The LCHF diet explained: This is how a low-carb diet works for weight loss

The LCHF diet explained: This is how a low-carbohydrate diet works for weight loss

13 Apr

Low-carb diets have been around for decades, but interest in LCHF has never really gone away. On the contrary — the search trends show a stable interest year after year, and in Swedish health centers dietitians meet more and more often patients who have already tested lchf on their own. But what exactly is the principle behind the diet, how does it differ from keto, and what does the research say about long-term results?

What is LCHF and how does the diet differ from regular food

LCHF stands for Low Carbohydrate High Fat — in Swedish low-carbohydrate diet with high fat content. The basic idea is simple: you greatly reduce the intake of carbohydrates and replace that energy with fat and protein. The body, which normally runs on glucose from carbohydrates, is forced to change and instead begins to break down fatty acids for energy.

In a normal Western diet, approximately 45–60% of energy comes from carbohydrates. In the LCHF diet, it is cut down to less than 20 percent of energy, often less than 50–100 grams of carbohydrates per day, depending on the variant. It sounds dramatic, but in practice it involves cutting out bread, pasta, rice, potatoes and sugar — foods that dominate most dinner plates.

Fat intake is instead increased to 60–70% of energy, while protein stays at 20–25%. This distribution looks different to what we’ve learned since the public health messages of the 1980s, and that’s often what creates skepticism. Research from the last 20 years, however, has gradually re-evaluated the role of fat in the diet — saturated fat from eggs, meat and dairy products turns out to have more nuanced effects than previously thought.

LCHF beginners: the most common misunderstandings

Many people who start lchf think it’s all about eating as much bacon and butter as possible. That’s not quite right. The diet primarily emphasizes natural, unprocessed fats — avocados, nuts, fatty fish, olive oil — combined with meat, eggs, cheese and vegetables that grow above ground. Broccoli, spinach, zucchini, cauliflower and leafy greens are staples, while root vegetables and legumes are limited due to their carbohydrate content.

Fiber is another common issue. Carbohydrates in the form of dietary fiber are usually excluded from the total carbohydrate intake — it is “net carbon” that matters. An avocado does have carbohydrates, but the amount of fiber means that the net intake is minimal, and it fits perfectly into a lchf diet.

Keto vs LCHF: similarities, differences and what you actually need to know

Keto and lchf are often used interchangeably, but there is an important distinction. The ketogenic diet is a stricter version of the low-carb diet where the goal is to achieve a metabolic state called ketosis — the body produces ketone bodies from fat that replace glucose as the primary fuel for the brain and muscles.

To reach ketosis, carbohydrate intake needs to be a maximum of 20–30 grams per day, sometimes even lower. It’s a narrow margin. One banana is enough to knock out ketosis for the day. LCHF is broader — you can eat up to 100 grams of carbs and still be in an lchf context without being in ketosis.

|Property|LCHF|Keto|

|Carbohydrates per day|50–100 g (sometimes up to 150 g)|Under 20–30 g|

|Ketosis|Not necessary|The goal of the diet|

|Fat proportion of energy| 60–70% | 70–80% |

|Flexibility|Relatively flexible|Strictly|

|Suitable for|Long term, everyday meals|Shorter periods, medical use|

In practice, many choose a middle ground — they eat under 50 grams of carbohydrates without actively measuring ketone values. In terms of results, the difference between keto and general lchf weight loss seems to be small in the long term, but keto can give faster initial results thanks to the metabolic adjustment and fluid outflow during the first weeks.

What the research says about LCHF and weight loss

Lchf weight loss is among the most studied dietary intervention in the 21st century. A 2020 systematic review summarizing over 60 randomized control trials found that low-carb diets produced comparable or slightly better weight loss results than low-fat diets over 6–12 months. However, the differences even out after one year, suggesting that compliance — not diet type — is the deciding factor.

What distinguishes lchf from other diets in the studies is the effect on blood fats and blood sugar. Triglyceride levels consistently drop, HDL (the “good”) cholesterol rises, and blood sugar control improves markedly — especially relevant for people with type 2 diabetes or prediabetes. A study published in the New England Journal of Medicine showed that a ketogenic diet over 24 weeks produced an average weight loss of 12.9 kg compared to 6.7 kg for a low-fat diet.

The mechanism behind the weight loss is still debated among scientists. Three explanations dominate:

• Feeling of satiety increases — protein and fat are more satiating per calorie than carbohydrates, and many spontaneously find that they eat less without counting calories

• Insulin levels drop — lower insulin reduces fat storage and facilitates the release of stored energy from fat cells

• Metabolic advantage — ketone production and gluconeogenesis (the body’s production of glucose from protein and fat) require more energy than burning glucose directly, which may contribute to a slightly higher calorie burn

There is no consensus on how large the metabolic benefit actually is. Studies by Kevin Hall at the NIH show that calorie restriction itself explains the majority of weight loss, regardless of macro distribution. That does not rule out that lchf is effective — on the contrary, the diet seems to make it easier for many to eat fewer calories without hunger.

