A Complete Guide to the Low-Carb Diet
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Medically reviewed by Elizabeth Barnes, RDNMedically reviewed by Elizabeth Barnes, RDN
Low-carb diets are dietary patterns that limit carbohydrates, which are macronutrients concentrated in foods like grains, fruits, and legumes.
There are several types of low-carb diets, some of which are lower in carbs than others. Research has linked low-carb diets to several potential health benefits, including weight loss, improved blood sugar, and reduced heart disease risk factors.
However, some low-carb eating patterns, like the ketogenic (keto) diet, may have certain downsides or limitations that may not be appropriate for everyone.
How the Low-Carb Diet Works
Low-carb diets are eating patterns that provide fewer than 130 grams (g) of carbs, or less than 26% of total calories from carbs, per day. Low-carb diets typically fit into one of two categories:
Very low-carbohydrates diets: These eating patterns contain fewer than 50 g of carbs, or less than 10% of calories from carbs, per day. The keto diet is considered a very low-carb diet.
Low-carbohydrate diets: Low-carb diets contain fewer than 130 g of carbs, or less than 26% of calories from carbs, per day. There are many types of low-carb diets, such as the Atkins diet and the Dukan diet.
Low-carb diets are much lower in carbs than what health organizations recommend. The National Academy of Medicine (NAM) developed the Acceptable Macronutrient Distribution Range (AMDR) to determine the ideal percentage of energy (calorie) intake from each macronutrient. This ideal percentage balance is meant to reduce chronic disease risk while providing the body with adequate amounts of nutrients.
The AMDR for carbs is currently set between 45-65%, which is significantly higher than what low-carb diets provide.
However, this macronutrient range recommendation may not be appropriate for many people, including people with blood sugar regulation issues, insulin resistance, and high triglycerides, as everyone has different nutritional needs.
For example, research has shown low-carb diets benefit people with diabetes and people who need to lose excess body fat for medical reasons.
Guidelines To Follow
Because there are so many types of low-carb diets, rules and guidelines vary.
Some types of low-carb diets, like the keto diet, require a person to strictly monitor their carb intake to stay within the optimal carbohydrate range to induce ketosis, a metabolic state in which the body burns fat for fuel instead of carbs.
More moderate low-carb diets that allow for higher carbohydrate intake usually don't require a person to count carbs. However, some people might still choose to track their carb intake to help them stay within their daily carb allotment.
In addition to following a daily allotted carb range, some low-carb diets require you to keep track of other macronutrients as well. For example, on the classic keto diet, you'll need to take in 90% of your energy from fat, 6-8% from protein, and 2-4% from carbs. This is much higher in fat and much lower in carbs than traditional diets.
Other types of low-carb diets are higher in protein. For example, high-protein, low-carb diets typically contain less than 130 grams of carbs and between 1.8-3 g of protein per kilogram (kg) or 0.8-1.36 g per pound (lb) of body weight per day. This is significantly more than the recommended daily intake (RDA), which is currently set at 0.8 g/kg or 0.36 g/lb per day.
There are other types of low-carb diets that involve stages and specific rules, such as avoiding certain foods. For example, the Atkins diet is a low-carb diet that has four phases, which start with a very low-carb diet and slowly transition into a more moderate low-carb diet.
You can also work with a healthcare provider or registered dietitian to develop your own low-carb diet using different macronutrient ratios that work best for you. If you're keeping your carb intake under 130 g per day, you're following a low-carb diet.
Types of Low-Carb Diets
There are many kinds of low-carb diets, each with different macronutrient recommendations and rules. Here are a few of the most common types:
The ketogenic diet: The keto diet is one of the most popular types of low-carb diets and is commonly used to boost weight loss and reduce blood sugar. There are several versions of the keto diet, but all restrict carbs to fewer than 50 g per day and are very high in fat.
High-protein, low-carb diet: There are many types of high-protein, low-carb diets, but all of them provide significantly more protein than the current RDA and contain fewer than 130 g of carbs per day.
