Though weight loss is a goal for many people, others hope to gain weight, often to look and feel more muscular or to improve athletic performance. Regardless of your reason, the most critical component of gaining weight is consuming more calories than you burn on a daily basis. For people who struggle to eat enough to gain weight, mass gainer supplements are an effective way to increase your calorie intake. Unlike typical protein supplements, mass gainers are not only rich in protein but also carbs and sometimes other ingredients like amino acids.