The ketogenic diet is a high-fat protocol designed to push the body to use fat instead of carbohydrates as a primary source of energy. Advocates believe it can help address a range of health situations, from food cravings to cancer recovery. And research suggests that a ketogenic approach may work wonders for a variety of ailments — at least for some of us.
The keto diet, as it’s known, was developed in the 1920s as a treatment for childhood epilepsy, after doctors found that it substantially reduced seizures. Today, its popularity extends well beyond its medical uses: Many health-minded people now embrace a ketogenic approach to burn fat, lose weight, and promote overall fitness.
The protocol involves consuming substantially more fat than any other macronutrient — specifically, four parts fat to one part carbohydrate or protein at every meal, according to Adrienne C. Scheck, PhD, who researches metabolic regulation as a therapy for brain tumors at Phoenix Children’s Hospital. This puts the body into a state of nutritional ketosis, burning mainly fat for fuel.
Studies suggest that ketosis can be extremely beneficial, at least in the short term. It may help promote weight loss, improve mental focus, ease acne, reduce the progression of some types of cancer, reverse insulin resistance, decrease symptoms of polycystic ovary syndrome, or PCOS, and reduce inflammation more generally.
Research also shows that a keto diet might be useful as a supplemental therapy for neurological conditions, such as ALS and Parkinson’s. Some experts even believe the ketogenic protocol can prevent cancer.
“The major benefit of the diet, especially from a cancer point of view, is for prevention,” says Colin Champ, MD, an oncologist at the University of Pittsburgh Medical Center. “We have a century of some human studies and many animal studies that would suggest a ketogenic diet, [undertaken] even periodically, may help the body prune itself of cancer cells and make it harder for them to latch on.”
Still, severely restricting carbohydrates and protein is harder than it sounds. When the keto diet is implemented poorly, partially, for too long, or without medical supervision, it can set the stage for nutrient deficiencies, inadequate protein, high cholesterol, and insufficient fiber to maintain a healthy microbiome and efficient digestion.
And even when the diet is followed to the letter, it won’t benefit everyone. Bioindividuality and current health status play roles in its effectiveness and safety. Still, the potential benefits are notable enough to warrant a closer look.
The ketogenic protocol requires adherence to a detailed diet, down to the measuring and weighing of portions. Over the course of a day, keto adherents must carefully apportion 80 to 85 percent of their calories as fat, 10 percent as protein, and 5 percent as carbs.
This often means eliminating grains and starchy vegetables altogether, since even a tiny amount of extra carbs can knock the body out of ketosis. Because being precise is key, many people opt to work with a healthcare provider or nutrition coach for help staying on track.
It usually takes a couple of days for the body to shift into ketosis, and experts often recommend jump-starting the process with a 24- to 48-hour fast. Fasting clears the remaining carbs from the system and accelerates the metabolic shift from carb burning to fat burning.
During the first few days of a ketogenic diet, people sometimes experience headaches, fatigue, irritability, and distraction. Known as the “keto flu,” these symptoms can result from the sudden drop in insulin levels, which triggers the body to jettison more sodium through the urine. This tends to pass in several days. Consuming additional electrolytes (natural sources include salt, lemons, magnesium, and leafy greens) may relieve some of these symptoms.
For many, the challenges of a ketogenic protocol are far outweighed by its benefits, including the following:
There are several reasons the switch from carb burning to fat burning often results in weight loss. Eating higher-fat and lower-carb meals encourages satiety, reducing total food intake. At the same time, the body is burning fat for energy — fat it may have already stored.
In addition, restricting carbohydrates triggers the pancreas to produce less of the insulin needed to process them. Insulin serves many important functions, but one thing it does with ruthless efficiency is signal the body to store fat.
Put all these factors together — consuming fewer calories, burning stored fat, producing less of the fat-storage hormone insulin — and the keto diet is a triple threat for weight loss.
While supporting weight loss, well-controlled insulin may also help reduce the risk of type 2 diabetes, cardiovascular disease, cognitive dysfunction, and other chronic conditions, all of which are linked to chronically high insulin production.
It affects food-related moodiness as well. “One reason people feel good on diet-induced ketosis is they have fewer extreme swings of blood sugar,” explains functional-medicine neurologist David Perlmutter, MD, author of Grain Brain. This is because the blood-sugar roller coaster — when blood glucose and insulin soar and then plummet after a high-carb meal — can cause headaches, mood swings, dizziness, irritability, and low mood.
High blood sugar and insulin dysregulation are often, but not always, associated with excess body weight. “Some folks are ‘normal weight’ but insulin resistant, and these people will likely feel better on a keto diet, despite not needing to lose weight,” says nutrition expert Robb Wolf, author of Wired to Eat and The Paleo Solution.
At the same time, some people are overweight but not insulin resistant and would be unlikely to lose weight with a keto approach. Wolf says these people are usually better served by a “high-protein, low-fat, moderate-carb diet that focuses on whole foods.”
Many find that tracking their blood-sugar response to particular foods (using finger-prick blood tests at home, for instance) can help establish whether keto will be a valuable weight-loss strategy. Working with a healthcare provider who is savvy about keto to interpret the results can be a big help.
Experts long believed that blood-sugar and insulin regulation accounted for the apparent magic of the ketogenic diet. Additional research, however, suggests there may be another explanation.
During ketosis, insulin levels are so low that the liver converts fat into a type of chemical called ketones and releases them into the bloodstream to fuel the body in the absence of glucose. (This is why, in diabetics, ketones are a sign that blood sugar is dangerously low.) Urine and blood tests, as well as keto-specific Breathalyzers, can detect ketones, indicating when fat-burning ketosis has been achieved.
