Unintentional Weight Gain

  • Manal AndijaniMSc genes and proteins in disease - Sheffield Hallam University, UK

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When an individual experiences weight gain without an increase in food consumption or a decrease in physical activities, the most likely reasons for weight gain include illness or injury, hormonal changes, the side effects of medication, or fluid retention. Unintentional weight gain can be temporary, recurring, or continuous. Some diseases that cause unintentional weight gain are Hypothyroidism, Cushing’s syndrome, Polycystic ovary syndrome (PCOS), and insulin resistance. The following are explanations of how those diseases and lifestyle changes can cause unintentional weight gain.

Medical causes


Hypothyroidism is clinically linked to obesity.1 Since obesity has become more related to hypothyroidism patients, there are novel indications that obesity could be secondary to thyroid dysfunction. Recent studies have also revealed the relationship between obesity and thyroid autoimmunity, with a key link between the two conditions being the hormone leptin. Leptin is usually made by adipose cells and regulates the long-term energy balance.  

Cushing's syndrome

Cushing Syndrome is an endocrine disease caused by chronic and excessive production of cortisol hormone.2 The disease leads to several clinical complications and increases mortality. Metabolic syndrome is one of the clinical complications that cause changes in body composition, with fat redistribution resulting in the accumulation of visceral adipose tissue. The metabolic syndrome features can persist longer, even after the normalization of cortisol. 

Polycystic ovary syndrome (PCOS)

Polycystic Ovary Syndrome (PCOS) is a condition that develops in people assigned to females at birth (AFAB) who are genetically predisposed to its development. 6%-10% of AFABs develop PCOS during adolescence. It is highly common for AFAB who suffer from PCOS to be obese or overweight.3

Clinical features of PCOS include hyperandrogenism, where excessive hormone production can manifest with numerous features, including acne, excessive hair growth (hirsutism), and reproductive dysfunction. Metabolic syndrome is another clinical manifestation of PCOS, with epidemiological data showing that 38% -88% of women with PCOS are actually suffering from obesity or overweight.3

Insulin resistance

The link between obesity and insulin resistance has become an area of research that attracts interest and focus due to its huge public health impact.

Insulin is a hormone produced by the pancreas (specifically by β cells of islets of Langerhans). Insulin controls the cellular uptake and metabolism of sugars, proteins, and fats. Insulin resistance is a condition where the insulin receptors on the surface of cells become non-responsive to insulin stimuli; this can play a key role in the development of obesity and other complications such as type 2 diabetes and cardiovascular disease.4


Weight gain and obesity are increasing worldwide; some medications can result in weight gain. Drugs can increase appetite; consequently, an individual can eat more. Other medications may affect the way the body metabolizes glucose, and as a result, fats will be stored in the midsection of the body.  

Antipsychotics, antidepressants, antihyperglycemics, antihypertensive drugs, and corticosteroids are all noted to have weight gain as a side effect.5 

Most medication side effects appear within the first six months; therefore, if you have started a new medication and seen yourself gaining weight during this period, ask your health provider if the medication causes weight gain. It is not just about getting extra pounds; weight gain can make other health conditions, such as diabetes, high blood pressure, metabolic syndrome, and high cholesterol, worse. 

Behavioural and lifestyle causes

Overeating and binge eating

Binge eating is a disorder characterized by the consumption of a large amount of food with the feeling that one has lost control during eating. Binge eating is more common among older individuals who have longer periods of suffering from diseases and can be associated with psychiatric and medical complications.6 

People with binge eating disorders typically eat highly caloric meals and snacks throughout the day in high quantities. People who binge eat are likely to be experiencing body dissatisfaction and frequent weight fluctuations. It is reported that the combination of binge eating and obesity may significantly cause health and economic problems with regard to illness complications.7
In the current situation of readily available and inexpensive food, it can be difficult to avoid the temptation of overeating.

Sedentary lifestyle

It is well known that obesity and a sedentary lifestyle are associated with the risk of cardiovascular disease and other chronic illnesses. A long period of inactivity reduces the metabolism of the body and the breakdown of fats.

Sleep deprivation

Sleep deprivation causes hormonal imbalances in the body that can promote overeating and, consequently, weight gain. Leptin is a hormone that controls appetite; with sleep loss, the hormone production is changed and leads to overeating.  


Studies and evidence have shown that stress and glucocorticoid, a stress hormone production, are highly associated with obesity. The stress hormones are responsible for the redistribution of the adipose tissue and promote appetite for high-caloric food (comfort food). Research has shown that long-term cortisol release is strongly related to abdominal obesity.  

Other causes

In addition to the mentioned causes of obesity, some others worth mentioning to consider such as the environment, the world nowadays influences people to live in a certain way that can lead to gaining weight unintentionally, like not having enough parks or places for pedestrians, food portion size is increasing. As a result, calorie intake is increasing. Some people don’t have access to fresh and healthy food. Some genetic disorders can directly cause obesity.  

Diagnosis and evaluation

Medical history and physical examination

Obesity is one of the health risks worldwide and costs the economy millions every year. Being overweight or obese puts people at risk of getting chronic diseases like type 2 diabetes, high blood pressure, and cardiovascular diseases. If those diseases run in the family, It is highly recommended for an individual who suffers from excessive weight to consider examination, as being overweight is a common risk factor for chronic diseases. 

