(Newser) – Like many people, one middle-age woman in an Israeli study just couldn't seem to find a diet that worked. The problem: The seemingly healthy tomatoes she was eating multiple times per week were actually causing her blood sugar levels to spike. The New Zealand Herald reports the researchers from the Weizmann Institute of Science have made a key insight in the science of dieting, discovering that the bodies of different people can respond differently to the exact same meal—even an apparently healthy one. "There are profound differences between individuals," researcher Eran Segal says. "In some cases, individuals have opposite responses to one another." What that means is a diet that works for one person might be ineffective for another, and the future of dieting could lie in meal plans created specifically for individuals.

Researchers monitored 800 volunteers for a week and surveyed nearly 47,000 meals with a focus on the glycemic index, which ranks foods based on how they affect blood sugar, according to a press release. Doctors and nutritionists have long used the index to recommend diets, believing it to be a constant for everyone. Instead, the study in Cell found that the glucose levels of volunteers responded differently to the exact same foods, independent of age or BMI, the Herald reports. "I think about the possibility that maybe we're really conceptually wrong in our thinking about the obesity and diabetes epidemic," Segal says. The assumption is that people who gain unwanted weight are ignoring advice because they're unable to control their eating—"but maybe people are actually compliant, but in many cases we were giving them wrong advice." (It was easier to be thin 20 years ago.)

