What, Exactly, Should You Eat? Inside the $190 Million Study Trying to Find the Answer

Scientists agree broadly on what constitutes a healthy diet—heavy on veggies, fruit, whole grains and lean protein—but more research is showing that different people respond differently to the same foods, such as bread or bananas. (Photo: Christiana Botic for WSJ)
Scientists agree broadly on what constitutes a healthy diet—heavy on veggies, fruit, whole grains and lean protein—but more research is showing that different people respond differently to the same foods, such as bread or bananas. (Photo: Christiana Botic for WSJ)

Summary

Scientists are investigating how different people respond to different diets.

BATON ROUGE, La.—At a biomedical center here, there’s a man scarfing down Frosted Flakes and tater tots while hooked up to an IV. His job? To help the government figure out what you should eat.

That man, Kevin Elizabeth, a 28-year-old tech worker, is one of 500 Americans who will be living at scientific facilities around the country for six weeks, eating precisely selected meals and undergoing hundreds of medical tests. He is part of a new study, costing $189 million, that is one of the most ambitious nutrition research projects the National Institutes of Health has ever undertaken.

If the study succeeds, it could help Americans get healthier and cut through years of confusion about nutrition guidance.

Chronic diseases linked to our diets are on the rise. Sometimes-conflicting advice hasn’t helped—remember the low-fat craze?—and has resulted in little improvement in our health. The percentage of U.S. adults ages 20 and over with obesity is 41.9%, according to Centers for Disease Control and Prevention data collected from 2017 to 2020. That is up from 30.5% in 1999 to 2000. About 15% of American adults have diabetes, up from 10.3% in 2001 to 2004, according to CDC data.

The NIH study will involve 10,000 participants in total, some of whom are signing up for intense measures, like monitors that follow them and make sure they don’t eat smuggled food, or special eyeglass attachments to record what they eat.

If all goes according to plan, in a few years you’ll be able to walk into your doctor’s office, get a few simple medical tests, answer questions about your health and lifestyle, and receive personalized diet advice, says Holly Nicastro, coordinator for the NIH’s Nutrition for Precision Health study.

A diet plan, just for you

Scientists agree broadly on what constitutes a healthy diet—heavy on veggies, fruit, whole grains and lean protein—but more research is showing that different people respond differently to the same foods, such as bread or bananas.

Elizabeth and his fellow participants spend two weeks each on three different diets. One is high fat and low carb; another is low on added sugars and heavy on vegetables, along with fruit, fish, poultry, eggs and dairy; a third is high in ultra-processed foods and added sugars.

The study’s scientists aren’t going in with any particular hypotheses about which foods are best. Instead, they will take the vast amounts of data they are collecting to create algorithms that, they hope, can predict what a particular diet will do for any one of us. They’re recruiting participants with a range of ages, ethnicities, backgrounds and health conditions to make sure the results apply broadly.

“We might be able to fine-tune diets," said Alice H. Lichtenstein, director of the Cardiovascular Nutrition Team at Tufts University, who isn’t involved in the NIH study. “So it will work out better if one person in the family gets a little more protein and somebody else gets a little more fat and another gets a little more carbohydrate."

And with more customized guidance, nutrition researchers hope that more Americans will see results—like blood-sugar levels dropping or blood pressure improving—and stick to healthier diets.

“There can be this public perception out there that ‘Oh, everyone knows what you’re supposed to eat, but it doesn’t work for me.’ But if this is for me and based on me," people might be more likely to follow the plan, Nicastro said.

Tater tots and a heart monitor

Elizabeth was encouraged to consume every last morsel of his Frosted Flakes breakfast, down to the sugary milk left behind in the cereal bowl. Scientists at the facility here, Pennington Biomedical Research Center, part of the Louisiana State University System, want to know exactly how much he’s eating of his carefully designed meal.

He wore a heart-rate monitor, a device to record his physical activity, and a continuous glucose monitor to measure blood sugar. An IV stuck out of his hand. Nine times over the next four hours, a technician drew Elizabeth’s blood to measure his body’s response to the meal, including his insulin and glucose levels, along with dozens of other metrics. Elizabeth gave samples of urine, stool and saliva. Scientists had already collected specimens of his hair and nails, and put him through a DEXA scan, a full-body X-ray that quantifies the amounts of fat, bone and muscle.

“I thought it would be nice if I could do something meaningful for, like, science and, personally, just to learn more about diet and how it affects me personally," said Elizabeth, who works in technology at a company that rents out heavy equipment to businesses.

Since he works remotely from his Baton Rouge home, his schedule hasn’t changed much during the study. But he misses his fiancée, who’s a nurse elsewhere at Pennington Biomedical, and their two cats.

Elizabeth was on day 13 of the largely ultra-processed diet when he had his blood drawn around his Frosted Flakes breakfast. The diet resembled what Elizabeth typically eats at home (a lot of convenience foods like frozen pizza), though he said he felt more tired than usual, especially during exercise.

“Just not feeling great," he said. He felt better and had more energy during the two weeks he was on the veggie-heavy diet, though sometimes “it was hard to eat so many vegetables," he said.

A smart toilet paper device and camera glasses

One novel tool being used in the study: small cameras that attach to eyeglasses and start recording when the wearer chews. The cameras were designed to overcome one challenge in a lot of nutrition studies, which is that people don’t often accurately report what they eat. This way, the cameras can record the eating.

The glasses have been a tough sell. “A lot of the participants are wondering if it captures other things," said Catherine Champagne, professor of dietary assessment and nutrition counseling at Pennington Biomedical and Louisiana State.

Study workers periodically blend the meals into a giant smoothie and have them analyzed by an outside lab, to make sure all the sites’ daily menus have consistent proportions of fats, carbs, protein and other components.

Staffers monitor participants who are staying at Pennington Biomedical to make sure they are sticking to the plans. Someone watches them eat their study meals and encourages them to eat the whole thing. Escorts accompany participants to the gym and on walks to prevent any sneaky vending-machine dashes. Visitors have to leave bags outside the study area and open their pockets, to root out any contraband food.

And then there’s the bathroom. Some participants elsewhere in the NIH study are using a new “smart" toilet paper device to collect stool samples. The researchers are particularly interested in how the three diets affect the gut microbiome—and how that influences how people respond to a diet.

On that Tuesday morning at Pennington Biomedical, Elizabeth was lying down in a hospital bed with a clear plastic hood covering his head. He was instructed not to move or talk. Biomedical engineer Isabella Reed was conducting a test to measure Elizabeth’s resting metabolic rate, basically the number of calories he burns just by being alive and awake. A TV was on.

“They can’t watch the Food Network," said Reed, who said even looking at food can change the test results. Anything scary is out, too; being freaked out can burn calories. “We watch a lot of Hallmark movies and HGTV," Reed said. “We keep it pretty chill."

Write to Andrea Petersen at andrea.petersen@wsj.com

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