Some people need to eat sweets instead of tomatos to lose weight

Most people find most diets don't work for them. That's why the diet industry is so lucrative, with so many disenchanted dieters still willing to try the latest new plan in their pursuit of weight loss.

Yet a team of Israeli scientists may have found a 'miracle' diet that really does work for everyone.

In a remarkable new study, they have shown that people's bodies react very differently to the same foods and this may be why some people stay stubbornly heavy however healthily they eat, while others can consume all sorts of junk food without getting fat.

For instance, it turns out that some people can eat croissants without a problem, and yet they needed to go very easy on apricots; others were fine - and even lost weight - eating ice cream as part of their diet, but tomatoes were bad news.

What this study suggests is that the standard dietary advice - that some foods are fattening and some aren't - is wrong. Instead, the foods that make someone else slimmer and healthier aren't necessarily the 'good' foods for you.

These remarkable findings by researchers at the Weizmann Institute in Tel Aviv, and published in the prestigious journal Cell, are a real game-changer.

The key is blood sugar - specifically the different effect a food can have on the blood sugar levels of different people.

We all need blood sugar (or glucose, to give it its medical name) for energy. Most of it comes from carbohydrates found in foods such as bread, rice, apples and peanuts.

Our digestion breaks down the carbohydrate into sugar, which is released into the bloodstream. After eating, a slight rise in our blood sugar - known as the post-prandial glucose response (PPGR) - is normal, but large and regular increases raise your risk of weight gain and obesity, and disorders such as type 2 diabetes, high blood pressure and heart disease.

Thirty years ago, Canadian scientists developed a way of measuring a food's effect on blood sugar. Known as the Glycaemic Index (GI), this system rated foods according to how much they will push up blood sugar after eating.

This was later turned into a diet based on the idea that everyone's blood glucose response to a food will be much the same.

So high-GI foods, such as white bread or croissants, will produce a rapid spike, while low-GI ones, such as vegetables that release carbs slowly, will keep the post-prandial glucose response down.

Today, healthy eating advice often recommends low-GI foods. But the new research turns this on its head.

'The take-home message from this study is that the GI approach may not suit everybody,' says Professor Eran Segal, a computational and systems biologist who led the study. 'If a diet didn't work for you, it may not be your fault, just that you were on the wrong one.'

His co-author Dr Eran Elinav, an immunologist, adds: 'Clinicians believe diets fail because people don't follow instructions properly. But now it seems likely the problem is many people have been getting advice that was wrong for them.'

For their study, known as the Personalised Nutrition Project, the researchers collected an impressive amount of data about the minute-by-minute effect of food on the blood sugar levels of 800 volunteers.

Each volunteer was monitored with an unobtrusive hi-tech device, about the size of a watch, that was taped to their stomachs to measure the changes in their blood sugar, round the clock, for a week.

By the end, the researchers had information on the response to 46,898 meals and recorded more than 1.5 million blood sugar measurements from a total of 4,435 days. Such a detailed analysis had never before been done.

The scientists compared this data against the detailed daily food and activity diaries all the volunteers kept to discover which foods pushed up their blood glucose level or had little or no effect.

'Many of the volunteers discovered they responded very differently to foods with the same GI,' explains Dr Elinav. For instance, the response of four different volunteers to a daily slice of bread varied widely.

'And two participants had completely opposite responses to a banana and a cookie: the glucose response of one shot up with a cookie but stayed flat after a banana, and vice versa.'

Academics and researchers point to evidence that a high-fat, low-carb diet is better for weight loss and improving diabetes. Now it looks as though both camps may have a point - it just depends on your individual response.

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