Why do you feel fuller when you eat meat than you eat fruits?

Because meat is a protein

This is put with an energy exercise.

Food energy is expressed in food calories (labeling: EU kcal, U.S. calories) or kilojoules (kJ). Food calories, or the "calorie" units used often in nutritional contexts, measure amounts of energy 1000 times greater than the units in scientific contexts known also as calories, or gram calories (cal). Food calories are thereby referred to less ambiguously in some formal contexts as kilocalories (kcal). One food calorie is equal to 4.184 kilojoules. Within the European Union, both the kilocalorie (kcal) and kilojoule (kJ) appear on nutrition labels. In many countries, only one of the units is displayed.

Carbohydrates, fiber, fats, proteins, organic acids, polyols, and ethanol all release energy during respiration — this is often called 'food energy'.[1] When nutrients react with oxygen in the cells of living things energy is released. A small amount of energy is available through anaerobic respiration. Fats and ethanol have the greatest amount of food energy per mass, 9 and 7 kcal/g (38 and 30 kJ/g) respectively. Proteins and most carbohydrates have about 4 kcal/g (17 kJ/g). Carbohydrates that are not easily absorbed, such as fiber or lactose in lactose-intolerant individuals, contribute less food energy. Polyols (including sugar alcohols) and organic acids have less than 4 kcal/g.

HM -- please include the source of your quotation.

Wikipedia.

What is the name of this Wikipedia article?

Food energy.

well, nice article, but it does not answer the question.

When you eat meat, you may feel fuller because it contains high amounts of protein and fat. These macronutrients take longer to digest compared to carbohydrates found in fruits. Here's a breakdown of why you might feel more satiated after eating meat:

1. Protein content: Meat, especially lean cuts like chicken, fish, or turkey, is a concentrated source of high-quality protein. Protein takes longer to digest and requires more energy for your body to break it down. As a result, it stays in your stomach for a longer time, leaving you feeling fuller.

2. Fat content: Meat tends to have higher fat content than fruits. Fats take longer to digest compared to other macronutrients. They contribute to a sense of fullness and can slow down the digestion process, prolonging the feeling of being satisfied.

3. Nutrient density: Meat is rich in essential nutrients like iron, vitamin B12, and zinc, which are often limited in plant-based foods. These nutrients play a role in appetite regulation. When your body receives an adequate supply, it helps signal satiety.

On the other hand, fruits have high water content and are rich in fiber, which can make you feel full, but the sensation may not be as lasting as with meat. Additionally, fruits tend to have less protein and fat, which are highly satiating. However, they are still important for a balanced diet due to their vitamins, minerals, and overall health benefits.