6 hidden reasons why we gain weight


Losing weight often feels like an uphill battle, but it’s even tougher when we don’t know what’s causing our weight gain. You could be trying everything from diet and exercise to weight-loss medication, yet the extra pounds still refuse to budge. 
Sometimes, there can be some underlying factors resulting in weight gain that we aren’t even aware of. Knowing what these hidden causes are can help you to confront them head-on and take back control of your weight - and your overall health - for good. 

Medical conditions

Losing weight is usually as straightforward as “calories in, calories out”. It’s not always that simple, though, if you suffer from a chronic medical condition that directly causes weight gain. 
Here are just a few of the health conditions and illnesses that can lead to weight gain:


Hypothyroidism, or an underactive thyroid, is a condition where your thyroid gland doesn’t produce enough hormones. The most common symptoms of hypothyroidism are tiredness, weight gain and low mood. 
When the thyroid isn’t producing enough hormones, the body’s metabolism slows down and it’s easier to gain weight. 

Polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common fertility problem that affects the way a woman’s ovaries work. It can cause irregular periods, difficulty getting pregnant, excessive hair growth or thinning hair, acne and weight gain. 
PCOS can cause insulin resistance, which happens when the body finds it difficult to convert food into energy. This can cause the body to produce more insulin, which may lead to increased hunger that makes it very easy to gain weight. 


Fluctuating hormone levels during menopause can affect the way women store fat. 

Similarly to PCOS, menopause can lead to insulin resistance that makes our body store calories rather than burn them. As well as this, extra weight will tend to settle around the middle instead of being evenly distributed around the body, so an extra pound might feel more noticeable than it used to be. 

Cushing’s syndrome

Cushing’s syndrome is an uncommon condition that mostly affects people who have been taking steroid medicine for a long time.It happens when there’s too much of a hormone called cortisol in the body and it can be serious if left untreated. 
The main symptom of Cushing’s syndrome is weight gain, particularly around the chest and stomach. This is because cortisol can increase your appetite, making overeating and weight gain much more likely. 



If gaining weight because of a medical condition wasn’t bad enough, the medications we take to manage our health can often lead to weight gain too! Below are three types of drugs that lead to weight gain: 


Insulin therapy is a common treatment for diabetes which can often lead to weight gain.
Insulin is a hormone that regulates blood sugar levels by helping your body’s cells to absorb glucose. It can cause weight gain when the cells absorb too much glucose, as your body will convert the excess into fat. 


Medicines that contain steroids - such as prednisone, used to treat inflammation in many health conditions - affect the metabolism and how the body deposits fat. 
Steroid use, in turn, can cause fluid retention and an increased appetite that often leads to weight gain. Many patients who use steroids will notice their body fat is distributed differently, often settling in the face, neck or stomach.


Antipsychotic drugs, used to treat mental health disorders such as schizophrenia and bipolar disorder, often cause patients to put extra weight on.This is because they change the way your brain and hormones work together to control your appetite. 
The side effect of this process is often an increased appetite for sugary or fatty foods, which in turn make weight gain much more likely. 


Many people find that they gain weight more easily as they get older. This is because our basal metabolic rate, the number of calories our body needs to survive, starts to decrease with age. 
That means we can easily gain weight as we get older, even if we aren’t eating any more calories than usual. As well as this, it can be a lot harder to keep physically active as we get older due to lower energy levels and age-related health conditions. 
Eating the right amount of calories and staying active is vital for keeping a healthy weight, so we might have to reconsider our nutritional and fitness needs as we age. 


Mental health

Certain mental health disorders such as stress, anxiety and depression can have a major impact on our appetite. 
A chemical in the brain called serotonin can affect our mood and appetite - sometimes we’ll have too much or too little. People with low serotonin may have an increased appetite with cravings for carbohydrate-rich foods. 
People who suffer from chronic stress may also experience an elevated appetite due to high levels of the stress hormone cortisol. Some eating disorders can be directly linked to weight gain as well, particularly binge eating disorder or night eating syndrome. 


If you’re concerned about weight gain, you might have to start looking at your sleeping habits

That’s because some research has suggested a lack of sleep can contribute to weight gain. This is probably down to a lack of energy caused by sleep deprivation, which makes us more likely to reach for high-calorie foods that will give us a quick boost. 
On top of this, our metabolism might not be able to work properly if we’re not getting enough high quality sleep. Studies have shown that our levels of a hormone called leptin, which decreases your appetite to prevent excessive eating, tend to be lower when we’re sleep-deprived. 
That means we’re much more likely to overeat when we haven’t slept enough, and if this becomes a recurring problem, we’ll gain extra weight as a result. 

Food labelling

When you start a diet, it can be tempting to start buying ‘low-fat’ versions of your favourite snacks. Whilst this can certainly be beneficial at times, some low-fat foods will instead contain high levels of sugar to compensate.
Sugar contains a lot of calories, so even if you’re reducing your fat intake, you won’t necessarily be reducing the number on the scale. Make sure to look at the calorie content above anything else to avoid falling for any misleading promises on the packaging. 
You’ll also need to take note of the specific portion size in the nutritional information. Sometimes, the recommended serving can be much smaller than you’d expect, which makes it really easy to eat a larger, higher-calorie portion without even realising it. 

There are plenty of things we can all do to keep a healthy weight. We can all benefit from eating a balanced diet, getting our five a day and keeping active with regular exercise. 
If you’re finding it particularly hard to lose excess weight, there are even medical treatments you can try to help you along the way. 
With that said, weight loss isn’t easy and there’s no shame in seeking extra support if you need to. As we’ve learned, there is a whole range of underlying causes that might be contributing to your weight gain - you may just need some help in identifying or managing them. 
If you’ve attempted all the tried and tested ways to drop the extra pounds without success, don’t hesitate to speak to your GP for expert advice.

Faye Bonnell - Medical Content Writer
James O'Loan - CEO & Superintendent Pharmacist
James O'Loan , CEO & Superintendent Pharmacist on 16 March 2023
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