Even though health gurus and infomercials often push products that promise overnight success, healthy weight gain takes time. That's especially true if you're a woman trying to gain weight, since you don't have the testosterone levels to add lots of lean mass to your frame in a relatively short time. Trying for quick weight gain likely means you'll be padding your frame with excess fat, which could push you to an unhealthy body fat level and increase your risk of disease. Instead, take your time with weight gain; while it will take longer to reach your goal, you're more likely to be satisfied with your physique when you do.
Set Realistic Goals for Weight Gain
Staying healthy as you gain weight requires adding lean muscle to your frame, not just fat. And to gain a healthy ratio of lean mass to fat, you'll need to take your weight loss slow instead of severely overeating and hoping for quick results. Even if you're brand new to exercise -- and will therefore get rapid "newbie gains" compared to someone who's already muscular -- you'll still only add about 3/4 to 1 pound a month of muscle, writes sports medicine expert Leigh Peele on her website.
Aim to gain half a pound each week, which you can achieve by consuming an extra 250 calories a day. For example, if you need 1,500 calories each day to maintain your weight, boost your intake to 1,750 calories daily to gain a half-pound weekly. Estimate your current calorie needs using an online calculator, add 250 to that number, and make a rough weight gain schedule based on your goal weight. For example, if you'd like to gain 20 pounds, plan to stick to your weight gain schedule for 9 to 10 months to achieve your goal.
Increase Your Protein Intake for Muscle Gain
Following a healthy diet can maximize your muscle growth, so you'll look shapely and toned as you gain weight. You'll need to eat slightly more protein to gain weight -- between 0.73 and 0.82 grams of protein for each pound of body weight, compared to just 0.36 grams per pound for a sedentary person. For example, a 125-pound woman trying to gain weight should eat 91 to 103 grams of protein each day, while a sedentary woman at that same weight would need just 45 grams.
Up your protein intake by starting your day with an omelet, tofu scramble or Greek yogurt parfait. Serve grilled salmon or chicken breast at lunch and dinner, and work other sources of protein -- like quinoa, almonds, turkey breast, beans and lentils -- into your meal plan. You can also boost your protein intake with supplements such as whey, but they aren't necessary for weight gain, as long as you're eating enough protein-rich foods.
Pump Iron to Gain Weight
While many women shy away from the weight room -- less than one in five women meet the CDC-recommended aerobic and strength training guidelines, reports Boston University -- lifting weights will help you gain weight healthfully. Adding a few pounds of muscle to your frame boosts your metabolism and gives you a shapely, athletic frame. Use a combination of planks, crunches, push-ups, tricep extensions, rows and lat pulldowns to tone the muscles in your arms, shoulders, back and abs, and strengthen your lower body with lunges, step ups, squats and deadlifts.
Don't feel like you have to stick to light "girly" weights; once you've picked up the proper technique, add enough weight that the last couple reps in your set feel very challenging. Lifting heavy weights won't make you bulky, but it will make you look fit and healthy.
Support Weight Gain with a Post-Workout Snack
Optimize your recovery after each workout with a snack. A good post-workout meal not only supplies calories, which count toward your total daily calorie intake goals, but also contains protein and carbs you'll need to repair and refuel your muscles. Try drinking a whey or casein protein shake after your workout. Studies have shown these foods increase protein synthesis -- the process your body uses to repair muscle tissue -- in men and women after a workout, reports a literature review published in the Journal of the International Society of Sports Nutrition in 2012.
If you'd prefer not to buy supplements such as whey powder, regular foods and beverages from the grocery store work well for post-workout snacks, too. Another study, outlined in the literature review, reported that women who drank fat-free milk after their workout gained more lean mass and increased their strength more than women who drank a beverage that only contained carbohydrates.