A gainer is a type of dietary supplement designed to help individuals increase their calorie intake, primarily for muscle gain and weight gain. These products typically contain a blend of carbohydrates, proteins, and fats, providing a high-calorie option for those who struggle to consume enough calories through regular meals. Gainers are often used by athletes, bodybuilders, and individuals with high metabolic rates. They can be consumed as shakes or mixed into foods, making it easier to meet daily caloric and nutritional needs. Popular brands include Optimum Nutrition and BSN, which offer various flavors and formulations.