13 Reasons Why You’re Suddenly Gaining Weight

by Rakib Sarwar, RPh on May 13, 2024
Last updated on May 13, 2024

Gaining weight out of the blue can surprise you quicker than a cheetah sprinting! It matters a lot since it might signal your body’s sending out SOS signals about your health.

person standing on white digital bathroom scale

For most people, weight gain often comes with side effects such as depression due to dissatisfaction with one’s body, lack of confidence, and eating disorders (1).

Fortunately, the cause of sudden weight gain can sometimes be easily detected. This also means that it can be successfully controlled by suppressing or eliminating the harmful factors that cause it.

In this article, you can read more about the top 13 reasons why rapid weight gain occurs and how to successfully control this problem.

Symptoms of Sudden Weight Gain

Depending on the cause, symptoms of sudden weight gain may vary from person to person. They are usually associated with abdominal discomfort or flatulence, and can also be presented in the form of weight gain, especially in the abdominal region but also in other parts of the body.

Although sudden weight gain is sometimes a symptom of many diseases, you may also notice the following signs related to sudden weight gain that is telling you that there is something wrong:

  • fever
  • skin sensitivity
  • difficult breathing,
  • swollen legs,
  • cardiac palpitations,
  • increased sweating,
  • fatigue, and exhaustion.

If these symptoms accompany sudden weight gain, they can indicate serious health problems. Many different health conditions and disorders can cause weight gain. We will talk about the most common ones, including three that are perfectly normal, natural processes in a woman’s body: menstrual cycle, pregnancy, and menopause. First, let’s learn how sudden weight gain is diagnosed.

Sudden Weight Gain – Diagnosis

Sudden weight gain is usually diagnosed based on the clinical image and some additional medical history information. Your doctor will likely ask you some questions about the possible symptoms, your lifestyle, and a thorough medical history.

Also, a blood sample should be taken to check for hormone levels, kidney function, and other health markers that may indicate medical problems (2). Sometimes, an ultrasound may be required, but this is not always the case.

Causes Behind Your Sudden Weight Gain

Sudden weight gain often occurs due to excessive intake of unhealthy food or beverages in combination with decreased physical activity (3). It also often happens due to fluid retention, constipation, or pregnancy.

In such situations, sudden weight gain is an entirely logical consequence that can occur periodically (e.g., during the different phases of the menstrual cycle in women) but may also take some time (e.g., during pregnancy).

However, rapid fluctuations in weight can often occur due to some other causes that need to be treated. You must visit the doctor not only for weight regulation but also to find the core causes behind such a sudden weight gain.

Let’s take a look at the most common reasons why you are gaining weight in a short time.

1. Menopause

During this period, women experience several hormonal changes during which estrogen, the hormone responsible for menstruation and ovulation, begins to decrease. Estrogen depletion can cause menopausal women to experience sudden weight gain, especially around the abdominal region (4).

There are certain supplements that women take upon their doctor’s prescription that can alleviate the negative effects of menopause, including weight gain. Visit your doctor if you are approaching menopause, have entered it, or are dealing with these issues.


Similarly, hormonal changes can result in the appearance of the polycystic ovary syndrome, which is often known as PCOS. It often causes sudden weight gain in women who cannot successfully regulate and treat this disorder. In other words, hormonal changes result in a slowdown in metabolism leading to weight gain (5). Moreover, this syndrome is the most common hormonal disorder in women.

In most cases, women with this syndrome have enlarged ovaries and have many small fluid-filled cysts. Although the exact cause of polycystic ovary syndrome is unknown, the contributing factors to this problem are too much insulin, chronic inflammation in the body, hereditary factors, and abnormal fetal development in the womb. The most common signs and symptoms of polycystic ovary syndrome are sudden weight gain, menstrual problems, too many androgenic (male) hormones, and polycystic ovaries themselves.

Possible complications include type 2 diabetes, high blood pressure, and endometrial cancer. That’s why you must visit your doctor as soon as you suspect you might be dealing with PCOS or notice any of the symptoms mentioned above, including sudden weight gain.

3. Menstrual cycle

Occasional sudden weight gain is often a consequence of the different phases of your menstrual cycle. Women may experience water retention and bloat during the cycle, and changes in estrogen and progesterone levels can cause sudden and temporary weight gain.

