Everyone experiences fluctuations in their weight at some point in their lives, but that does not make it less frustrating. Stepping onto the scales and seeing as the number is increasing can be quite devastating, especially if you are left unaware of the true reason behind these events. 

The truth is that there are a lot of factors being involved in trying to maintain our body weight. Often, without our knowledge, these factors cause our body weight to increase. Sometimes it is a certain health issue that is sneaking behind our back with unexplained weight gain being only one of the many symptoms that are has been causing. Other times, it is a combination of unhealthy habits that lead to this unwanted result. In today’s article, we thought we would explore both the most common health issues and the most common unhealthy habits that are leading to unintentional weight gain.

10 medical causes for unintentional weight gain

Often, the unexplained fluctuations in our weight are not in our control, being caused by a variety of different medical conditions and issues. There is a long list of health issues that are to be blamed for the unintentional weight gain that many of us have experienced in the past. In the following, we will discuss some of the most common health issues that have been linked to unintentional weight gain in the past.

  • Use of certain medications

  • Although this is not a health issue exactly, there is a list of certain medications that have weight gain listed among their potential side-effects. Certain medications can cause people to gain up to several pounds a month, as an unwanted side-effect, according to the Obesity Action Coalition (1).

    Often, it is the medications that are being used to control and treat seizures, high blood pressure, diabetes, and depression, that are linked to unintentional weight gain. However, even if this is the case, it is of vital importance not to discontinue your use of the prescribed medication without consulting a medical professional first.

  • Insomnia

  • Past research has shown that a lack of sleep can contribute to an unexplained weight gain. Scientists have backed up their findings with solid scientific proof, listing many reasons as to why that is. One of the more significant reasons is that restricting sleep influences the appetite-suppressing hormone, leptin, levels causing them to decline while increasing the appetite-stimulating hormone, ghrelin, levels at the same time (2).

    A 2013 study also showed that insufficient sleep often leads to increased carbohydrate intake as a way to meet the daily energy needs, which are normally satisfied with the 8 hours of sleep a day (3). The participants of the study also introduced more calories in their diet, thus contributing to their weight gain.

  • Hypothyroidism

  • Hypothyroidism, or underactive thyroid, can often lead to unexplained weight gain, due to the slowing down of the metabolism. The thyroid issues can also cause additional kidney problems, thus causing fluid retention, which will also lead to weight gain (4).

    Unfortunately, many people go on living unaware of their existing thyroid issue, thus exposing themselves to the many risks of leaving hypothyroidism untreated. Other symptoms that often occur alongside the unexplained weight gain are brittle nails, dry skin, dry hair, stiff joints, constipation, etc.

  • Polycystic ovary syndrome

  • Women who are struggling with polycystic ovary syndrome (PCOS) often struggle with weight gain, which is often focused around their belly and waist area. It is the high androgen levels that lead to the characteristic PCOS symptoms, including weight gain, body hair growth, acne, irregular periods, etc. (5).

    Not to worry, though. Despite the fact that there is no cure for PCOS, your doctor can recommend a series of lifestyle changes in combination with hormonal therapy to help you manage your symptoms better, which includes reducing your body weight as well.

  • Cirrhosis

  • Unexplained weight gain is a combination with an enlarged abdomen can easily point out to undiagnosed cirrhosis. Cirrhosis is a condition that causes healthy liver tissue to be replaced with scar tissue instead, thus causing fluid build-up in the abdominal cavity. This will result in the enlarged abdomen that we mentioned earlier. Cirrhosis also makes it more difficult for your body to process nutrients properly, which makes it harder for it to manage healthy body weight in the process (6).

    Additional symptoms that may follow the unexplained weight gain are insomnia, nausea, muscle cramps, and others. Cirrhosis is a potentially life-threatening condition that can lead to multiple complications, which only draws attention to the importance of this condition to be treated as soon as possible.

  • Mood disorders

  • Although there is no clear link between depression and anxiety, as the two most common mood disorders, and unintentional weight gain, a lot of the symptoms that these mood disorders are causing often lead to unexplained weight gain. For example, they often cause symptoms such as fatigue, irritability, and lack of focus and concentration. 

    All of these symptoms easily interfere with your everyday activities and routines, making it difficult to head to the gym and eat clean. In moments such as these, depressed and anxious individuals often find themselves snacking on unhealthy food choices and even binge eating, which also contributes to the weight gain in the process. In addition, we also have the medications that we mentioned earlier, which are used to treat both of these conditions and which are often causing weight gain to happen (7).

  • Heart failure

  • Unintentional weight gain, when occurring in combination with swelling in particular body parts such as the ankles, legs, feet, and stomach area can be the early signs of heart failure. These symptoms occur due to the fluid retention that is happening inside the body of the patient.

    The American Heart Association considers that a weight gain over 2-3 pounds over 24 hours or 5 pounds a week is a sign of heart failure (8). Additional symptoms that can occur are dizziness, confusion, loss of appetite, frequent coughing, etc. 

  • Cushing’s syndrome

  • Cushing's syndrome is the term that is being used to describe a condition in which the body produces too much cortisol, which is the so-called stress hormone, over a prolonged period of time. The most common cause for Cushing's syndrome is the long-term use of glucocorticoids, which are used to manage conditions such as rheumatoid arthritis, asthma, and systematic lupus erythematosus, among others.

