Making lifestyle changes can help you get fit and gain weight, even if you have a naturally slim physique. Your diet can provide energy and nutrients needed to keep you going through tough workouts, while a well-designed workout plan can trigger progressive muscle growth, so you'll fill out your frame with lean mass. Getting in shape can take weeks, months or years, though, so create a weight gain plan you'll be able to sustain long term.
Get the Calories Needed for Weight Gain
At its heart, weight gain is simple; you just need to eat more calories than you burn, and you'll gain weight storing the excess energy. Even "junk" foods like burgers and fries will lead to weight gain if they make you create a calorie surplus.
If you want to lose weight healthily and make sure a significant portion of your weight gain comes from muscle, you'll need to plan more carefully. Start by calculating your current energy needs -- how many calories you eat to maintain your weight -- using an online calculator. For example, a 24-year-old man, who is 6 feet tall, weighs 150 pounds, and is active for an hour a day needs about 3,020 calories to maintain weight.
To gain weight, you should add 250 to 500 calories to your daily intake. So the 24-year-old man would need 3,270 to 3,520 calories each day to gain 0.5 or 1 pound each week, respectively.
Figure out a calorie surplus you'd like to start with, and then adjust as needed to get 0.5 to 1 pound of weight gain weekly. For example, if you're a "hard gainer" and have trouble putting on weight, you should start with a 500-calorie surplus -- and possibly add to it as you continue gaining weight. If you typically put on weight somewhat easily, try a 250-calorie surplus.
Gain Weight With Carbs, Protein and Fat
Any food in excess can trigger weight gain, but, if you want to look fit and healthy once you reach your goal weight, you'll need to follow a nutritious diet. That means getting energy-boosting carbs from healthy sources, like beans, whole-grain rice, whole-wheat pasta and bread and potatoes or sweet potatoes. You'll also need healthy sources of fat, such as avocado, olive oil, fatty fish, flaxseed and nuts. Flax and fatty fish can be especially important, since they supply omega-3 fatty acids that your body not only can't make on its own, but actually relies on for health benefits, such as lower inflammation.
Gaining lean mass requires making protein an essential part of your diet. You need a surplus of amino acids -- the compounds that make up protein -- to build muscle tissue, so you'll need plentiful protein in your diet to provide them. To get your target protein intake in grams, multiply your weight -- in pounds -- by 0.8. For the 24-year-old man who weighs 150 pounds, that equals 120 grams of protein every day. Eat chicken, turkey, eggs and egg whites, nonfat dairy, nuts, seeds and beans to get your recommended daily intake.
Round out your diet with healthy veggies. While these don't typically supply many calories, they're packed with minerals and vitamins you need for good health, which will support your fitness journey.
Boost Your Calories, Easily
Gaining weight -- especially if you don't put on weight easily -- might mean eating more food than you're comfortable with just to meet your daily calorie target. Instead of trying to gorge on three massive meals each day, try three slightly smaller meals plus two to three snacks to spread your calorie intake over a longer period of time. Add healthy fats to your meal to boost calories; garnish your salads or soups with a spoonful of olive oil, add coconut oil to your smoothies and toss vegetables in oil before grilling to increase their calorie content. Load up on nuts and nut butters, which contain a high energy density -- a single 2-tablespoon serving of peanut butter will add 188 calories to a slice of toast. And take in liquid calories, whether it's from protein shakes, 100 percent juice or milk. Liquid calories don't make you feel satisfied like calories from solid food, so you can drink more calories without feeling overly full.
Get in Shape With Exercise
Exercise is an essential part of your weight gain diet; you can't expect to look fit if you don't work out, and without exercise you're likely to just gain fat, not muscle. Resistance train two to three times each week on non-consecutive days. Strength training temporarily damages your muscle fibers, and, during your rest days, your body rebuilds the muscle so it's slightly bigger and stronger than before. Use weights that feel challenging to perform large, compound exercises: lower-body push exercises like squats and lunges; lower-body pull exercises like deadlifts; upper-body push exercises like pushups and bench presses; upper-body pull exercises like pullups and rows; and abdominal exercises like planks and wood chops.
Don't forego cardio entirely when you're trying to gain weight, but don't spend endless hours on the treadmill, either. Each week, perform two to three moderate-intensity cardio sessions that are 20 to 30 minutes each.