How to gain weight fast for women: Safe, healthy, and effective strategies

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Is your weight too low? Understanding BMI and what it means

A Body Mass Index (BMI) below 18.5 is classified as underweight. You can calculate your BMI using an online tool like the CDC's BMI calculator. For example, if you're 5'7" and weigh 99 pounds, your BMI would be approximately 15.5 — which is significantly below the healthy range and may require medical attention.

For women, a BMI between 18.5 and 24.9 is generally considered healthy. Here’s how BMI categories break down:

• Underweight: Less than 18.5

• Healthy weight: 18.5 to 24.9

• Overweight: 25 to 29.9

• Obese: 30 and above

That said, it’s important to understand that BMI doesn’t reflect differences in body composition, like muscle mass versus fat, and isn’t a perfect indicator for everyone.

Let’s take two examples using the same height: 5'7" (170 cm).

If a woman weighs 121 pounds (55 kg), her BMI would be around 19.0 — which falls within the healthy range.

If she weighs 99 pounds (45 kg), her BMI drops to about 15.5 — indicating underweight status.

In this case, gaining weight would likely be recommended to support energy levels, hormonal balance, and overall health. Chronic low weight can lead to nutrient deficiencies, fatigue, reproductive issues, and a weakened immune system — and should be addressed with the support of a healthcare provider.

What causes underweight and why is it dangerous?

Being underweight poses serious health risks:

• Weakened immunity: The body lacks the resources needed to combat infections and viruses, leading to more severe illnesses and a higher risk of complications.

• Poor skin, nail, and hair health: Skin may look dull or dry, nails can become brittle, hair may thin or shed more than usual, and even dental health can decline.

• Reduced sexual health and fertility: Low body weight can disrupt the menstrual cycle, decrease sexual desire (libido), and may even lead to infertility.

• Bone and joint issues: Bones lose strength, and joints become less flexible.

• Mental health risks: In severe cases, being underweight can contribute to depression and other mental health challenges.

The most typical reasons for being underweight

Eating disorders

When calorie expenditure consistently exceeds intake, the body enters a calorie deficit and begins to lose weight. This can become especially harmful for young women who follow restrictive diets or misuse appetite suppressants and laxatives in an effort to lose weight. In many cases, the weight they’re trying to lose isn’t actually “excess” — but rather a result of distorted body image or unrealistic appearance standards. This disconnect can increase the risk of developing disordered eating patterns, including anorexia nervosa.

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Digestive disorders

Diabetes, gluten intolerance, enzyme deficiency, and gastrointestinal disorders are all conditions that prevent the body from absorbing nutrients.

Other reasons

Even if the body receives and absorbs all necessary nutrients, they may not reach the tissues if something else is using up these resources — like parasites (such as tapeworms). Other, less harmful factors, like overly intense training, can also cause this issue. In such cases, simply reducing physical activity can help.

More serious underlying causes to be aware of include:

• Parasitic infections — Certain parasites can interfere with nutrient absorption, leading to unintended weight loss.

• Hyperthyroidism — An overactive thyroid speeds up metabolism, increasing energy demands and potentially causing weight loss.

• Tumors — Some tumors consume large amounts of energy, which may result in unintentional weight loss.

• Chronic or acute infections — The body may divert energy toward fighting infection, leading to decreased appetite and weight loss.

If you haven’t changed your diet or lifestyle and notice a sudden, unexplained weight loss of 6 to 11 pounds (3 to 5 kilograms) over a short period of time, it’s important to consult a healthcare provider — even if you feel fine. Early evaluation can help identify and address any underlying health concerns.

Nutritional correction

Focus on nutrient-dense meals — think salmon with quinoa and avocado, or full-fat Greek yogurt with granola and berries. Avoid relying on fast food for calories, as it may increase body fat without supporting muscle growth or overall health.

Proper nutrition

Nutritionists recommend a macronutrient ratio of proteins, fats, carbohydrates — 25/30/45. If the goal is to gain muscle mass, the balance may be adjusted in favor of proteins, and the amount of carbohydrates could be reduced — 30/30/40.

• The diet should include: eggs, meat, fish, tofu, cheese, cottage cheese, legumes — these are all sources of protein.

• Add healthy fats — fatty fish with Omega 3, avocado, extra virgin olive oil, ghee, nuts.

• Among carbohydrates, preference is definitely for complex carbohydrates: whole grain bread, steel-cut oats, pasta from durum wheat, and vegetables.

Calorie counting is the key to gaining weight 

To gain weight, you need to consistently consume more calories than your body burns. Your exact daily calorie needs depend on factors like age, sex, body composition, activity level, and metabolism. To get a personalized estimate, you can use an online calorie calculator or consult a registered dietitian.

If your goal is to gain weight quickly, consider increasing your intake by about 700 to 1,000 calories per day above your maintenance level. For a more gradual and sustainable approach, a daily surplus of 200 to 300 calories is typically effective.

