Can’t Gain Weight? Understand Why & How to Safely Put on Pounds

The problem of wanting to gain weight but being unable to is something many people face. While others might say they are envious, for the individuals themselves, it can be a serious issue affecting health, appearance, and self-confidence. If your weight is below the standard range or you struggle to reach your target weight, understanding the reasons and gaining weight in a healthy manner is important. This article explains the potential reasons why you might be thinking, “I want to gain weight but can’t,” discusses healthy and effective methods for gaining weight through diet and exercise, and suggests consulting with experts.

What are the Reasons for Not Being Able to Gain Weight?

There isn’t just one reason why someone might not gain weight or even lose weight unintentionally. It can be a combination of various factors. Let’s look at some of the main potential reasons.

Due to Body Type or Genetics

Among those who feel they are “naturally thin” or “can’t gain weight no matter how much they eat,” body type and genetics may play a role. Some individuals may have a basal metabolic rate that is naturally higher, meaning they burn more calories even at rest, or there may be individual differences in digestive and absorption capabilities.

The human body uses consumed calories as energy and stores any surplus as fat or muscle. Basal metabolic rate is the energy required to maintain basic life functions at rest, and this is influenced by genetic factors. People with a high basal metabolic rate tend to find it harder to gain weight than those with a lower basal metabolic rate, even when eating the same amount. There are also body types that are genetically predisposed to build muscle slowly or store fat less easily, and these can be factors preventing weight gain.

While body type and genetics aren’t everything, it’s plausible that individuals differ in their energy expenditure efficiency or nutrient metabolism compared to others. However, you don’t have to give up just because of your body type. By understanding your body’s characteristics and adopting appropriate diet and exercise methods, it is possible to gain weight. The key is to know your body’s specific traits and consistently apply an approach tailored to them.

Insufficient Food Intake or Calorie Consumption

One of the most common reasons for not gaining weight is that calorie intake is lower than calorie expenditure. Simply put, to gain weight, you need to consume more calories than your body needs.

It’s difficult to accurately know exactly how many calories you burn in a day, but you can estimate your Total Daily Energy Expenditure (TDEE), which is determined by your basal metabolic rate and activity level. Many people who say “I want to gain weight but can’t” may be burning more calories through daily activities than they realize, or they might not be consuming as many calories as they think they are.

For example, even if you feel like you are “eating a lot,” when you actually record your food intake and calories, you might find your consumption is less than you thought. This is especially common when individuals fill up on vegetables and water, leading to insufficient intake of carbohydrates, fats, and proteins, which are sources of energy. Furthermore, an unbalanced diet or irregular meal times can also prevent you from getting enough necessary calories and nutrients.

To gain weight, you need to consciously consume more calories than usual. Specifically, it is recommended to consume about 300 to 500 kcal more per day than your TDEE. Consuming these extra calories from nutrient-dense foods in a balanced way is key to healthy weight gain.

Excessive Activity Levels or Overtraining

Individuals with very high daily activity levels or those who are dedicated to exercise may also find it difficult to gain weight. This is because they burn a lot of calories through their activities and workouts. Especially if you engage in prolonged and frequent cardiovascular exercises (like running, swimming, or cycling) which consume a lot of energy, much of the calories consumed through meals will be burned off by exercise, making it hard to gain weight.

For instance, people with physically demanding jobs or those who walk long distances for commuting already burn a significant amount of calories without even realizing it. If you add exercise on top of this, you need to consume an enormous amount of calories from food to match the expenditure if your goal is weight gain.

Overtraining not only increases energy expenditure but also heightens the demand for nutrients required for muscle and body recovery. If sufficient nutritional replenishment is not provided, the body can become energy-deficient, potentially leading to muscle breakdown or difficulty recovering from fatigue.

Incorporating exercise is very effective for aiming for weight gain, but you need to consider its purpose and content. If your weight gain goal is to increase muscle mass, focusing on strength training rather than cardiovascular exercise is more efficient. Also, it is important to be mindful of replenishing the calories burned through exercise with proper meals.

Stress and Psychological Factors

Stress and psychological factors can also affect body weight. When you experience severe stress, the balance of the autonomic nervous system can be disrupted, leading to loss of appetite or impaired digestive function. This can result in reduced food intake or difficulty in digesting and absorbing consumed nutrients, making it harder to gain weight.