    Unintentional weight gain is often caused by Cushing's syndrome. The areas that are most commonly being affected are the face, neck, abdomen, and upper back. On the other hand, the arms and the legs may appear thin, which is a characteristic sign of an existing Cushing's syndrome (9).

  • Ovarian cancer

  • Ovarian cancer often results in sudden or unintentional weight gain and bloating, especially in the belly area. In addition to the unintentional weight gain, symptoms such as lower back pain, vaginal bleeding, constipation, painful intercourse, and others can be expected as well (10).

    We are talking about a potentially dangerous and life-threatening condition, especially if it is a malignant tumor being present. If you notice any of these symptoms, please talk to a healthcare professional as soon as possible, especially if you have a family history of ovarian or any other cancer type. 

  • Perimenopause and menopause

  • Perimenopause and menopause are time periods that every woman will experience at some point in her life, but they are also periods that are filled with multiple body changes due to the hormonal changes that are happening inside. Usually, it is the mood changes, the unexplained weight gain, and the hot flashes that are announcing the presence of perimenopause and then menopause in most cases (11).

    It is the abdominal obesity that is causing the most worries among the menopausing women who are always happy to learn that it is not something that cannot be managed. With a few healthy habits and a regular workout routine, nothing is impossible, and if not, hormonal therapy is here to help you.

    Bad habits that lead to unintentional weight gain

    As much as you hate hearing this, it is not always a certain health issue to be blamed for the unintentional weight gain that you are experiencing right now. A sudden weight gain in the stomach and thighs, which might as well be caused by no other than your bad habits. Let's go through some of the worse eating habits known to men, and maybe you will discover the reason for your unintentional weight gain right here!

  • Eating too many processed foods

  • If your diet consists of sugary cereals, frozen meals, fast food, and late microwave dinners, then, unfortunately, you are struggling with a much explained if not intentional weight gain. All of these the mentioned foods are classified as unhealthy sources of empty calories, with no nutrients whatsoever, but with a lot of saturated fats, preservatives, and added sugars, which all explain why the scale has been showing an increase in your weight lately.

  • Eating too much sugar

  • Diabetes type 2 and heart disease are not the only complications that occur due to your habit of eating way too much sugar. There is obesity, as well as many other potential health complications to be considered as well (12)

    But it is not only the candy, cakes, and ice cream that you have been rewarding yourself way too often with that is to be blamed for your unintentional weight gain. Do not forget the common intake of sugary drinks as well. In fact, the intake of sugary drinks has been closely linked to obesity among children and adults in the United States, according to a review published in 2018 (13).

    • Lacking enough physical activity

    Inactivity is one of the main risk factors for obesity and the long list of chronic diseases and health issues, as science has said in the past (14, 15). If your job involves sitting in front of the computer for eight hours a day and you go on to do the same thing at home after work, avoiding any physical activity as much as possible, then once again, you are not struggling with an unexplained weight gain.

    Doctors all around the world have warned us against the dangers of the sedentary lifestyle with weight gain being one of them. So if you are avoiding any physical activity, it is only a matter of time when you are about to face weight gain, especially if you combine that inactivity with an unhealthy diet. 

  • Dealing with too much stress

  • Trying to juggle between work and the million things outside the office is putting way too much stress on everybody. But the thing with chronic stress is being a common issue that is affecting your weight as well, among other things related to your health. High-stress levels equal high cortisol levels, the stress hormone that is guilty of increasing your appetite, especially your appetite for empty calories, thus leading to unintentional weight gain (16). Incorporating relaxation techniques, along with some smart dietary changes, will reflect positively on your weight loss journey and your mental health for sure.

  • Eating way too many calories 

  • And last but not least important, we have overeating, which serves as a prominent cause of weight gain. It is quite simple – if you eat more calories than you burn during the day, you are more likely to gain weight in the future unintentionally. Eating way too many calories, especially through frequent snacking, drinking sugary drinks, and making nutrient-poor dietary choices during the day, will reflect negatively on your weight, causing the scales to show a larger and larger number every week.


    Weight gain is hardly unexplained, although a lot of the times are unintentional. Caused by an underlying medical issue such as hypothyroidism or ovarian cancer, the unintentional weight gain can serve as one of the clues that can lead the doctor to the true diagnosis. Other times, eating too much candy and sugar in general while sitting in front of the TV, forgetting to go by the gym, is what has been causing you to notice the meaningful changes in your weight and in front of the mirror.


    1. https://www.obesityaction.org/community/article-library/prescription-medications-weight-gain/
    2. https://annals.org/aim/article-abstract/717987/brief-communication-sleep-curtailment-healthy-young-men-associated-decreased-leptin?doi=10.7326%2f0003-4819-141-11-200412070-00008
    3. https://www.pnas.org/content/pnas/110/14/5695.full.pdf
    4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4911848/
    5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2861983/
    6. https://www.hindawi.com/journals/ijh/2011/801983/
    7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4059657/
    8. https://www.heart.org/en/health-topics/heart-failure/warning-signs-of-heart-failure/managing-heart-failure-symptoms
    9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4553096/
    10. https://www.medicalnewstoday.com/articles/322654.php
    11. https://www.ncbi.nlm.nih.gov/pubmed/22978257
    12. https://www.ncbi.nlm.nih.gov/pubmed/23763695
    13. https://www.ncbi.nlm.nih.gov/pubmed/23763695
    14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5451443/ 
    15. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2996155/
    16. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5958156/

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