Researchers are just beginning to explore exactly how ketones boost health in nondiabetic people, but current cancer studies shed some light on their potential.
“Originally, people thought cancer loved sugar and that you could starve cancer with a ketogenic diet,” explains Scheck. “But when my colleagues and I took aggressive brain-tumor cells that had been grown in a solution with a lot of sugar and then added ketones, the ketones inhibited the growth of the tumor cells. More importantly, it made the chemotherapy work better.”
In an animal study, Scheck and her team found that ketones notably improved standard-of-care treatment. “We made the tumor disappear in nine of the 11 animals that had radiation combined with chemotherapy and that were also on a ketogenic diet,” she says.
To the team’s surprise, blood sugar wasn’t particularly low in the tumor-free mice. “Ketones must be doing something in addition to reducing glucose,” she says.
Still, Scheck cautions against replacing conventional cancer care with a keto diet, noting that its real power seems to be in boosting the potency of the conventional treatment.
Perlmutter, with an eye to brain health, also sees great potential in ketones. He singles out one in particular — beta-hydroxybutyrate, or BHB — as especially powerful.
“Blood levels of beta-hydroxybutyrate correlate with brain levels of beta-hydroxybutyrate,” he says. “And we know that BHB is an incredible way to power brain cells, reduce inflammation in the brain, and enhance production of BDNF,” or brain-derived neurotrophic factor, which promotes the growth of new brain cells and supports learning and memory.
Research has found that ketones may protect the brain by reducing oxidative stress, so the ketogenic diet might have benefits for patients with neurological conditions, including Alzheimer’s, Parkinson’s, and multiple sclerosis.
These results suggest that ketones have health benefits beyond those produced by lower blood sugar.
As these health benefits have become better known, popular variations of the ketogenic diet have emerged. For example, one version recommends eating ketogenically five or six days a week and then eating freely on the remaining days. But experts have doubts about this approach.
“Being in ketosis for a few days and then eating a bunch of carbs will pave the way toward insulin resistance,” explains Perlmutter, because the sudden reintroduction of carbs puts the body back on the blood-sugar roller coaster.
Another modification involves eating one keto meal a day, which is largely pointless, because the body won’t shift into ketosis. It can likewise set the stage for insulin problems.
There are still other challenges posed by the keto protocol’s required nutrient ratios:
Protein: The liver will turn protein into sugar for fuel when there are limited carbs available. This is why protein is restricted on the ketogenic protocol, along with carbohydrates. But protein is critical for muscle density, so limiting it could lead to decreased lean muscle mass.
Carbohydrate: Attempting to lower carb intake to just 5 percent of calories may lead some to eliminate carbs entirely, including vegetables. But this means losing out on the vitally important phytonutrients and fiber they contain. Fiber is critical for lowering insulin levels, stabilizing blood sugar, and keeping the microbiome healthy.
Perlmutter offers a corrective: Net carbs, or the amount of carbohydrate minus the amount of fiber, in a food is the calculation that matters. Fiber is plant material the body can’t absorb, so it does not count toward the carb total. “People can eat all the fiber-rich plant foods they want,” he says.
For example, a medium sweet potato has about 21 grams of carbohydrate and about 3 grams of fiber, so its net-carb amount would be about 18 grams. A cup of fiber-rich, nonstarchy spinach, meanwhile, contains only 1 gram of net carbs — so even on the keto protocol, one could consume a lot.
Fat: Because fat makes up so much of the keto diet, to thrive on it requires good fat absorption. But problems with bile and pancreatic enzyme production or gallbladder issues are fairly common and can hinder the process.
Even switching from a low-fat to a high-fat protocol can temporarily trigger symptoms of fat malabsorption (including greasy stools and gassy belching after meals). If you suffer from these conditions, try gradually increasing fat consumption before switching to a full keto protocol.
It’s also critical to choose high-quality fats, says functional-medicine physician Amy Savagian, MD. Processed oils and feedlot meat are high in fats that promote inflammation, but organic plant-based sources of fat (like avocados and olive oil) as well as grassfed meat and dairy, can be part of an anti-inflammatory diet and help guard against disease.
Because remaining in ketosis requires such strict discipline, many find it difficult to maintain the regimen long term. And the longer one stays on the diet, the greater the risk of nutrient deficiencies. The nutrient ratios may trigger other problems, and the diet’s precision can also set the stage for disordered eating in vulnerable individuals.
Hence the million-dollar question: Given its challenges and possible dangers, are the benefits of pursuing ketosis worth the risks?
Many providers still believe the answer is a conditional yes: The ketogenic diet seems most beneficial when it’s pursued for a short time, by individuals who feel good doing it, as a means to achieve specific health goals.
“Most data only looks at six to 12 months,” says functional physician Sara Gottfried, MD. “So I recommend switching to a Mediterranean diet with intermittent fasting after 12 months — sooner if there are signs of increased inflammation on blood tests.”
Another option is to practice the protocol seasonally. “Do keto during the winter and eat a low-glycemic diet in other time periods,” suggests Terry Wahls, MD, a functional physician who uses this seasonal approach to manage her own multiple sclerosis. She notes that, in the distant past, many people followed a similar cadence, living mostly on fats during cold months when berries and other carbohydrate-rich plant foods weren’t available.
Will Cole, FMCP, DC, author of Ketotarian, recommends that people try eight weeks of primarily plant-based keto and then check in with their bodies. “Ask yourself, ‘How do I feel? When does my body feel the best?’”