The ketogenic diet, or "keto" diet, has gained considerable attention as a potential weight-loss strategy. It involves drastically reducing carbohydrate intake and increasing fat consumption, shifting the body's primary fuel source from glucose to ketones. While the keto diet is often associated with weight loss, it also has a long history of therapeutic use, dating back to the 19th century when it was used to manage diabetes and, later, epilepsy in children.
Understanding the Keto Diet
"Keto" refers to ketogenesis, a process in the body that results from significantly reducing the carbohydrates in your diet and increasing your fat intake, says Bede. When you're on the ketogenic diet, you are in a state similar to fasting - your body is using fat for fuel. Normally your body gets energy from readily available carbohydrates, but on a keto diet, your carb intake is slashed. However, without regular replenishing of carbohydrates, the body begins to break down fat for energy, resulting in the formation of ketones. The move from carb to fat fueling is marked by an adaptation phase. This phase can come with some lethargy and other symptoms as your body adjusts (we discuss this more later) but you'll start to notice weight loss as well as more steady energy and less hunger. The key to keto is knowing what's in your food. "On a standard diet, most people consume approximately 50-55 percent carbohydrates, 20-25 percent protein and 20-25 percent fat," says Bede.
The premise of the ketogenic diet for weight loss is that if you deprive the body of glucose-the main source of energy for all cells in the body, which is obtained by eating carbohydrate foods-an alternative fuel called ketones is produced from stored fat (thus, the term “keto”-genic). When ketone bodies accumulate in the blood, this is called ketosis. Healthy individuals naturally experience mild ketosis during periods of fasting (e.g., sleeping overnight) and very strenuous exercise.
Macronutrient Ratios in Keto
There is not one “standard” ketogenic diet with a specific ratio of macronutrients (carbohydrates, protein, fat). The ketogenic diet typically reduces total carbohydrate intake to less than 50 grams a day-less than the amount found in a medium plain bagel-and can be as low as 20 grams a day. Generally, popular ketogenic resources suggest an average of 70-80% fat from total daily calories, 5-10% carbohydrate, and 10-20% protein. For a 2000-calorie diet, this translates to about 165 grams fat, 40 grams carbohydrate, and 75 grams protein.
Foods to Eat and Avoid
A typical keto diet will consist of foods high in protein and healthy fats, including red meat and poultry, fatty fish, non-starchy vegetables, dark, leafy greens, avocado, coconut oil, keto-style coffee, bone broths and of course plenty of water. Many versions of ketogenic diets exist, but all ban carb-rich foods. Some of these foods may be obvious: starches from both refined and whole grains like breads, cereals, pasta, rice, and cookies; potatoes, corn, and other starchy vegetables; and fruit juices. Some that may not be so obvious are beans, legumes, and most fruits. Most ketogenic plans allow foods high in saturated fat, such as fatty cuts of meat, processed meats, lard, and butter, as well as sources of unsaturated fats, such as nuts, seeds, avocados, plant oils, and oily fish. Strong emphasis on fats at each meal and snack to meet the high-fat requirement. Some dairy foods may be allowed. Although dairy can be a significant source of fat, some are high in natural lactose sugar such as cream, ice cream, and full-fat milk so they are restricted. Protein stays moderate. Certain fruits in small portions like berries. Fruits other than from the allowed list, unless factored into designated carbohydrate restriction.
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Potential Side Effects
During the transition to a keto diet, you might experience some minor side effects. Don't get discouraged - it's a normal part of the process. Bede explains that new diet adopters might feel symptoms of "keto flu," including headaches, nausea, fogginess, muscle cramping and fatigue. Make sure you are not too low on electrolytes - sip on broth or take a salt tablet to get needed sodium. Remember that this transition might last about three to five weeks, and the benefits can certainly outweigh the immediate side effects. Bede notes that you might notice increased energy throughout the day and some people report a feeling of greater mental clarity or focus.
The Role of Protein in a Ketogenic Diet
Protein is one of three macronutrients, or nutrients that are needed in large quantities and that provide calories. Protein has a big role in the diet. Proteins can be broken down into amino acids, which the body uses to build new tissues. However, this isn’t the only role of protein. Protein helps to slow down digestion, so it keeps you feeling fuller for longer. Additionally, because it takes longer to digest, it burns more calories during the digestion process. Getting adequate protein while losing weight can also help to “spare” your muscles. While in many cases people lose some muscle mass when they lose weight, a ketogenic diet with adequate protein may help prevent these muscle losses. Additionally, protein can help to prevent blood sugar spikes from eating carbohydrates. This is important to remember when you choose to go off of the keto diet, even temporarily.
When following a ketogenic diet, particularly for therapeutic purposes when treating a psychiatric condition like bipolar disorder, schizophrenia, depression, or other brain-based disorders, protein plays a crucial role. However, there’s a common concern about consuming “too much” protein, potentially triggering gluconeogenesis, converting protein to glucose, and impacting ketone levels.
