Eating all the fat you want sounds like a delicious way to lose weight—but is it worth sacrificing carbs?

Watch: The Beginner’s Guide to Keto

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MEAT AND CHEESE lovers, rejoice: a diet plan that allows you to keep your favorite foods that still helps you lose weight. The ketogenic diet has been helping people lose weight since its humble beginnings as a treatment for epilepsy in the 1920s.

Its popularity has ebbed and flowed over the past hundred years. But, it has picked up steam recently, thanks in part to the hoards of celebrities touting it as the reason they got in shape (if you’ve been waiting on the Jersey Shore cookbook, the Keto Guido Cookbook is here to answer your prayers). Success stories aren’t hard to find— you probably know a person or two who have seen great success doing keto.

It’s all about sticking to, well, the meats and the cheeses. Following the keto diet means consuming about 60 to 80 percent of your calories from a source of fat—preferably healthy fats like olive oils, avocados, nuts, and eggs. Around 20 percent is dedicated to protein, like chicken, tofu, turkey, and beef. Lastly, a measly 10 percent gives carbohydrates some wiggle room into your diet, so you can get a nibble of bread, rice, and pasta.

The idea revolves around the understanding that our bodies burn carbohydrates first as fuel source when we need energy. After all the carbohydrate stores are burned off, the body turns to fat stores to power its functions.

When it comes to weight loss, “there is no question that ketosis does work in the short term,” Konstantinos Spaniolas, M.D., associate director of the Stony Brook Metabolic and Bariatric Weight Loss Center in New York.

It makes sense in theory, and the keto diet entices people by allowing those who participate many cult-favorite foods. Come on, a diet where you can eat endless amounts of bacon and Gouda? We’re sold (maybe).

So, exactly how far do the benefits of this diet reach?

It’s not without its fair share of controversies. The diet has received some criticism for its high fat intake and its effect on heart health.

Its rigid macronutrient counts can be tough to stick to, too. But if you have the motivation and don’t give into the temptation in food-form that is bread, then you may see some great success with the keto diet.

So, in short, keto is facing a reality check. If you’re thinking about trying keto and want to determine if it’s worth sacrificing carbs, here’s a healthy dose of perspective.

What Is Ketosis?

Ketogenesis has existed as long as humans have.

If you eat a very low amount of carbohydrates, you starve your brain of glucose, the organ’s main fuel source. Your body still needs fuel to function, so your brain flips the switch to tap into your reserve of ketones, which are compounds the liver creates from fat when blood insulin is low. This process is known as ketosis: It’s like when a hybrid car runs out of gas and reverts to pure electricity.

There’s nothing inherently magical about ketones. In fact, you already have them in your body. “Your liver produces ketones all the time, but the rate depends on carbohydrate and protein intake,” says Jeff Volek, Ph.D., R.D., a professor of human sciences at Ohio State University.

When the majority of your diet is made up of carbs and protein—as the average American diet is—ketogenesis (the process of producing ketones) slows. Replacing carbs and protein with fat will put your body into ketosis, thus ramping up ketone production. Essentially, you’ll burn fat instead of carbs for energy. Ketosis is not instantaneous, and the process takes about three days to induce—often with some side effects during the transitioning stages. (More on those later!)

What Can You Eat On the Keto Diet?

To understand which foods you should and which you should avoid on the keto diet, you have to first consider three key nutrients: fat, protein, and carbohydrates.

A ketogenic diet generally requires that fat comprise 60 to 80 percent of your total calories. Protein take up about 20 percent, while the remaining 10 percent comes from carbs. Proponents of a ketogenic diet often recommend limiting your carb intake between 20 to 30 grams per day in order to maintain ketosis. For perspective, that’s the equivalent of about half a medium bagel.

Yes, that all. Half a medium bagel.

Precision Nutrition

And remember, carbs aren’t just present in processed foods; a cup of chopped broccoli has 6 grams of carbs, a cup of chopped carrots has 12 grams, and a cup of Brussels sprouts has 8 grams. In other words, eating the recommended five servings of vegetables per day (because fruits, which are higher in carbs, are pretty much off the table) will probably put you at your max carb allowance.