Furthermore, anxiety and worries can make it difficult to focus on eating or even make eating feel like a chore. Conversely, some people overeat due to stress, but for those who “want to gain weight but can’t,” stress often leads to appetite suppression or decreased digestive function.

Additionally, lack of sleep is another factor that can affect weight. Sleep deprivation disrupts hormone balance, reportedly increasing the hunger-stimulating hormone (ghrelin) and decreasing the appetite-suppressing hormone (leptin). This can make appetite unstable, ultimately hindering the regular meals and nutrient intake needed for healthy weight gain.

Mental and physical health are crucial for weight management. Managing stress and ensuring sufficient sleep can help stabilize appetite and allow the body to utilize nutrients properly. Incorporating relaxation, making time for hobbies, and seeking professional help if needed can also help reduce stress.

Underlying Diseases and Medications

If you are unintentionally losing weight or struggling to gain weight, it’s also necessary to consider the possibility of an underlying disease or the medications you are taking. Several illnesses can cause loss of appetite, indigestion, malabsorption, or hypermetabolism, leading to weight loss or difficulty gaining weight.

For example, the following diseases could be considered:

• Gastrointestinal Diseases: Inflammatory bowel diseases (Crohn’s disease, ulcerative colitis), celiac disease, and chronic pancreatitis can interfere with nutrient absorption.
• Hyperthyroidism: Excessive production of thyroid hormones can lead to abnormally high metabolism and weight loss.
• Diabetes: Weight loss can be observed, especially if it’s poorly controlled.
• Malignancies: Cancer can alter metabolism and cause weight loss.
• Mental Illnesses: Depression and eating disorders (such as anorexia nervosa) can severely affect appetite and eating behavior, leading to weight loss.
• Infectious Diseases: Chronic infections can deplete the body’s energy and cause weight loss.

Also, certain medications can have side effects such as loss of appetite or gastrointestinal discomfort, which can affect body weight.

If you are losing weight unexpectedly or consistently struggling to gain weight without any clear reason, it is crucial to consult a doctor without self-diagnosing. If an underlying disease is found, treating it may resolve the weight problem. Even if no specific disease is found, you can receive medically sound advice on how to gain weight healthily and possibly be referred to a specialist like a registered dietitian.

Healthy Ways to Gain Weight Through Diet

To gain weight healthily, it’s not just about eating a lot; it’s about what foods you eat and how you eat them. Aim to increase muscle mass along with fat.

Calculate Your Calorie Balance

The foundation of healthy weight gain is to create a “positive calorie balance,” where your calorie intake exceeds your calorie expenditure. Start by getting an estimate of your Total Daily Energy Expenditure (TDEE). TDEE is calculated by multiplying your Basal Metabolic Rate (BMR, the energy needed to maintain life at rest) by your activity level. Many online tools are available to calculate your TDEE by entering your age, gender, weight, height, and activity level.

Once you know your TDEE, aim to consume slightly more calories than that number. Generally, it is recommended to add 300 to 500 kcal per day to the calories needed to maintain your current weight. For example, if your TDEE is 2000 kcal, aim for an intake of 2300 to 2500 kcal.

Adding calories too quickly can strain your digestive system or lead to gaining only body fat. It’s better to start conservatively and gradually increase the intake while observing your body’s response. Adjust your calorie intake based on how your weight changes. A gain of about 0.25kg to 0.5kg per week is considered a healthy and sustainable pace.

Calorie counting might feel tedious at first, but recording your meals and calories for even a few days can help you get a sense of how much you are eating and the calorie content of different foods. Using smartphone apps can make recording easier.

Focus on Nutrient-Dense Foods

While increasing calorie intake is important for weight gain, what you choose as your calorie source is crucial. Gaining calories from junk food or sugary drinks can lead to gaining only body fat, lacking essential nutrients, and potentially harming your health. If you’re aiming for healthy weight gain, focus on consuming the three macronutrients (protein, carbohydrates, fat) in a balanced way, primarily from nutrient-dense foods.