The Atkins diet: The Atkins diet is a type of low-carb diet that is split into four phases. During the first phase, carbs are restricted to 20-50 g daily. However, during the final stage of the diet, most people shift into a more moderate low-carb eating pattern.
There are many other types of low-carb diets, some of which have no specific rules other than keeping your carb intake under 130 g per day.
What To Eat on the Diet
When following a low-carb diet, you need to limit food high in carbohydrates and prioritize foods higher in fat and protein.
The foods allowed in your diet depend on which type of low-carb diet you're following. More moderate low-carb diets will allow for a higher intake of foods that contain moderate to high amounts of carbohydrates.
In general, people following low-carb diets should focus on the following foods:
Non-starchy vegetables: Asparagus, kale, broccoli, spinach, zucchini, onions, tomatoes, cucumbers, cauliflower, and artichokes
Proteins: Chicken, turkey, fish, shellfish, eggs, steak, and low-carb protein powders
Nuts and seeds: Almonds, cashews, pecans, Brazil nuts, macadamia nuts, no-sugar-added nut butters, hazelnuts, and walnuts
Fats and oils: Olive oil, coconut oil, avocados, avocado oil, butter, and ghee
Limited amounts of low-carb fruits: Raspberries, lemons, blackberries, coconut meat, and strawberries
Herbs and spices: Basil, garlic, ginger, rosemary, and parsley
Carb-free drinks: Black coffee, herbal teas, water, and sparkling water
If you're following a specific type of low-carb diet, like the keto diet, you may have more restrictions on your food choices.
Foods Not In the Diet
When following low-carb diets, you'll need to restrict your intake of carb-rich foods and drinks.
Foods and beverages high in carbohydrates that you may need to limit or avoid include:
Bread, pasta, and high-carb baked goods: Pasta, bread, bagels, muffins, and croissants
Grains: Couscous, oats, quinoa, rice, and barley
Sweeteners and high-sugar foods: Honey, maple syrup, table sugar, corn syrup, cookies, sweetened yogurts, ice cream, and sugary cereals
High-carb snack foods: Pretzels, chips, crackers, and granola bars
Starchy vegetables and legumes: Corn, potatoes, butternut squash, sweet potatoes, chickpeas, and lentils
Fruits, including fresh and dried fruit: Grapes, bananas, dried mango, raisins, pineapple, peaches, and apples
Sweetened condiments: Sweetened ketchup, some salad dressings, sweet chili sauce, and barbecue sauce
Sugary drinks: Soda, juice, sweetened sports drinks, and sugary coffee and tea drinks
If you're following a moderate low-carb diet, you can still include some of these foods in your diet, such as fruits and starchy vegetables.
Meal Ideas for the Low-Carb Diet
Low-carb meals can be nutritious and tasty. A day of eating on a low-carb diet may look like:
Breakfast: Egg omelet with mushrooms, spinach, and cheddar cheese with a side of sliced avocado
Lunch: Large green salad topped with salmon, hard-boiled eggs, cucumber, artichoke hearts, cherry tomatoes, pecans, and blue cheese
Snack: Full-fat Greek yogurt with sunflower seeds and raspberries
Dinner: Bean-less vegetable and turkey chili
In order to ensure you're taking in adequate fiber and nutrients, it's best to consume low-carb vegetables and fruits, like greens, artichokes, and avocados, at every meal and snack.
Benefits of Low-Carb Diets
Research has shown low-carb diets are associated with several health benefits. Here are a few ways transitioning to a low-carb diet may improve health.
Could Help With Weight Loss
A common reason people transition to a low-carb eating pattern is to promote fat loss. Studies show that low-carb diets are effective for encouraging weight loss, at least in the short term.
A review of eight studies that included data on 611 people with type 2 diabetes found that people following a ketogenic diet were more likely to lose more body weight and reduce their waist circumference compared to people on other types of diets, such as low-fat diets.
