You might hear more about the dangers of weighing too much than weighing too little, but being underweight can affect your health. A very low body weight can mean it takes longer to recover from an illness, and, if you're a woman, being extra slim might also affect your reproductive health. Gaining weight healthfully means taking it slow -- you won't be able to avoid gaining any fat at all, but slower weight gain minimizes how much fat you'll put on. Healthy lifestyle modifications will help you gain lean mass, as well as boost your overall well-being.
Take Your Weight Gain Slow
The key to gaining weight without putting on much fat is to prepare for slow, steady progress -- not overnight results. Generally, you should try to gain only a half-pound per week, which you'll achieve if you eat an extra 250 calories per day, beyond the number of calories you need to maintain your weight. That means even a minor weight gain will likely take months, and you should expect to put on, at most, about 25 pounds a year.
While slow weight gain doesn't deliver fast results that keep you motivated, it allows your body time to build muscle, so that most of your new weight comes from lean mass instead of fat. If you try to gain weight quickly, such as a pound a week or more, you'll put on mostly fat tissue, and won't get the results you want.
Plan Your Diet Around Protein
When you're trying to gain lean mass, you may need to boost your protein intake. The strength training required to gain mass also increases your protein requirements, from 0.4 grams per pound of body weight for sedentary people to 0.8 for strength trainers who are looking to bulk up. Meet your protein needs by enjoying fatty fish, lean beef, skinless, white-meat poultry, eggs and dairy, as well as plant-based sources of protein like soy, beans and lentils, quinoa, nuts and seeds.
Don't forget about other nutrients too, though -- the healthy carbs found in vegetables, fruit and grains help keep your muscles powered up and energized, so you can get more results from each workout. Fats help you absorb essential nutrients, and they're also a great source of energy during your workouts. Eat foods high in the healthy fats, such as seeds, nuts, fatty fish and avocado, and use healthy oils -- like coconut oil, olive oil and flaxseed oil -- in recipes to boost your fat intake.
Avoid Fat Gain With Strength Training
Focus on strength training to gain weight without adding too much fat. Strength training, combined with a healthy diet, will stimulate new muscle growth, which ensures that a significant part of your weight gain will come from healthy lean mass. Strength training has other health benefits -- it's good for your bones, improves your posture, and strength training moves that get your heart pumping are good for your cardiovascular system, too.
Schedule two or three strength-training sessions into your weekly plan, allowing 48 hours between each workout so your muscles have enough time to recover. You'll get the best results -- especially as a newbie -- by making each strength session a full-body workout that includes a few exercises for your lower body, upper body and core. As you become more advanced -- and add more exercises to your routine -- you can split your strength-training sessions into upper body and lower body days.
Complement your strength training with a small amount of cardio to burn fat, or build fat-burning exercises into your strength training routines. Try a weight training circuit that includes exercises that get your heart pumping -- like jumping jacks, mountain climbers or kettlebell swings -- to burn more fat. Check with your doctor before beginning your exercise regimen, to make sure what you're planning is safe for your fitness level and health.
Manage Stress and Sleep
Gaining weight healthfully isn't just about diet and exercise -- you should consider other aspects of your lifestyle too. Stress management and healthy sleep hygiene help control your body's cortisol level, which is key for maintaining your health, especially as you gain weight. Abnormal cortisol levels can send a signal for your body to start burning protein for energy, which can make it harder to gain lean mass. Cortisol also redistributes your fat, taking fat molecules from the relatively harmless fat under your skin to the disease-causing visceral fat deep in your abdomen. Since weight gain involves gaining at least some fat, as well as muscle, you want to control your cortisol levels and make sure you're not gaining visceral fat, since this type of fat increases your risk of heart disease.
Make sure you're getting enough sleep -- between 7 to 9 hours each night, depending on your individual needs -- to help regulate your cortisol levels. Spend a few minutes each day on stress-relieving activities, whether you relax with some meditation when you get home from work or do a few yoga poses before you go to sleep.