Here is the full transcript of computational biologist Eran Segal’s TEDx Talk: What is the Best Diet for Humans? at TEDxRuppin conference. This event took place on June 23, 3016.
Listen to the MP3 Audio: What is the best diet for humans by Eran Segal at TEDxRuppin
Eran Segal – Computational biologist
This is me ten years ago. I weighed 40 pounds more than today, and like many people, I wanted to lose weight.
Like many people, I wanted to know what is the best diet for humans. Many of us actually have an opinion about this question. Some believe that a low fat, plant-based diet is the best. Others, that a low-carb diet, rich in protein and animal fat, is the best. Others have opinions on how much sugar we should eat, or how much salt, cholesterol, saturated fat, eggs or dairy products we should have in our diet.
But the question of what the best diet is, is a scientific one, so there should be no room for opinions or beliefs. If Diet A is really better than Diet B, then a study that compares the two on enough people should show that definitively. No opinions, no beliefs, just hard data, right?
What is also clear is that if the best diet does exist, then we haven’t yet found it, because the incidence of diet-related disease has increased dramatically in the past several decades. Now, you might think it’s because people don’t listen to what we tell them. But in fact, that’s not true, people actually generally do follow dietary guidelines.
But according to the Center for Disease Control, if you live in the United States, there’s over a 70 percent chance that you’re either overweight, diabetic or have non-alcoholic fatty-liver disease. And there’s overwhelming evidence that diet and lifestyle are major drivers of these conditions.
So why is it that after so much research, we still don’t have an answer to the seemingly simple question of what is the best diet for humans? What I’d like to propose to you today is that the reason we don’t have an answer is because we’ve been asking the wrong question.
And it’s the wrong question because it assumes that the best diet depends only on the food and not on the person eating it. But what if differences in our genetics, lifestyle, our gut bacteria cause us to respond differently to food? What if these differences explain why some diets work for some people but not for others? What if our nutrition needs to be personally tailored to our unique make-up? This is exactly the question we set out to ask in our own research, which I did with my colleague Eran Elinav and several graduate students from the Weizmann Institute of Science.
To take a scientific approach, we first searched for a metric of healthy nutrition that we should study. Most studies examine weight loss or risk of heart disease after some diet. But the problem is that these are affected by many factors unrelated to diet, they take many weeks to change, and in the end, you get a single measure of success.
And if it didn’t work, well then it’s very hard to understand why. And so instead, we searched for a metric that would still be relevant for weight management and diet-related disease, but one that we could also easily and accurately measure across many people.
And this led us to focus on blood glucose levels, and more precisely, changes in blood glucose levels after a meal. We call this a “meal glucose response”. Why is it important? Well, because high glucose levels after a meal promote both hunger and weight gain. After we eat, our body digests the carbohydrates in the food into simple sugars and releases them into the bloodstream. From there, with the help of insulin, cells throughout our body remove the glucose from the blood so that they can use it as a source of energy.
But insulin also signals our body to convert excess sugar into fat and store it, and that’s a primary way by which we gain weight. In addition, fast flow of glucose into the blood often causes our body to release too much insulin, which could lower our glucose levels to below baseline, making us feel hungry and eat more.
Meal glucose responses are also very relevant for our health because they’ve been shown to be risk factors for obesity, diabetes, cardiovascular disease and other metabolic disorders. A recent study that followed 2,000 people for over 30 years found that higher meal glucose levels after meals predict overall higher mortality. Finally, and not least important, with recent technological advances, we can now follow a person’s glucose levels continuously for an entire week.
And since the average person eats around 50 meals a week, it allows us to measure glucose responses to 50 meals in just a single week. Meal glucose responses also provide us with a way to directly measure the effect of every single meal, as opposed to common approaches that only evaluate the effect of an overall diet.
Now, of course, there are many factors beyond glucose levels that influence a healthy diet. But this is a very important one, and solving it can be a major step forward. Luckily for us, we managed to convince 1,000 healthy people of this idea, and we connected them to one of these small glucose sensors and tracked their glucose levels continuously for an entire week.
And during that week, participants logged everything that they ate on a mobile app that we developed. And so that allowed us to measure glucose responses to 50 different meals for each person and around 50,000 different meals across all 1,000 participants, making our study the largest one that was ever done on this problem until today.