What are the main reasons why some people don't gain weight? + Effective ways for underweight individuals to gain weight

Tuesday, March 04, 2025  Read time7 min

How can skinny people gain weight? Does their inability to gain weight have a specific cause? Maybe you are dealing with the issue of eating food but not gaining weight! There are many reasons why some people don't gain weight, and in this article from Saadnews, we will explore these causes.

What are the main reasons why some people don't gain weight? + Effective ways for underweight individuals to gain weight

While most people around the world are facing obesity problems, there are some individuals who try to gain weight but fail for various reasons. If you are one of those people and always ask yourself, "Why can't I gain weight?", keep reading this article.

Why is being underweight harmful to health?

Just like obesity, being underweight can also negatively impact health. The most important consequences of being underweight include:

Osteoporosis

Dry skin

Hair loss

Weakened immune system and increased risk of diseases such as colds

Fatigue

Anemia

Menstrual disorders and increased risk of infertility

Growth disorders in children and adolescents

How do we know if we are underweight?

There are many indicators used to identify underweight individuals, but the BMI (Body Mass Index) is one of the most reliable. If your BMI is below 18.5, it means you are underweight and should consider this condition as a health issue and seek treatment. To calculate your BMI, you can use an online BMI calculator.

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Why can't I gain weight?

If you're underweight and want to reach a healthy weight, you should know that being underweight, just like being overweight, could result from poor eating habits or some illnesses that threaten your health. If you always wonder why you can't gain weight, here are some possible causes:

A proper weight gain diet is important, but not all exercises are helpful. For example, muscle-building exercises can be beneficial.

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Fear of adding fat: Many of us want to gain weight without adding fat to our bodies. Gaining weight with this mindset is impossible. The right way is to accept the fat gain initially and then think about converting that fat into muscle once you reach your goal.

Incorrect exercise routine: Exercise is important alongside a proper weight gain diet, but not every type of exercise is suitable. Muscle-building exercises can help us gain weight.

Lack of consistency in eating habits: No method will work unless it's followed consistently. If you follow a diet for a few days and then ignore it, don’t expect any results.

Wrong beliefs about gaining weight: One of the barriers to gaining weight is our belief system. We believe that because family members are slim, we too will remain slim.

Losing hope for weight gain: We expect to see results the day after starting a diet! Constantly checking the scale without knowing that it takes at least a month to see results can lead to discouragement. These actions often lead to despair, and we may say, "I will never gain weight, I will live skinny forever."

Family history: Some individuals, due to genetic factors and family traits, are naturally slim and struggle to gain weight.

Lifestyle factors: You might ask yourself, "Why can't I gain weight?" but fail to notice that you may not be consuming enough calories during the day. Skipping meals or not eating sufficient, appropriate food can prevent you from gaining weight. Additionally, if you exercise but don't eat enough to compensate for the calories burned, you won’t gain weight.

High metabolism: If you have a fast metabolism, your weight may not increase significantly even if you eat calorie-rich foods.

Excessive physical activity: Athletes or individuals who engage in a lot of physical activity tend to burn a significant amount of calories. This, especially when combined with insufficient food intake, can lead to weight loss and make gaining weight harder.

Suffering from various diseases: The following conditions can affect your weight and cause weight loss:

Hyperthyroidism: In this condition, the levels of thyroid hormones increase, which regulate metabolism. This leads to a higher metabolism and more calories burned throughout the day. If untreated, even increased food intake will not lead to weight gain.

Type 1 diabetes: This autoimmune condition attacks the pancreas cells responsible for producing insulin, leading to low insulin and high blood sugar levels. If uncontrolled, excess sugar is excreted in urine, leading to unintended weight loss.

Inflammatory bowel disease (IBD): IBD, which includes conditions like ulcerative colitis and Crohn’s disease, causes inflammation in the intestines and negatively affects weight. Patients often reduce their food intake due to diarrhea and other gastrointestinal issues, leading to weight loss.

Psychological conditions: Mental health issues such as depression, anxiety, obsessive-compulsive disorder, and anorexia nervosa can affect appetite and eating habits.

Use of certain medications: Some medications can reduce appetite, cause nausea, vomiting, or diarrhea, leading to weight loss. For example, digestive issues are common side effects of antibiotics and chemotherapy, making it difficult for those undergoing such treatments to gain weight.