In this case, we are not talking about significant weight gain. We are talking about several pounds. Also, this type of weight gain usually ceases when the menstrual cycle is approaching its end. Unfortunately, weight gain may reappear early in the next cycle. Some women, usually dealing with other related disorders or conditions, can experience weight build-up over numerous cycles if they don’t manage to lose any weight. However, weight regulation is possible through certain simple methods if you don’t suffer from any other disorder.

Sudden weight gain can sometimes be a result of PMS and PMS-related behaviors. It is not uncommon for women to reach for sweets, cakes, cookies, and ice-cream during this period. These are not necessarily harmful if consumed moderately. However, the limit may get out of your hand, which is why some women have problems with weight gain during certain phases of their cycle.

 4.  Pregnancy

Pregnancy is a period in which many women gain weight. However, this is a normal reaction to many changes that occur in their body that usually consist of the baby’s growth itself, the placenta, amniotic fluid, increased blood supply, and enlarged uterus (6).

However, many women intentionally eat more, trusting the myth that they should eat “for two” during their pregnancy. That is wrong. A baby normally develops when a woman eats the same amount of food as before pregnancy, or maybe a little more than before. More importantly, a pregnant woman must pay attention to the quality of her diet. A healthy and balanced diet is essential. Consequently, this alone cannot cause such a sudden weight gain.

In other words, weight gain in pregnancy is normal and inevitable because of these changes in the body, but what you can regulate is your healthy diet that, among other things, can only benefit you and your baby.

Weight monitoring during pregnancy still has clinical implications for predicting the outcome of the childbirth itself. Namely, excess weight gain during pregnancy is associated with poor maternal and infant outcomes, including gestational diabetes, hypertension, the increased risks of performing a cesarean delivery, etc.

5. Fluid retention in the body

Sudden weight gain can be a result of fluid retention in the body. It is also known as edema and can cause swelling of certain parts of the body.

People who have heart problems or certain kidney disease may have difficulty losing weight because fluid stays in their body.

6. Medicines

One of the most common side effects of using various medications is the rapid and sudden weight gain (7). Unfortunately, these side effects are difficult to prevent if you have to take a certain medication simply because you are not sure whether the side effect would occur or not before taking the medication. Also, these side effects don’t have to occur in every patient.

However, indeed, many different types of medicines can often slow down one’s metabolism or increase appetite, which is why weight gain is sometimes even inevitable. Remedies that can cause sudden weight gain are

  •  corticosteroids,
  • antidepressants,
  • antipsychotics,
  • contraceptive pills.

You should talk to your doctor about sudden weight gain you noticed after taking medicine and consider the alternatives.

7.  Stress

As we all already know, stressful situations cause an increase in the level of the stress hormone – cortisol. As a result, various physiological reactions can interfere with the normal functioning of the metabolism causing sudden weight gain (8).

Unfortunately, stressful situations are sometimes difficult to avoid. However, you can learn to practice some useful coping strategies so that you can behave properly in the same or similar situations in the future in order to alleviate the negative effects of stress.

Sometimes, cortisol levels can exceed normal values, so Cushing’s syndrome may occur. This is an endocrine disorder of elevated cortisol hormone levels in the blood. Sudden weight gain is one of the consequences of this condition. Be sure to consult your doctor if you suspect any of these issues.

8. Depression

One of the most common psychological problems in today’s society is depression, which has recently been affecting more and more people from different age groups. A growing number of people is suffering from depression and relying on excessive food intake a one way of alleviating psychological distress.

Depression reduces the desire for any kind of physical activity and often causes people to have severe emotional conditions that trigger taking too much food and leading unhealthy lifestyles.

In addition, people being treated for depression with medicines called antidepressants may experience rapid weight gain due to the side effects of the medications (9).

9. Various diseases

Sudden weight gain can also occur as a result of several diseases, and it is usually related to the thyroid gland diseases that cause the majority of weight gain problems in many patients (e.g., hypothyroidism).

In addition, weight gain that starts suddenly can also be caused by ovarian cysts, which require strict diet rules in order to go back to the desired form.