If this sounds like the Atkins Diet from the 1990s, it’s close, but “ketogenic diets tend to be more severe in carb restriction and have a more moderate protein restriction,” says Spencer Nadolsky, D.O., author of The Fat Loss Prescription.

Though you can eat bacon on a ketogenic diet, the rest of the spectrum is limited. Starchy vegetables like potatoes, corn, and squash are too high in carbs. Same with most fruits. Milk, beans, rice, pasta, bread: nope.

To stay as healthy as possible, keto dieters should eat plenty of low-carb vegetables like red bell pepper, kale and cauliflower. These vegetables contain important micronutrients (AKA vitamins and minerals), as well as fiber, which is linked to a lower risk of heart disease, diabetes, and cancer.

The rules of keto impact more than just mealtime, too, since juices, sodas, and alcohol will knock you out of ketosis.

So what does a typical day of eating look on the ketogenic diet?

Sample keto meal plan

Breakfast: 4 eggs, 1/2 avocado, 1 to 2 Tbsp olive oil
Lunch: 4 oz baked salmon with 1 Tbsp olive oil, 1/2 bunch asparagus with 1 to 2 Tbsp butter
Dinner: Rib-eye steak, 2 cups spinach with coconut oil, 2 oz macadamia nuts

Most men consume nearly half of their calories from carbs, according to the Centers for Disease Control and Prevention. And that’s not a bad thing; it’s actually within the range of what the Dietary Guidelines for Americans recommend for optimal health. So, it goes without saying that cutting your intake to less than 10 percent will be a challenge, and may pose some risks.

We’ll get into those a little later, but, first, the ketogenic does have some benefits that are worth highlighting.

How Do You Know If You’re In Ketosis?

Sure, eating bacon and cheese may sound like a dream but achieving ketosis isn’t easy, says Melanie Boehmer, a registered dietitian at Lenox Hill Hospital.

“Sometimes people try and teeter into it and they won’t lower their carbohydrates enough,” Boehmer says. She recommends eating no more than 20 to 30 grams of carbohydrates per day to maintain the ketogenic state.

Often people think they can eat unlimited amounts of meat on the diet, but that isn’t true. Consuming too much protein will also decrease ketone levels.

Cheat days, even if they are rare, and drinking alcohol can take you out of ketosis, too.

You can determine whether you’re actually in ketosis by purchasing an over-the-counter test. However, they’re not always accurate, warns Ginger Hultin, M.S., R.D.N., spokesperson for the Academy of Nutrition and Dietetics.

“They sell testing strips for urine, though those can get false reads for a number of reasons, like hydration levels,” she previously told Men’s Health.

So, in short, it’s kind of tough to tell. You just have to stick to your macros and hope the number on the scale drops.

What Are The Benefits of Keto?

Well, you can lose weight on keto. And maintaining a healthy weight can reduce the risk of and alleviate symptoms related to heart disease, diabetes, and a whole host of other challenging conditions.

Ethan Calabrese

Anecdotally, plenty of men have told Men’s Health that the keto diet helped them lose large amounts of weight. According to Spaniolas, keto helps with weight loss by reducing cravings.

Some studies show that keto may lower blood sugar for people with type 2 diabetes, but there is not enough long-term research to determine whether it’s safe and effective for diabetics.

Also, side note, although studies have shown that the keto diet can reduce seizures for children with epilepsy, there is no evidence indicating that keto helps with other brain disorders or improves mental cognition, according to Harvard Health Publishing.

So, in the short term, yes, a keto diet can help you lose weight, which may reduce your risk of disease—but more indirectly than directly. But what about in the long term?

Does Keto Work For Long-Term Weight Loss?

It’s still too soon to tell. In fact, the rapid weight loss which occurs at the start of a keto diet may not be fat loss at all.

