Can heart failure cause sudden weight gain?

What can cause weight gain with heart failure?

When people think about weight gain, they often think about eating too much or eating unhealthy foods which lead to putting on body fat.

However, having heart failure can also cause weight gain, but not because of extra body fat.

The weight gain happens because your body is holding onto too much fluid. This is known as fluid retention and happens because when your heart is not pumping as strongly as it should, fluid can build up in your body.

It often shows up in places like your tummy, legs, ankles, or feet, causing swelling. You may also feel short of breath if fluid collects in your lungs – a condition called 'pulmonary oedema'.

Your body may try to compensate for this build-up of fluid by holding on to even more water and salt, which means your kidneys may struggle to get rid of the extra fluid.

Is it slow or sudden weight gain?

One of the differences between weight gain from overeating or having a poor diet and fluid retention is the time it takes for your weight to increase.

Weight gain from eating habits usually happens over weeks and months.

Whereas, with fluid retention it happens suddenly – sometimes leading you to put on as much as 3kg in just 1 or 2 days.

Signs of fluid build‑up include:

• sudden weight gain
• swollen legs, ankles or feet
• shoes or clothes feeling tighter
• feeling more breathless
• a bloated or full feeling in your tummy
• needing extra pillows at night to breathe comfortably.

If you notice any of these changes, it’s important to let your healthcare team know. Your medicines or treatment may need adjusting.

How is fluid retention treated?

If you gain weight because of fluid retention, your healthcare team may prescribe medicines called diuretics or ‘water tablets’ to help your body get rid of extra fluid.

You may also be advised to reduce how much fluid you have each day – this is called fluid restriction. You may be asked to reduce your salt intake too.

To help catch fluid retention early, your doctor or nurse may ask you to weigh yourself every day.

Try to:

• Weigh yourself at the same time each morning.
• Weigh yourself after going to the toilet.
• Wear similar clothes every time you weigh yourself.
• Track your weight over time by writing your weight down each time you measure it.

Remember, not all weight gain is caused by food. In heart failure, it’s often a sign of fluid retention.

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