Cardiovascular diseases and kidney diseases can also cause many problems with weight, including the sudden and abrupt weight gain. However,  proper treatment of the primary disease can result in successful weight management.

10.  Pulmonary edema and congestive heart failure (insufficiency)

Pulmonary edema or abnormal swelling and water retention as a result of heart problems are more serious potential causes of rapid weight gain (10). The sudden increase of your weight resulting from pulmonary edema may indicate congestive heart failure, an extremely serious condition when one’s heart pumps too small amounts of blood through the body.

When it comes to sudden and fast weight gain because of problems like this, the additional pounds accumulate mostly on your feet. If you suddenly gain weight and become overweight, and some parts of your body swell, seek medical care immediately as this is a serious situation that can have fatal consequences.

11.   Physical inactivity

Just as regular physical activity helps you keep your body in top shape and is very good for your health, physical inactivity causes all the counter-effects. The weight gain we often consider to be a consequence of the aging process and attribute it to some natural processes such as menopause can actually be a result of reduced physical activity. As extra pounds accumulate faster as we reduce our physical activity, the true causes of weight gain can often not be recognized easily.

Experts recommend two and a half hours of moderate or 75 minutes of intense physical activity per week for all adults unless you are unable to engage in physical activity for any health reason. If you have recently gained a lot of weight in a short period of time and have reduced your physical activity, you probably know yourself who the main culprit is.

You should gradually increase the duration and intensity of your physical activity and turn to a healthier diet if you want to lose weight successfully. Since sudden weight gain can indicate many different illnesses and health conditions, consult your doctor before starting a diet and sports.

12.  Insulin resistance

In some cases, your body can become resistant to the hormone insulin, which leads to the build-up of fat in your body and can later lead to type two diabetes. An increased number of cells secreting insulin in the pancreas or pancreatic cancer can cause insulin resistance where the main symptom is sudden weight gain around the waist. Consult your doctor if you notice this type of sudden weight gain.

13.   Lazy intestine

If you have problems with your bowel movement and slow metabolism, this could be an important reason for your abrupt weight gain. If you do not have a regular bowel movement, it could be affected by dehydration, reduced fiber intake, or certain medications. You can help yourself by always drinking enough water and consuming enough fiber, and your daily consumption of probiotics can also help. You should work on speeding up your metabolism naturally. Also, you should visit a doctor if you are dealing with a lazy intestine condition.

Why Are Teens Suddenly Gaining Weight?

Oscillations in body weight are a completely normal part of the process of physical development in teens. If you are overweight or have other symptoms of various diseases or conditions, then there may be a cause other than normal hormonal changes during puberty.

Sudden and unexpected weight gain in children and teenagers can also occur as a side effect of some medications, because of thyroid gland problems, and also because of psychiatric disorders such as depression. If your child is suddenly feeling tired, fatigued for no apparent reason, and gains weight, talk to your doctor about the symptoms.


Treatment of sudden weight gain depends on the cause being treated, primarily to achieve the optimum level of body weight. The best treatment method depends on the success of controlling the root cause.

For example, if the cause of weight gain is a hormonal imbalance, your doctor may prescribe medications that can balance your hormone levels and help you regulate your weight. If the medication itself is the cause of the problem, the doctor will find other treatments to prevent further weight gain and still keep the original health problem under control.

Final Words

Keep in mind that sudden weight gain is sometimes a consequence of an unhealthy lifestyle. In some people, the consequence of such a lifestyle can be seen at once, which is why causes are usually sought in diseases that may not necessarily be present in the background of weight gain.

Lack of physical activity in today’s sedentary lifestyle is also one of the main causes that may lead to sudden and excessive weight gain. Try to change this type of lifestyle by gradually increasing physical activity. This will also help you combat stress.

In other words, this means that practicing a balanced diet and a healthy lifestyle can and should regulate any weight gain or at least minimize its effects even if there is a certain disease. Of course, there are diseases that require immediate and thorough treatment.

If you notice that you are suddenly gaining weight, you should consult your doctor immediately. Try to keep a diary that will keep track of your weight oscillations over some time. Keep track of your diet and physical activity as well. Note any medications and supplements you are taking. This information is extremely valuable for your doctor and can decide on the course of your treatment and the outcome of the condition.


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