What is the Ketogenic Diet?

A plate with steak, asparagus and lemon slices

The ketogenic diet, or keto diet, is a low-carb, high-fat diet that’s skyrocketed in popularity over the past couple of years. Its history dates back to 1923 when it was first used as a treatment for epilepsy. The diet was prescribed by a physician and patients were carefully monitored by a dietitian to ensure they followed a very specific “macronutrient ratio” (90 percent fat, 6 percent protein and 4 percent carbohydrates).

Today, the keto diet is commonly used for weight loss. While modifications exist with slightly tweaked macronutrient ratios, the diet’s high-fat, moderate protein, low-carb core remains the same. Recommendations typically involve eating between 65 and 90 percent fat, 15 to 30 percent protein and less than 10 percent carbohydrates per day.

How the Keto Diet Works:

Eating a high-fat, moderate protein, low-carb diet encourages the body to convert fatty acids into ketones in the liver. Elevated levels of ketones in the blood trigger a metabolic state known as ketosis. When the body is in ketosis, it burns fat instead of carbohydrates for energy, resulting in weight loss. 

How do you know you’re in ketosis? One sign, unfortunately, is bad breath! (Tip: Be sure to brush your teeth often and keep sugar-free mints or gum on hand.) Many keto followers also report reduced appetite, increased mental clarity, increased energy and weight loss. The only way to really determine if you’re in ketosis is to measure ketone levels by taking a blood, urine or breath test—all of which can be done at home (test prices vary). 

Note that some people will require higher percentages of fat to trigger ketosis; others can achieve ketosis with a 65 percent-fat diet.

Getting Started on a Keto Diet

First, you’ll need to determine the macronutrient ratio that’s right for you. (Remember, it’s always a good idea to talk to your healthcare provider before starting any diet.) You can consult with a registered dietitian, or do research on your own. Books, websites and apps are available for guidance and can help you plan and track your diet when you’re ready to begin. 

What You Can (And Can't!) Eat 

Low-carb veggies, including leafy greens, lettuce, celery, mushrooms and zucchini are allowed on the keto diet. Starchy plant foods such as corn, beans and potatoes should be avoided.

For protein, choose high-quality meats such as grass-fed beef, free-range chicken and wild salmon. Watch out for processed meats, such as cured bacon or deli slices, that may contain added sugar. For fat, load up on butter, ghee, heavy cream and olive oil, which are all considered top-quality keto fats.

Steer clear of processed and carb-heavy foods such breads, pastas, fruit juices, rice and beer. 

Keto-friendly snacks: Luckily, snack ideas are just about endless for keto dieters. Feel free to graze on low-carb cheese sticks, hard-boiled eggs, avocados, roasted almonds, sunflower seeds and pork rinds.

Keto-friendly meals: Need a keto diet-friendly lunch in a hurry? Try a BBLT (bacon, brie, lettuce, tomato) wrap. Simply layer bacon, sliced brie, sliced tomato, mayo and black pepper on romaine lettuce – then roll and eat! For dinner, toss some spiralized, steamed veggie noodles (zucchini noodles, a.k.a. zoodles, are great) with butter, sea salt and a squeeze of fresh lemon. Top with a grilled salmon fillet or grilled shrimp, toasted sesame seeds and a dash of black pepper. 

Safety Considerations for Keto Dieters

Some followers consider keto a short-term diet, while others consider it a lifestyle. According to research, short term may be the safer option for most. 

Extreme limitations on food intake can lead to nutrient deficiencies, making supplementation necessary. Iron, calcium, vitamin D and B vitamins are just a few of the vitamins and minerals keto dieters may be lacking.

Research also suggests that a lack of fiber-rich foods may affect the health of the gut or microbiome. Chia seeds, flax seeds, nuts and vegetables are great ways to ramp up your fiber on the keto diet. You might also consider taking a fiber supplement. 

For some people, the level of saturated fat in the keto diet may not be recommended and cholesterol levels may need to be checked often to monitor heart health.  

The keto diet is not recommended for children or adolescents unless it’s specifically prescribed and monitored by a doctor for epilepsy.

Again, before making any drastic dietary changes, consult your healthcare provider or a registered dietitian to be sure the keto diet is appropriate for you and that you are getting the nutrients you need.