Just as one size does not fit all when it comes to almost any pursuit in life, the same is true for dieting – in fact, nutritionists have observed that what may work for weight loss for one person doesn’t always work for another. And now, a study in the journal Cell begins to figure out why this is the case. It turns out that people metabolize food very differently depending on their individual makeup – and the makeup of their gut microbes. What may lead to a slow, steady rise in blood sugar for one person may lead to a bizarre spike in blood sugar for another. So knowing that foods that are healthy to one person may be unhealthy to another could lead to a fundamental shift in the way dietary recommendations are made moving forward.
Researchers from the Weizmann Institute measured a number of variables in 800 people: From physical measurements to glucose levels to gut microbes through stool samples to blood tests. They sometimes gave people identical meals to measure how each person responded to the same food, and provided them with a mobile app to keep tabs on the foods they were consuming in their daily lives. Their main aim was to monitor how each person’s blood sugar responded after they ate a given food.
As you’d expect, things like body mass index and age affected how people’s blood sugar response. But there were many individual differences beyond those basic variables. For instance, one woman who’d struggled with weight her whole life had a particularly strong blood sugar spike after eating tomatoes, which she regularly ate. Which is all the more bizarre since tomatoes are typically considered a low-glycemic food, meaning that they very definitely don’t spike blood sugar.
“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,” said study author Eran Elinav. “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.”
What this means is that what’s a healthy food for one person may not be so good for another.
To understand more about why these difference exist, the team analyzed stool samples from the participants: They wanted to determine the makeup of their gut microbes and see how it related to glucose response. The team was then able to come up with an algorithm, which could predict how any given person would respond to any given food. They created individualized diets for a group of new participants, and lo and behold, their bodies, including their blood sugar levels after meals, responded accordingly. And over time, their gut microbes also shifted in a similar direction, despite being fed very different diets.
And again, this research expands on what healthcare professionals have already noticed: That not everyone responds the same way to a given diet. And, of course, most anyone who has tried various diets to lose weight can personally attest to that reality. But the new study starts to understand more about why this is true metabolically, and offer some sense of where nutrition might go in the future.
“After seeing this data, I think about the possibility that maybe we’re really conceptually wrong in our thinking about the obesity and diabetes epidemic,” says author Eran Segal. “The intuition of people is that we know how to treat these conditions, and it’s just 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.”
Hopefully as more studies like this come out, we’ll understand more about individual differences in dieting. In the meantime, if one diet doesn’t appear to be effective for you, it might make sense to switch to another. Keep in mind that all diets are not created equal, and it may just be a matter of playing around till you find a better match.
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