If you've ever tried out the latest diet fad only to find yourself gaining weight and feeling awful and wondered what you were doing wrong, scientists now have an explanation for you.
Israeli researchers, writing in the journal Cell this week, have found that different people's bodies respond to eating the same meal very differently - which means that a diet that may work wonders for your best friend may not have the same impact on you.
Lead authors Eran Segal and Eran Elinav of the Weizmann Institute of Science focused on one key component used in creating balanced diet plans like Atkins, Zone or South Beach. Known as the glycemic index or GI for short, it was developed decades ago as a measure of how certain foods impact blood sugar level and has been assumed to be a fixed number.
But it's not. It turns out that it varies widely depending on the individual.
The researchers recruited 800 volunteers and collected data through health questionnaires, body measurements, blood tests, glucose monitoring and stool samples. They also had the participants input lifestyle and food intake information into a mobile app that ended up collecting information on a total of 46,898 meals they had.
They found that age and body mass index appeared to impact blood glucose level after meals but that so did something else. Different individuals showed vastly different response to the same food even though their own responses remained the same day to day.
"There are profound differences between individuals - in some cases, individuals have opposite responses to one another," Segal explained.
The researchers said the findings show that tailoring meal plans to individuals' biology may be the future of dieting and that the study yielded many surprises for individuals. One example involves a middle-aged woman who tried and failed with many diets. Tests showed that her blood sugar levels spiked after eating tomatoes - indicating it is a poor diet choice for her since blood sugar has associated with heart problems, obesity and diabetes - but since she didn't know this, she was eating them as part of her healthy diet plans several times a week.
Elinav said the work "really enlightened us on how inaccurate we all were about one of the most basic concepts of our existence, which is how we eat and how we integrate nutrition into our daily life."