The ketogenic (keto) diet is one of the most searched diets in the world, but most people only know the headline: "low carb, high fat." Here are the facts that help you understand why keto works the way it does, and what to keep in mind before you start.

1. Keto started as a medical diet, not a weight-loss trend

Doctors developed the ketogenic diet in the 1920s to help manage epilepsy in patients whose seizures were hard to control. It is still used under medical supervision for that purpose today. The weight-loss popularity came much later.

2. "Ketosis" just means your body is burning fat for fuel

Normally your body runs mostly on glucose from carbohydrates. When carbs are cut very low, the liver starts turning fat into molecules called ketones (mainly beta-hydroxybutyrate, or BHB), which your brain and muscles can use for energy. That state is called ketosis. A mild version also happens naturally during fasting or long exercise.

3. The carb limit is lower than most people think

Most standard keto plans keep net carbs around 20 to 50 grams a day. For reference, one medium banana has about 24 grams of net carbs. This is why reading labels, including on supplements and gummies, matters on keto.

4. You can still eat some fruit

Keto does not mean zero fruit. Avocado, olives, raspberries, blackberries and strawberries are lower in net carbs and fit into many keto plans in small portions. High-sugar fruits like bananas, grapes and mangoes are harder to fit in.

5. Not all fats are equal

High fat is not a free pass for fried fast food. Most keto guides focus on:

• Monounsaturated fats: olive oil, avocado, nuts.
• Omega-3 fats: salmon, sardines, chia and flax seeds.
• Moderate saturated fat: butter, cheese, coconut oil.

Trans fats, found in some processed and fried foods, are best avoided on any diet.

6. The "keto flu" is common in the first week

Many people feel tired, foggy or get headaches during the first days of keto. This is often linked to losing water and electrolytes as carbs drop. Drinking enough water and getting sodium, potassium and magnesium from food usually helps.

7. Apple cider vinegar became a keto favorite

Many people on keto add apple cider vinegar (ACV) to their routine because it has almost no carbs. Since the liquid is sour and hard on teeth, ACV gummies became a popular alternative. Just check the label: gummies contain a small amount of sugar, so count it in your daily carbs. Learn more in ACV gummies vs liquid ACV.

The bottom line

Keto is a big change in how your body gets energy, so it is worth understanding before you start. If you have a medical condition, take medication, or are pregnant or nursing, talk to your doctor before changing your diet or adding supplements.