A high-fat weight-loss plan built on beef, butter and cheese? Before you shout “Sign me up!” weigh the facts. 

By Amy Paturel, MPH
Photo by Marcus Nilsson

The ketogenic (or keto) diet pretty much defies all the traditional nutritional thinking we were brought up on. You’re encouraged to load up on butter, cream and other fats while ditching whole grains, sugar and most fruits and vegetables. And, in answer to the big question everyone has: Yes, you’ll probably lose weight.

To be exact, the popular fat-focused plan requires dieters to get 70% to 80% of their daily calories from fat, 15% to 25% from protein and less than 10% from carbohydrates. That means you’ll need to limit carb intake to less than what you’d get from a plain bagel. Instead, you’ll be reaching for avocados, nuts and something called Bulletproof Coffee (that’s the black stuff made with butter, coconut oil and maybe a little whipping cream). 

Eating this way forces the body to burn fat instead of carbohydrates. And this process of burning fat—called ketosis—produces acids in the blood called ketones, which our bodies and brains use for fuel. The ketogenic diet was originally a go-to for controlling seizures among children with epilepsy. (Experts aren’t exactly sure why it worked, but they believe eating this way improves how neurons in the brain function, reducing—and sometimes eliminating—seizures.) As it turned out, there was an interesting side effect: It was effective for weight loss too. If  you’re thinking of  joining the caravan, take a second to learn how the keto diet impacts you from head to toe.

Photo by Marcus Nilsson

What happens to your body on keto?

Your Brain

The jury’s out on how keto impacts your thinking. Scientists used to believe glucose (from carbs) was the brain’s preferred source of fuel. Now they’re not so sure. Since the brain is nearly 60% fat, some researchers believe ketones (from fat) may provide a more efficient energy source. Happy dieters often say they didn’t just lose weight, they also felt their mind got sharper and their moods stabilized, although hard science doesn’t support that just yet, says Neal Malik, DrPH, assistant professor of nutrition at Bastyr University in San Diego. In fact, extreme dieting of any sort is likely to make you a tad cranky.

Your Hydration

“You have to drink enough water,” explains Kristin Kirkpatrick, RDN, a consultant for Wellness Nutrition Services at the Cleveland Clinic Wellness Institute. “Cooked whole grains can retain water, and fruits and vegetables naturally contain water, so cutting these may lead to dehydration.” She also notes that you excrete more sodium on this diet, which can add to the  problem. Try leaving a glass of water on your counter or desk at all times as a reminder to help you drink roughly eight glasses a day.

—Consuming higher amounts of protein and fat may help keep cravings in check.

Your Heart

“In the short term, total cholesterol drops, good cholesterol goes up and bad cholesterol goes down,” Malik says. Weight loss, regardless of how you achieve it, has heart-protective benefits. But thereare no long-term studies on keto and your heart—and excess dietary fat may cause the body to produce by-products called lipid peroxides, which can damage cells and tissues, including the heart. Since we don’t know how your numbers might fare in the long run, if you do stick with keto, make sure you (and your doctor) keep an eye on your blood work.

—Kiss carbs goodbye. Your shopping list will need to cut way back on bread, pasta and more.

Your Liver

This organ will be working overtime. “Your liver is responsible for metabolizing protein and producing ketones,” explains David Katz, MD, author of The Truth About Food. So when you go on this diet, there’s an extra burden placed on your liver as you up your intake of protein and your reliance on ketones. While experts say there could be adverse effects, more research needs to be done.

Your Muscles

Workouts might become tougher to get through. Although some dieters say they have more energy, experts think this may be a result of feeling lighter from weight loss, and they offer a word of caution. “If your carbohydrate intake is low, prolonged and high-intensity exercise can get very difficult,” says David C. Nieman, DrPH, director of the Human Performance Lab, Appalachian State University and North Carolina Research Campus

Your Waistline

The scale will become your BFF. In one small study, people who followed a low-calorie ketogenic diet shed more pounds, lost more body fat and took more inches off their waistlines compared to those who followed a traditional low-calorie diet plan. The caveat: As happens with a lot of diets, many people have trouble sticking to the regimen over the long haul and end up regaining any lost weight as soon as they begin eating normally again.

