How to Gain Weight for Skinny Girls With a Fast Metabolism

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While your fuller-figured friends may think your fast metabolism is a blessing, it doesn't feel that way to you. You'd love to wear a mini and a fitted top without feeling self-conscious about your petite waist or thigh gap, but you haven't discovered the trick to putting on pounds. Don't give up though, because if you're willing to make some simple dietary and lifestyle changes, you can gain weight little by little until you're happy with your body size. If you're really struggling to gain weight, consider consulting your doctor to rule out any underlying medical issues.

Strength training can help slender women build muscle.
Image Credit: dima_sidelnikov/iStock/Getty Images

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Is "Skinny" Unhealthy?

Your desire to gain weight is a wise one, but not only for fashion reasons. A body size small enough to be classifed as "underweight" can affect your health, increasing your risk for infections, osteoporosis and anemia. Your hormones may be affected as well, leading to absence of your menstrual period. Putting on weight -- some fat and some muscle -- can help you look and feel better and be healthier.

If you're on the slender side, but aren't sure if you're actually underweight from a medical standpoint, calculate your body mass index, or BMI. To calculate your BMI, all you need is your height and weight, which you can plug into an online BMI calculator, or use this equation:

BMI = weight / (height in inches x height in inches) x 703.

So a girl who's 5 feet, 7 inches tall and weighs 115 pounds would calculate her BMI like this:

BMI = 115 / (67 x 67) x 703 = 18.0.

A BMI value under 18.5 indicates an underweight status, so this young woman is classified as underweight. She'd only need to gain about 4 pounds to put her in the healthy BMI range, which is between 18.5 and 24.9.

Gain Weight Slowly With a Fast Metabolism

It's best to have realistic expectations for weight gain. A young woman who's always been thin probably has a genetic component to her fast metabolism, and may even have family members who are on the lean side. If you fit into that category, you'll probably gain weight a little more slowly than you'd like. But if you consistently eat 250 to 500 more calories a day than you burn, a slow and steady gain of 1/2 to 1 pound a week is doable.

You can take a scientific approach by counting the calories in the extra foods you eat. There are online sites where you can look up the calorie content of foods, such as Or you can learn which healthy foods tend to be high in calories -- like peanut butter or avocado -- and plan your meals and snacks around those types of foods, without worrying too much about your calorie count.

Ditch the Junk Food

Speaking of calories, junk foods are usually loaded with them. It's easy to hit the drive-thru for french fries and a sweet tea, or maybe a cheeseburger and a milkshake to get the calories you need for weight gain. There's no doubt you can put on weight eating fast food and processed junk foods, but it's not the healthiest way to go. Fries, soda and prepackaged treats may amp up your calories, but those calories come mostly from sugar and questionable sources of fat, with chemical additives and sodium thrown in -- but few healthful nutrients.

Popular candy bars have 200-plus calories, mostly from sugar and fat – including hydrogenated oils, which means they contain some harmful trans fat. What makes up the 200 calories in a 16-ounce cola? You guessed it: sugar. The fizzy water also has some additives, like caramel color and sodium benzoate.

Even for a thin gal with a fast metabolism, eating processed foods is unhealthy. An occasional splurge is fine, but over time, a habit of noshing on sweets and greasy fast food in hopes of upping your weight may lead to health problems such as heart disease and cancer.

Fill Your Pantry With Calorie-Dense Foods

One reason junk foods are bad for you is because they're processed, so it follows that eating whole and natural foods is healthier. Fortunately, lots of minimally processed foods are high in calories and full of nutrients your body needs for weight gain and good health.

Protein foods include meat, poultry, fish, eggs and soy. For balanced nutrition -- and to make sure you gain some muscle, not just fat -- eat some protein at every meal. Higher-calorie protein choices include ground beef, dark meat poultry and fatty fish, such as salmon. For vegetarian-friendly options, reach for beans, lentils, soy, nuts and seeds.

Gram for gram, fats contain more than double the calories of protein and carbohydrates, which makes them "calorie-dense." That's why healthy fats are your best friend when it comes to gaining weight. Using olive oil, coconut oil, avocado, olives, nuts, nut butters and seeds as "add-ins" to your meals and snacks provides a calorie boost in a tiny volume of food. For instance, a tablespoon of olive oil has 120 calories and half an avocado has 160 calories. Any chance you get, mix healthy fats into recipes while you're cooking, or add them to your food at the table.

While fats pack in the most calories, other food groups have higher- and lower-calorie options. It's a good idea to learn which choices are more calorie-dense, and eat those more often.