Side effects and the transition phase — keto flu and what you can do about it

One of the most common reasons people stop the lchf diet early is the unpleasant symptoms that can occur during the first 3-7 days of the transition. It’s informally called the “keto flu” or the keto flu, and it’s a real phenomenon with a physiological explanation.

Why keto flu occurs and how long it lasts

When the carbohydrate intake decreases drastically, the body depletes the glycogen stores in the liver and muscles. Each gram of glycogen binds about 3 grams of water — which means you’ll quickly lose 1-3 kg of fluid in the first few days. With the fluid outflow, electrolytes follow: sodium, potassium and magnesium disappear in larger quantities via the urine.

The symptoms are similar to the flu: fatigue, headache, dizziness, muscle cramps, irritability and difficulty concentrating. The intensity varies greatly between individuals — some barely notice it, others are bedridden for a few days.

Counteracting the keto flu is almost exclusively about electrolyte balance:

• Increase the salt in your food — good sea salt or Himalayan salt will help replace sodium

• Eat magnesium-rich foods such as nuts, seeds and leafy greens, or consider a supplement of 300-400 mg of magnesium glycinate per day

• Potassium is found naturally in avocado, salmon and spinach

• Drink enough water — but overconsumption of water without salt worsens electrolyte loss

Keto flu is temporary. Most people who make it through week one report markedly improved energy and mental acuity in week two and beyond — a feeling often described as more stable energy levels without the highs and lows that come with high-carb meals.

Other side effects to be aware of

Constipation occurs in some, especially if fiber intake drops when grains are removed. The solution is to fill the plate with fiber-rich vegetables and possibly add psyllium husks. On the contrary, some experience a looser stomach during the transition — this is because bile acid production increases when fat intake is increased, which speeds up bowel emptying temporarily.

A side effect that is rarely discussed is altered breath during the first weeks. Ketones are excreted via exhaled air and can give a fruity or slightly metallic smell. It is harmless and disappears in most people when the body adapts.

What you actually eat on LCHF — foods to choose and avoid

A normal day at lchf need not be boring or expensive. Breakfast can be eggs and avocado with smoked salmon, lunch a cobb salad with grilled chicken and feta cheese, dinner a meat sauce served on zucchini spaghetti or cauliflower rice.

Foods that fit well into the lchf diet:

• Meat and poultry: beef, lamb, pork, chicken, turkey — preferably unprocessed varieties

• Fish and shellfish: salmon, mackerel, sardines, prawns, cod

• Eggs in all forms

• Dairy with a high fat content: butter, cream, cheese, crème fraîche — please choose full-fat varieties

• Vegetables that grow above ground: broccoli, cauliflower, spinach, zucchini, peppers, cucumber, celery

• Fats: olive oil, coconut oil, avocado oil, avocado

• Nuts and seeds: walnuts, almonds, macadamia nuts, chia seeds, flax seeds

What you primarily limit is sugar in all forms, grain products (bread, pasta, rice, oats), potatoes and root vegetables, most fruits except berries, legumes and processed products with hidden carbohydrates.

Reading tables of contents becomes a habit. Industrial products labeled as “light” or “reduced fat” often contain added sugar to compensate for the taste — exactly the kind of hidden carbohydrates that sabotage lchf.

Is LCHF right for you and when should you consult a doctor

Low-carbohydrate diets are suitable for most healthy adults, but there are situations where medical advice is necessary rather than desirable. If you take medications for type 2 diabetes — especially insulin or sulfonylureas — blood sugar levels can drop quickly when carbohydrate intake is reduced. Dose adjustment is often required already during the first week, and this should be done in collaboration with your doctor.

The same applies to blood pressure medications. The fluid reduction during the first weeks can lower blood pressure noticeably, which can be positive in the long term but problematic if you are already taking medication.

For people with a healthy metabolism, no diabetes and no cardiovascular diseases, the risk with a well-composed lchf diet is generally low. Long-term studies of up to two years show no negative effects on kidney function or bone health with normal protein intake. However, extremely high protein intakes — over 2.5 grams per kg of body weight — are not recommended, not even for lchf practitioners.

One thing that many underestimate is the psychological aspect. Lchf requires you to cook, plan purchases and learn to read labels. In social contexts — dinners, conference lunches, vacations — the diet demands flexibility and preparation. Those who succeed in the long term are often those who find simple routines rather than those who strive for perfection every day. A single deviation does not throw off your metabolic readjustment — the short-term increase in carbohydrates is quickly absorbed, and you are back in lchf mode within 24 hours if you return to the diet.

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