Without diving into sports nutrition science, three things matter when you're starting out.First, eat at maintenance or slightly above if you're trying to build muscle, slightly below if you want to lose fat. No insane surplus, no extreme deficit. In the first few months, the body responds well even at maintenance, you can build muscle while losing a bit of fat (recomposition).Second, protein. Aim for 0.7 to 1 gram of protein per pound of body weight per day. At 155 pounds, that's roughly 110 to 155 grams. Spread across 3 to 4 meals, it's doable without juggling: eggs at breakfast, beans or meat at lunch, yogurt as a snack, fish or chicken at dinner.Third, hydration and overall quality. Water throughout the day, fruits and vegetables, carbs around your training, quality fats (olive, avocado, nuts). No miracle diet, no forbidden food. Consistency over weeks beats perfection over three days.To dial in the numbers for your profile, you can calculate your macros. If your goal is to put on weight, the muscle gain guide lays out the full strategy. If you want to lean down while keeping muscle, check the weight loss guide.