When a hardgainer experiences a plateau in weight gain despite maintaining a calculated caloric surplus, what specific, data-driven nutritional adjustment should be the first line of action?

The first specific, data-driven nutritional adjustment when a hardgainer experiences a plateau in weight gain despite maintaining a calculated caloric surplus should be to further increase the total daily caloric intake, prioritizing carbohydrates as the primary macronutrient for this increase. A hardgainer is an individual who struggles to gain weight and muscle mass, often due to a higher basal metabolic rate or greater non-exercise activity thermogenesis. A plateau signifies that the body's weight gain has halted, indicating the current calculated caloric surplus, which is consuming more calories than the body expends, is no longer sufficient to support further growth. Increasing carbohydrate intake is the optimal first step because carbohydrates are the body's most efficient and preferred energy source for high-intensity exercise, which is essential for stimulating muscle growth. Adequate carbohydrate consumption ensures the replenishment of muscle glycogen stores, which are crucial for workout performance and prevent the body from breaking down protein for energy, a process known as protein sparing. Carbohydrates also trigger a robust insulin response, and insulin is a powerful anabolic hormone that facilitates the uptake of nutrients, including amino acids, into muscle cells, directly supporting muscle repair and synthesis. Practically, adding carbohydrates is often easier to digest and consume in the necessary quantities to achieve a significant caloric boost compared to increasing fats or protein, helping the hardgainer overcome the challenge of consuming sufficient calories. A common practical adjustment involves adding an extra 250 to 500 calories per day, predominantly from carbohydrates, which translates to an additional 60 to 125 grams of carbohydrates.