Unintentional weight gain can often be due to age-related physical changes, underlying diseases, or side effects of medications. Weight gain is not always due to overeating or less exercise.

Some people have a very low diet, yet their weight keeps increasing. In such a situation, the question arises whether there is any serious disease behind this? Let us tell you about those diseases in which weight starts increasing even without eating much.
Why does weight increase suddenly?
According to Harvard Health (2023), unintentional weight gain can often be due to age-related physical changes, underlying diseases, side effects of medications, or changes in gut bacteria (microbiome). Weight gain is not always due to overeating or less exercise. According to Dr. Sanjay Gupta, an endocrinologist at Fortis Hospital, Delhi, weight gain does not depend only on calorie intake. Hormonal imbalance, lack of sleep and stress etc. affect the body's metabolism, which can lead to weight gain.
Weight increases due to these diseases
Hypothyroidism: Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormone. This condition slows down the metabolism, which leads to weight gain. Due to this, fatigue and weakness are felt. Also, weight starts increasing suddenly. Apart from this, problems like dryness in the skin, hair loss, inability to tolerate cold, muscle pain and stiffness in the joints also occur.
Dr. Rita Sharma, a thyroid expert at Mumbai's Lilavati Hospital, says that timely diagnosis and treatment of hypothyroidism is necessary. Weight can be controlled with thyroid hormone replacement therapy, but medicine should not be taken without consulting a doctor.
Polycystic ovary syndrome (PCOS): PCOS is a hormonal disorder caused by excessive production of male hormones (androgens) in the ovaries of women. PCOS increases insulin resistance, which increases the risk of weight gain.
Cushing's Syndrome: Cushing's syndrome occurs when the level of cortisol hormone (stress hormone) in the body increases abnormally. This condition can be caused by long-term use of steroid medications or a tumor in the adrenal gland.
Depression and Anxiety: Mental health problems such as depression and anxiety can affect appetite and eating habits. People suffering from depression are often attracted to 'comfort foods', which are high in calories and low in nutrients.
Sleep Deprivation and Stress: Lack of sleep and stress increase the level of cortisol, which leads to increased hunger and slows down metabolism. People who sleep less than 6 hours a night face this problem more.
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