What are the ways to gain weight?

Unlike most people who are trying to lose weight, some of us are concerned with gaining weight. Just as losing weight can be difficult, some people face challenges with weight gain. If the question "Why can't I gain weight?" concerns you and you want to gain weight, here are some tips:

Increase your calorie intake

The most important thing for gaining weight is that the calories you consume must exceed the calories you burn throughout the day. To gain weight, you need to consume at least 300-500 extra calories daily. Since many underweight individuals suffer from lack of appetite, it's better to focus on calorie-dense foods. Here are some foods rich in calories relative to their weight:

Nuts: Almonds, walnuts, pistachios, and peanuts

Dried fruits: Raisins, dried berries, and dates

Fats: Extra virgin olive oil, olives, and avocado

Whole grains: Oats

Meats: Chicken, beef, or lamb

Starchy vegetables: Potatoes and corn

Dark chocolate

Since many of these foods are filling, you might have to push yourself to eat them. Avoid eating large quantities of vegetables as they can reduce appetite. Eating fresh fruits, particularly those like bananas, which require less chewing, can be a good option.

Ensure sufficient protein intake

Protein is the most important nutrient for weight gain. Since muscles are made of protein, if you increase your calorie intake but don't consume enough protein, much of the additional calories will turn into fat. Studies show that a high-protein diet helps convert many of the extra calories into muscle. However, protein can act as a double-edged sword because it's quite filling and can reduce appetite. If you want to gain weight, aim for 1.5 to 2.2 grams of protein per kilogram of body weight. Sources of protein include red meat, fish, chicken, eggs, dairy, and legumes.

Ensure adequate intake of carbohydrates and fats

If you're wondering why you can’t gain weight, you should avoid restricting your carbohydrates and fat intake because doing so will make it difficult to consume enough calories. If you want to gain weight, ensure that each meal contains enough protein, fat, and carbohydrates. Healthy fats can be found in nuts, olives, avocado, and plant oils, while the best sources of carbohydrates include bread, rice, pasta, legumes, fruits, and dairy products.

Increase the number of meals

Many underweight individuals have a small appetite and get full quickly. It's better to increase the number of meals you eat and reduce the size of each meal. If you're facing this issue, you could have three main meals and 2-3 snacks throughout the day.

Lift weights

To ensure the extra calories you consume are turned into muscle rather than fat, you need to engage in weightlifting exercises. Go to the gym and work out 2-4 times a week. Start with lighter weights and gradually increase them. If you're new to exercising and not in optimal physical condition, it's best to work with a trainer. If you have any medical conditions, consult a doctor before starting any workout regimen.

Important Tips for Weight Gain:

Use smoothies and milkshakes: Don't fill your stomach with unhealthy drinks like soda. Instead, drink smoothies or milkshakes made from healthy ingredients like dairy and fruits.

Avoid drinking water before meals: Water can fill your stomach, making it harder to consume enough calories.

Drink milk: Drink milk when you're thirsty to increase your protein and calorie intake.

Use large plates: Using larger plates for meals can help you consume more food.

Add cream to your coffee: This simple step can easily increase your calorie intake.

Get enough sleep: Adequate sleep helps with muscle growth and recovery.

Eat protein first, then vegetables: When you have a combination of foods on your plate, eat high-calorie, high-protein foods first and save vegetables for later.

Don’t smoke: Smoking tends to decrease weight, and quitting smoking can lead to weight gain.

When should you see a doctor?

If you are trying to gain weight but aren’t succeeding, it's important to consult a doctor. Also, if you experience unintended weight loss without changing your diet, it's crucial to consult a doctor. The doctor will review your health history and conduct tests to determine the underlying cause of the issue. If no specific medical conditions are found, the doctor may refer you to a nutritionist to help you gain weight through a healthy diet.

So, if you've ever wondered why you can't gain weight, know that there are various reasons for this issue. Sometimes an unhealthy lifestyle, genetics, a high metabolism, and excessive exercise lead to weight loss, but diseases can also affect weight and make gaining weight challenging. If you've lost weight unintentionally or find it difficult to gain weight, consult a doctor to identify the root cause. Understanding the underlying issue can help you address it effectively. I hope you enjoyed this article, and for those who want to reach their ideal body, feel free to share it. You can also visit Saadnews’ Sports World section for more informative content. Thank you for your time.