W hy only a tailor-made diet will help you stay slim

IT’S a familiar story among slimmers. You follow the diet a friend recommends – but while they lose pounds, you struggle to shift it.

Now scientists think they have worked out why some eating regimes work for some but not for others.

It seems our bodies all react in a unique way to a wide range of everyday foods, making a one-size fits-all diet difficult to design.

Even products considered healthy – such as tomatoes – can cause blood sugar levels to surge in some people, a study found. In other instances, blood sugar fell after eating ice cream or even pizza.

Slimmers had highly variable responses to starchy foods such as bread and rice – with some more ‘carbohydrate sensitive’ than others. Researchers said the diverse reactions is to do with the make-up of bacteria in our guts, which vary greatly from individual to individual.

Although slimmers have found much success with the Atkins, the Dukan or the 5:2 diets, experts now suggest many could follow personalised eating plans instead.

Scientists in Israel made the discovery while monitoring 800 people over the course of 46,898 meals.

Researchers recorded how much sleep and exercise the participants took, while each subject noted everything they ate on a smartphone app, and monitored their blood sugar levels continuously on a portable glucose monitor. Blood sugar is an important factor in obesity as well raising the risk of diabetes, heart and liver disease and high blood pressure.

The huge amount of personal data was then analysed by computer to see what effect certain foods had on the individual’s body.

In general, foods rich in fibre were found to help reduce blood sugar levels overall, while a lack of sleep, salty food and having an existing high cholesterol level all had a negative effect on blood sugar, the authors wrote in the journal Cell. But there were surprising results among foods that dieters would normally steer clear of. Both ice cream and pizza led to rises in blood sugar in some individuals – but not in others.

The authors suggest that giving each food a ‘glycaemic index’ – how much sugar it produces in the blood – is not useful because it varies greatly

‘Big hole in the

literature’

between individuals. Eran Segal, of the Weizmann Institute near Tel Aviv, said: ‘There are profound differences between individuals – in some cases, individuals have opposite response to one another, and this is really a big hole in the literature.’

He said the findings could force experts to look at how diets work in a new light, adding: ‘The intuition ... is that people are not listening and are eating out of control – but maybe people are actually compliant, but in many cases we were giving them wrong advice.’

His colleague, Eran Elinav added: ‘In contrast to our current practices, tailoring diets to the individual may allow us to utilise nutrition as a means of controlling elevated blood sugar levels and its associated medical conditions.’

In one case a middle-aged obese woman with pre-diabetes – who had failed to succeed on a range of diets over the years – learned that her blood sugar ‘spiked’ after eating tomatoes.

Dr Elinav added: ‘For this person, an individualized tailored diet would not have included tomatoes but may have included other ingredients that many of us would not consider healthy, but are in fact healthy for her.

‘Before this study was conducted, there is no way that anyone could have provided her with such personalized recommendations, which may substantially impact the progression of her pre-diabetes.’