“Early weight loss at the beginning of the Keto diet is likely related to fluctuations in fluid,” says Ashley Harpst, R.D., a sports dietitian and the owner of Go For the Gold Nutrition in San Diego. “Three to four ounces of water is retained for every 1 gram of carbohydrate stored as glycogen in the muscles to use for energy.” So, as your glycogen stores are depleted and you enter ketosis, there’s less water in your body as well.

There’s also no long-term data on ketogenic diets versus other diets. In a 2015 Italian study, those on a ketosis diet lost 26 pounds in three months. About half of the participants stayed on the diet for a year but lost little additional weight in the next nine months. People in a 2014 Spanish study who followed a very-low-calorie ketogenic diet lost an average of 44 pounds in a year—but a third of them dropped out, possibly because it was too hard to maintain.

Another study, published in 2020 in The BMJ, analyzed the results from 121 previously conducted clinical trials that looked at the effectiveness of various diets (low-fat, low-carb, low-calorie, etc.) for weight loss and lowering markers of cardiovascular disease risk, like blood pressure and LDL cholesterol. Based on data from nearly 22,000 adults, the researchers found that while all of these diets led to weight loss and improvements in cardiovascular health markers in the first six months, virtually all of those benefits had disappeared at the one year mark.

The bottom line: Keto (and any other diet) may lead to weight loss and improved health in the first several months, but even if you’re able to stay on the diet for longer, those benefits will likely disappear after about a year.

Do Ketone Supplements Work?

No.

While it is possible to elevate your ketones by taking them, “without the low-carb stimulus, there is no net increase in ketone production, no decrease in insulin, and no net increase in fat oxidation,” says Volek.

So don’t trust trainers or “body hackers” who say that you can induce ketosis quickly via a pill, powder, or potion—without changing your diet.

What Are The Side Effects?

There are a few. Let’s hit them one at a time.

Keto flu

People who begin the diet often develop “Keto Flu,” as their bodies get accustomed to eating fewer carbs. During this time you may experience headaches, nausea, fogginess, muscle cramps and fatigue. Symptoms last about a week, but staying hydrated and getting ample sleep will help with cramps and exhaustion.

Bad breath

Aside from Keto Flu, you may notice a few other unpleasant side effects. Acetone—yes, the ingredient in nail polish remover—is one of the compounds found in ketones, so your breath may be stinkier than normal. Pooping may be difficult since cutting carbs will lower fiber intake, but a fiber supplement will help keep you regular.

Omaha Steaks

Nutrient deficiencies

There’s also the risk of nutrient deficiencies when you’re on the keto diet. “An individual who cuts out whole grains may become deficient in vitamin B1 (thiamine) and B3 (niacin),” Harpst says.

These essential vitamins are added to grain products through fortification, as it’s tough to eat enough of them through food alone, and deficiencies can lead to adverse health effects. Iron and vitamin B9 (folate) are also added to grains, and while it’s relatively easy to get enough iron by eating animal products, eliminating grains can lead to folate deficiencies, as well. (This is particularly concerning for women who may become pregnant, as folate is essential for neural tube development in the first month of pregnancy, before most women even realize they’re expecting.)

And, while there’s not enough long-term research on keto diets specifically, a 2021 review published in Frontiers in Nutrition concluded that foods and nutrients typically consumed at higher than average levels on the keto diet (namely red meat, processed meat, and saturated fat) are linked to an increased risk of kidney disease, heart disease, cancer, diabetes and Alzheimers, whereas restricted foods like fruits, vegetables, legumes, and whole grains are associated with lowered risk of these same conditions. “Current evidence suggests that for most individuals, the risks of such diets outweigh the benefits,” the authors state.

Is It Bad To Eat This Much Fat?

This depends on what kind of fats you’re taking in. There are four major kinds of fats found in food: saturated, trans fats, monounsaturated, and polyunsaturated.

Trans fats are the ‘bad kind’. Saturated fats are typically found solid at room temperature, and are a big component of butter, lard and cream. Trans fats are found in heavily processed and fried foods, such as frozen pizzas and doughnuts.

The good fats, polyunsaturated and monounsaturated, can be found in plant-based oils like olive and sunflower oil, as well as avocados, some fish, and nuts. If you focus on these healthy types of fats, then no, it’s not too much fat!

