Since the Atkins Diet started in the 1960s, low-carb, high-fat diets (LCHF) have been popular with. Today, the ketogenic diet, another LCHF diet, continues trending on TikTok. These promise faster, easier weight loss within the need to count calories. But, like any diet, a low-carb, high-fat diet plan comes with its own considerations and potential risks.

Before you jump into an LCHF diet, you should understand what it entails and how it might affect your body, both now and in the future. This diet, as the name suggests, dramatically cuts carbohydrates—a pretty important macronutrient—while increasing fat.

To help you make an informed decision, here are three crucial things to know before starting an LCHF diet, according to MyFitnessPal registered dietitian Katherine Basbaum.

1. There’s No Strict Definition of a Low-Carb, High-Fat Diet

There is no single agreed-upon protocol or rules for a low-carb, high-fat diet. The term is thrown around a lot, but this way of eating takes many different forms. Most research considers a daily intake of 20 to 50 grams daily “low carb.” 

“A low-carb diet is an umbrella term used when referring to several different diets,” explains Basbaum. You may also know this diet by names like the keto diet or the carnivore diet.

Basbaum breaks it down into categories:

• Very low-carbohydrate diet: “This is typically  one that has less than 10% carbohydrates or 20 to 50 grams of carbs per day,” she says. 
• Low-carbohydrate diet:This is the less extreme version of the low-carb diet. It allows for up to 26% of your daily calories to come from carbohydrate sources. “Usually less than 130 grams per day,” says Basbaum.
• Moderate-carbohydrate. On a moderate carbohydrate diet, you get 26%-44% of your daily calories from carbohydrate sources.

If you’re going to cut back on carbohydrates, Basbaum suggests considering the moderate carbohydrate route and avoiding very-low carbohydrate diets. 

The range of carbs on different plans allows for some flexibility in how you implement the diet. Understanding this variability is important to tailoring the diet to your personal needs and lifestyle, if you choose to pursue it.

2. LCHF Diets Lead to Weight Loss—At Least in the Short Term

One of the primary reasons people are drawn to LCHF diets is their potential for quick weight loss. 

“Low-carb diets are appealing due to the early weight loss and relative ease of following the diet for the first few weeks or months,” says Basbaum. This initial success can be motivating and provide a sense of achievement.

But it’s important to note that the long-term health outcomes of LCHF diets are not well-studied. There is a lack of extensive research on their effects over long stretches of years and decades. 

Additionally, the restrictive nature of these diets can make them hard to stick to over time, according to Basbaum. It can lead to yo-yo dieting and weight regain if you return to your usual way of eating. 

“Even in the short-term, a low-carb diet is not appropriate and safe for everyone. It is important to discuss the pros and cons with your healthcare practitioner before starting a diet like this,” she notes. Before starting a low-carb diet or any other new way of eating, make an appointment to go over it with your doctor or a dietitian.

3. There Are Short- and Long-Term Health Risks Associated with LCHF Diets

While LCHF diets might help with quick weight loss, they are not without potential health risks. In the short term, diets like the ketogenic diet can cause the nausea and brain fog known as “keto flu.”  

The long-term issues can be more serious. “Many low-carb diets, especially the very low carbohydrate diets such as the ketogenic diet, promote the intake of large amounts of saturated fats (red meat, bacon, butter, cheese, etc.) that may increase your risk of heart disease,” warns Basbaum.  

If you have certain health issues, this may not be a diet for you. “I would only recommend this diet to someone with no history of heart, kidney, or liver disease or diabetes,” says Basbaum. Even if you don’t have any issues, due to the limited research available on long-term adherence, Basbaum suggests following a LCHF diet for no more than a few weeks or months, ideally under the supervision of a doctor or dietitian. It may be useful for some as a  jump start, but “Then I recommend transitioning to a more balanced and sustainable eating plan,” she says. 

The low fiber content of these diets is another concern. A lack of fiber can negatively impact gut health. Fiber helps your body maintain a healthy digestive system and supports the gut microbiome, a community of microorganisms, including bacteria, fungi, and viruses, that live in your gut and may impact your health.

“Again, talking to your doctor or dietitian can help because they can customize a diet like this for you to make it as safe and effective as possible,” says Basbaum.

If you do decide to try a LCHF diet, keep these recommendations in mind: 

• Aim for 25 to 30 grams of fiber per day. 
• The American Heart Association recommends getting no more than 5% to 6% of your daily calories from saturated fat–if you’re eating 2,000 calories a day, that’s a limit of about 13 grams of saturated fat a day.

If you are restricting carbs, it’s a good idea to track your fiber and saturated fat by using a food tracking app like MyFitnessPal to make sure the diet isn’t getting in the way of a healthy diet. 

The Bottom Line

Remember, you don’t need to drastically cut carbs or any food group to achieve a healthy weight. Basbaum says that a better alternative to a low-carb, high-fat diet is to cut back on highly processed carbohydrates (think: chips, cookies, ice cream, frozen pizzas, pastries) instead of limiting all kinds of carbs. 

Plenty of whole-food carbohydrates, like fruits, vegetables, beans, and minimally processed grains, are good for your health and can help you lose weight. Track your carbohydrates and other macros in the MyFitnessPal App. 

Originally published September 3 2020; Updated August 19, 2024