What Can Cause Rapid Weight Gain?

It is common for people to experience weight fluctuations and gain weight over time. If there is rapid weight gain in a short period of time, however, it could signify the presence of an underlying health condition.

In situations where weight gain is unrelated to an underlying health condition, some of the most common causes include the following:

  • Anxiety, depression, or stress
  • Female menstrual cycle
  • Inadequate sleep
  • Increased intake of calories
  • Menopause and perimenopause
  • Reduced physical activity
  • Retention of water from excess salt or dehydration
  • Slower metabolism from the natural aging process

It is important for patients who experience unexpected and rapid weight gain to follow up with their doctor. The following article will review common causes for rapid weight gain.


Some types of medications can result in rapid weight gain. In some cases, a side effect of certain medicines is that the patient will gain several pounds a month. Some medications which are known to cause rapid weight gain include drugs which are used to treat the following:

  • Depression and psychiatric disorders
  • Diabetes mellitus
  • High blood pressure
  • Seizures

If patients are considering no longer taking a medication, it is critical to first discuss this with their doctor.


Research demonstrates that is an association of lack of sleep and weight gain. In addition, when there are changes in the patient’s sleep cycles, it can impact their eating patterns and overall mood. This often results in overeating. A study conducted in 2013 found that sleep-deprived people specifically ate more carbohydrates than needed in order to have increased energy. The study’s participants also consumed more calories, particularly following dinner.


When some people cease smoking tobacco, they experience weight gain. Some experts suggest that this is from nicotine suppressing the appetite. In addition, withdrawal symptoms often include stress, which can result in overeating.

Polycystic Ovary Syndrome

Patients who have polycystic ovary syndrome (PCOS) often find that they are especially prone to gaining weight around their middle section. With PCOS, the ovaries produce abnormally high amounts of male sex hormones. Some of the other most common symptoms related to PCOS include:

  • Acne
  • Discolored skin and dark patches near the armpits, breasts, or neck
  • Excess hair on the patient’s back, chest, or abdomen
  • Hair thinning or loss
  • Irregular menstrual cycles

While there is no known cure for PCOS, doctors will often suggest lifestyle changes in order to manage the condition. This can include exercising more and eating a more balanced diet, which can help reduce severe symptoms. In some cases, hormonal medications are used to help control the symptoms.

Heart Failure

When a patient experiences rapid weight gain or swelling in specific areas of the body, it may be from fluid retention and a sign of heart failure. Based on information from the American Heart Association, gaining more than 2–3 pounds over 24 hours or 5 pounds in a week may suggest the presence of heart failure.

It is important to note that the weight of a patient will typically fluctuate by a few pounds throughout the day. If the weight eventually returns to normal, and there are no additional symptoms, the weight increase could be from normal bloating or retaining fluids. When the blood is flowing slowly to and from the heart, it can impact how other major organs in the body function. This can allow fluid to collect in the tissues, resulting in rapid swelling and weight gain.

What Diseases Can Cause Weight Gain?