• Protein: Essential for building muscle, which is very important for weight gain. Actively consume sources like meat (chicken breast, beef, pork), fish, eggs, dairy products (milk, yogurt, cheese), and soy products (tofu, natto). Ideally, include a protein source with every meal.
• Carbohydrates: The body’s primary energy source. Consume rice, bread (like whole wheat), pasta, udon, soba, potatoes, sweet potatoes, corn, and fruits. Choose complex carbohydrates that are rich in fiber, vitamins, and minerals, such as brown rice or mixed grains instead of white rice, and whole wheat bread instead of white bread.
• Fat: High in energy density, allowing you to consume many calories in a small amount. Healthy fat sources include avocados, nuts, seeds, olive oil, and fish oil (from fatty fish like mackerel and sardines). These fats are also essential for hormone production and cell membrane structure. However, be cautious of excessive intake of foods high in saturated fats and trans fats (fried foods, processed foods, fast food, etc.).

By combining these nutrients in a balanced way, you can consume the necessary calories while ensuring your body gets the essential nutrients it needs.

Recommended Food List for Gaining Weight

Food Category	Recommended Foods	Nutrient Characteristics (Related to Weight Gain)	Tips for Consumption
Carbohydrates	Rice (white, brown, mixed grains), Pasta, Bread (whole wheat)	Energy source. Brown rice and whole wheat are also rich in vitamins, minerals, and fiber.	Eat substantial amounts as a staple food with every meal. Use sauces and toppings for pasta and bread to increase calories.
	Oatmeal	Complex carbohydrate that is filling. Rich in fiber and B vitamins.	Eat with milk, nuts, and dried fruits for breakfast.
	Potatoes, Sweet Potatoes, Corn	Provide carbohydrates plus minerals like Vitamin C and potassium.	As a side dish or part of a main meal. Add butter or cheese for extra calories.
Protein	Chicken (thigh, with skin), Beef (lean cuts), Pork (select cuts)	Good source of quality protein. Parts with skin or red meat tend to be higher in calories.	Incorporate into various dishes. Vary cooking methods to keep it interesting.
	Fish (Mackerel, Saury, Sardines, Salmon, Tuna)	Good source of quality protein, healthy unsaturated fats (DHA, EPA), and Vitamin D.	Grilled, boiled, or as sashimi.
	Eggs	Complete protein source containing essential amino acids in good balance. Also rich in vitamins and minerals.	Boiled eggs, omelets, scrambled eggs, etc., using various cooking methods.
	Dairy products (Milk, Yogurt, Cheese)	Rich in protein and calcium. Full-fat milk, full-fat yogurt, and natural cheeses are also high in calories.	As a beverage, added to dishes, or as a snack.
	Soy products (Tofu, Natto, Edamame)	Plant-based protein source. Also contains fiber and isoflavones.	Easily incorporated into Japanese cuisine.
Fats	Nuts (Almonds, Walnuts, Cashews)	Rich in healthy fats, protein, fiber, Vitamin E, and minerals. High energy density.	As a snack in small amounts. Also as a topping for salads and yogurt.
	Avocado	Rich in healthy monounsaturated fats, fiber, Vitamins K, C, E, folate, and potassium.	Eat as is, make into dips, or add to smoothies.
	Olive oil, Sesame oil, and other vegetable oils	Healthy unsaturated fats. High energy density.	Replace cooking oils with these. Drizzle on salads or dip bread.
	Butter, Ghee	Effective for calorie boosting. Can consume energy in small amounts.	Use in cooking or spread on bread.
Others	Dried Fruits	Concentrated nutrients, easy to consume calories and sugars. Also contain fiber and minerals.	As a snack, with nuts. Mix into yogurt or oatmeal.
	Honey, Maple Syrup	Natural sweeteners with calories. Some contain vitamins and minerals.	Add to drinks, yogurt, pancakes, etc., to increase calories.

Consciously including these foods in your daily meals will help you consume calories and nutrients healthily and efficiently, supporting your weight gain efforts.

Increase Meal Frequency

For those who cannot eat large amounts at once, increasing the frequency of meals is an effective way to consume the necessary calories. By adding 2 to 3 snacks between your three main meals, you can increase your total calorie intake without overeating at any single meal.

