burn at rest. Likewise, eating too much protein puts undue strain on your kidneys. Plus, your body will convert the excess protein to carbohydrates for fuel, and that’s the exact opposite goal of the keto diet.
Experts say to shoot for around 15% of calories from high-fat protein sources like those below. Some protein sources (such as Greek yogurt, eggs, and cheese) also provide important vitamins to keep your hair, eyes, and immune system strong, while others should only be consumed in small doses. “While processed meats like sausage and bacon are technically permitted on the keto diet, I’d recommend limiting them since they’re high in sodium,” Hyman says. Instead, opt for organic, pasture-raised, and grass-fed meat and poultry, if possible.
Good examples of protein keto diet foods:
- Chicken, dark meat if possible
- Turkey, dark meat if possible
- Natural cheeses
- Unsweetened, whole milk plain Greek yogurt
- Whole milk ricotta cheese
- Whole milk cottage cheese
Fat (70-80% of calories)
- Approximate grams of carbs per day based on a 2,000-calorie diet: 165
Fat is where the bulk of your intake comes into play. Yes, it may get a bad rap, but it’s actually an essential macronutrient that’s used as a fuel source for building cell membranes, absorbing vitamins, and minerals, and other bodily processes. A higher-fat diet has also been shown to reduce cravings (as well as your levels of ghrelin and insulin, which are appetite-stimulating hormones), but just make sure you’re going with full-fat foods rather than those with trans-fats and overly processed polyunsaturated fats.
Instead of stressing over the dietary cholesterol content, focus on consuming a higher ratio of unsaturated fats (like flaxseed, olive oil, and nuts) to saturated fats (such as lard, red meat, palm oil, butter). “There’s a misconception that keto is all bacon, butter, and cheese — and while some people take that approach, it’s not the only way,” Shoemaker says. “While the diet is high fat, if your goal is weight loss, then it’s important to moderate your fat intake so that your body can burn your stored body fat.”
Since you’re consuming a vast majority of calories from fat, it’s crucial to focus on fueling up with options that are less likely to clog your arteries and less likely to increase your cancer risk. “Focus on filling meals that contain a balance of protein, non-starchy vegetables, and healthy fat sources like nuts and seeds, olive oil, avocado oil, coconut oil, or avocado,” Shoemaker adds.
Good examples of fat keto diet foods:
- Olive oil
- Avocado oil
- Chia seeds
- Pumpkin seeds
- Sesame seeds
- Hemp hearts
- Natural, no-sugar-added nut butters
Foods to avoid on a keto diet
Now that you know what keto diet foods are safe to eat, you should also know what not to eat on a keto diet. According to Hyman, you can make it easier to stay within the macronutrient framework of the keto diet by steering clear of these foods:
- Beans, peas, lentils, and peanuts
- Grains (like rice, pasta, and oatmeal)
- Low-fat dairy products
- Added sugars and sweeteners
- Sugary beverages, including juice and soda
- Traditional snack foods, such as potato chips, pretzels, and crackers
- Most fruits (except for lemons, limes, tomatoes, and small portions of berries)
- Starchy vegetables, including corn, potatoes, and peas
- Trans fats, such as margarine or other hydrogentated fats
- Most alcohols, including wine, beer, and sweetened cocktails
Possible side effects of a keto diet
There are a number of immediate side effects people transitioning over to a keto diet may experience. According to Shoemaker, some people will experience stomach issues and gastrointestinal distress due to such a drastic change in diet. “A condition informally known as the ‘keto flu’ — which often includes fatigue and muscle cramps — can be caused by shifts in the way your body holds fluid when you first begin,” she says. “This eases up in a few days, and you can lessen these symptoms by drinking plenty of fluid and taking an electrolyte supplement.”
Some people may also experience a halitosis known as “keto breath” that’s attributed to an increased production of acetone, which is one of the ketone bodies. “Keep breath mints handy, and know that this will subside in a few days as well,” Shoemaker suggests.
The bottom line
After about a year of following the diet, the weight loss advantage may plateau and disappear all together, so keto shouldn’t be considered a lifelong lifestyle change. Health experts have even warned dieters about the possible longer-term cardiovascular side effects for people who follow the diet for several years. Currently, there are no long-term studies on how the keto diet impacts a person’s health if followed for years, which leaves some doctors worried about the negative outcome eating so much fat over a long period of time could have on the body’s bad cholesterol. To keep safe, make sure to always follow the guidance of your doctor or nutritionist as you go about your health journey.
Karla Walsh is a Des Moines, Iowa-based freelance writer and level one sommelier who balances her love of food and drink with her passion for fitness. (Or tries to, at least!) Her writing has been published in Runner’s World and Fitness Magazines, as well as on Shape.com, EatThis.com, WomensHealthMag.com, and more.
Corinne Sullivan is an Editor at Cosmopolitan, where she covers a variety of beats, including lifestyle, entertainment, relationships, shopping, and more. She can tell you everything you need to know about the love lives of A-listers, the coziest bedsheets, and the sex toys actually worth your $$$. She is also the author of the 2018 novel Indecent. Follow her on Instagram for cute pics of her pup and bébé.