The low-carbohydrate, high-fat diet (LCHF) has been popular since the beginning of the Atkins diet in the 1960s. Today, the ketogenic diet (another LCHF diet) continues to be popular on TikTok. These promise faster, easier weight loss without the need to count calories. However, like any diet, a low-carb, high-fat eating plan has its own considerations and potential risks.
Before starting the LCHF diet, you should understand what it is and how it affects your body now and in the future. As the name suggests, this diet drastically reduces carbohydrates (a very important macronutrient) while increasing fat.
To help you make an informed decision, here are three important things to know before starting the LCHF diet, says MyFitnessPal registered dietitian Katherine Basbaum.
1. There is no strict definition of a low-carbohydrate, high-fat diet.
There is no single protocol or rule for a low-carb, high-fat diet. The term is thrown around a lot, but this way of eating comes in many different forms. Most studies consider 20 to 50 grams of carbohydrates per day to be “low carb.”
“Low-carb diet is an umbrella term used to refer to several different diets,” Basbaum explains. You may also know this diet by its names, such as the keto diet or the carnivore diet.
Basbaum divides them into several categories:
- Very low-carb diet: “This is typically a diet with less than 10 percent carbohydrates or 20 to 50 grams of carbohydrates per day,” she says.
- Low-carb diet: This is a less extreme version of the low-carb diet. It allows up to 26% of daily calories to come from carbohydrate sources. “Usually less than 130 grams per day,” Basbaum says.
- Moderate carbs. On a moderate carbohydrate diet, 26%-44% of your daily calories come from carbohydrates.
If you’re planning on cutting back on carbs, Basbaum recommends considering a moderate carb route and avoiding very low-carb diets.
The range of carbohydrates in the different plans allows you some flexibility in how you implement your diet. If you choose to pursue the diet, understanding this variability is important in order to tailor the diet to your personal needs and lifestyle.
2. The LCHF diet can lead to weight loss—at least in the short term.
One of the main reasons people are attracted to the LCHF diet is its potential for rapid weight loss.
“A low-carbohydrate diet is attractive because it allows for early weight loss and is relatively easy to follow during the first few weeks or months,” Bussbaum says. This initial success can be motivating and provide a sense of accomplishment.
But it’s important to note that the long-term health outcomes of the LCHF diet have not been fully studied. Extensive research on its effects over years and decades is lacking.
Additionally, Basbaum said the restrictive nature of these diets may make them difficult to adhere to over time. Yo-yo dieting and weight regain may result if you return to your usual eating patterns.
“Low-carb diets are not suitable and safe for everyone, even in the short term. It’s important to discuss the pros and cons with your health care practitioner before starting such a diet,” she points out. Before starting a low-carb diet or any other new way of eating, make an appointment to discuss it with your doctor or nutritionist.
3. The LCHF diet has short- and long-term health risks
While LCHF diets may help with rapid weight loss, they are not without potential health risks. In the short term, a diet like the ketogenic diet can cause nausea and brain fog, known as “keto flu.”
Long-term problems may be more severe. “Many low-carb diets, especially very low-carb diets such as the ketogenic diet, promote the consumption of large amounts of saturated fat (red meat, bacon, butter, cheese, etc.), which may increase the risk of heart disease. Busbaum warned.
If you have certain health conditions, this may not be suitable for you. “I would only recommend this diet to people who don’t have a history of heart disease, kidney disease, liver disease or diabetes,” Bussbaum says. Even if you don’t have any problems, Basbaum recommends following the LCHF diet for no more than a few weeks or months, ideally under the supervision of a doctor or nutritionist, because of limited research on long-term adherence. For some people, this may be 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 problem. A lack of fiber can negatively impact gut health. Fiber helps your body maintain a healthy digestive system and supports your gut microbiome, a community of microorganisms including bacteria, fungi, and viruses that live in your gut and may affect your health.
“Again, talking to your doctor or nutritionist can be helpful because they can tailor such a diet for you to make it as safe and effective as possible,” Bussbaum says.
If you decide to try the LCHF diet, keep these tips in mind:
- Aim for 25 to 30 grams of fiber per day.
- The American Heart Association recommends getting no more than 5 to 6 percent of your daily calories from saturated fat—if you eat 2,000 calories a day, limit your daily saturated fat intake to about 13 grams.
If you’re restricting carbs, it’s a good idea to use a food tracking app like MyFitnessPal to track your fiber and saturated fat to make sure your diet isn’t getting in the way of healthy eating.
bottom line
Remember, you don’t need to drastically reduce carbs or any food group to achieve a healthy weight. A better alternative to a low-carb, high-fat diet is to reduce highly processed carbohydrates (think: chips, cookies, ice cream, frozen pizza, pastries) rather than limiting a variety of carbohydrates, Bussbaum says.
Plenty of whole-food carbohydrates, such as fruits, vegetables, legumes and minimally processed grains, are good for your health and can help you lose weight. Track your carbs and other macros in the MyFitnessPal app.
Originally published September 3, 2020; updated August 19, 2024
