Whether you're a vegetarian, vegan or flexitarian, the basics of weight gain stay the same -- you need to consume more calories than you burn to put on weight. While a plant-based diet won't get in the way of weight loss, it might take some careful consideration and planning to get the protein you need for muscle growth, as well as healthy fats that can speed post-workout recovery. But by following a higher-calorie, well-rounded diet -- paired with a weightlifting program designed to trigger muscle growth -- you can achieve your weight gain goals.
Weight Gain Basics: Increasing Calorie Intake
The most important aspect of any weight gain diet is creating a calorie surplus. That means you're getting more calories than you need for your day-to-day activities, so your body has the extra energy it needs to grow new muscle tissue.
Exactly how much you should eat on your weight gain diet depends on how many calories you need to maintain weight; use an online calculator to figure that out, based on your activity level, age, height and weight and body size. Then add between 250 and 500 calories to get your new calorie target for weight gain.
For example, a 37-year-old woman who is 5 feet, 6 inches tall, weighs 150 pounds and lives a moderately active lifestyle needs around 2,450 calories to maintain weight. To gain, she could eat 2,700 calories and gain a half-pound a week or eat 2,950 calories daily to gain 1 pound weekly. Don't try to gain more than a pound a week, or you'll just put on too much fat.
Eat More Vegetarian-Friendly Protein
Gaining weight -- especially in the form of healthy lean mass, including muscle -- requires eating a higher-protein diet than you might be used to. Calculate your protein needs by multiplying your weight by 0.8 -- that's how many grams of protein you should aim for. Include pulses in your diet as rich sources of plant-based proteins -- a cup of lentils or chickpeas, for example, supplies 18 and 15 grams of protein per cup, respectively. A cup of tempeh offers 31 grams of protein per cup, while a 2-tablespoon serving of peanut butter or a cup of quinoa offer 8 grams of protein each.
Get your protein from a range of plant-based sources to get the amino acids you need for weight gain, since most plant-based proteins -- with the exception of soy and quinoa -- are short in at least one amino acid you need from your diet. Pair grains -- like whole-wheat bread -- with legumes or seeds, serve nuts with legumes and pair corn and legumes to get the amino acids you need.
You can also get some protein from vegetarian animal-derived sources, which are "complete" proteins with all the amino acids needed for muscle growth. A cup of milk boosts your protein intake by 8 grams, while a large egg supplies 6 grams. Greek yogurt, cottage cheese and low-fat cheese also contain high-quality protein.
Promote Muscle Recovery With Healthy Fats
Focus on omega-3 fatty acids to help you reach your fitness goals. While your body can make several types of fatty acids -- and use them for fuel -- omega-3 fatty acids need to come from your diet. Getting enough omega-3s helps suppress inflammation after your workouts, which might reduce muscle soreness you'd otherwise experience after a tough workout, according to a literature review published in the Journal of Sports Science & Medicine in 2011. Including these healthy fats in your diet can help you recover after a workout, so you're ready to take on another tough weightlifting session at the gym.
Vegetarians should pay special attention to their omega-3 fatty acid intake, because the type of omega-3 found in plant-based foods -- called alpha-linolenic acid, or ALA -- has to get converted to more active forms before your body can use it. Because that conversion isn't very efficient, you might need more omega-3 fatty acids than someone who gets omega-3s from meats, like fatty fish. Include lots of flaxseeds, walnuts and chia in your diet, and use flaxseed oil to make a salad dressing rich in omega-3 fatty acids.
A Day on a Vegetarian Weight Gain Diet
Gaining weight likely doesn't require a huge change from your daily diet; you can easily make up the extra 250 to 500 calories you need to serving larger portions or eating an extra snack or two throughout the day.
Start with a high-protein tofu scramble or egg omelet, served with a small chia pudding -- chia mixed with almond milk, until it forms a gel -- on the side. Stay energized by eating an ounce of almonds mid-morning as a snack, and serve a black bean and corn salad with your favorite veggies in a whole-grain pita for lunch. Enjoy a small post-workout smoothie -- made from almond milk, frozen fruit, a tablespoon or two of ground flaxseed and either Greek yogurt or soft silken tofu. Then finish your day with dinner made from grilled tempeh paired with quinoa pilaf and a cup or two or roasted vegetables and a side salad topped with homemade flax oil vinaigrette.
The portion sizes you eat depend on your daily calorie intake, so you can scale the size of your meals up or down to suit your preferences. If you still need extra calories, serve your meals with a cup of soy milk or dairy milk, or enjoy a double-serving of tofu or tempeh at breakfast and dinner, respectively.