New Study Explains Why there’s No Diet that Fits-All

Sharon Moore November 26, 2015

Most nutritionists would agree that there’s no diet that fits all. While certain diet programmes work for others, they don’t provide similar result for the rest. But why is it so? According to a new study, even if we eat the same meal every day, it is how it’s metabolised by our body that makes the difference.

The study, led by Eran Segal and Eran Elinav of the Weizmann Institute of Science in Israel, found that glycaemic index (GI) of any food- a standard measure for monitoring glucose levels in the body, is not a set value. It actually depends per individual.

For the study, the researchers looked at health questionnaires, body measurements, blood tests, glucose monitoring, stool samples, and a mobile-app report lifestyle and food intake and tracked the blood sugar levels of 800 people. In addition, the volunteers received a few standardised as well as identical meals for their breakfasts.

As expected, age and body mass index (BMI) were found to be associated with blood glucose levels after meals. But what is surprising is that different people show vastly different responses to the same food, even though their individual responses did not change from one day to another.

Participants received feedback daily through the mobile app about how their breakfast affected their blood sugar levels. The individualised feedback yielded many surprises. In one case for example, a middle-aged woman with obesity and pre-diabetes, who had tried and failed to see results with a range of diets over her life, learned that her "healthy" eating habits may have actually been contributing to the problem. Her blood sugar levels spiked after eating tomatoes, which she ate multiple times over the course of the week of the study.

"Most dietary recommendations that one can think of are based on one of these grading systems; however, what people didn’t highlight, or maybe they didn’t fully appreciate, is that 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," says Segal.

He adds that tailoring diets to the individual may be a key factor in utilising nutrition as means of controlling elevated blood sugar levels and its associated medical conditions.

Segal and his team seek to further develop a much better way of providing a personalised nutrition feedback that would involve fewer number of inputs.

Their study was published yesterday in the journal Cell.