The advantage of increasing meal frequency is that it allows you to continuously supply energy and nutrients to your body without putting excessive strain on your stomach at one time. This approach can be particularly beneficial for individuals with smaller appetites or those who feel their digestion and absorption capabilities are not strong, as eating smaller amounts more frequently may be easier on the body and more efficient for nutrient intake.

For example, try scheduling light snacks in the morning, afternoon, and before bed, in addition to breakfast, lunch, and dinner. When doing this, it’s important to choose nutrient-dense foods, not just something to fill your stomach. Snacks like nuts, yogurt, or protein bars, as discussed in later sections, are suitable.

Setting fixed meal times and making them a habit can help you consistently meet your calorie intake goals. Also, enjoying your meal times can stimulate appetite.

Incorporate Healthy Snacks

Snacks taken between meals play a crucial role in your journey to gain weight. By choosing healthy snacks, you can easily supplement necessary calories and nutrients.

Recommended healthy snacks include:

• Nuts: Almonds, walnuts, cashews, etc., are rich in healthy fats, protein, fiber, vitamins, and minerals, and have a high energy density. You can consume a significant amount of calories even in a small portion. Choose unsalted and unsweetened varieties.
• Dried Fruits: Raisins, prunes, apricots, etc., are concentrated sources of sugar, allowing for easy calorie replenishment. They also contain fiber and minerals like potassium. Eating them with nuts is also recommended.
• Yogurt (Full-Fat): Rich in protein and calcium, and contains beneficial bacteria that improve gut health. Choosing full-fat yogurt provides extra calories. Add granola, fruit, or honey to boost its nutritional value further.
• Cheese: Rich in protein and calcium, and fat. Eat it with crackers or by itself.
• Boiled Eggs: A convenient source of high-quality protein. They are also filling.
• Protein Bars / Protein Drinks: Many are available commercially, providing an easy way to consume protein and calories. Check the nutritional information and choose one that suits you.
• Avocado: Versatile, can be eaten plain, made into a dip, or added to smoothies. Rich in healthy fats and nutrients.

By strategically incorporating these snacks between meals, ensuring the intervals aren’t too long, you can increase your total calorie intake without forcing yourself. However, be careful not to fill up on snacks to the point that it reduces your appetite for the next meal. Think of snacks as supplementary to your main meals to make up for what you couldn’t consume during those times.

Utilize High-Calorie Drinks and Smoothies

If consuming large amounts of solid food is difficult, obtaining calories from beverages is an efficient method. High-calorie drinks and smoothies are relatively easy to consume and less likely to cause digestive discomfort.

• Milk: Contains a balanced mix of protein, fat, carbohydrates, and calcium. Full-fat milk, in particular, is higher in calories and serves as a convenient nutrient source.
• Juices: Fruit and vegetable juices provide vitamins and minerals, but commercially available ones can be high in sugar and potentially unbalanced in nutrients. Homemade smoothies are often better as you can control the nutritional content.
• Smoothies: Combine fruits, vegetables, milk or soy milk, yogurt, protein powder, nut butter (peanut butter, almond butter), avocado, chia seeds, flax seeds, etc., to create nutrient-rich, high-calorie smoothies. For example, blending 200ml milk, 1 banana, 1 scoop protein powder, and 1 tablespoon peanut butter can easily create a smoothie with around 500kcal. Combining various ingredients also adds variety to the taste.
• Nutritional Supplement Drinks: Some commercially available nutritional drinks are designed to provide high calories and necessary vitamins and minerals in a small serving. They are convenient when you have a poor appetite or need a quick nutritional boost.

However, be cautious about excessive sugar intake. Especially sugary soft drinks and juices are calorie-dense but lack other nutrients and can cause rapid spikes in blood sugar. Whenever possible, choose smoothies based on milk or soy milk that also provide protein and fat.

Effective Exercise for Weight Gain

If your goal is to gain weight by increasing muscle mass rather than just fat, incorporating appropriate exercise is essential. Especially muscle-building strength training is highly effective.

Strength Training to Increase Muscle Mass

Muscle is denser than fat, and increasing muscle mass directly contributes to weight gain. Furthermore, increased muscle mass slightly boosts your basal metabolic rate, helping you burn calories more easily while building a healthy and toned body. Strength training should be the primary form of exercise when aiming for weight gain.

