Why Am I Gaining Weight? Common Causes & Prevention Tips

By Chris Bodle, MD
Medically reviewed checkmarkMedically reviewed
March 25, 2020

Contrary to diet advertisements, gaining weight isn’t always a bad thing. Some weight fluctuations are normal. Much of the weight you gain and lose on a daily basis, for instance, is the result of the calories you eat and water that you drink over the course of the day.

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.

For adults who have issues staying lean, weight gain, particularly sudden or unexplained weight gain, can feel like a difficult challenge to overcome. If you’re frustrated by a change in your weight, you are not alone: An estimated 71% 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.

What Is a Healthy Weight?

An individual has a healthy body weight when they weigh an appropriate amount for their height. To determine whether an individual weighs an appropriate amount, doctors will calculate an estimate of their body fat called their body mass index (BMI).

Although relying on BMI metrics is both useful and popular, it has some limitations: BMI can overestimate body fat in individuals with more muscular builds, like athletes, and may underestimate body fat in older individuals who have lost musculature due to aging.

Individuals are considered overweight when they weigh more than is considered appropriate for their height. If you have a BMI of 25 to 29.9 and have a high percentage of body fat to muscle, you can be at risk for weight-related conditions like heart disease, diabetes, hypertension, gout, and asthma.

Individuals who are underweight, or weigh less than is considered appropriate, may suffer from malnutrition, osteoporosis, and poor immune function.

If an individual has a BMI of 30 or above, they are considered medically obese, and if they have a BMI of 40 or above, they are considered extremely obese. Generally speaking, the higher the BMI, the higher the risk for developing weight-related health conditions.

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When to Worry About Weight Gain

Some weight gain and loss over the course of the day is natural and appropriate. If your weight is changing and you can directly attribute those gains to lifestyle developments like an altered exercise routine or a poor diet, it may not be cause for concern.

If, on the other hand, you are experiencing sudden or rapid weight gain and can’t explain why, it’s time to call your doctor. Sudden weight gain can indicate a medical condition or issue with a current medication that requires medical attention.

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, 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.

If you are inexplicably, suddenly, or rapidly gaining weight, it can be helpful to look at other aspects of your life for any abnormalities that might help explain the changes your body is experiencing. If you are gaining weight and find yourself:

  • Eating lots of sweets: That could indicate that your body may no longer be managing insulin as it once did.
  • Feeling chronically fatigued: That could suggest a problem with your thyroid, which can affect your metabolism and lead to weight gain.
  • Feeling sad or “blue”: You might be experiencing depression, which can both negatively impact your ability to care for yourself and lead to hormonal changes that can lead to weight gain.
  • Having trouble breathing at night: That could indicate sleep apnea, a condition that disrupts your sleep, which can in turn affect how your body responds to exercise.
  • Feel sore or stiff in your joints: That might suggest that arthritis is making it more difficult for you to exercise.
  • Experiencing abdominal pain, constipation, or other GI issues: Stomach pains can indicate a variety of conditions that affect how you digest and process food.
  • Have periods that are irregular or painful: Unusual menstrual pain can indicate changes in your ovaries and hormone cycle that can cause 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.

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 every day 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, among others

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 woman 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.

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Losing Weight

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 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.

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.

How K Health Can Help

Did you know you can get affordable primary care with the K Health app? Download K to check your symptoms, explore conditions and treatments, and if needed text with a doctor in minutes. K Health’s AI-powered app is HIPAA compliant and based on 20 years of clinical data.

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.

Chris Bodle, MD

Dr. Bodle is a board certified emergency medicine physician. He received his medical degree from Indiana University School of Medicine, and completed his residency in emergency medicine at Emory University. In addition to K Health, he currently works as an Emergency Medicine physician in an Urban, Level 1 Trauma Center in the south east.

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