The Nordiska diet, developed with the help of experts at Newcastle University, is based on the premise that genetic testing can determine the right food and exercise regime for your body type.
Thought to be the first genetic-based diet available in the UK, it is being sold online at 99 pounds for the gene test alone, and in a 159-pound package including three months of follow-up advice from dietitians.
A trial on 7,700 people in Denmark saw nine out of ten lose weight, with some losing up to 26lb (12kg) in four months.
Dieters are asked to complete a questionnaire and send a DNA swab of their mouth in for laboratory analysis.
The diet's creator, cell biologist Dr Carolyn Horrocks, said her firm, myGenomics, examines the swab for eight variants of seven genes.
These genes relate to how quickly an individual metabolizes fat and carbohydrate, appetite control and muscle activity.
A 30-page personalized report assigns the individual one of four types of diet: low in fat; low in carbohydrate; low glycemic; or healthy balanced.
This is combined with a type of exercise: endurance or high-intensity.
All dieters are recommended three meals and three snacks a day, to a total of 1,300 to 1,800 calories.
No foods are forbidden, just restricted, and those with the 159-pound package must fill in weekly food diaries so the company's dietitians can provide regular feedback.
Dr Horrocks teamed up with Danish GP Carl Brandt on the diet concept after she came up with the idea while researching the risk factors for Type 2 diabetes.
"Each of us has a unique genetic fingerprint which shows why some types of diet work for people and not for others," the Daily mail quoted her as saying.
"I realized genetic variants were being analyzed for very technical purposes but they could be used by people in their everyday life to control their weight and help prevent the sort of diseases such as diabetes and heart disease that I was working on.
"If something is right for your body, it will be easier to stick to, less arduous and we have shown you have a greater chance of keeping the weight off," she said.
She said the approach is intended to produce "slow and steady" weight loss, and is not related to the blood group diet, which has been criticized by experts.
"It's not a fad diet, all our dietitians and trainers are registered and have a science background," she added.
The Denmark trial was carried out by Newcastle University and colleagues in Copenhagen on men and women with an average age of 40 who had a BMI of 30 to 35.