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Diet

If you're underweight, you may be eating too little or too infrequently. To gain weight, you’ll need to eat more often and rethink portion sizes.

Nutritionists recommend eating 5 to 6 times a day — either three main meals and two to three snacks, or four smaller meals and two snacks. Larger plates can make portions feel less overwhelming. To boost calories without increasing volume, add cream to your coffee, toss nuts into salads, or choose whole milk over water.

Drink fluids between meals rather than before, so they don’t reduce your appetite.

Looking for healthy recipes? Don’t miss our helpful collection — simple, tasty, and good for you! 💚

What exercises to choose

Strength training is key when trying to gain weight in the form of lean muscle — not just body fat. Focus on basic compound movements that engage multiple muscle groups and promote functional strength.

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Push-ups: Start with wall or knee push-ups and gradually progress to full-body versions. Keep your body in a straight line, engage your core, and lower yourself with control. Push back up on the exhale.

Pull-ups: Begin with assisted or reverse-grip pull-ups, which are often easier due to biceps engagement. Can’t do a full pull-up yet? Try inverted rows (also known as Australian pull-ups) using a low bar to build upper body strength.

Squats: Stand with your feet hip-width apart and lower your body until your thighs are parallel to the floor. Keep your back straight, core tight, and drive through your heels to return to standing.

For best results, aim to train 2–3 times per week and allow time for muscle recovery between sessions.

How often should you work out to gain weight

It depends on the intensity and structure of your workouts. If you're doing light bodyweight exercises with 10–12 reps per move, daily sessions are fine. But if you're doing multiple sets (like 3 sets of 12–15 reps), two to three strength workouts per week are ideal. Recovery days are essential — muscles grow and rebuild when you rest.

How to structure your workout

Start with a 5–10 minute warm-up to get your blood flowing. Then move into resistance training using your body weight — such as push-ups, squats, pull-ups, and lunges. You can gradually add resistance with dumbbells or resistance bands. End your session with static stretching to help with flexibility and recovery.

Why protein and carbs matter when gaining weight

Protein helps build and repair muscle, while carbohydrates provide the energy your body needs to train and function. Both are essential for healthy weight gain.

How much protein do you need?

Most adults need about 0.8 grams of protein per kilogram of body weight (around 0.36 grams per pound). If you're active or strength training, your needs may increase to 1.2–2.0 grams per kilogram.

Where to get protein

Animal-based foods like meat, poultry, fish, eggs, and dairy are rich in complete proteins — meaning they contain all nine essential amino acids your body can't produce on its own. Plant-based options like legumes, tofu, and quinoa also provide protein, though vegetarians and vegans may need to combine sources to meet their needs.

Table of foods with the highest protein content

While protein is essential for muscle growth, it's important not to overdo it. Consistently consuming excessive amounts of protein can place stress on the kidneys and may lead to side effects like dehydration, headaches, and electrolyte imbalances — especially if your fluid intake is low. For most people, staying within recommended ranges and focusing on high-quality sources is both safe and effective.

Choosing the right carbs for healthy weight gain

Carbohydrates are your body’s primary energy source — and they’re especially important when increasing your calorie intake. A general recommendation for weight gain is around 4 to 5 grams of carbohydrates per kilogram of body weight per day. Focus on complex carbohydrates, which are digested slowly and help provide steady energy over time, rather than being quickly stored as fat.

Complex carbs include dietary fiber, resistant starch, and glycogen from whole food sources.

Nutritional supplements

If you’re not getting enough protein from food alone, supplements can help fill the gap. The sports nutrition market offers a wide range of options — including protein powders, amino acid blends, and BCAAs (branched-chain amino acids).

Which supplement should you choose?

Look for products with minimal ingredients — ideally free of added sugars and artificial additives. Protein shakes are a convenient choice, delivering high-quality protein in a quick, easily digestible form. Choose a type that suits your needs and diet: whey (fast-absorbing), casein (slow-release), or plant-based (vegan-friendly).

If you're not working out and your diet already provides enough protein, extra supplementation likely isn’t necessary.

About motivation

Willpower alone can be difficult to sustain, especially when building new habits. That’s why setting clear, personal goals and visualizing how your life could improve with a healthier weight can be so powerful. Think about the strength, confidence, and energy you’ll gain — and how that might open new doors for you.

Having the support of family and friends can make a big difference. Encouragement from loved ones helps you stay focused and confident. But what if your support system isn't there? That’s tough — but it can also be empowering.

Psychologists often point out that internal motivation is more sustainable than external validation. So instead of depending on others’ opinions, focus on your own reasons and long-term vision. Building that confidence from within helps create the resilience needed for real, lasting change.

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Wishing you success on your journey — and remember, movement matters.

Regular exercise doesn’t just shape your body — it supports your energy, confidence, and overall well-being. 

✅ Eat well. Train regularly. Stay consistent. You’ve got this.
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