Recommended Protein Intake
The RDA for protein is set at 0.8 grams per kilogram of reference body weight. However, this recommendation is set at the minimum to avoid protein deficiency in sedentary individuals. The RDA is often insufficient for those looking to improve their metabolic health by building muscle mass. Instead, the focus should be shifted to consuming adequate protein to support overall health and wellness. However, according to ketogenic diet experts Stephen Phinney, MD, PhD, and Jeff Volek, PhD, RD, the most ideal way to calculate protein needs for people on keto is actually grams per kilograms of body weight (g/kg body weight). They recommend sticking to a target range of 1.2-2.0 g/kg body weight, depending on lifestyle.
In no case should dietary protein intake be reduced below 1.2 g/kg in the context of a well-formulated ketogenic diet. This range; 1.2 g/kg at the low end and 2.0 g/kg at the upper end, with a 1.5 g/kg mid-range moderate intake target, can be translated into daily consumption of protein-rich foods in ounces in the table below.
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Why Moderate Protein Is Key
The protein amount on the ketogenic diet is kept moderate in comparison with other low-carb high-protein diets, because eating too much protein can prevent ketosis. If you eat too much protein while following a low carb diet, your body can actually start to produce glucose from the excess amino acids through a process called gluconeogenesis. Because your body prefers to use carbohydrates as its source of energy, it will do anything it can to get enough glucose.
Benefits of Adequate Protein Intake
Increasing protein intake can have several benefits, including improved satiety, enhanced bone health, and better muscle maintenance. Muscles have high energy demands and utilize glucose efficiently, helping regulate blood sugar: Muscle gains lead to improved overall metabolic health.
Risks of Inadequate Protein Intake
However, an inadequate protein intake over time could lead to several problems, including muscle mass loss, appetite changes, weight gain, delayed wound healing or injury recovery, and fatigue. In children and adolescents, inadequate protein intake can lead to stunted growth and diseases of malnourishment.
Protein Sources on Keto
There are several keto-friendly foods that are rich sources of protein. However, there are also several protein sources that are high in carbohydrates. These should be avoided on keto. Some examples of high-protein, low-carb foods include:
- Meats, including poultry, fish, and red meat (heart-healthy options such as salmon, mackerel, anchovies, sardines, and herring, Derocha says).
- Eggs
- Healthy fats and oils such as avocados and olive oil
- Low-carb vegetables such as broccoli, kale, spinach, and cucumbers
- Cheese
- Nuts
- Cauliflower rice
- Beans, legumes, and lentils
- Greek yogurt
- Tofu and tempeh
- Lower-carb fruits such as raspberries and blackberries
Tips to Meet Your Protein Goals
Now, let’s translate all of this information into useful, practical tips to help you meet your protein goal. A piece of meat the size of a deck of cards is roughly 20 grams of protein. You can use this knowledge to build each meal, ensuring that you’re getting adequate protein. Most people will need at least 60 grams of protein per day, so you can aim to include at least a “deck of cards” worth of meat at each meal. Spreading protein intake evenly throughout the day is the easiest way to meet your goals. Protein is extremely filling, so it can be difficult to meet your goal if you’re trying to cram it all into one meal. Nuts, seeds, and cheese can easily boost your protein intake. If you’re finding that you’re just a little bit short on your protein intake each day, having nuts or cheese as a snack - or adding a sprinkle of cheese or seeds to your meals - can help push you over the edge to your goal. However, if you’re trying to lose weight, you probably shouldn’t depend on these foods as your primary protein sources. Meat and protein powder are the easiest ways to significantly increase your protein intake. Need to significantly increase your protein intake? For more exact numbers, a food scale is a worthwhile investment.
Read also: Optimizing Fat Intake for Keto Success
Potential Risks and Considerations
A keto diet is an option for people looking to lose fat and build muscle, but like any diet, it's not the best choice for everyone. Pregnant women, serious endurance athletes and people managing Type 1 diabetes as well as other conditions may have trouble with the restrictions of a keto diet.
High Cholesterol
Some protein sources - such as fatty cuts of meat, whole dairy products, and other high-fat foods - can raise cholesterol, increasing your chance of heart disease. However, studies showed that people on the Atkins diet for up to two years actually saw a drop in “bad” cholesterol levels.
Nutrient Gaps
Because carbohydrates include many food groups (like fruits and vegetables), you face a higher risk of missing out on certain nutrients when you cut carbs, Derocha says.
Kidney Problems
If you have any kidney problems, eating too much protein puts added strain on your kidneys. This could worsen kidney function.
