Fatty acids can help children in exams and improve their behaviour in class and at home, a study suggests.

Overweight children who took fatty acid dietary supplements showed dramatic improvements in concentration, reading, memory and mental agility. The advances that their brains made in three months would normally take three years, researchers found.

One teenage boy who was hooked on watching television and hated books before the experiment became an avid reader after and dismissed programmes as too boring to bother with.

Researchers said that the results, while based on a small sample, supported recent findings that fatty acids boost brain development and suggest that fast food may stunt mental growth, because processed foods do not contain these acids.

Improvement were made in every area of academic activity but the most surprising change, said researchers, was in levels of Nacetylaspartate, or NAA, a biochemical indicator of brain development.

According to brain scans carried out at St George’s Hospital, southwest London, the levels of NAA rose far more than expected in the three boys and one girl taking a supplement containing the omega-3 and omega-6 fatty acids.

“The results were astonishing,” said Professor Basant Puri, who led the study. “In three months you might expect to see a small NAA increase. But we saw as much growth as you would normally see in three years. It was as if these were the brains of children three years older. It means you have more connections and greater density of nerve cells, in the same way that a tree grows more branches.

“For all the children there was a marked change, but in the three boys there was a massive, massive increase in NAA. I was quite startled by what I saw.”

The children taking part in the research were classified as overweight. Zach, aged 8, weighed 8st (51kg), George and Rachael, both aged 11, weighed 11st, and Gareth, who was 13, weighed 12st.

At the start of the pilot study, the children were given a supplement called VegEPA. They took two capsules a day and were encouraged to cut down on fatty snacks and fizzy drinks and be more active.

After three months the children’s reading abilities were a year ahead, their handwriting was neater and more accurate and they paid more attention in class.

“Gareth’s parents told me how he had suddenly found TV boring, as he wanted to read. Three months earlier he was saying he couldn’t understand people who loved books,” said Professor Puri, of the Division of Clinical Sciences at Imperial College, London.

“The concentration of all the children improved enormously and they seemed a lot calmer and happier. Even before I started testing them their parents were saying how much better they were.”

The children were asked to change their diet but there was no evidence that they did to any great extent and Professor Puri believes that the changes were caused by the supplement, which is derived from oily fish and evening primrose oil. It contains an essential fatty acid called EPA, but significantly, another type of fatty acid, DHA, is absent. Previous studies by Professor Puri have shown this formula can improve brain function in adults.

His study features in a Five TV documentary, Mind the Fat: Does Fast Equal Food Slow Kids?, to be broadcast on Thursday.

Professor Kishore Bhakoo, of the the Clinical Sciences Centre at Imperial, said: “The thing that amazed me was how much change in biochemistry you could see in three months . . . You’d expect some variation, but they were all going in the same direction.”

He said that the results had implications for the “junk food” debate: “Processed food doesn’t contain these substances.”

Times Recommends

• Please help: maimed children of war want their lives back
• Unlocking the cruellest prison
• Prince Charles named in £81m court battle