Blood and imaging tests

It is important to seek professional medical check help when it comes to diagnosing obesity and how it impacts overall health. Tests include:

  1. Cholesterol Level: Low (HDL) good cholesterol and high (LDL) bad cholesterol is normally associated with obesity
  2. Fasting blood sugar: to check for prediabetes or diabetes.
  3. A thyroid test: to check thyroid disease or hormonal imbalance
  4. Liver function test: to check for fatty liver diseases.

Monitoring weight and body measurements

It is important to avoid gaining extra weight or specifically fat to consider following certain measurements:

  1. Regulate food intake as the primary measurement
  2. Maximise energy expenditure in the sedentary modern life
  3. Calculate Body mass index (BMI), shape, waist circumference, body composition, and disease risk   

Treatment and management

Patients with obesity and overweight are highly advised to lose weight, especially if they suffer from chronic diseases such as diabetes and hypertension. In most cases, health providers advise patients to lose 5% to 10% of their weight as an initial goal. Lifestyle intervention, including dietary changes and increased physical activities, is highly recommended. Medication and bariatric surgery may be suggested for some patients.


Obesity prevention means decreasing the rate at which the population reaches the upper limit of BMI. To accomplish this, adults are required to maintain their healthy weight and BMI, and children follow a healthy food plan to avoid gaining extra weight when they are adults. Strategies and actions taken are different depending on the environment, but the most promising approach is population-based, which requires several sectors to participate. The general approach to prevent obesity is to avoid junk food, consume more healthy options, increase activities, maintain reasonable portion size to avoid extra calorie consumption, and learn how to reduce daily stress


In conclusion, people usually experience fluctuation in their weight, and it is normal to gain weight with time. However, if an individual experiences weight gain for unknown reasons, this might be a result of a medical condition or side effect of medication.
When gaining weight is not disease-related, common causes include:

  • Overeating 
  • Less physical activities
  • Menstrual cycle
  • Menopause
  • Lack of sleep
  • Stress and depression
  • Water retention

You should see a doctor if you experience rapid weight gain for none of the mentioned reasons.  


  1. Sanyal D, Raychaudhuri M. Hypothyroidism and obesity: An intriguing link. Indian J Endocrinol Metab [Internet]. 2016 [cited 2023 Mar 13];20(4):554–7. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4911848/
  2. Ferraù F, Korbonits M. Metabolic syndrome in Cushing’s syndrome patients. Metabolic Syndrome Consequent to Endocrine Disorders [Internet]. 2018 [cited 2023 Mar 13];49:85–103. Available from: https://www.karger.com/Article/FullText/486002
  3. Barber TM, Franks S. Obesity and polycystic ovary syndrome. Clin Endocrinol [Internet]. 2021 Oct [cited 2023 Mar 13];95(4):531–41. Available from: https://onlinelibrary.wiley.com/doi/10.1111/cen.14421
  4. Wondmkun YT. Obesity, insulin resistance, and type 2 diabetes: associations and therapeutic implications. Diabetes Metab Syndr Obes [Internet]. 2020 Oct 9 [cited 2023 Mar 13];13:3611–6. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7553667/
  5. Wharton S, Raiber L, Serodio KJ, Lee J, Christensen RA. Medications that cause weight gain and alternatives in Canada: a narrative review. Diabetes, Metabolic Syndrome and Obesity [Internet]. 2018 Dec 7 [cited 2023 Mar 14];11:427–38. Available from: https://www.tandfonline.com/doi/abs/10.2147/DMSO.S171365
  6. Berg KC, Peterson CB, Crosby RD, Cao L, Crow SJ, Engel SG, et al. Relationship between daily affect and overeating-only, loss of control eating-only, and binge eating episodes in obese adults. Psychiatry Research [Internet]. 2014 Jan 30 [cited 2023 Mar 14];215(1):185–91. Available from: https://www.sciencedirect.com/science/article/pii/S0165178113004836
  7. Ruhm CJ. Understanding overeating and obesity. Journal of Health Economics [Internet]. 2012 Dec 1 [cited 2023 Mar 14];31(6):781–96. Available from: https://www.sciencedirect.com/science/article/pii/S0167629612000938
  8. Barnes AS. Obesity and sedentary lifestyles. Tex Heart Inst J [Internet]. 2012 [cited 2023 Mar 14];39(2):224–7. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3384027/
  9. Gadde KM, Martin CK, Berthoud HR, Heymsfield SB. Obesity. Journal of the American College of Cardiology [Internet]. 2018 Jan [cited 2023 Mar 15];71(1):69–84. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0735109717415841

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Manal Andijani

MSc genes and proteins in disease, Sheffield Hallam University, UK

Experienced Research Specialist with a demonstrated history of working in the higher education institution, highly skilled in DNA sequencing, specifically Next generation sequencing and single-cell RNAseq. I have ten years of experience as a Research Specialist in Genomics laboratories and Stem cell and regenerative medicine. In addition, I am a qualified fitness personal trainer with an ambition to help women over 40 and with chronic conditions reach their health goals and maintain a healthy lifestyle.

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