Scientists are warning would-be slimmers to be careful about using 'DNA-diets' on the internet.
Dieters may be tempted by 'DNA diets'
A team at Exeter University are to investigate nutrigenomic diets - which offer personalised eating plans.
They suggest people should alter their eating habits based on their genetic make-up.
Lead researcher Dr Paula Saukko said her team would investigate diets on the market: "There have been claims that the public has been misled."
Kits sold by companies over the internet can cost up to £1,000, if they involve personal consultations.
Nutrigenomics is the study of food and diet, and how each interacts with specific genes to increase the risk of certain diseases.
Research has been carried out which has suggested some links between genetic variations and being vulnerable to certain illnesses or disorders which might react to certain diets.
But work has not yet been done which shows the reverse - that eating a certain diet can protect against a disease which your genes make you vulnerable to.
This study, led by researchers the Economic and Social Research Council (ESRC) Centre of Genomics in Society at the University of Exeter, and funded by the Wellcome Trust, is the first to look at claims diets can be based on DNA.
It will also focus on the marketing of commercial 'nutrigenomic' tests, which offer DNA-based dietary advice, and look at whether companies and websites promoting such diets need to be regulated.
Dr Saukko added: "For the first time we are going to investigate what the public is being told by commercial companies and the scientists themselves.
"We are concerned, not just about what is being said in marketing, but what is said to people after they have been through the tests."
She added: "In the USA there are claims you can make your children more intelligent by tailoring their diet according to their genetic make-up.
"There is also the 'DNA diet', which claims you can lose weight, tone up and even live longer by following advice based on analysis of your DNA.
"These tests are available over the internet so there's nothing to stop the British public from buying them also."
She said an analysis was needed so a "threshold" could be drawn setting down what should and should not be sold to the public.
Clare Matterson, director of medicine, society and history at the Wellcome Trust, said: "Nutrigenomics is an emerging new field in relation to diet and our health.
"The work of Dr Paulo Saukko and her team at Exeter, is extremely topical coming at a time when we are bombarded by mixed messages about implication of our diet and lifestyle."