A low-carb, high-fat diet involves a person reducing the number of carbohydrates they consume and replacing them with healthful fats. In recent years, this type of diet has become popular among people trying to lose weight.

A low-carb, high-fat diet (LCHF) involves using ketones from fat for energy instead of glucose, which comes directly from carbohydrates. When a person significantly reduces or limits the number of carbs they consume in a day, it forces the body to use fat stores as fuel, which may lead to weight loss.

However, science does not always agree on the safety of LCHF diets. Although some research supports their use to help a variety of health conditions, other studies report that LCHF diets can be dangerous. Read on to learn more about LCHF diets, how to begin, and learn if they are safe.

Is a low-carb, high-fat diet good for you?

Eating a diet that is high in protein and fat tends to make a person feel full faster than they would if they consumed only carbohydrates, particularly simple carbohydrates, such as sugar. As well as weight loss, some evidence supports the use of LCHF diets to help certain medical conditions. An LCHF diet may have a positive effect on the following conditions:

• Type 2 diabetes
• Certain cancers
• Polycystic ovarian syndrome
• Alzheimer's disease
• Heart disease

However, scientists need to carry out more research to understand the LCHF diet's long-term effect on overall health. There is conflicting evidence on the safety and effectiveness of the LCHF diet. One study suggests that diets low in carbohydrates may lead to premature death from heart disease, cancer, and stroke.

How to start

For some people who want to lose weight, simple lifestyle changes, such as exercise and a balanced diet, might be all they need to improve their overall health and well-being. However, for those who want to follow an LCHF diet, it is essential that they implement it in a healthful, well-planned way. It is always a good idea to consult a health-care professional before beginning an LCHF diet, particularly for those people with a medical diagnosis.

It might be a good idea to ease into an LCHF diet by first cutting out refined and processed carbs, such as white bread and processed sugar and focusing on whole food-based carbohydrates, such as fruits, beans, legumes, and whole grains. This may be a good start to reaching weight loss and health goals without having to drastically reduce the number of carbs eaten.

Consider a formal dietary plan

An LCHF diet can include anything from a casual reduction in carbohydrate intake to following a much more structured plan. However, any LCHF diet involves reducing carbohydrate consumption. Most LCHF diets recommend that a person eat 50 grams (g) or less of carbohydrates in a day.

The Atkins diet

The Atkins diet is a popular LCHF diet that promotes weight loss. The Atkins diet involves four phases:

• Phase 1: A person eats no more than 20 g of carbohydrates a day for 2 weeks
• Phase 2: A person can start to add more foods, such as nuts, fruits, and low-carb vegetables, into the diet
• Phase 3: As the person approaches their goal weight, they can consume more carbohydrates
• Phase 4: A person can eat whole grain carbs and other healthful carbohydrates as long as they do not start gaining weight

Many of the pre-packaged products linked to the Atkins diet are processed and contain sugar alcohols and artificial sweeteners. Some research links these types of sweeteners to metabolic syndrome, type 2 diabetes, heart disease, and weight gain. If following an Atkins-type diet, it is a good idea to focus on whole food sources rather than processed foods and bars.

The ketogenic diet

The ketogenic, or keto, diet also encourages a low-carbohydrate and high-fat intake. Though there are a few variations, a ketogenic diet typically involves a person consuming no more than 5%–10% of carbohydrates in their daily diet—this equates to about 20–50 g of carbs per day.

The ketogenic diet aims to help the body achieve a state of ketosis. Ketosis occurs when there are not enough carbohydrates available for the body to use for energy, so it starts to break down fat stores to use instead. This effect typically induces weight loss and may have other health benefits for some people. However, the diet may also have side effects and scientists need to carry out further research to identify the long-term benefits and dangers of the ketogenic diet.

Meal planning

When a person starts an LCHF diet, it is essential that they plan their meals. Meal planning can help a person:

• Buy only the food they need, which will save wastage and money
• Avoid eating the same foods repetitively
• Cut out meals heavy in carbohydrates

For those following an LCHF dietary plan, such as the Atkins or ketogenic diet, there are many resources available to help plan meals and create shopping lists.

Foods to eat

LCHF diets typically require a person to eat foods that are low in carbohydrates. In general, a person following an LCHF diet should include lean proteins and healthful fats in their daily diets. It is essential to be mindful of portion sizes to avoid overeating. Some sources of fat and protein for LCHF diets include:

• Meat, including beef, pork, chicken, and turkey
• Fish, such as salmon, tuna, herring, and cod
• Cheese
• Butter
• Avocado
• Oils, such as olive, coconut, flaxseed, and avocado oil
• Nuts, such as peanuts, almonds, walnuts, and cashews
• Seeds such as sunflower, chia, and flax
• Eggs

Some fruits and most non-starchy vegetables are low in carbohydrates. These include:

• Spinach and other dark leafy greens
• Berries, such as strawberries, blueberries, and blackberries
• Broccoli
• Cauliflower
• Asparagus
• Brussels sprouts
• Carrots
• Small portions of melons, peaches, and apples

In moderation, a person can also eat dark chocolate and drink dry wine and still stay low-carb. Depending on the exact dietary plan a person is following, they may choose to include small amounts of the following higher-carb food items:

• Quinoa
• Sweet potatoes
• Potatoes
• Beans and legumes
• Brown rice
• Oats
• Other tuber vegetables
• Other whole grains

People following an LCHF diet should avoid drinks that contain large amounts of added sugar, such as sodas, sweetened teas, and juices. Unsweetened teas, coffee, and water are excellent choices.

Foods to avoid

The most obvious foods to avoid are those that contain high carbohydrates with little nutritional value or fiber, such as refined and overly processed foods. This includes sodas, cakes, and cookies. These often contain a lot of added sugar, including artificial sweeteners and sugar alcohols. Other foods that people can avoid or consume in smaller quantities include:

• White pasta
• White rice
• Bread and rolls
• Baked goods such as pastries, cakes, and muffins
• Candy
• Drinks with added sugar, such as energy drinks, soft drinks, and fruit juices
• Beer
• Sugar-heavy coffees
• Diet drinks
• Low-fat foods, as they may contain extra sugar

Some people may choose to avoid starchy vegetables, such as potatoes, beans, and whole grains. However, a person might not need to exclude all these foods to maintain an LCHF diet.

Side effects

When a person suddenly cuts down on the number of carbohydrates they eat, they may experience some temporary side effects, including:

• Weakness or fatigue
• Muscle cramps
• Headache
• Constipation or diarrhea
• Skin rash
• Bad breath

As the body adjusts to these dietary change, these effects should go away. There is currently not a lot of research into the long-term side effects of LCHF diets. However, some potential risks may include:

• A higher chance of developing heart disease from eating animal protein and fat
• Increase in the risk of developing chronic diseases
• Nutritional deficiencies

Children and teenagers should not attempt a diet that reduces their carbohydrate intake. Nutritional deficiencies could lead to bone density loss or impaired growth. People with medical conditions or other concerns should speak to their health-care provider before starting an LCHF diet.

Takeaway

In the short-term, an LCHF diet may help a person lose weight. However, there is little research on the long-term health effects of LCHF diets. Some studies indicate that the diet may help a person avoid heart disease and other medical conditions, while others suggest it may lead to more chronic conditions. Before starting an LCHF diet, a person should speak to their health-care professional.