Strength training involves applying resistance to muscles to cause micro-tears in muscle fibers, which then repair and grow thicker and stronger during the recovery process. To perform effective strength training, several points are important:

• Train the entire body: It’s important to train major muscle groups throughout the body in a balanced manner, not just isolated areas. Compound exercises like squats (lower body), deadlifts (back, lower body), bench press (chest, arms), pull-ups (back, arms), and shoulder press (shouders) are efficient as they work multiple muscles simultaneously.
• Appropriate weight and repetitions: To build muscle, you need to lift a weight that is challenging. A general guideline is to perform 3 to 4 sets of 8 to 12 repetitions with a weight that makes it difficult to complete more. Performing exercises with correct form is most crucial to prevent injuries and maximize effectiveness.
• Sufficient rest: Muscles don’t grow during the workout; they grow during the rest and recovery period after training. Ideally, allow 48 to 72 hours of rest for the same muscle group before training it again. Aim for strength training 3 to 4 times per week.
• Principle of progressive overload: To continuously stimulate muscle growth, you need to gradually increase the load (weight, repetitions, sets, etc.) over time.
• Timing of nutrition: After training, it’s recommended to quickly consume protein and carbohydrates to promote the repair and growth of muscle fibers. Consuming a protein drink or a high-protein meal within 30 minutes to an hour after your workout is ideal.

When starting strength training, learning the correct form is extremely important. If you are at a gym, consider getting guidance from a trainer, or refer to reliable resources such as books, websites, or videos. Start within a manageable range and gradually increase the intensity to ensure consistency.

Minimize Cardiovascular Exercise

If you are aiming to gain weight, especially by increasing muscle mass, it is wise to minimize energy-consuming cardiovascular exercises. Long-distance running, cycling, or swimming can burn a lot of calories, potentially negating the surplus calories you consume through diet and making it harder to gain weight.

However, this doesn’t mean cardiovascular exercise is completely unnecessary. Moderate cardiovascular exercise can improve cardiovascular health, promote blood circulation, and potentially stimulate appetite. It can also help maintain your body’s condition and improve your performance in strength training.

If you want to include cardiovascular exercise without hindering weight gain, pay attention to the following points:

• Frequency and duration: Limit cardiovascular exercise to once or twice a week, for about 20 to 30 minutes per session, at a moderate intensity.
• Timing: Do cardiovascular exercise on separate days from strength training, or if on the same day, do it for a short duration after your strength training session. Using too much energy before strength training can compromise the quality of your workout.
• Type: Choose relatively low-intensity activities like walking or light jogging.

It’s crucial to be mindful of replenishing the calories burned through cardiovascular exercise with subsequent meals. If weight gain is your top priority, reducing the emphasis on cardiovascular exercise and focusing on strength training and adequate nutrition is a more efficient approach.

Consulting an Expert if You Still Can’t Gain Weight

If you have tried the diet and exercise methods mentioned above but are still struggling to gain weight, or if you are unintentionally losing weight, it is highly recommended to consult an expert rather than dealing with it alone. To rule out the possibility of an underlying disease, visiting a medical institution first is important.

Cases That Require Consultation with a Doctor

Consult a doctor (e.g., an internist) as soon as possible in the following cases:

• Unintentional and continuous weight loss: If your weight continues to decrease despite increasing food intake, or if you experience rapid weight loss, it could be a sign of an underlying disease.
• Symptoms like loss of appetite, chronic fatigue, indigestion, abdominal pain, or diarrhea: These could indicate gastrointestinal issues or malabsorption.
• Unexplained symptoms such as fever or night sweats: This could be a sign of infection or other illnesses.
• Having a history of illness or currently being treated for a specific condition: Existing illnesses or medications can potentially affect your weight.
• A family history of illnesses related to being underweight: Genetic factors or familial diseases might need to be considered.
• Persistent severe stress or psychological distress: Since mental and physical health can impact weight, consider consulting a psychiatrist or psychosomatic specialist.

A doctor will conduct interviews, physical examinations, and if necessary, blood tests or imaging studies to identify the root cause of why you’re not gaining weight. If an illness is found, treating that illness will be prioritized. Even if no specific illness is found, you can receive medically sound advice on how to gain weight healthily and may be referred to a specialist like a registered dietitian.

