Since the Atkins diet began in the 1960s, low-carb, high-fat (LCHF) diets have been popular. Today, the ketogenic diet, another LCHF diet, is still trending on TikTok. These promise faster, easier weight loss without the need to count calories. But like any diet, a low-carb, high-fat eating plan has its own considerations and potential risks.
Before you jump into a low-carb, high-fat diet, you need to understand what it entails and how it can affect your body, both now and in the future. This diet, as the name suggests, drastically reduces carbohydrates (a very important macronutrient) while increasing fat.
To help you make an informed decision, here are three crucial things you should know before starting an LCHF diet, according to MyFitnessPal registered dietitian Katherine Basbaum.
1. There is no strict definition of a low-carb, high-fat diet
There is no agreed-upon protocol or rules for a low-carb, high-fat diet. The term is used a lot, but this way of eating takes many different forms. Most research considers a daily intake of 20 to 50 grams to be “low carb.”
“A low-carb diet is an umbrella term used to refer to a number of different diets,” Basbaum explains. You may also know this diet by names like the ketogenic diet or the carnivore diet.
Basbaum divides it into categories:
- Very low-carb diet: “This is typically a diet that is less than 10% carbohydrates or between 20 and 50 grams of carbohydrates per day,” she says.
- Low-carb diet: This is the least extreme version of the low-carb diet. It allows up to 26 percent of daily calories to come from carbohydrate sources. “Typically less than 130 grams per day,” says Basbaum.
- Moderate Carbohydrate: On a moderate carbohydrate diet, 26% to 44% of daily calories come from carbohydrate sources.
If you’re going to cut back on carbs, Basbaum suggests considering the moderate-carb route and avoiding very low-carb diets.
The variety of carbohydrates in the different plans allows for some flexibility in how you implement the diet. Understanding this variability is important in order to tailor the diet to your personal needs and lifestyle, should you choose to follow it.
2. Low-carb diets lead to weight loss, at least in the short term
One of the main reasons people are drawn to LCHF diets is their potential for rapid weight loss.
“Low-carb diets are appealing because of 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 accomplishment.
But it’s important to note that the long-term health effects of low-carb, high-fat diets have not been well studied. There is no comprehensive research on their effects over long periods of years and decades.
Additionally, the restrictive nature of these diets can make them difficult to stick to over time, Basbaum said. It can lead to yo-yo effects and weight gain if you return to your usual way of eating.
“Even in the short term, a low-carb diet isn’t right or safe for everyone. It’s important to discuss the pros and cons with your doctor 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 discuss the topic with your doctor or a dietitian.
3. There are short- and long-term health risks associated with low-carb diets.
While low-carb diets can help you lose weight quickly, they are not without potential health risks. In the short term, diets like the ketogenic diet can cause nausea and brain fog known as “keto flu.”
The long-term problems can be more serious. “Many low-carb diets, especially very low-carb diets like the ketogenic diet, promote the intake of large amounts of saturated fats (red meat, bacon, butter, cheese, etc.) that can increase the risk of heart disease,” Basbaum warns.
If you have certain health issues, this diet may not be for you. “I would only recommend this diet to someone who has no history of heart, kidney or liver disease or diabetes,” says Basbaum. Even if you don’t have any issues, because of the limited research available on long-term adherence, Basbaum suggests following a low-carb, high-fat diet for no more than a few weeks or months, ideally under the supervision of a doctor or dietitian. It can be helpful for some people as a starting point, but “I then recommend transitioning to a more balanced and sustainable eating plan,” she says.
The low fiber content of these diets is another cause for concern. A lack of fiber can negatively impact gut health. Fiber helps the body maintain a healthy digestive system and supports the gut microbiome, a community of microorganisms, including bacteria, fungi and viruses, that live in the gut and can affect health.
“Again, talking to your doctor or dietitian can help because they can customize a diet like this to be as safe and effective as possible,” Basbaum says.
If you decide to try an LCHF diet, keep these recommendations in mind:
- Aim for 25 to 30 grams of fiber a day.
- The American Heart Association recommends getting no more than 5% to 6% of your daily calories from saturated fat — if you eat 2,000 calories a day, that’s a limit of about 13 grams of saturated fat a day.
If you are restricting carbohydrates, it’s a good idea to track your fiber and saturated fat intake using a food tracking app like MyFitnessPal to make sure the diet isn’t interfering with a healthy diet.
The final result
Remember that you don’t need to drastically cut carbs or any food group to reach a healthy weight. Basbaum says a better alternative to a low-carb, high-fat diet is to cut back on highly processed carbs (like chips, cookies, ice cream, frozen pizzas, and pastries) rather than limiting all types of carbs.
Eating plenty of carbs from whole foods, such as fruits, vegetables, legumes, and minimally processed grains, is good for your health and can help you lose weight. Track your carbs and other macronutrients in the MyFitnessPal app.
Originally published September 3, 2020; updated August 19, 2024
