3 Things To Know Before Starting a Low-Carb, High-Fat Diet

Ever since the Atkins Diet gained popularity in the 1960s, low-carb, high-fat diets (LCHF) have been all the rage. The ketogenic diet, another LCHF diet, continues to trend on TikTok today. These diets promise quick and easy weight loss without the need to count calories. However, like any diet, a low-carb, high-fat diet plan has its own set of considerations and potential risks.

Before diving into an LCHF diet, it's essential to understand what it entails and how it can impact your body both in the short term and the long term. This diet involves significantly reducing carbohydrates—a crucial macronutrient—while increasing fat intake.

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

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

There is no universal protocol or guidelines for a low-carb, high-fat diet. The term is used broadly, encompassing various eating patterns. Most research considers a daily intake of 20 to 50 grams as "low carb."

"A low-carb diet encompasses several different eating patterns," explains Basbaum. You might be familiar with names like the keto diet or the carnivore diet.

Basbaum categorizes it as follows:

• Very low-carbohydrate diet: Typically contains less than 10% carbohydrates or 20 to 50 grams of carbs per day.


• Low-carbohydrate diet: Allows up to 26% of daily calories from carbs, usually less than 130 grams per day.


• Moderate-carbohydrate diet: Provides 26%-44% of daily calories from carbohydrate sources.

If you decide to reduce carb intake, Basbaum recommends considering the moderate carbohydrate route and avoiding very-low-carb diets.

The varying carb ranges in different plans offer flexibility in implementing the diet. Understanding this variability is crucial for tailoring the diet to your individual 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 main attractions of LCHF diets is their potential for rapid weight loss.

"Low-carb diets are attractive due to the initial weight loss and the relative ease of following the diet in the early weeks or months," says Basbaum. This initial success can be motivating and give a sense of accomplishment.

However, it's important to note that the long-term health effects of LCHF diets are not well-researched. Extensive studies on their effects over extended periods are lacking.

Additionally, the restrictive nature of these diets can make them challenging to sustain over time, leading to yo-yo dieting and weight regain if you revert to your previous eating habits.

"Even in the short term, a low-carb diet may not be suitable or safe for everyone. It's essential to discuss the pros and cons with your healthcare provider before embarking on such a diet," she advises. Before starting a low-carb diet or any new eating plan, schedule a consultation with your doctor or a dietitian.

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

While LCHF diets may aid in rapid weight loss, they are not without potential health risks. In the short term, diets like the ketogenic diet can result in symptoms like nausea and brain fog, known as "keto flu."

The long-term consequences can be more severe. "Many low-carb diets, especially those very low in carbohydrates like the ketogenic diet, promote high intake of saturated fats (red meat, bacon, butter, cheese, etc.) that could elevate the risk of heart disease," Basbaum cautions.

If you have certain health conditions, this diet may not be suitable for you. "I would recommend this diet only to individuals with no history of heart, kidney, or liver disease or diabetes," Basbaum advises. Even for those without underlying conditions, due to limited research on long-term adherence, Basbaum recommends following an LCHF diet for only a few weeks or months, ideally under medical or dietitian supervision. It may serve as a jump start for some, but she recommends transitioning to a more balanced and sustainable eating plan afterwards.

The low fiber content in these diets is another concern. Inadequate fiber intake can negatively impact gut health. Fiber is crucial for maintaining a healthy digestive system and supporting the gut microbiome, a community of microorganisms that reside in the gut and influence health.

"Consulting with your doctor or dietitian can help tailor a diet like this to make it as safe and effective as possible," Basbaum emphasizes.

If you decide to try an LCHF diet, keep the following recommendations in mind:

• Aim for 25 to 30 grams of fiber daily.


• The American Heart Association recommends limiting saturated fat intake to no more than 5% to 6% of daily calories—if consuming 2,000 calories daily, this equates to about 13 grams of saturated fat per day.

If you are cutting back on carbs, use a food tracking app like MyFitnessPal to monitor your fiber and saturated fat intake and ensure that your diet promotes overall health.

The Bottom Line

Remember, drastic carb reduction or elimination of any food group is not necessary to achieve a healthy weight. Basbaum suggests a better alternative to a low-carb, high-fat diet is reducing highly processed carbohydrates (e.g., chips, cookies, ice cream, frozen pizzas, pastries) instead of all carb sources.

A variety of whole-food carbohydrates like fruits, vegetables, legumes, and minimally processed grains are beneficial for health and weight loss. Track your carb and macronutrient intake using the MyFitnessPal app.

Originally published on September 3, 2020; Updated on August 19, 2024