- A new study followed 1,100 people for two weeks in the US and UK and found that no two-person body responded in exactly the same way as ordinary foods.
- Lead researcher Tim Spector said a good rule of thumb is still eating a variety of plants, including nuts, seeds, fruits and vegetables, incorporating some fermented foods into your diet.
- The researchers behind this study are developing a personalized nutrition company called Zoe.
- Visit the Business Insider homepage for more stories.
There are many different ways to eat, and many people will tell you that your plan is the best way to stay in shape.
But a new study is calling its bluff.
Scientists had 1,100 adults in the United States and the United Kingdom who consumed the same common foods (such as breakfast cakes and sandwiches at lunch) and monitor participants' glucose levels before and after meals. The results showed that the reactions of two individuals were not the same – more evidence that there is no perfect, one-size-fits-all diet.
"We were even surprised by the results," said Tim Spector, an epidemiologist and professor at King's College in London who led the study to Business Insider. "Just because some diet or recommendation is out there does not mean that it fits you."
The findings confirm another recent work that undermines the conventional wisdom of "eating this, not that" on diets.
"On a personal level, we now know that there is no diet or food intervention that is appropriate for everyone, or even for an individual throughout life," a new group of nutrition researchers recently wrote in The Lancet.
Study participants ate many muffins
Spector presented some of his research – done in conjunction with researchers at Harvard and Massachusetts General Hospital – at this month's American Society of Nutrition conference. For the study, participants received a "large standard meal package" to eat. Sensors called continuous glucose monitors were inserted under the skin of the arm to track their blood sugar levels, and they also received a tool to measure glucose, fats, and insulin through blood samples collected by finger bites.
The subjects – 60% of whom were identical twins – then tracked their reactions to what they ate for 14 days. They also wore bracelets to monitor their exercise and sleep habits and took pictures of all the foods they ate during the study.
Almost every morning for the two week study period, participants ate a muffin for breakfast.
"I know Americans love cookies for breakfast, but some Brits did not find it as good as English breakfast," Spector said.
Three types of cookies were on the menu: a cookie rich in fat and low in sugar; a standard muffin with a mean amount of fat and carbohydrates; and a third muffin called "light" that had more sugar but less fat and was "easier to digest," Spector said. Researchers wanted to know: Would all participants' insulin levels rise after they eat the muffins, or would glucose monitors register only a small signal, reflecting a reasonably stable insulin response? Would one of the muffins perform better across the board?
But it was difficult to generalize. Some participants responded well to foods such as muffins, bread or bananas, while others did not.
The researchers found that it was easier to predict how a person could react to a given food based on their own previous glucose monitor readings, rather than any dietary guidelines that should be applied across the population. The level of fitness was also not a predictor of glucose response.
"There was not a difference between sports and non-sports people that we could see," Spector said. "There were a lot of people running every day who had a bad fat response."
It is further evidence that everyone – even identical twins – are different when it comes to nutrition.
"We should customize diets and not just try to squeeze everyone in the same shoe size," Spector said. "For most people, we can make basic recommendations about how they respond to carbohydrates in general, or fatty foods."
To track these findings, Specter is launching another US study on nutrition in the near future, along with scientists at Stanford, Harvard and Tufts. (The team is enrolling attendees now.)
Spector said he lost 20 pounds in 3 years
Researchers hope that data collected on participants' responses to different meals can help each participant determine which specific foods their body responds best. It could even give them clues as to what time of day to eat and exercise, based on the real-time measurements of their glucose monitors.
"The glucose monitors were recording every few minutes, automatically during the two weeks," Spector said. "You could not have done this study five years ago, the technology just was not there."
(Continuous glucose monitors have only been on the market for about two and a half years.)
Specter also tried this strategy of monitoring glucose in his own body. He said his own blood sugar readings seemed to increase every time he ate his tuna sandwich with grapes.
"All these tests showed that I responded very poorly to bread and grapes," he said.
Unwillingly (Spector said he loves grapes and bread), he began to incorporate more apples and walnuts into his lunches instead of grapes and bread, since his body seems to respond better to them. Specter said he now only eats grapes once a week, opts for carbohydrates like rice or pasta instead of bread and tries to include more nuts, seeds and fermented foods like cheese and kefir in his meals.
So far, the changes seem to be working: Spector said he lost 20 pounds in three years.
He was also co-founder of a customized nutrition company based on this research called Zoe. The Zoe team raised $ 27 million from investors and wants to use the results of this and future studies to develop a home-based test and app that will help people evaluate their bodies' reactions to food and adjust their diet and exercise patterns. (Zoe funded the new study)
What you can do for your gut: eat a wide variety of plants
For now, Specter's findings suggest that it is difficult to know how his body's response to certain foods compares with that of others. But he said there are still some things everyone can do to eat well.
One of the best ways to improve your health is to stimulate your microbioma – the microorganisms in your gut that help the body absorb nutrients from the food you eat and avoid disease. Scientists like Spector are increasingly discovering that eating a variety of plants is important for a healthy microbiome.
"Most people in the US have not several microbes and they definitely could improve their intestinal health," said Spector. "We think the more microbes you have, the better your metabolism is."
To boost your microbioma, it helps you incorporate more fiber into your diet (which is easy to get from fruits, vegetables, nuts, seeds and whole grains) and consumes a variety of fermented foods.
"The more junk food you eat, the more [your microbiome] shrinks, "said Spector.
A 2018 study tracked the microbiomes of 10,000 people in the United States, the United Kingdom and Australia and compared people who ate 10 or fewer different plants per week (including soup ingredients and bread grains) to those who ate 30 or more different plants.
Unsurprisingly, plant lovers have been shown to have much healthier microbiomes.