Personalised diets may be the key to combating the diabetes crisis, according to new research.
Tailoring food advice to individual patients helps them shed up to seven times more weight - and could stem the rising tide of cases.
People with pre-diabetes, meaning they are on the cusp with raised blood sugar, should eat differently from those with the full blown illness.
The condition affects about three in ten British adults.
A fibre rich diet including as much fruit, vegetables and wholegrains they want is very effective at reducing risk, say scientists.
But patients with diabetes do better by eating healthy, plant based fats from olive oil, nuts and avocados to shed the pounds.
This can also be effective without restricting calories.
The team said no one solution will work for every patient. But for many these strategies are likely to be more effective than a generic, 'one size fits all' approach.
There are now more than four million people living in the UK with diabetes, most of whom have the type 2 form caused by lifestyle factors such as obesity.
Professor Arne Astrup, of the University of Copenhagen, said: "Our research shows weight loss strategies should be customised based on an individual's biomarkers, which is a big step forward in using personalised nutrition to help people achieve greater weight loss success.
"These findings are particularly important as they allow us to provide those with prediabetes a custom strategy to help them lose weight, which can ultimately prevent or delay the development of type 2 diabetes."
The specific diets that work differ based on whether a patient has normal blood sugar, prediabetes or is living with diabetes.
Results from three trials involving more than 1,200 volunteers found fasting blood sugar and insulin levels - several hours after food or drink has been consumed - can select the best.
They can even help predict how much weight an individual with pre-diabetes, or diabetes, will lose.
Prof Astrup said: "Remarkably, for many patients, use of these biomarkers can lead to a six to seven-fold greater weight loss.
"Going forward, we can educate patients when a diet they planned to follow would actually make them gain weight, and redirect them to a strategy that we know will work for them."
The study published in the American Journal of Clinical Nutrition said the strategy is remarkably simple.
Prof Astrup said: "Recognising fasting plasma glucose as a key biomarker enables a new interpretation of the data from many previous studies, which could potentially lead to a breakthrough in personalised nutrition.
"The beauty of this concept is its simplicity. While we are looking into other biomarkers, it is quite amazing how much more we can do for our patients just by using those two simple biomarkers.
"We will continue to participate in and support research to explore additional biomarkers such as gut microbiota and genomics approaches, which may offer more insights and help to more effectively customise the right diet for specific individuals."