Your Stomach

Even though your belt might go down a notch or two, you could still be bloated. Eating a high-fat diet can be constipating. Getting enough fiber to keep things moving on a diet that nixes whole grains, legumes, most fruits and many vegetables can be pretty challenging. So it’s no surprise that tummy troubles are common. “We’re learning that a high-fat diet changes the microbiome and may decrease the amount of good bacteria in the gut,” explains Malik. You’ll have a better chance of staying regular if you focus on keto-approved veggies—including leafy greens, tomatoes, bell peppers and broccoli—consider taking fiber supplements, stay active and drink plenty of fluids.

Cooking on Keto

Keto Kitchen

One reason the keto diet is difficult to maintain: “You have to cook everything from scratch and temptations are everywhere,” says Amanda Rose, 49, mom to 16- and 9-year-old boys in Northern California. To minimize your time in the kitchen—and avoid becoming a short-order cook for non-keto family members—try these strategies:

Find the overlap.

Save yourself from making multiple meals by figuring out what keto foods your kids will like. Think eggs and bacon or keto pancakes with almond flour for breakfast.

Cook less for yourself.

Keep keto staples—avocados, nuts, seeds, cheese, salmon—close at hand so you can quickly assemble them into a meal for yourself. Just add some lettuce. 

Clean up your kitchen.

Remove temptations by asking your partner and kids to keep their non-keto snacks hidden away (say, in a cabinet you never open).

Train your crew in convenience foods.

Teach non-keto kids to fend for themselves. Each week, show them how to make a different emergency food, such as grilled cheese, or microwave some rice if they want to pair that with the meat you’re making.


Sample Daily Menu 

Morning Coffee

16 oz coffee with 3 tbsp heavy whipping cream 


Scrambled eggs with cheese, spinach and mushrooms, cooked in coconut oil 


Cheddar with beef summer sausage

Shop smart. Packaged foods can contain hidden carbs, so read the labels. 


Roasted salmon topped with 1 tbsp veggie cream cheese; spinach salad with Caesar dressing; roasted cauliflower with garlic, thyme and olive oil


Fatty tea made with heavy whipping cream and supplemental nutrients, like magnesium

She tried the keto diet.

When 49-year-old Lynn Clark visited the doctor for a standard check-up, she discovered her cholesterol, blood sugar, and triglyceride levels were elevated and she was at high risk of developing heart disease. The boudoir photographer and mom of a 16-year-old daughter had been struggling with her weight for decades. “I tried every diet imaginable,” she says. “So when one of my clients raved about the keto diet, I figured, why not?”


Lynn lost 11 pounds in the first 10 days (!) and roughly 25 pounds in 5 months, down to 185 from 211. Not only did her bust go from a very uncomfortable 40DDD to a 36DD, but she trimmed more than 6 inches from her waist and dropped two clothing sizes. 

“I knew the keto diet was really working when I felt my XL undies fall down during a shoot,” Lynn says. “My focus and creativity have improved, and I have so much more energy. Even more amazing, most of my pain is gone. I suffer from chronic knee pain, which I’ve had since an injury in my teenage years.” 

Lynn’s daily diet includes plenty of butter, heavy whipping cream, cheese and sausage. She uses cocoa powder and a sugar substitute called Swerve to satisfy her sweet tooth. And she loads up on electrolytes and supplements to compensate for any nutrients she might be missing. 

Lynn’s stick-to-it strategies 

Get support.

Facebook and other social networks are great for this—just watch out for rigid groups, since the people who run those are usually not doctors or dietitians. Want a group that’s not too extreme? Try “A Keto for Everyone” on Facebook.

Allow for moodiness.

“The first six weeks were tough,” Lynn says. “The weight was coming off, but I was not a pleasant person to be around. If you hang in there, though, your body will adjust.”