Can I Do Keto If I Have Diet Restrictions?

Depending on the restrictions… probably not. With this diet being high in fats and proteins, it’s not the best fit for those straying away from animal products. Vegans and vegetarians may struggle a bit too much in finding substitutions for all the protein requirements to make this diet worth it.

The Keto diet may, however, work out very well for someone with celiac disease or a general gluten intolerance. Carbs are heavily cut out anyway in this diet, making little room for gluten. It would be pretty easy to follow the Keto plan and avoid gluten at the same time.

Is The Keto Diet Best For You?

This may sound like a cop out, but the best diet is the one you stick with. For Volek, who’s been following an ultra-low-carb diet for two decades, it works.

If you can’t stick to it, then it probably won’t.

“This is the problem I have with all of these fad diets,” registered dietitian Andy Yurechko, M.S., R.D., of Augusta University Medical Center in Georgia, previously told Men’s Health. “A healthier type of diet is something you can do every day of your life.”

Because maintaining ketosis requires strict carb counting, this diet works best for people who are diligent. And, it’s probably not a good idea for athletes or avid gym-goers to do the keto diet long-term.

“There is no conclusive research to support any athletic performance benefit [of keto],” Harpst says. “Research continues to show that training on a low carb diet impairs intensity and decreases endurance, recovery and cognitive function.”

It can also impair muscle strength, she says, since carbohydrates are muscle’s preferred energy source during workouts, and because muscle synthesis (AKA, repairing and building muscle in order to get stronger) requires both protein and carbohydrates.

Keto Diet Tips

Still, there are a few healthy habits from the keto diet that are easy to adopt:

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Eat fewer processed carbs

Instead of thinking about the total carbs you’re eating, assess what those carbs provide to you. Do the majority of your carbs come from fruits, vegetables, whole grains, and legumes, all of which deliver loads of and health-supporting fiber and antioxidants? Fantastic. Or are you consuming them mostly in the form of added sugars (cookies, candy, soda) or refined flour? It’s fine to enjoy your favorite sweet treats and processed foods sometimes, but the bulk of your carbs should come from whole food sources.

Don’t fear fat

The ketogenic diet may seem like the Jekyll to the Hyde-like low-fat craze of the 1990s. The bulk of current research finds that the middle ground between the two extremes is more beneficial for overall health. Make it easy for yourself: Eat at least two servings a week of fatty fish (salmon, sardines, mackerel) and cook with a variety of quality fats (olive oil, canola oil, avocado oil) throughout the week.

Pack in the greens

Leafy vegetables are loaded with nutrients and they’re keto-friendly. There’s kale, spinach, bok choy, Swiss chard, collards, watercress, mizuna, and arugula. Dig in.

Oh, and you might be wondering—how’d things turn out with the bacon beaus? Their experiment worked until life changed. They had a kid. They made a big move. They stopped the diet. “It was too hard to maintain,” she told me. Proof that all the bacon you can handle even grows boring after a while.

Watch Your Calories

If you’re starting the keto diet to lose weight, it’s important to remember that weight loss is about burning more calories than you take in. Lowering your carb count doesn’t necessarily mean you’re automatically lower your calorie count. One gram of fat holds 9 calories, and one gram of carbohydrates holds 4 calories. If you’re upping your fats as much as you do to properly follow the ketogenic diet, your calorie intake may increase

“A ketogenic diet is designed to use fat for fuel … but if you’re consuming too many calories for your needs, it is still possible that you’ll be storing fat just as you would on any dietary pattern,” Ginger Hultin, MS, RDN, CSO, spokesperson for the Academy of Nutrition and Dietetics, told Men’s Health.

Take Alcohol Off The Table

Drinking alcohol temporarily bumps you out of ketosis. So, if you’re really going hardcore on the keto lifestyle, you should nix alcohol all together. Plus, some alcohols are very carb-heavy, like wine and beer. If you want to stick to the diet as much as possible, but still want to raise a glass at your friend’s wedding, opt for liquor.