The low-carb and ketogenic diets are popular among many people who are trying to lose weight quickly.
While both can be effective for quick weight loss, many registered dietitians are skeptical regarding their long-term effectiveness.
Low-Carb Diets Overview
The 2020-2025 Dietary Guidelines for Americans recommend consumers get 45% to 65% of total calories from carbohydrates. With a low-carb diet, the percentage of your calories from carbohydrates is lower than what is normally advised for individuals. Usually, on a low-carb diet, one would get about 25% to 40% of their caloric intake from carbohydrates, says Julie Zumpano, a registered dietitian with Cleveland Clinic’s Center for Human Nutrition.
Typically, with eating regimens that aren’t low-carb, the number of calories from carbohydrates is similar the amount of calories from fat and protein.
Low-Carb Diet Basics
A low-carb diet recommends a lower amount of carbohydrates than the daily recommendation by the dietary guidelines. On a low-carb diet, it is encouraged to choose complex carbohydrates such as whole grains, legumes, fruit and starchy vegetables, for they will provide more fiber and protein, healthy fats and protein from lean meats, fowl and fish.
There’s no one version of the low-carb diet. For example, low-carb diets include:
- South Beach.
The diets share some similarities but aren’t the same. For example, there are different iterations of the Atkins Diet, depending on how much weight you want to lose. Generally speaking, the theory behind the Atkins is that by limiting carbs, your body has to turn to an alternative fuel – stored fat. People on the Atkins diet can consume sugars and “simple starches” like potatoes, but little or no white bread and rice. Protein and fat, including chicken, meat and eggs, are embraced.
On the other hand, the paleo diet is based on the premise that if cavemen didn’t eat it, you shouldn’t either. So, followers of this regimen say no to refined sugar, dairy, legumes and grains; they can consume meat, fish, poultry, fresh fruits and vegetables.
Meanwhile, the South Beach diet is based on the idea that there are good carbs and fats, and there are unhealthy carbs and fats. The key to weight loss is choosing the best of each. Therefore, the South Beach eating regimen emphasizes plenty of nonstarchy vegetables; eggs; full-fat dairy; whole grains and nuts; and protein like chicken and turkey.
In general, here are foods you can eat on a low-carb eating regimen:
- Eggs and lean meat, fowl and fish (beef, chicken, turkey, tuna and more).
- Cruciferous vegetables.
- Dairy products.
- Dark chocolate.
- Fats and oils.
- Leafy greens.
- Nuts and seeds (almonds, cashews, flaxseeds, hazelnuts, pistachios, pumpkin seeds, sunflower seeds).
Keto Diet Overview
The ketogenic or keto diet is a low-carbohydrate and fat-rich pattern of eating that is sometimes used to treat epilepsy, says Lana Nasrallah, manager of clinical nutrition at UNC Health, a not-for-profit integrated health care system based in Chapel Hill, North Carolina. It’s owned by the state of North Carolina.
There are multiple versions of this diet, such as modified keto and dirty keto. Some individuals stay on keto indefinitely, whereas others cycle in and out.
A keto eating plan focuses on low intake of carbohydrates, moderate intake of protein and high intake of fat, where 70% to 80% of calories from the diet comes from fat, Nasrallah says.
Keto emphasizes weight loss through fat burning. You slash the carbs you consume and fill up on fats instead. By doing so, you enter a state of ketosis, according to diet proponents. In ketosis, your body breaks down both dietary and stored body fat into substances called ketones. Your fat-burning system now relies mainly on fat – instead of sugar – for energy. That can lead to quick weight loss.
Signs of ketosis can include:
- Blood or urine test results.
- Fruity breath.
- Reduced hunger.
- Weight loss.
- Foggy brain.
In general, keto plans call for restricting carbs to about 15 to 20 net carbs a day. Fat intake makes up roughly 70% of daily calories. In comparison, the 2015-20 Dietary Guidelines for Americans call for 130 grams of daily carbs and fat intake ranging from 25% to 35% of daily calories.
Foods from all food groups can be incorporated into a keto eating plan. The key is to make sure the ratio of fat, carbohydrate and protein are sufficient to produce ketosis. Since the keto diet has a high-fat requirement, fat must be consumed at each meal – and even with snacks for some keto diet plans.
In a daily 2,000-calorie diet, that might look like 165 grams of fat, 40 grams of carbs and 75 grams of protein. However, the exact ratio varies between individuals.
Keto flips traditional thinking on diets. Here’s how a keto diet might look:
- Cocoa butter.
- Instead of skinless poultry and lean cuts of meat, protein sources include ribeye steak, skin-on chicken thighs, pork roast and snacks like bacon.
- Whole-dairy foods are encouraged.
- You counter sugar cravings with desserts like dark chocolate and nut butter.
