Several conditions and medications can make it difficult to gain weight. If you’re not sure why you aren’t gaining weight, talk with a healthcare professional to determine the underlying cause.

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From fad diets to fitness plans, weight loss is a commonly discussed topic in the health and wellness world. However, there are plenty of people out there who struggle to gain weight.

Whether it’s due to genetics or an underlying medical condition, gaining weight and maintaining a healthy weight can be a difficult task for some people.

In this article, we’ll discuss some potential reasons why you may have difficulty gaining weight and what you can do it about it.

Genetics play a role in body types and may dictate a naturally lean body type for some people.

For others, underlying medical conditions and certain medical treatments may cause weight loss or difficulty gaining weight. These include the following conditions.


An overactive thyroid, or hyperthyroidism, causes an excess of thyroid hormone in the body. Thyroid hormone is responsible for many elements of human metabolism, including regulation of metabolic rate.

People with hyperthyroidism have an overactive metabolism and often burn more calories throughout the day. Without the proper medication, hyperthyroidism can cause trouble gaining weight, even when food intake is increased.

Type 1 diabetes

Type 1 diabetes is a type of autoimmune condition in which the body destroys the cells in the pancreas that are responsible for the production of insulin.

Insulin is the hormone responsible for the metabolism of glucose. When type 1 diabetes goes unmanaged, it causes high levels of blood glucose, which is then excreted in the urine. This excess glucose excretion can lead to unintentional weight loss.

Inflammatory bowel disease

Inflammatory bowel disease (IBD) is a blanket term for a series of conditions characterized by inflammation of the intestines. These conditions, such as Crohn’s disease and ulcerative colitis, can have negative impacts on someone’s ability to maintain weight.

These conditions may limit the types and amounts of food that a person can eat. They may also cause frequent diarrhea, which can cause weight loss in some cases.

Eating disorders

While there are many different types of disordered eating conditions, people with eating disorders that limit food intake may have trouble maintaining a healthy weight.

In its most extreme form, anorexia nervosa causes extreme weight loss and sometimes the inability to gain weight entirely. Other conditions, such as bulimia, can make it hard for a person to keep enough calories down to maintain weight.

Medications and treatments

Certain medications and treatments that cause appetite loss, nausea, vomiting, and diarrhea can make it difficult to maintain a healthy weight.

For example, medications like antibiotics and treatments like chemotherapy are commonly known for causing gastrointestinal side effects.

Generally, people who require these types of treatments may experience weight loss and have difficulty gaining weight throughout treatment.

Outside of having an underlying medical condition, the truth is that it’s more difficult for some people to gain weight than others.

If you’re having trouble gaining weight, there are certain lifestyle changes you can make to give yourself the best chance of increasing your body weight in a healthy manner.

Build more muscle

Both cardio and weight training are important for overall health, but weight training is an absolute must when you want to build more muscle.

Since muscle weighs more than fat, weight training can help you increase your overall weight without just increasing your overall body fat.

Eat frequent meals

Eating meals more frequently can allow you to consume more calories throughout the day — especially if you’re someone who doesn’t enjoy huge meals.

Breaking bigger meals into smaller, more frequent meals can allow you to eat more calories without having to uncomfortably stack your plate or fill your stomach.

Enjoy high calorie foods

Meals high in whole grains and healthy fats tend to have more calories than meals consisting of lower calorie foods, such as lean proteins and vegetables.

Start each meal with at least a cup of grains, and try to incorporate various fats, such as oils, nuts, or other condiments. Finally, finish with some lean protein and at least a few servings of vegetables.

Use more condiments

Condiments, especially those that are high in fat, can add at least a few hundred calories to any meal.

For example, light drizzling oils and mayonnaise-based sauces can help bulk up a sandwich, wrap, or even a salad.

Try shakes and supplements

If you’re still struggling to meet your daily calorie goals, protein shakes and supplements can help add extra calories to your daily intake.

Meal replacement shakes tend to be higher in calories and are aimed at maintaining weight for people who can’t consume regular food. Also, some protein shakes are formulated specifically for building body mass.

Don’t fill up on water

For a lot of people, drinking water before a meal can help them avoid overeating — but this trick can backfire if you’re trying to gain weight.

It’s still important to drink water frequently throughout the day, but if you’re having trouble eating meals because of fullness, avoid drinking too much water before you sit down to your meal.

Body mass index (BMI) is a health screening tool that’s frequently used to determine someone’s overall body composition. BMI estimates the amount of one’s body fat based on their height and weight.

According to the Centers for Disease Control and Prevention (CDC), you’re considered underweight if your BMI falls below 18.5. Below, you’ll find a full BMI chart for what health professionals consider underweight, normal weight, overweight, and obese for adults.

BMIWeight status
18.5 or belowUnderweight
30.0 or aboveObese

It’s important to note that there are many factors that influence overall health, and BMI should not be used as a definitive measure of someone’s health. Even if you’re “underweight” according to the BMI chart, that doesn’t necessarily mean that you’re “unhealthy.”

However, if you’re underweight and having trouble gaining weight, it may be time to reach out to your doctor.

For the most part, minor weight fluctuations are normal. However, if you’ve noticed unexplained weight loss that’s not the result of intentional lifestyle or dietary changes, you should schedule an appointment with a doctor.

A doctor can review your health history and perform the appropriate testing to determine if an underlying condition is causing changes in your weight.

If there are no underlying conditions causing your weight loss or difficulties gaining weight, a doctor can refer you out to a dietitian or nutritionist. These trained nutrition professionals can help create a well-rounded diet plan to help you gain weight in a healthy way.

Healthy weight gain generally involves choosing a good balance of healthy high-calorie foods and building muscle through weight training. For many people, making these simple changes is enough to start seeing increases in weight and BMI.

Remember, if you’ve been having trouble gaining weight or keeping on weight, even after making changes to your diet, schedule a visit with a doctor. They can help you determine if any underlying conditions are present and refer you to a nutritionist, if needed.