What Is a Low-Carb Diet, and What Should I Know Before Going Low-Carb?

updated Jan 27, 2020
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Credit: Joe Lingeman: Food Styling: Cyd McDowell

Low-carb diets are not a new phenomenon. The ultra-low-carb keto diet was created almost 100 years ago as a way to treat epilepsy and the Atkins Diet first launched in 1972. But in recent years, low-carb diets have become much more prevalent: In addition to the ketogenic diet and Atkins, there’s Low-Carb High-Fat (or LCHF), Whole30, and Paleo. (The low-FODMAP diet also cuts out certain — but not all — carbs.)

There are so many eating practices today that focus on lowering carbs — but is it healthy to cut carbs, and is it the right type of diet for you? 

What are the different kinds of low-carb diets?

There are many different ways that you can eat a carb-restricted diet and multiple “low-carb” diets to follow. Each diet defines what’s considered “low” differently. Here’s what the typical carbohydrate intake is like for several of the more popular low-carb diets:

Keto Diet

This diet is perhaps the most strict at limiting carbs, as the goal is to get your body into ketosis — burning fat for fuel, which it will only do when it runs out of carbs. To be in ketosis, most people can’t eat more than 15 grams of carbohydrates per day. (For reference, there are 15 grams of carb in a single slice of bread.) The keto diet also moderates the amount of protein you eat, and encourages eating more fat. 

Learn more: What Is the Keto Diet?

Atkins Diet

Depending on your diet goals, there are three versions of Atkins — Atkins 20, Atkins 40, and Atkins 100 — where you limit yourself to 20, 40, or 100 grams of carbohydrate a day. This is also a high-fat diet.

Low-Carb High-Fat

As its name suggests, this is a catchall term for a variety of non-keto, non-Atkins diets that are low-carb and high-fat, and what actually constitutes “low” is highly dependent on the individual.


It’s not touted as a low-carb diet, but following this way of eating will ultimately result in consuming fewer carbs that the typical American. For 30 days you eliminate sugar, alcohol, dairy, legumes, and grains — all of which are fairly carb-heavy. 

Learn more: What Is the Whole30 Diet?


This diet also technically does not advertise itself as low-carb. However, the Paleo diet, which focuses on trying to eat as our hunter-gatherer ancestors did, eliminates processed foods as well as legumes and grains (among other things), and so followers tend to eat fewer carbs. The diet does allow fruit — and sweeteners in their natural state, which other low-carb diets tend to avoid. 

Learn more: What Is the Paleo Diet?

What do you avoid on a low-carb diet? 

To limit carbohydrates means cutting back or eliminating almost all bread, pasta, rice, and other grains from one’s diet. However, fruits, vegetables, and even dairy also deliver carbohydrates and often must be cut back or eliminated, depending on the constraints. Because sugar is essentially a simple carb, sweets, baked goods (which are mostly made from flour), and alcohol also must typically be avoided.

What can you eat on a low-carb diet? 

What you can and can’t eat will vary with the type of low-carb diet you choose to follow. In general, though, your diet will lean heavily on proteins and/or fats. For your overall health, it’s important to not just turn to animal proteins (red meat, poultry, eggs, etc.) and animal fats (butter, ghee, etc.), but to lean on plant-based proteins and fats (think: nuts, seeds, their butters and oils, and legumes if allowed). There’s also typically room for some fruits such as berries and avocado, as well as vegetables such as cauliflower, zucchini, mushrooms, spinach, celery, asparagus, broccoli, kale, Brussels sprouts, and lettuces. 

What are the health benefits of following a low-carb diet? 

Perhaps the most significant (and also scientifically-supported) benefit of going low-carb is weight loss. Research shows it can help you lose weight faster compared to other diets like low-fat plans — and some research suggests eating low-carb will make it easier to keep weight off (though this isn’t settled; other studies found less difference).

Related: A very recent study, published in the journal Nutrients, reported that adults who followed a carb-restricted diet for four weeks significantly cut their food cravings, particularly for fat-rich foods. Women were also able to tame their sweet tooth. In this particular study, 14 percent of participants’ diet was carbohydrate, 58 percent was fat, and 28 percent was protein.

A low-carb diet may also have benefits for your heart. There are multiple studies that look at eating a low-carb diet for heart health, but this one is particularly notable: A 20-year study of over 82,000 women found that those who ate low-carb diet, and then replaced those carbohydrates with mostly vegetables sources of protein and fat, lowered their risk of heart disease by 30 percent.

The women who cut carbs and turned to mostly animal fats and proteins, however, didn’t lower their risk of heart disease by any statistically significant amount. There’s also other research that shows when you cut back on saturated fat (in an effort to help your heart and improve your cholesterol), but replace those fat calories with carbohydrates, and especially “refined” white carbs, you may actually worsen your cardiometabolic health (versus if you were to replace those saturated fats with unsaturated fats). 

Finally, eating a lower carbohydrate diet is sometimes recommended if you have diabetes, pre-diabetes, or even are at risk of developing diabetes.

Are there any drawbacks to eating a low-carb diet?

Carbohydrates — when broken-down into glucose — are our brain’s primary and preferred fuel source (“preferred” is key). This is in part because they can easily fuel our bodies with energy, or be stored for use later on. Also, carbohydrates increase our body’s serotonin release — serotonin is our “feel good” hormone that keeps us happy. Other research has shown that eating carb-rich fruits and vegetables is associated with a lower risk of depression

Another drawback is a potential lack of fiber. Fiber is one nutrient that most Americans don’t get enough of already. Eliminating foods like grains or fruits, and vegetables from your diet makes getting adequate amounts of fiber more challenging. And fiber has been linked in the scientific research with a long list of perks. It can lower your risk of heart disease, diabetes, and obesity. It can improve your cholesterol and encourage weight loss (or, help with maintaining weight). And, of course, it keeps you regular!  

It’s important to also keep in mind that not all carb-laden foods are nutritionally equal. Compare, for example, whole fruit to packaged fruit snacks. Both are carb-heavy foods, but one comes with a variety of great-for-you nutrients and fiber, while the other often trades those for added sugars and synthetic food dyes. Similarly oatmeal, farro, and other whole grains are typically much more nutritionally-beneficial than, say, cupcakes made from white flour, and sugar.

Ultimately, whether you decide a low-carb diet works for you or not, there’s a great deal of benefit to choosing whole foods, eating plant-based fats, and getting enough fiber — things that every low-carb diet allows.