There’s a simple, scientific reason that diets almost never work

“Good for you” doesn’t mean the same thing to all of us.
“Good for you” doesn’t mean the same thing to all of us.
Image: Reuters/Umit Bektas
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Each day, we make hundreds of food decisions. Some of us eat and feel well. Others eat and over time, gain weight, or worse, develop disease. One third of the world, or 2.1 billion people, are overweight. In our global quest for thinner waistlines and better health, we are learning why our diets are failing.

Our microbiomes.

The microbiome, comprised of trillions of microbes, inhabits all portals of entry into our bodies, but mostly resides in our gut. We are learning that our microbiomes are far from cellular hitchhikers and are, instead, critical to our overall health; they filter everything that goes into our bodies, including food, medicine, and environmental toxins. Diet interventions will continue to be highly ineffective if we ignore that we are essentially “superorganisms” with active microbiomes that sustain each of us differently. If we learn more about our microbiomes on a genetic level, we can tailor foods to rebalance our individual microbiomes, avoid failed diets, and radically improve our health.

A recent, groundbreaking study showed how foods impact people differently, suggesting a reason for the inadequacy of the one-size-fits-all diet. An Israeli research team, led by Dr. Eran Segal of the Weizmann Institute of Science, showed how unhealthy foods affect people differently based on variation in individual microbiomes, physiologies, and lifestyles. The study tracked 800 people’s blood glucose levels in response to meals, and found that one person’s blood glucose spikes in response to a particular food, like a banana or cookie, but another person’s glucose lowers from that food. This study suggests that people with specific proportions of bacteria in their microbiomes can withstand impacts of certain “unhealthy” foods, while others cannot.

The same study’s authors acknowledge that what we eat impacts our microbiome, creating a cycle: we eat, our food impacts our microbiomes, and our microbiomes influence how food impacts our health. Many physiological and lifestyle factors impact our microbiomes, but our diets are the biggest influencers. The average microbe lives 20 minutes, so our microbiomes can look different day to day, meal to meal.

An unhealthy microbiome is complicit in a variety of diseases—from autism to depression, Type II diabetes, and obesity. Once we understand the health impact of microbiome-nourishing foods like probiotics and prebiotics, we will be able to customize diets to help treat the many diseases that seem to have roots in our guts. Some dietary advice might be universal, like the age-old council to eat more vegetables, but other prescriptions might involve intricate combinations of specific bacterial strains that complement our individual microbiomes or prebiotics that feed specific bacteria. As we learn about how individual foods impact our microbiomes, we will develop personalized dietary recommendations that optimize for foods’ microbiome-friendly properties, like content of polyphenols, which are high in berries. We’ll also see data-driven personalized guidelines of how to stay within a healthy range of eating.

For optimal health, we need to live and eat to support healthy microbiomes. A perfect picture of a healthy microbiome isn’t yet clear, but researchers are investigating the profiles of various microbiomes—which bacteria, in which proportions—and health outcomes. Eating meat and processed food, for example, correlates with bacterial populations that are high in obese people. Eating prebiotic foods, like leeks, whole wheat, and bananas, correlate with higher numbers of bacteria most often found in thin people. Prebiotics are foods high in fibers that are indigestible to humans but that nourish gut bacteria. Additionally, microbiome diversity has been found to be correlated with healthy outcomes.

Experts predict that a combination of genetic, behavioral, and other data will be used to develop personal diets as early as five years from now. Individual genetic testing of our microbes—99% of our DNA is microbial—is already bringing a revolution in diets and health, with innovation focused on smaller, faster, and cheaper microbiome testing technologies like smart toilets.

We’ll need rapid, affordable, and regular testing of our microbiome for any dietary intervention that seeks to treat our individual imbalances. Doctors, dietitians, and nutritionists might prescribe such testing. Based on the results, the doctor would then tailor diet advice to maintain health or help treat disease. Since processed foods, antibiotics, and pathogens disrupt healthy microbiomes, we may see a “disruption index” indicating whether our lifestyles are driving our microbes out of balance.

To eat and feel good, however, we can’t just dutifully obey our personal dietary algorithms. We’ll also need a revolution in the way we make, distribute, and market food. With microbiome research maturing [into clinical application], consumers will soon see both our food and healthcare systems make major adjustments towards tending to our life partners—our microbes—to capture the opportunity to have a wide-reaching impact on our wellbeing.