Scientists have identified a natural seaweed fibre that prevents the body absorbing fat.
Tests show that alginate, found in sea kelp, can suppress the digestion of fat in the gut.
Researchers investigated the ability of alginate to reduce fat break-down by a digestive enzyme, pancreatic lipase.
Blocking the action of the enzyme results in lower amounts of fat being absorbed by the body.
Lead scientist Professor Jeff Pearson, from the University of Newcastle's Institute for Cell and Molecular Biosciences, said: "We have already added alginate to bread and initial taste tests have been extremely encouraging.
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"Now the next step is to carry out clinical trials to find out how effective they are when eaten as part of a normal diet."
The researchers found that alginates containing more of a sugar molecule called guluronate were best at blocking fat digestion.
They compiled a list of the most promising seaweeds, including a brown sea kelp known as "tangle" or "cuvie", bladderwrack, and bull kelp.
The findings, published in the journal Food Chemistry, showed that a four-fold increase in one type of tangle alginate boosted anti-fat absorption activity by 75%.
Dietary fibre avoided the side effects of conventional anti-obesity drugs that inhibit enzyme activity, said the researchers.
They wrote: "The inclusion of an alginate into foods.. has the potential to reduce the intake of dietary triacylglycerol (fat) and could greatly help in weight management."