What Is a Low-Carb Diet?

Eating a balanced diet ensures the body gets all the necessary nutrients it needs to function. When people want to lose weight, limiting carbohydrates can help.^1-3

Many fad diets come and go, but low-carbohydrate diets seem to stick around. This may be because they deliver fast results. A low-carb diet for obesity management may work for some people.¹

What are carbohydrates?

Food is grouped into 3 types of macronutrients. These are proteins, fats, and carbohydrates – also called carbs. Carbs are found in grains, starchy vegetables like potatoes and corn, and fruits. There are 2 main kinds of carbs – simple and complex.^1,2

Simple carbs are sugars that are quickly digested. They provide a fast energy boost. Simple carbs are found in natural foods. Examples are lactose from milk or fructose from fruit. But they are also found in refined foods. An example is sucrose, or table sugar.²

Complex carbs break down into simple sugars during digestion. They take longer to digest. They provide energy over a longer period of time compared to simple carbs. Complex carbs are found in:²

• Beans
• Lentils
• Nuts and seeds
• Barley
• Quinoa
• Whole grains, like oats, bread, and cereals
• Potatoes and sweet potatoes

What does low-carb mean?

A low-carb diet limits the amount of carbs you eat. There are many kinds of low-carb diets. Some diets limit the percentage of carbs from your total daily calorie intake. Others may limit the total amount of carbs eaten, usually in terms of grams.³

Here are some guidelines for understanding moderate-, low-, and very low-carb diets:³

• Moderate-carb – 26 to 44 percent of daily intake from carbs
• Low-carb – 26 percent or less of daily intake from carbs; or less than 130 grams per day
• Very low-carb – less than 10 percent of daily intake from carbs, or 20 to 50 grams per day

In comparison, American dietary guidelines say 45 to 65 percent of your daily food intake should be carbs. Experts do not agree on what amount of carbs are okay to eat.¹

What can you eat on a low-carb diet?

People following this diet may eat:^2,4,5

• Proteins
• Fats
• Non-starchy vegetables

When eating a low-carb diet most of your energy will come from proteins and fats. Protein choices include:^2,4,5

• Meats – chicken, fish, grass-fed beef
• Eggs
• Lentils
• Beans
• Plant-based protein – tofu, tempeh

When choosing fats to add to your diet, make sure they are nutrient-dense and not overly-processed or fried foods. Good fat choices include:^2,4,5

• Butter
• Dairy products – cheese, cottage cheese, plain yogurt
• Nuts and seeds
• Olive oil and olives

Non-starchy vegetables can be eaten in a low-carb diet. These foods are a good source of fiber and vitamins. Choices include (but are not limited to):⁴

• Artichokes
• Asparagus
• Beans
• Bean sprouts
• Beets
• Carrots
• Cauliflower
• Eggplant
• Greens
• Kale
• Onions
• Mushrooms
• Peas
• Tomatoes
• Zucchini

What should you not eat on a low-carb diet?

Low-carb diets usually limit:²

• Bread
• Fruit
• Pasta
• Starchy vegetables (corn and potatoes)
• Sweets
• Whole and refined grains

Does a low-carb diet help with weight management?

Yes, it can. Research shows that low-carb diets can lead to rapid weight loss. In many people, water weight may be shed first. But when someone sticks to a low-carb diet, fat is lost next.³

Low-carb diets can also help manage other health conditions, like type 2 diabetes. Low-carb diets have also been found to lower triglyceride levels in some people. This is may be a sign of an improved metabolism.³

Are there any health concerns about eating this diet?

Yes. Some studies connect low-carb diets with a higher risk of heart disease. Specifically, studies have found some people experience an increase in low-density lipid (LDL) cholesterol levels when following a low-carb diet. LDL is also known as the bad cholesterol.³

Researchers also found a higher risk of death linked to a total daily intake of less than 40 percent carbs. But the quality of foods eaten may matter the most. One study followed 2 groups of people that ate a low-carb and low-fat diet. One group ate healthy, high-quality foods and the second group ate unhealthy, low-quality foods. The study found a higher risk of death in the group that ate lower-quality foods.³

There may also be an increased risk of cancer when eating a diet high in animal protein.²

Some people may experience muscle cramps when they suddenly eat less carbs. They may also become constipated due to the decreased fiber intake. This is when someone has difficulty passing a bowel movement.²

People following very low-carb diets may also experience ketosis. Ketosis is a process that happens when your body starts to break down fat for energy. It can lead to:²

• Bad breath
• Headache
• Feeling tired or weak

How long do people follow a low-carb diet?

While low-carb diets can produce rapid initial weight loss, few studies have found a benefit of sticking to a low-carb diet for more than a year or 2.²

In fact, there is little evidence to support the benefits of following a low-carb diet long-term. This is based on many low-carb studies. The primary reason for weight loss while following a low-carb diet is due to people eating fewer calories overall. Reduced calorie intake is likely due to increased protein and fat, which help you to feel fuller longer.²

When to talk with your doctor

Before starting a low-carb diet for obesity, talk with your healthcare provider. Some questions to ask them may include:

• Is this diet right for me?
• How long should I stick to this diet?
• How might this diet affect other health conditions I have?
• What are my personal benefits and risks of following a low-carb diet?