Diet fads come and go, but some attract more attention than others. In case you’ve somehow missed it, the keto diet is the latest obsession taking over the weight loss world. Adherents claim the high-fat, low-carb eating regimen has helped them lose weight in a short period of time—all while eating (most of) the foods they love.

But nutritionists, including Jaclyn London, MS, RD, and CDN of Good Housekeeping Institute, remain unconvinced. “The Ketogenic diet may work for you personally right now, and if that’s the case, then go for it—as long as you inform your physician about your diet, medical history, and medications,” she writes in The 5 Most Common Arguments for the Keto Diet, Debunked. “But from a public health standpoint, making a sweeping generalization in support of this diet would be negligent. Collectively, the existing information indicates that the keto diet can lead to nutrient deficiencies and prove difficult to adhere to long-term.”

In London’s view, the diet’s goal of achieving ketosis—the metabolic process by which the body uses fat instead of carbs for energy—can have potentially harmful effects. Besides, the lack of verifiable scientific research and the fact that the diet requires tremendous effort make it difficult to defend. Most nutritionists, such as those with the U.S. News and World Report, agree that the Mediterranean diets and its spin-offs (i.e. DASH, MIND, and TLC) have more research behind them and incorporate wholesome, nutrient-dense foods that promote improved eating patterns and manageable weight loss.

But if you’re still curious about what “going keto” requires, and if you want to include some (but not all) of these insights in your daily diet regimen, we provided a list below. The basic premise is pretty simple: eat mostly fat, some protein, and almost no carbs at all so you can activate the metabolic process known as ketosis, when our bodies use fat for energy instead of sugar.

Here’s a rundown of what you can (and can’t) eat on a keto diet.

What You Can Eat:

Meat: chicken, pork, steak, ground beef, lamb, bacon, ham, turkey, and sausage.

Fats and Oils: butter, coconut oil, olive oil, ghee, lard, avocado oil, and mayonnaise.

Vegetables (that grow above ground): cabbage, avocado, broccoli, cauliflower, zucchini, pepper, eggplant, tomato, asparagus, cucumber, onion, mushroom, spinach, lettuce, olives, and green beans.

High-fat Dairy: cheese, heavy cream, cream cheese, sour cream.

Nuts: almonds, hazelnuts, walnuts, peanuts, macadamia nuts, pecans, almond butter, etc.

Seafood: salmon, snapper, trout, tuna, cod, catfish, halibut, clams, crab, scallops, oysters, halibut, and mussels.

Some Berries: blackberries, blueberries, raspberries.

Alcohol: hard liquor, dry wine, champagne (no beer!).

Eggs, unsweetened tea and coffee, spices.

What You Can’t Eat:

Fruit: bananas, apples, oranges, grapes, watermelon, peaches, melon, pineapple, cherries, pears, lemons, limes, grapefruits, plums, mango, etc.

Grains and Starches: wheat, rice, rye, oats, corn, quinoa, barley, millet, bulgur, buckwheat, sprouted grains, etc.

Root vegetables: potatoes, carrots, yuca, yams, parsnips, beets, and turnips.

Grains: bread, pasta, cereal, crackers, pizza, oatmeal, popcorn, granola, flour, etc.

Legumes: kidney beans, black beans, navy beans, soybeans, peas, chickpeas, lentils, etc.

Sweeteners: cane sugar, honey, maple syrup, Splenda, aspartame, agave, corn syrup.

Sweets: chocolate, cakes, buns, pastries, candy, etc.

Oils: soybean oil, grapeseed oil, canola oil, sesame oil, sunflower oil.

Alcohol: beer, cider, sweetened alcoholic beverages, sweet wines, etc.

Drinks: smoothies, drinks, soda, sweetened tea and coffee.

Low-fat dairy products: skim milk, skim mozzarella, fat-free yogurt, etc.

Is Keto Worth It?

According to experts, the best way to get into ketosis is by eating less than 20 to 50 grams of carbs per day, or the equivalent of a slice or two of bread. “So people on a ketogenic diet get 5 percent of their calories from carbohydrates, about 15 percent from protein, and 80 percent from fat,” writes Julia Belluz. “Note that that’s a much lower ratio of protein and a lot more fat than you’d get on other low-carb diets, but it’s this ratio that will force the body to derive much of its energy from what are called ketones. If you eat too much protein, or too many carbs, your body will be thrown out of ketosis.”

In terms of your diet, that means eating mostly meats, eggs, cheese, fish, nuts, butter, oils, and vegetables—and avoiding sugar, bread and other grains, and high-sugar fruits. Most nutritionists think that’s asking a lot for a diet that isn’t scientifically proven to shed pounds or promote optimal health.

One thing science can confirm is the idea of treating people suffering from epilepsy with the keto diet, which came about in the 1920s when researchers observed that people who fast experienced fewer seizures. Today, studies have shown that children and adults whose epilepsy doesn’t respond to medications seem to experience a significant reduction in seizures when adhering to a ketogenic diet. That doesn’t, however, prove that the diet works for other conditions, or even as a weight loss mechanism.

So, if you’re still interested in beginning a keto diet, you might want to talk to your health physician first. There are plenty of other weight loss plans out there, and they might have more research behind them than keto. If you do end up giving it a try, buyer beware: the keto diet seems to be taking away more than it gives, and in the long run, it looks a lot like other fad diets.

Here’s a list of resources to take a deeper dive into the health risks and potential benefits of the keto diet.

Ketogenic Diet: Is the Ultimate Low-carb Diet Good For You?

The Keto Diet, Explained

The Keto Diet is Gaining Popularity, But is it Safe? 

BodyKetosis: Keto Made Simple

By: Nico Picciuto