• Is there a medical reason you've put on weight? (Tina Stallard/Getty Images)Source: Tina Stallard/Getty Images
If you haven't changed your diet or lifestyle recently and have put on a dramatic amount of weight over a short period of time, there's a possibility you might be battling an undiagnosed health issue.
Emily Nicol

1 Sep 2017 - 1:25 PM  UPDATED 11 Sep 2017 - 9:50 AM

Weight gain: it happens to many of us following a period of over indulgence, intense socialising or inactivity.

But how do you explain suddenly moving from a healthy weight to being classified as overweight or obese if nothing else has changed? Perhaps you’ve got an underlying health condition that you should be aware of?

Here are some of the most common conditions, which – if left undiagnosed – could be causing you to gain weight.

An underactive thyroid 

Affecting more women than men, there are a range of diseases that can affect the thyroid – a gland sitting at the base of the throat that secretes hormones and plays a crucial role in nourishing every tissue in the body.

One common disease is Hashimoto’s thyroiditis: an autoimmune condition that causes the thyroid to attack itself, often resulting in an underactive thyroid. If left untreated, symptoms include lethargy and fatigue, depression, weight gain and fluid retention.

For *Katherine, a woman now aged in her late 30s, the initial diagnosis of thyroid disease was welcome for one key reason – it explained the range of uncomfortable and at times scary symptoms she had been experiencing for years, including putting on 20 kilograms over two months despite the fact she exercised and ate well.

“The thing about thyroid diseases is that they often progress over time, without you knowing what is happening to your body," says Katherine.

"The symptoms can be put down to having a fast paced life, working too much or not sleeping enough. So it's not until everything hits you at once, health-wise, that you think to go to the GP."

Like most people, Katherine's diagnosis came through the results of a blood test and, like most patients, she was put on thyroxine (a synthetic replacement for the missing thyroid hormone) as a way to manage the illness – “medication I’ll remain on forever as there is currently no cure”.

The right diet and a healthy, stress-free lifestyle can also reduce the factors that can trigger a drop in thyroid hormone. Katherine tells SBS that after medication, acupuncture and a strict shake diet (followed in consultation with her GP), she shed the kilos and returned to her original weight pre-Hashimoto’s disease - for a while.  

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Polycystic Ovarian Syndrome

Almost a decade after Katherine was diagnosed with Hashimoto’s, she was told she had Polycystic Ovarian Syndrome (PCOS).

Polycystic means multiple (poly) cysts on the ovaries. PCOS is shown to affect between 12-18 per cent of women of reproductive age and up to 21 per cent in some high-risk groups, such as Indigenous Australian women.

It can cause women to gain weight and, due to a state of insulin resistance, have trouble losing it.

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“Although I found out I was fighting a weight war on two fronts, PCOS and Hashimoto’s, it was a relief to know what was going on,” she says. “It was also good news to learn that PCOS can be reversed somewhat as you lose weight.

“But it's a catch-22: you can't lose weight easily because of the PCOS. Your body is working against you because you are insulin resistant.

“Again, that's where medication, improvements in lifestyle and GP support can often help. ...For the first time in years, I’ve now started to lose weight with the help of a holistic health plan and my doctor’s support.

“I don't care if it takes four months of dieting to lose what another healthy person could drop in half the time. I forgive myself for having thyroid illness and PCOS, and realise that when you have an uphill weight battle, slow and steady will win my race.”

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Congenital Heart Failure

Unexplained weight gain can also be a symptom of Congenital Heart Failure (CHF). This disease occurs when your heart muscle doesn’t pump enough blood to the rest of your body due to an irregularity. The result is that fluids can start to build up, causing congestion and weight gain, and often an enlarged heart.

There are many risk factors involved in the onset of this condition including diabetes, high blood pressure and decreased kidney function and one of the warning signs of the onset is sudden weight gain.

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Your gut flora

The gut has been shown to influence hormone levels, including insulin, appetite control and cortisol levels, and therefore impact weight.  

“There is a lot of research happening at the moment with respect to your gut flora influencing whether or not you are obese,” Professor Robert Wilson from Sydney Institute Obesity tells SBS.

“If you eat food high in roughage and fibre you stimulate the growth of fermenting bacteria, which is different to the bacteria you have in your gut when you don’t eat any fibre and you eat a lot of meat and highly processed food.

“You don’t get the same kind of fermentation that you get when you have a vegetarian diet, and that change in the gut flora has a whole bunch of effects on the hormones that affect body weight.”

Diabetic nephropathy

Diabetic nephropathy is a type of progressive kidney disease that may occur in those who have either type I or II diabetes. Within the kidneys there are over a million nephrons, responsible for the clearing of waste. Diabetes causes the thickening and scarring of nephrons reducing the ability to get rid of waste and remove fluid from the body.

The symptoms are similar to other diseases here including fatigue, general overall unwell feeling, loss of appetite, headache and weight gain.

It has a slow onset. But, if caught early enough and with the right treatment can be slowed down or stopped altogether. 

*Not her real name. 

Please note: this list of conditions which, when left undiagnosed, could cause weight gain is not conclusive. SBS encourages anyone wrestling with unexplained weight gain to go and see their GP and/or seek out the opinion of a qualified, trained medical professional. 

WatchThe Obesity Myth on Mondays from 4 September at 7:30pm on SBS. The show will be available for viewing on SBS On Demand after broadcast. 

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