Utilizing Advice from Dietitians and Experts

Even if a doctor’s examination finds no specific illness, if you are struggling with weight gain, consulting a nutrition professional, especially a Registered Dietitian, is very effective. Registered Dietitians can provide specific and practical nutrition guidance tailored to your body type, lifestyle, food preferences, and goals.

Consulting a Registered Dietitian can offer the following benefits:

• Creation of a personalized nutrition plan: They can help you create a realistic meal plan that fits your lifestyle. You’ll receive specific advice on what foods to eat, how much, and when.
• Review of calorie intake and nutritional balance: They can assess if your current calorie and nutrient intake is appropriate and guide you on how to improve it.
• Advice on specific recipes and food choices: They can suggest easy-to-prepare, nutrient-dense recipes and recommend foods that are readily available at grocery stores.
• Guidance on incorporating snacks and supplements: You can get specific advice on choosing healthy snacks, appropriate timing, and portion sizes.
• Advice regarding supplements: If necessary, they can provide professional advice on which nutritional supplements (like protein powder, vitamins, minerals, etc.) might be beneficial, including dosage and timing.
• Maintaining motivation: Regularly talking with an expert can help you stay motivated towards achieving your goal.

Registered Dietitians possess knowledge based on scientific evidence and can provide guidance and support for safe and effective weight gain without being misled by unreliable information online. In some cases, consultations may be covered by health insurance or available for free through company health consultation services, so it’s worth checking.

Tips for Sustaining Healthy Weight Gain

Weight gain is a long-term goal, not a short-term one, and requires continuous effort. Even after reaching your target weight, it’s important to build habits for maintaining a healthy weight.

• Set Realistic Goals: Rapid weight gain puts a strain on your body. Aim for a gradual increase of about 0.25kg to 0.5kg per week, or 1kg to 2kg per month, proceeding at a pace that is sustainable.
• Keep Records: Recording your meals, calorie intake, weight changes, and exercise can help you track your progress. This helps you analyze what is effective and what isn’t and adjust your plan accordingly.
• Don’t Rush Results: The rate of weight gain varies depending on body type and lifestyle. Don’t get discouraged if results don’t appear immediately; approach it from a long-term perspective.
• Enjoy the Process: Having a positive attitude towards trying new foods and exercises can help with consistency. Try different recipes or various types of exercise.
• Sufficient Sleep and Rest: Adequate sleep and rest are essential for the body to recover and grow. Make an effort to get quality sleep.
• Manage Stress: Stress can negatively affect appetite and digestion. Find stress relief methods that work for you and maintain a healthy state of mind and body.
• Seek Understanding and Cooperation from Others: If possible, inform family or close friends about your goal and seek their understanding and cooperation, which can make the process easier.
• Regular Consultation with Experts: If needed, continue regular consultations with a doctor or registered dietitian to receive proper guidance and aim for healthy and sustainable weight gain.

Conclusion

“I want to gain weight but can’t” can be due to a complex interplay of various factors, including body type, food intake, activity level, stress, and underlying diseases. To gain weight healthily, it is crucial to first understand the root cause.

Instead of just eating more, effective strategies include focusing on a balanced diet with nutrient-dense foods, increasing meal frequency, incorporating healthy snacks and high-calorie drinks/smoothies. Also, adjust your exercise routine to include strength training to build muscle mass while minimizing energy-consuming cardiovascular exercise.

If you try these methods and still struggle to gain weight, or if you are unintentionally losing weight, consult a doctor promptly to rule out the possibility of an underlying disease. If you need expert nutritional advice, consulting a registered dietitian can provide you with a personalized meal plan and guidance tailored to your needs.

Healthy weight gain is not achieved overnight. Setting realistic goals, approaching it methodically through both diet and exercise, and maintaining consistency are key. Don’t rush the process, enjoy the changes in your body, and aim for a healthy physique.

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Disclaimer: This article is for informational purposes only and is not intended as medical diagnosis or treatment. If you have concerns about your weight or any health issues, please consult a medical professional for guidance and advice. We are not responsible for any decisions or actions you take based on the information in this article.

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