Dried fruits are a concentrated source of calories, while bananas, pineapples and mangoes pack a heftier calorie punch than other fresh fruits. For vegetables, leafy greens are on the low end calorie-wise, while starchy veggies top the list -- include potatoes, sweet potatoes, corn, peas, dried beans and legumes in your diet for weight gain.

Higher-calorie healthy grain choices include quinoa, brown rice and barley, as well as pasta and whole-wheat bread. Full-fat dairy products such as cheese, whole milk and yogurt are calorie-laden choices too. Stock your pantry with a variety of calorie-dense, nutrient-rich foods like these to ensure you have healthy weight-gain foods within arm's reach.

Go for Three and Three

To leave your "skinny girl" label behind, eat as often as possible to get in enough calories each day. A plan with three meals and three snacks works well, and means you'll eat about every three hours throughout the day.

Good calorie-dense snacks include cheese and crackers, fruit with peanut butter or a trail mix made of nuts, seeds, dried fruit and dark chocolate chips. If you have a favorite treat, like oatmeal cookies or strawberry ice cream, it's OK to work those in once in a while.

Choosing caloric drinks, such as milk or 100 percent fruit juice, helps boost your calories. If your appetite is small, try not to fill up on beverages at mealtime; instead, drink some calories with your snacks. Smoothies make great weight-gain snacks because you can sneak high-calorie ingredients and protein into them. For instance, you might blend whole milk, dry milk powder, avocado, mango and honey for a nourishing bedtime beverage.

Dress Up Your Usual Faves to Add Calories

A meal plan for gaining weight can include all of your favorite foods. The trick is to use your arsenal of calorie-dense add-ins to dress up the dishes. That way you're eating a similar volume of food – but with more calories.

At breakfast, power up your plain cereal flakes with raisins or a sliced banana, or replace it with granola doused in whole milk. If you prefer a bowl of hot oatmeal, cook it in whole milk instead of water and add a pat of butter, a spoonful of chopped pecans and a drizzle of honey. The milk and mix-ins give you an extra 300 calories. In place of over-easy eggs, whip up a calorie-and-protein-rich frittata with 2 or 3 eggs, whole milk, shredded potatoes and chopped bell pepper cooked in coconut oil and topped with shredded cheddar. Have half a cinnamon raisin deli bagel on the side and you'll munch 100 more calories than what's in a slice of toast.

For lunch and dinner, choose entrees with protein and carbs, and add calories with add-ins. For example, drizzle extra olive oil over your shrimp stir-fry or into your sauce for spaghetti and meatballs. Blend powdered milk into chicken casseroles, beef stew, meatloaf and creamed soups or sprinkle grated cheese over chili or fajitas.

Change up your side dishes to pack in more calories. Instead of a raw spinach salad, saute several cups of fresh spinach in olive oil, and toss in slivered almonds and dried cranberries. If you normally mix cucumber chunks and grape tomatoes into your pasta salad, add in black olives and cheese cubes, then sprinkle with sunflower seeds. Make your own dressing with olive oil, vinegar and herbs; if you prefer it creamy, blend in a dollop of sour cream.

Lift Weights and Do Light Cardio

It may seem counterintuitive, but exercise can help you achieve your weight-gain goals. Even though it burns calories, light cardio -- like walking on a treadmill or taking a dance class -- can help stimulate your appetite. Just keep it short at first, maybe 20 minutes a few days a week, and increase it as you gain endurance.

If you feel like you're dragging most days, take it slow as you gain weight and get your energy back. In fact, it's a good idea to get your doctor's OK before beginning an exercise program if you've had any kind of medical condition that contributed to your low weight.

Strength-training is an essential part of gaining weight, because it helps ensure you gain lean muscle mass along with body fat. Start out by lifting hand weights or using exercise bands to help you build muscle strength. The American College of Sports Medicine suggests starting with two or three sessions a week, with a day off in between to rest. Begin with two sets of eight to 12 repetitions for each exercise. As you feel stronger, add exercises for all your major muscles, including your arms, shoulders, back, abdomen, buttocks and legs.

If you're not ready for full-fledged strength training yet, work in some exercises for flexibility, balance and core strength -- such as stretching and yoga – to help you tone up and feel more fit. You many want to consult a fitness professional who can design an exercise plan tailored to your weight-gain goals.

Over time, your enhanced nutrition and exercise plan will pay off as you fill out and feel healthier -- and your "skinny girl" days will be in the past.

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