There's an old saying that you can never be too rich or too thin. But the reality is that being underweight is unhealthy and it can never hurt to add some lean muscle mass to your frame. To bulk up, you'll need to make changes to your routine. Adding more calories to your diet and hitting the gym regularly is a good way to add lean muscle mass to your body.
Create a 500 to 1,000 calorie surplus each day. A calorie surplus is when you consume more calories than you burn from exercise and throughout the day. According to dietitian Nancy Clarke, eating an extra 500 calories per day should add up to about a pound of gain per week. But some people may need to consume more to achieve this result.
Add foods to your diet that get most of their calories from carbohydrates. Although you may need a bit of extra protein, carbs provide your muscles with the energy they need to do muscle-building workout, according to Clark.
Eat five or six times per day. According to the University of Texas at Austin's University Health Services website, you can increase your calorie intake by eating three or four meals a day with snacks in between. The majority of your calories should come from your meals, and the remainder should come from snacks spread throughout the day. This will help you to eat more, making it easier to create a calorie surplus.
Perform resistance training two or three days per week to build muscle mass. Aim to do six to eight exercises from each major muscle group, doing at least one set per exercise. You can do exercises using free weights, weight machines, resistance bands or even body-weight exercises like pullups and pushups. For the first four to six weeks of training you should choose a weight that lets you do 12 to 15 reps per exercise with only minimal fatigue. After four to six weeks increase the weight so you become fatigued at eight to 12 reps.