Is a Low-Carb Diet Healthy?

Low-carbohydrate diets are used as a way to accelerate weight loss. But does a diet's popularity mean that following it long-term is healthy, and will the results last?

woman cutting vegetables for a low-carb meal
Caitlin Beale, MS, RDN
— Signos
Health & Nutrition Writer
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Updated by

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Science-based and reviewed

April 23, 2024
March 2, 2022
— Updated:
March 16, 2022

Table of Contents

Low carb, Atkins, paleo, whole 30, keto. The low-carb diet movement may seem like a trend, but it's actually been around for a while and newly repackaged with slight variations. Each version may differ on the number of carbs included and so-called allowed foods. Still, they share the central premise: reduce overall intake of carbs.

Low-carbohydrate diets are used as a way to accelerate weight loss. But does a diet's popularity mean that following it long-term is healthy, and will the results last?

Almost any "diet" pattern works initially for weight loss – but it's really up to each person's individual metabolic response. An extensive systematic review<sup>1</sup> of more than 121 studies on 14 different diets found that though there were slight weight loss differences between diets at six months, by 12 months, weight loss slowed for all diets. 

Another review<sup>2</sup> on low-carb versus "balanced" carb diets for weight loss and cardiovascular risk factors for people with diabetes found little difference between the two up to two years follow-up.

So does this mean low-carb may not work? Not necessarily. For some people, a low-carb diet can be a game-changer for better blood sugar control, but how you follow it matters most, especially when it comes to the food choices you make. 

This article will examine the details behind low-carb diets to help you decide if the low-carb approach is the right choice for your lifestyle.

What is a low-carb diet?

A low-carb diet limits how many carbs you eat each day. Carbs are foods that break down into glucose, raise your blood sugar, and provide energy for the body.

Carbs are categorized as simple or complex:

  • Simple carbs rapidly raise blood sugar because they are digested quickly. This includes foods like white flour and rice, sweets, sodas, and pasta.
  • Complex carbs are digested more slowly, so blood sugar is less likely to spike (although a higher blood sugar response is still possible depending on your metabolism). They include whole grains, beans, fruits, and vegetables.

<p class="pro-tip">Learn about slow-digesting (complex) carbs from an registered dietitian</p>

Since carbs raise blood sugar, low-carb diets are often used to support better health by reducing insulin. Insulin is the hormone responsible for lowering your blood sugar. It stimulates cells to take glucose out of the blood and into the cells to use for energy or store as fat. 

But too much circulating insulin<sup>3</sup> isn’t a good thing, and it’s also associated with inflammation, weight gain, and fat storage. 

How many carbs in a low-carb diet?

There isn’t one standard definition of a low-carb diet, although they all focus on replacing refined carbs with protein, healthy fat, and vegetables. Some are more restrictive than others.

General recommendations are 45 to 65% of total calories come from carbs, so technically, anything less than this is considered low-carb. However, most low-carb<sup>4</sup> diets are less than 130 grams a day, and very low-carb diets are less than 10% of total intake from carbs, or below 50 grams a day.

The ketogenic (keto) diet is the most popular very low-carb diet. The keto diet isn’t just about lowering carbs but also increasing fat. When carbs are scarce, the body can use fat as an energy source instead (known as ketosis). Since carbs are so low, the keto diet is more challenging to follow long-term for many people. 

But aside from keto, many versions of low-carb do leave room for carb-containing foods, especially fruits and vegetables.

What foods are included on a low-carb diet?

Low-carb foods include:

  • Meat
  • Fish
  • Poultry
  • Vegetables
  • Fruit
  • Nuts
  • Seeds
  • Healthy oil like olive or avocado
  • Butter or ghee
  • Cheese 

The amount of each type of food may vary depending on the type of low-carb plan you follow. For example, fruit or starchy vegetables would be much more limited on keto, or dairy products are usually limited on a Whole 30 plan.

What foods are avoided on a low-carb diet?