- For a salad, greens such as spinach, kale and lettuce, along with broccoli, cauliflower and cucumbers, are OK, but starchy veggies – such as corn and sweet potatoes – are too high in carbs.
- Salad dressing could consist of oils like avocado, olive, canola, flaxseed and palm, or even mayonnaise.
- Nuts (walnuts, almonds, cashews).
- Seeds (pumpkin, sunflower, flaxseed, chia seeds).
- Nut butters (peanut, cashew, almond butters).
- Oils (avocado, olive, MCT, seasame, flaxseed, fish and coconut oils).
People can also meet the fat requirements by eating other foods that naturally contain fat, such as cheese, milk, yogurt, sour cream, butter, cream, poultry, animal meats, fish and shellfish.
Keto Diet Tips
A main worry people have when starting the keto diet is the risk of over-consuming carbohydrates, Nasrallah says.
These tips can be helpful to keep carbohydrates in the right range:
- Choose lower carbohydrate vegetables, specifically non-starchy vegetables like green beans, asparagus, tomatoes, mushroom, zucchini, yellow squash, salad greens, broccoli, cauliflower, Brussels sprouts and cabbage
- Consume unsweetened dairy products or dairy alternatives such as plain Greek yogurt and unsweetened almond milk.
- Avoid breaded and deep-fried foods such as fried chicken, breaded shrimp, mozzarella sticks and breaded vegetables like okra.
- Eat small portions of fruit that have high fiber content like raspberries, strawberries, small oranges and pears and apples with the skin.
Similarities Between Low-Carb and Keto Diets
For many people, low-carb and and keto diets are interchangeable, says Natalia Groat, a registered dietitian with UW Medicine at Harborview Medical Center in Seattle. The center is managed by UW Medicine, the formal brand name of the University of Washington’s health care system.
Meal delivery services are available for both diets. There are an array of low-carb meal delivery services, offering ready-made or quick-prep meals for prices ranging from about $7 to up to $20 per meal. Top keto diet meal services may cost slightly more, ranging from roughly $9 to $22 per meal.
As for the keto diet, research suggests it could be helpful in treating epilepsy. The classic ketogenic diet consists of a high-fat and low-protein and carbohydrate diet, with restricted calories and fluids, according to a study published in Frontiers in Neuroscience in 2019: “The CKD (classic keto diet) and its variants should be considered as an alternative for non-surgical pharmacoresistant patients (individuals who don’t respond to at least two anti-epileptic medications) with epilepsy, of any age. Each patient must have an individually designed diet; however, adult patients have more difficulty in maintaining the CKD.”
Low-carb and ketogenic diets carry similar risks. For example, research published in July 2021 in Frontiers in Nutrition suggests that very low-carb diets (which could be considered keto regimens) are associated with a raft of marked health risks.
- Pregnant women on such diets are more likely to have a child with a neural tube defect, even when supplementing folic acid.
- Increased risk of cardiovascular disease.
- Higher risk of cancer.
Other potential risks with the keto diet include:
You can lose weight on either diet. However, notes Groat, “I don’t know that either is sustainable.”
The low-carb approach to eating is probably more sustainable for people who are accustomed to it, like individuals with diabetes. Maintaining either diet for the long run is problematic because both are restrictive and not in line with a lot of people’s typical eating patterns.
Keto can lead to quick and dramatic weight loss, but sustaining it could be an issue. In restricting certain fruits and vegetables, you may not get enough vitamins and nutrients. Similarly, you may lose weight quickly on a low-carb eating regimen, but sustaining it over the long term is difficult because it doesn’t allow people to eat many of the foods they enjoy.
Following a keto diet is more likely to lead to quick, dramatic weight loss, which is why it lands near the top for Best Fast Weight-Loss Diets.
Which One Is Better?
Groat wouldn’t recommend either diet for most people. However, between the two diets, the low-carb regimen is less restrictive and allows you to consume more of the nutrients your body needs.
|Keto Diet||Low-Carb Diet|
|Health Benefits||Can be useful in treating epilepsy.||Can be helpful for people with diabetes.|
|Health Risks||Increased risk of cardiovascular disease, cancer, kidney stones, liver disease and diabetes.||Increased risk of constipation, headache and muscle cramps.|
|Weight Loss||Effective for quick and possibly significant weight loss, but may be difficult to sustain.||Effective for quick weight loss, but may be difficult to sustain.|
|Food||Ribeye steak; skin-on chicken; pork roast; bacon; nut butter; broccoli; cauliflower; cucumbers; whole dairy foods; nuts; tahini; apples; blackberries; raspberries; grapefruit; nectarines; watermelon; strawberries; peaches.||Avocados; eggs and lean meat, fowl and fish; cheese; cruciferous vegetables; dairy products; fats and oils; leafy greens; apples; blackberries; raspberries; grapefruit; nectarines; watermelon; strawberries; peaches.|