Conditions to Avoid Keto
Certain groups should avoid high-protein, low-carb diets due to related health risks, Derocha says. She suggests avoiding a high-protein, low-carb diet if you have certain conditions and health issues, such as:
- Kidney disease or kidney issues, as too much protein strains your kidneys
- History of disordered eating or eating disorders, as low-carb diets promote restrictive eating
- Pregnancy or breastfeeding, as nutrient-dense diets are critical during these stages
- Constipation concerns, as a low-carb, high-protein diet can lower your fiber intake and lead to constipation
Long-Term Sustainability
Following a very high-fat diet may be challenging to maintain. Some negative side effects of a long-term ketogenic diet have been suggested, including increased risk of kidney stones and osteoporosis, and increased blood levels of uric acid (a risk factor for gout). Possible nutrient deficiencies may arise if a variety of recommended foods on the ketogenic diet are not included. It is important to not solely focus on eating high-fat foods, but to include a daily variety of the allowed meats, fish, vegetables, fruits, nuts, and seeds to ensure adequate intakes of fiber, B vitamins, and minerals (iron, magnesium, zinc)-nutrients typically found in foods like whole grains that are restricted from the diet.
Keto Diet and Weight Loss
The ketogenic diet has been shown to produce beneficial metabolic changes in the short-term. Along with weight loss, health parameters associated with carrying excess weight have improved, such as insulin resistance, high blood pressure, and elevated cholesterol and triglycerides.
High-protein, low-carb diets can help you stay full after eating and lower cravings, which can help you lose weight. But some of the short-term weight loss is often due to losing water from cutting out carbs. A study of 39 obese adults placed on a ketogenic very low-calorie diet for 8 weeks found a mean loss of 13% of their starting weight and significant reductions in fat mass, insulin levels, blood pressure, and waist and hip circumferences. Their levels of ghrelin did not increase while they were in ketosis, which contributed to a decreased appetite. However during the 2-week period when they came off the diet, ghrelin levels and urges to eat significantly increased.
Long-Term Weight Loss
A study of 89 obese adults who were placed on a two-phase diet regimen (6 months of a very-low-carbohydrate ketogenic diet and 6 months of a reintroduction phase on a normal calorie Mediterranean diet) showed a significant mean 10% weight loss with no weight regain at one year. The ketogenic diet provided about 980 calories with 12% carbohydrate, 36% protein, and 52% fat, while the Mediterranean diet provided about 1800 calories with 58% carbohydrate, 15% protein, and 27% fat. Eighty-eight percent of the participants were compliant with the entire regimen.
Effectiveness Compared to Other Diets
Available research on the ketogenic diet for weight loss is still limited. Most of the studies so far have had a small number of participants, were short-term (12 weeks or less), and did not include control groups. A ketogenic diet has been shown to provide short-term benefits in some people including weight loss and improvements in total cholesterol, blood sugar, and blood pressure. However, these effects after one year when compared with the effects of conventional weight loss diets are not significantly different.
Keto Diet and Diabetes
There is also growing interest in the use of low-carbohydrate diets, including the ketogenic diet, for type 2 diabetes. Low-carb diets can help you control your blood sugar levels and manage diabetes and prediabetes. In a two-year, open label, non-randomized, controlled study, 349 participants received either standard care or were educated to follow a ketogenic diet. At the end of two years, those who had followed diets to stimulate ketosis had a 0.9% decrease in HbA1c versus a 0.4% increase in the standard of care arm. In addition, those following the ketogenic diet decreased their use of diabetic medications by 81%, while medication use increased in standard of care patients.
Sample Keto Meal Ideas
Here are a few meal ideas for high-protein, low-carb diets:
- Breakfast: Omelet with bell peppers, spinach, and cheese; tofu scramble with kale and broccoli; Greek yogurt with blackberries
- Lunch: Tuna salad with egg, feta, and avocado; chopped salad with shrimp, egg, and avocado; cobb salad with grilled chicken
- Dinner: Chicken and fried cauliflower rice; lettuce tacos with beef, veggies, and guacamole; spicy salmon nori wraps; salmon and steamed broccoli
Recipe: Grilled Tuna with Fresh Avocado Salsa
Here’s a recipe option you can try for lunch or dinner:
Ingredients:
- One cup of grape or cherry tomatoes, quartered
- One-quarter English cucumber, cut into small pieces
- Two scallions, chopped
- One tablespoon grated fresh ginger
- Three tablespoons chopped fresh cilantro
- One tablespoon fresh lime juice
- One tablespoon plus one teaspoon extra-virgin olive oil
- One-quarter teaspoon kosher salt
- One avocado, diced
- Two fresh wild tuna steaks (8 ounces each), 1-inch thick (like yellowfin or albacore)
- Half a teaspoon of freshly ground black pepper
Directions:
- Combine tomatoes, cucumber, scallions, ginger, cilantro, lime juice, olive oil, and salt.
- Add avocado after salsa is mixed together.
- Rub oil on both sides of the tuna and season with black pepper.
- Grill over medium-high heat for three to four minutes per side for a medium-rare steak, or a little longer for medium to well-done.
- Divide the tuna into four servings. Serve with salsa.