  • Pasta
  • Bread
  • Beans
  • Lentils
  • Soda
  • Juice
  • Sweets
  • Baked goods
  • Potatoes
  • Rice
  • Oats

Even though some of these carbs are considered complex, they don’t fit into a low-carb plan because they impact blood sugar and insulin response. That said, there may be some people who decide to eat small amounts of complex carbs on their low-carb diet to increase fiber intake, but still keep carbs limited in other areas.

Many low-carb diets still leave room for plenty of healthy carb options. For example, if you were trying to keep carbs under 100 grams, you could include the following foods<sup>5</sup> and still have a bit of wiggle room for extras:

  • 1 medium apple (15 grams of carbs)
  • 1/2 cup blueberries (10 grams of carbs)
  • 1/2 cup lentils (20 grams of carbs)
  • 3/4 cup garbanzo beans (22 grams of carbs)
  • 1 medium sweet potato (24 grams of carbs)

There’s really no one way to approach a low-carb diet. Some people choose a carb number to stay under and track it alongside protein and fat. Others don’t track at all and just choose what carbs to include in the diet. It’s highly customizable depending on how you want to do it.


What are the benefits of a low-carb diet?

There’s a lot of evidence supporting health benefits for low-carb diets, especially in the short term.

Low-carb diets and weight loss

Since weight loss is usually the first reason someone starts a low-carb diet, we will begin here too. There are several ways low-carb diets can support weight loss. To start, a low-carb diet could simply reduce your intake of processed foods that could contribute to weight gain.

Low-carb diets may also help with adipose (fat) tissue around the midsection<sup>6</sup> which is linked to metabolic syndrome, inflammation, and cardiovascular disease. Since insulin is linked to increased belly fat, reducing it by eating fewer carbs could help (although lowering blood sugar spikes with other methods like fiber or protein could also work).

Studies on low-carb diets have shown that they could be better at helping you lose weight than low calorie or low fat, at least in the short term. A study<sup>7</sup> comparing low-carb and low-fat diets for weight loss found that those following a low-carb diet lost significantly more weight over six months. Participants in the low-carb diet also saw improvements in triglycerides, insulin sensitivity, and blood sugar balance.

Many studies have found similar results, but the trick is to examine if the initial weight losses last. Over time the initial weight loss<sup>8</sup> effect appears to even out.

Low-carb diets reduce your intake of refined carbs to support cardiovascular health

There’s often an assumption that low-carb diets are bacon and butter heavy and terrible for heart health, but that’s a misconception. 

Low-carb diets also emphasize increasing the intake of fresh foods to replace refined carbs and processed foods that contribute to inflammation and cardiovascular disease.

Several studies point to the positive effect of lowering carbs and cardiometabolic<sup>9</sup> risk factors, including:

  • Improved triglycerides
  • Increased HDL (good) cholesterol
  • Healthy blood pressure
  • Improvements in insulin resistance

The foods replacing refined, simple carbs are usually behind these positive changes. When sugars and starches are replaced with fruits, vegetables, or protein, they can positively affect these markers by lowering the glycemic response.

Blood sugar balance

A significant benefit of low-carb diets is the positive effect on blood sugar. Since carbohydrates are the reason you have elevated blood sugar in the first place, cutting down on carbs lowers blood sugar and insulin levels. 

A review<sup>10</sup> on the safety of following two types of low-carb diets for people with diabetes for at least 12 weeks found that at six months, both diets significantly improved blood sugar for people with diabetes compared to control diets. 

It’s interesting to note that the researchers found that the less restrictive low-carb diet (less than 130 grams a day) was more successful than the very low carb diet that matched a keto pattern simply because participants were more adherent to a plan that allowed more freedom of food choices. In other words, finding a plan that feels sustainable and easy to follow is likely to be the most successful.

However, keto does work for some people. A two-year study<sup>11</sup> on ketosis for diabetes management saw reductions in A1c (a two to three-month measure of blood sugar control), fasting glucose, fasting insulin, weight, and other cardiovascular markers. Several participants were able to reduce their use of diabetes meds. 

