Excessive intake of which type of nutrient can lead to obesity?

Obesity is a condition characterized by an excess amount of body fat, which can result from a caloric surplus—consuming more calories than the body expends. All types of macronutrients—proteins, fats, and carbohydrates—can contribute to this caloric surplus when consumed in excessive amounts.

Fats are calorie-dense, providing 9 calories per gram compared to 4 calories per gram for proteins and carbohydrates. This means that even small increases in dietary fat can lead to significant surplus calorie intake. Similarly, carbohydrates, especially in the form of added sugars and refined grains, can also contribute excess calories to the diet, particularly if consumed in large quantities. Proteins, while generally considered less likely to contribute to weight gain, can still add substantial calories when consumed in excess as they also provide 4 calories per gram.

In conclusion, because each of these macronutrients can contribute to an overall caloric excess—potentially leading to obesity if consumed in excessive amounts—the option indicating that all of them can lead to obesity when taken excessively is appropriate.