The keto diet is a low-carbohydrate, high-fat eating plan that puts the body into a metabolic state called ketosis. It involves drastically reducing carbohydrates and replacing them with fat, leading to reductions in blood sugar and insulin levels. There are different versions of the keto diet, with the standard version being the most researched and recommended, involving 75% fat, 20% protein, and only 5% carbohydrates. The keto diet can help with weight loss and provide health benefits for conditions like diabetes.