It’s been suggested that the effects of low-carb (or any diets) on blood sugar improvements are due to weight loss. Losing 5% to 10% percent of body weight is associated with better blood sugar control. But low-carb diets may help lower blood sugar even without weight loss. 

A study<sup>12</sup> comparing two different diets for diabetes found that although both led to weight loss, the low-carb diet was even more successful at reducing A1c. A review<sup>13</sup> comparing low-carb and low-fat diets for people with diabetes also found that A1c dropped more for the low-carb diet, and this effect lasted up to 2 years, although weight loss diminished over time

Appetite and craving control

Your body has a physiological switch that turns on when you lose weight as a protective mechanism. Diets that significantly cut calories or rapid weight loss can increase the production of hormones that  make you feel more hungry, which is part of the reason these diets often don’t work.

On the other hand, low carb diets<sup>14</sup> don’t seem to have this impact, and could even slightly increase how many calories you burn during the day.

Is there anyone who shouldn’t follow a low-carb diet?

There are a few contraindications to following a low-carb (especially keto) diet:

  • History of eating disorder
  • Pregnancy or breastfeeding
  • Medication for diabetes or blood sugar
  • Underweight

If you have any health conditions or are taking any medications, it’s always a good idea to chat with your healthcare provider before making any significant diet changes. 

So, is a low-carb diet healthy?

There are a few factors to consider before starting a low-carb diet, and the main one is to ask if the diet is healthy for your body long-term?

The first consideration is finding an approach that doesn't feel like a temporary fix that won't last. Each of us will have a different metabolic response to food, and perhaps just as important, we all have different relationships with food.

For some people, a keto diet isn't sustainable and could negatively impact eating habits, but a moderate carb diet that includes plenty of fresh fruits and veggies and leaves room for fiber-rich legumes feels like a very natural way to eat with the added health benefits.

The second crucial thing to understand about low-carb diets is that what you eat instead of carbs matters just as much as lowering the intake. Yes, removing refined carbs is fantastic for your blood sugar and overall health, but replacing them with processed meats or other inflammatory foods doesn't help. Plus, overly restricting healthy, carb-containing foods like fruits, vegetables, or grains can leave out vitamins and minerals or nutrients like fiber<sup>15</sup> that are protective against many chronic health conditions.

It's an oversimplification to say that low-carb diets aren't healthy long-term. Instead, low-carb diets that remove all these wonderful nutrients could be a problem.

A study on Japanese adults<sup>16</sup> found high-carb and low-carb diets were both associated with mortality when they were high in animal products. But a low-carb diet rich in plant-based fats like nuts, seeds, and avocado were associated with a lower risk of death. This was echoed in another study<sup>17</sup> that found low-carb diets that emphasized plants, especially plant-based fats, were linked to lower cancer risks.

What do these results tell us? The type of fat and protein matters as much as the carb count. You can adjust your carbs, protein, or fat intake, but plants should always be an essential part of your overall diet, even while following a low-carb diet.

Use the principles of low-carb diets to fit your lifestyle

Should you follow a low-carb diet? It’s impossible to give a general answer since we are all so different.

If a low-carb diet feels like a good fit for you after reading all the above, you can always try and see how you feel. Play around with carb intake and see what works for you.

Studies can tell us the overall impact of a diet on a group of people, but each of us will have our own responses to food. However, if a low-carb diet sounds too restrictive or feels too much like a short-term plan, you can use the principles of a low-carb diet to work with your lifestyle. 

Signos can help you better understand your individual response to food so you can make food choices that match your physiology. Maybe fruit and starchy veggies work well for you, but oatmeal spikes your blood sugar immediately. In this case, you could customize the types of carbs you avoid instead of cutting them out altogether.

Finding a food pattern that matches your lifestyle, makes you feel good, and is sustainable long-term is the ultimate goal, and learning how your body responds to food can help you get there.

<p class="pro-tip">Read next: Does a low-carb diet for weight loss work?</p>

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About the author

Caitlin Beale is a registered dietitian and nutrition writer with a master’s degree in nutrition. She has a background in acute care, integrative wellness, and clinical nutrition.

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