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7 causes of unexplained weight gain

weight gain

Top tips on how to cope with unexplained weight gain


Weight gain can happen for a variety of different reasons – some of them more obvious than others. However, it’s important to note that despite what you might think, this isn’t always a bad thing!

Although society will often try to tell us that weight gain should be avoided at all costs, it’s often a completely normal, natural process. Gaining weight doesn’t mean that you should jump onto a crash diet or run to the gym immediately – sometimes there are other factors at play that you may want to consider.

This article will discuss some of the potential causes for unexplained weight gain, and why our health is not defined by the number on the scales.


Why am I gaining weight?

  1. Emotional factors

Emotional factors such as stress, anxiety or depression can play a role in weight gain. When people are experiencing these unpleasant emotions, they may use food as a coping mechanism: this is known as emotional eating and is much more common than you might think.

  1. Hormonal imbalances

Hormones are chemicals which regulate many aspects of our daily lives, including weight. When our hormones are out of balance, it can trigger physiological changes within the body such as an increased appetite and decreased energy levels.

  1. Low thyroid function

If the thyroid isn’t working correctly, the body will struggle to burn calories and may be inclined to store them instead. This can manifest itself as around 5-10lb of weight gain1, or more depending on the severity of the hypothyroidism.

  1. Polycystic Ovarian Syndrome (PCOS)

PCOS is a condition affecting the hormones that control ovulation, but it can also impact insulin and androgen, both of which can lead to weight gain. Up to 80% of women with PCOS reported being overweight2, making it an extremely common side effect of PCOS.

  1. Insulin resistance

One potential cause of unexplained weight gain is insulin resistance, where the body’s cells become resistant to the hormone insulin. Insulin is an essential part of glucose metabolism, so if your body can no longer respond to insulin effectively then you may begin to gain weight.

  1. Physical activity levels

If you have been less physically active than usual, your body is not going to be using up as much energy as normal, meaning more of the nutrients you take in will be stored instead. Alternatively, if you’ve been doing a lot of resistance training, you’ll be building up muscle mass, which is around 15% denser than fat mass3!

  1. Other lifestyle factors such as drinking or smoking

Drinking and smoking can contribute towards weight gain over time. More specifically, drinking in excess can lead to weight gain, whilst stopping smoking has the same effect – this is because smoking is an appetite suppressant.


When should I see a doctor or health care professional?

If you start to notice an increase in your weight despite your nutritional intake and physical activity level staying the same, it may be the case that you have an underlying medical condition causing you to gain weight.

If you are experiencing any other unusual symptoms alongside this weight gain, you may want to consider seeing a doctor for further investigations.

For example, changes in mood, appetite or energy levels, difficulty concentrating and making decisions, increased thirst or more frequent urination may indicate that there is something else going on.


What should I do if I start to gain weight unexpectedly?



Don’t panic! Weight gain is completely normal, and this doesn’t mean you should be trying to lose it.

Weight gain might be a sign that you are becoming more comfortable in your body, or that your muscles are growing to keep you fit and strong.

Maybe you’re going through a big life change, such as pregnancy or menopause, and this is causing natural fluctuations to your weight.

Whatever the reason, you don’t need to worry unless you are experiencing other symptoms that might indicate an underlying condition. If you are truly concerned and are feeling uncomfortable in your body, we urge you to book a free discovery call with a member of our team to investigate this further.



Consider what might be causing you to gain weight. If you think you may have a medical problem that is causing your weight gain, it might be worth checking in with your doctor to get to the bottom of it.

Weight gain can also be a side-effect of many different types of medication.

For example, individuals taking long-terms antidepressants are up to 85% likely to gain weight secondary to this4.

If you think you might be gaining weight because of a prescription medication, it could be a good idea to discuss with your GP whether this needs to be altered to discuss your concerns and expectations.



Embrace and accept your changing body. We are all human beings, after all – we’re not designed to say the same weight throughout our entire lifetime!

Sadly, weight stigma is still prevalent even currently, but the key thing to remember is this: you don’t need to be on a diet to be healthy.

Health comes in all shapes and sizes – gaining weight doesn’t change or define who you are as a person. Your weight is the least interesting thing about you!

Here at EHL, we’re here to smash diet culture and help you see your worth as more than a body! Our team of specialist dietitians can help you to build a healthy relationship with food and your body and guide you to becoming embodied.

Contact us now at [email protected] to start you journey towards food freedom!


Team EHL x

Robin Wileman, Student dietitian & EHL intern





1 American Thyroid Association (2019). Thyroid & Weight.

2 Sam, S. (2007). Obesity and Polycystic Ovary Syndrome. Obesity Management, 3(2), 69–73. 

3 Norman, J. (2018, August 24). But muscle is heavier than fat, right? – LifestylesFitness. Medium. https://medium.com/lifestylesfitness/but-muscle-is-heavier-than-fat-right-a50aece8c5db#:%7E:text=The%20principal%20factor%20responsible%20lies%20in%20both%20tissues,whereas%20fat%20tissue%20is%20just%200.92%20kg%2F%20litre

4 Uguz, F., Sahingoz, M., Gungor, B., Aksoy, F., & Askin, R. (2015). Weight gain and associated factors in patients using newer antidepressant drugs. General Hospital Psychiatry, 37(1), 46–48. 


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Embody Health London champions food freedom, positive body image, mental health and emotional wellbeing through a uniquely blended scientific and holistic approach. The EHL team specialises in treating chronic dieting and eating disorders by coaching clients to build confidence and reduce anxiety around their eating habits and food choices.

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