Many other studies have shown that low-carb diets, including more moderate low-carb diets, are effective for improving fat loss, including visceral fat, a type of deep belly fat linked to increased disease risk.
However, some studies have found that low-carb diets are no more effective than traditional calorie-restricted diets for promoting weight loss.
May Improve Blood Sugar Levels
Low-carb diets support healthy blood sugar regulation by reducing fasting and post-meal blood sugar levels, improving long-term blood sugar control, and reducing insulin resistance.
One of the most popular uses for the keto diet is to reduce blood sugar levels in people with diabetes. Because the keto diet cuts out high-carb foods, it helps support blood sugar management and has been shown to drastically improve both short and long-term blood sugar control.
The research review mentioned above found that keto diets significantly reduced levels hemoglobin A1c (HbA1c), which is a long-term marker for blood sugar control.
More moderate low-carb diets have also been shown to be effective for improving glycemic control.
A study that included 98 people with type 2 diabetes had participants follow a diet with a carb intake of 50–100 g per day that prioritized nutrient-dense, lower-carb foods with no set calorie intake for 16 weeks. The participants following this diet experienced significantly greater reductions in HbA1c and were more likely to decrease their need for diabetes medications compared to people who followed a control diet.
Other Benefits
In addition to improving blood sugar levels and boosting fat loss, low-carb diets may benefit health in several other ways.
For example, research has shown low-carb diets may improve certain heart disease risk factors, such as high triglyceride levels, low HDL cholesterol, and high insulin levels.
If you're following a low-carb, high-fat diet like keto, make sure to prioritize unsaturated fats to reap the heart-health benefits of a low-carb diet. Consuming high amounts of saturated fats—like those found in processed meats—can raise your LDL (bad) cholesterol and heart disease risk. Replacing these fats with mono- and polyunsaturated fats—like those found in fish, avocados, and nuts—can help lower your LDL cholesterol.
Other studies have found low-carb diets to be effective for managing certain medical conditions, including epilepsy, type 2 diabetes, Alzheimer’s disease, and polycystic ovarian syndrome (PCOS).
Safety
Low-carb diets are generally considered safe and aren't associated with significant health risks as long as they're executed appropriately.
More restrictive low-carb diets, such as the ketogenic diet, are linked with more side effects and potential health concerns than more moderate low-carb diets. Very low-carb diets, like the keto diet, cut out many nutrient-dense foods, like fruits and vegetables. Research shows that these dietary patterns tend to be low in fiber and several essential nutrients, including calcium and folate, and may lead to nutrient deficiencies over time.
Very low-carb diets could also result in side effects such as low blood protein levels, high cholesterol levels, kidney stones, and fatty liver. Experts advise against very low-carb diets for specific populations, including people with medical conditions like liver failure and pancreatitis, due to the diet's nutritional restrictions.
Though more moderate low-carb diets may be safe for most people, it's important to consult a healthcare provider before transitioning to a very low-carb diet, especially if you have a medical condition or are taking one or more medications.
Drawbacks
In addition to the potential downsides listed above, very low-carb diets can be restrictive and cut out many nutritious foods, such as fruits and higher-carb vegetables.
For this reason, very low-carb diets like keto diets have poor long-term adherence rates.
More moderate low-carb diets, such as diets that contain over 50 g of carbs per day, may be a better choice if you're looking for a diet you can maintain for the foreseeable future.
A Quick Review
Low-carb diets are diets that contain fewer than 130 grams of carbs per day. There are many types of low-carb diets, some of which restrict carbs more severely than others.
Though low-carb diets are linked to several health benefits, including promoting fat loss and improving blood sugar management in people with type 2 diabetes, very low-carb diets, like the keto diet, are linked with a few health concerns and are difficult to stick to long-term.
Fortunately, more moderate low-carb diets are easier to follow, less likely to cause side effects, and can be a better choice for long-term health benefits.
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