Just two portions of oily fish a week can reverse the damage caused by a junk food diet, new research suggests.

Being overweight from bingeing on fast-food can prevent the body from producing enough antibodies.

As a result, the immune system is more susceptible to bacteria, viruses and other diseases, scientists claim.

But regularly eating salmon and pilchards can reverse the damage caused to the immune system by obesity, the study found.

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Two portions of oily fish, including salmon, mackerel and pilchard, a week could reverse the damage of a high junk food diet

Researchers from Liverpool John Moores University tested two potential food supplements to see if they could reverse the changes of a junk food diet.

Omega-3 fatty acids, such as those found in oily fish and seaweed, as well as 2-hydroxyoleic acid, a synthetic substance derived from oleic acid, were assessed.

In the study, which was published in the journal Experimental Physiology, 32 mice were fed diets to ensure they became obese.

Signs of of oxidative stress - when the body isn't producing enough antioxidants - and immune system aging in the mice were identified by researchers.

The mice were then split into two groups and given food supplemented with either omega-3 or 2-hydroxyoleic acid.

After eight weeks, the researchers studied the rodents' spleens and found both supplements reduced the effects of obesity on the immune system.

A high junk food diet can age the immune system and reduce the body's ability to fight disease

Those fed 2-hydroxyoleic acid had the greatest improvement.

MORE BENEFITS OF OILY FISH Eating just small amounts of omega-3 fatty acid-rich foods after a bowel cancer diagnosis may reduce the risk of dying by 70 per cent. This occurred in patients who increased their daily intake by at least 0.15g a day compared to those who didn't change their intake, scientists at the Harvard Medical School and Massachusetts General Hospital in Boston revealed. Eating a 100g salmon fillet - an adult portion – once a week would provide the equivalent of 0.3g of omega-3 fatty acids daily. These amounts can also be found in around around 100g of herring, 200g of sardines or 200g of trout. Advertisement

Study author Dr Fatima Perez de Heredia said: 'This is the first study, at least to our knowledge, to suggest the efficacy of 2-hydroxyoleic acid for reversing obesity-associated immune alterations and improving oxidative stress.'

She advised people adopt a Mediterranean diet, including two portions of fish, with one being oily, once a week to reap 2-hydroxyoleic acid's benefits.

Dr Fatima warned, however, such effects may not occur in overweight people.

'It is not clear whether you could still receive the benefits of these supplements if you are still overweight.

'This could be the case for some people, but for others, they may have to lose the weight to get these benefits.'

This comes after research suggesting eating oily fish once a week may significantly improve bowl cancer patients' chance of survival.

The omega-3 fatty acids in sardines, salmon and trout are thought to suppress tumour growth and curb blood supply to cancer cells, according to US experts.