Why Am I Gaining Weight? Common Causes & Prevention Tips

By Craig Sorkin, DNP, APN
Medically reviewed checkmarkMedically reviewed
January 17, 2023

If you’re one of the six million Americans who are considered medically underweight, learning how to gain healthy weight can boost your immune system, increase your fertility, and lead to a better self-image.

If you experience sudden or unexplained weight gain, it can feel like a difficult challenge to overcome. An estimated 74% of American adults are considered overweight or medically obese, and nearly 50% of Americans reported trying to lose weight over a 12-month period between 2013-2016.

Causes of Weight Gain

Individuals gain weight for a variety of reasons. Sometimes added pounds can be directly attributable to changes in diet and exercise, but other times, it may be harder to identify a single cause. Genetics can play a role in whether someone gains weight, as well as their environment, daily stress, and socioeconomic status. Let’s look at some common causes of weight gain in detail.


Stress is a part of daily life, but consistently high levels of stress can lead to weight gain and obesity. When you are stressed, your pituitary gland releases a hormone called cortisol. While cortisol has many benefits—including lowering inflammation and regulating blood sugar—high levels of cortisol can cause increased appetite and sugar cravings. So if you feel constantly stressed, you might find yourself eating more sugary and fatty foods because of cortisol, which could result in weight gain.


Medication can also contribute to individuals gaining weight. For certain patients, taking diabetes medication, blood pressure medicines, hormonal birth control pills, or antidepressants like Cymbalta®, Prozac®, ZOLOFT®, and Lexapro®, weight gain can be a short-term or perennial challenge.

Health conditions

Certain health conditions can cause weight gain, including:

  • Breast cancer: Between 50%-96% of people gain weight during breast cancer treatment.
  • Depression: This can both negatively impact your ability to care for yourself and lead to hormonal changes that can lead to weight gain.
  • Sleep apnea: This condition disrupts your sleep, which can, in turn, affect how your body responds to exercise. It also negatively affects your leptin levels, which is a hormone that helps your body manage weight. 
  • Diabetes: Both type 1 and type 2 diabetes commonly result in weight gain because of your body’s inability to produce or manage insulin.
  • Chronic fatigue: That could suggest a problem with your thyroid, which can affect your metabolism and lead to weight gain.
  • Arthritis: Pain in your joints might make it more difficult for you to exercise.


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Lack of sleep

Multiple studies have shown a correlation between getting 5-6 hours of sleep or less at night and gaining weight. This could be due, in part, to an increase in eating during awake hours, but more data is needed.

Quitting smoking

Most people who quit smoking will gain between 4 and 10 pounds. This happens for a few different reasons. First, nicotine suppresses appetite. So without nicotine, your appetite may increase, causing you to eat more food and gain weight. Second, nicotine also speeds up your metabolism. Without nicotine, your metabolism may slow down, causing weight gain. 

Hormonal changes

Unusual menstrual pain can indicate changes in your ovaries and hormone cycle that can cause weight gain.

Similarly, hormonal fluctuations during menopause can also affect weight gain and weight distribution. The decrease in estrogen during menopause is associated with an increase in body fat and abdominal fat.

Fluid retention

Fluid retention can be the source of minor weight fluctuations. Your weight fluctuates by a few pounds every day, in part because of the food and water that you consume. In addition, people with periods may notice fluid retention, or bloating, on certain days of their menstrual cycle. However, their weight should return to its typical range a few days after their cycle begins.

Other forms of fluid retention, like edema, can result in more noticeable weight gain. Edema is a swelling in your feet, ankles, legs, or other parts of your body as a result of excess fluid in your tissues. This extra fluid can cause you to gain weight. Edema can be the result of eating too much salt, but it can also signify more serious underlying issues. If you notice unusual swelling, you should contact your healthcare provider.


Weight gain during pregnancy is very common and normal. Most people pregnant with one baby should gain approximately 30 pounds over the course of their pregnancy. In general, the first trimester has the least amount of weight gain, whereas the second and third trimesters have the most weight gain. However, much of your weight gain is related to the baby, and is not an accumulation of fat. Along with the added weight of the baby, the following also affect your weight during pregnancy:

  • Placenta
  • Amniotic fluid
  • Breast tissue
  • Blood supply
  • Fat stores
  • Uterus growth

If you find that you are unexpectedly, suddenly, or rapidly gaining weight, and are having trouble identifying why, call your doctor to discuss whether you should make an appointment to be tested for an underlying medical condition.

Preventing Weight Gain

If you are interested in maintaining your current body weight or preventing future gains, you can eat healthy, nutritious foods and engage in daily physical activity.

Choose a varied, balanced diet of unprocessed foods that nourish your body and give you energy. Every individual has different dietary needs, but a generally healthy diet includes a variety of vegetables and fruits; proteins like fish, chicken and eggs; carbohydrates like whole grains; and healthy fats found in olive oil, avocados, and certain fish. If you have questions about the kinds of foods you should be eating, talk to your doctor about what they recommend.

Staying fit is another important part of maintaining a healthy weight. Regular, daily physical activity can combat the shifts in metabolism that lead to weight gains in men and women as they age.

Although the amount of exercise that people require is ultimately individual to their body and circumstance, research suggests that individuals who engage in at least 30 minutes of moderate to intense physical activity five days a week have an easier time maintaining their weight. They also reduce their risk of osteoporosis, type 2 diabetes, high blood pressure, heart attack, stroke, and several forms of cancer.

Risk Factors and Complications

While the percentage of overweight and obese adults is rising across the U.S., certain people are more at risk for gaining unwanted weight than others. Those populations include those with:

  • Genetic predispositions toward obesity
  • No access to healthy, whole, unprocessed foods
  • Overeating habits or food addictions
  • Inactive or sedentary lifestyles
  • A lot of stress
  • Restrictive or “yo-yo” dieting
  • Undiagnosed medical conditions
  • Certain medications, including treatments for diabetes, psychiatric illnesses, epilepsy, high blood pressure, birth control, and asthma

There are a number of health risks associated with being overweight. People who are overweight or obese can develop heart disease, diabetes, kidney disease, fatty liver disease, sleep apnea, and stroke.

Being overweight can put you at greater risk for developing certain cancers, and if you are a person who is pregnant, being overweight can adversely affect the health and wellbeing of both you and your unborn child.

For some people, rapid weight gain causes physical discomfort like abdominal pain, bloating, and swelling in the hands and feet.

If you are gaining weight more rapidly than usual and are experiencing any physical discomfort, or have a fever, changes in vision, skin sensitivity, heart palpitations or difficulty breathing, call your doctor right away; these symptoms may be a sign that you have an underlying condition that requires medical attention.

Treating Unintentional Weight Gain

There are a number of steps you can take to shed unwanted weight in a healthy, sustainable way.

  • Cut back on sugar: Reduce your sugar intake to create a positive effect on your body, sleep patterns, and energy levels.
  • Eat whole, unprocessed foods: Make sure you are ingesting protein, vegetables, and healthy fats every day.
  • Check your portion sizes: Practice portion control to ensure you are eating an appropriate amount of food every day.
  • Engage in a physical activity that you enjoy for at least 30 minutes a day: If you can have fun while moving your body, it will make you more likely to exercise more often over the long term.
  • Eat a protein-rich breakfast: Begin your day with the right foods to help yourself cut back on the calories you consume over the rest of the day.
  • Add more steps to your daily routine: Aim for 10,000 steps a day. If that feels intimidating, start slow and build towards it by adding 500 new steps every few days.
  • Find time for self care: Manage stress with healthy coping techniques in order to cut down on the adverse impacts it has on your health and weight.

Before you begin any new diet or fitness routine, it’s important to talk to your doctor to make sure it will meet your needs and fit your goals.

Receiving a Diagnosis

Your health care provider will complete a full evaluation to determine the underlying cause of your weight gain. They will ask when you started to notice the weight gain, what else changed in your life at the same time, and whether you have any other symptoms. It’s important to provide them with as much detail as possible. They will also ask about:

  • Your medical history
  • Medication use
  • Changes in appetite
  • Sleep patterns
  • Other lifestyle factors

They may also conduct a physical exam or order additional tests, like a blood test, to check for underlying causes.


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When to See a Doctor

If you are suddenly or rapidly gaining weight, are gaining an unusually large amount of weight, or can’t explain why you are gaining weight, you should call your doctor to schedule an appointment.

If you are gaining weight and experience any physical discomfort associated with those gains, including abdominal pain or bloating, fluid retention, fever, sweating, heart palpitations, difficulty breathing, or skin sensitivity, your symptoms may indicate an underlying health condition that requires medical attention. Call your doctor to see if making an appointment is right for you.

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K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Craig Sorkin, DNP, APN

Craig Sorkin, DNP, APN is a board certified Family Nurse Practitioner with over 15 years experience. He received his Undergraduate and Graduate degrees from William Paterson University and his doctoral degree from Drexel University. He has spent his career working in the Emergency Room and Primary Care. The last 6 years of his career have been dedicated to the field of digital medicine. He has created departments geared towards this specialized practice as well as written blogs and a book about the topic.