At precisely 12 p.m., a tray of food was delivered to Nancy McKinnon on day nine of her stay at Pennington Biomedical Research Center in Baton Rouge.
This day, the tray contained a fajita bowl with sides of guacamole, salsa and sour cream. For dessert, a homemade peanut butter cup.
That’s a lot better, in her opinion, than a few months ago, when the tray held hot dogs, macaroni and cheese and soda – like “stuff you pick up at the gas station,” said McKinnon, a 66-year-old from Denham Springs who works remotely managing a plumbing company.
Participant Nancy McKinnon sits down for her lunch for a nutrition study at Pennington on Friday, April 12, 2024 in Baton Rouge, Louisiana.
STAFF PHOTO BY MICHAEL JOHNSON
It’s also better than a couple of weeks earlier when the meals involved potatoes and beans, which didn’t agree with her stomach. Plus, there wasn’t much seasoning, and “being from Louisiana, that’s just unacceptable,” said McKinnon.
Items for purple meals line trays as researchers carefully prepare each meal according to what each participants is assigned at a nutrition study at Pennington on Friday, April 12, 2024 in Baton Rouge, Louisiana.
STAFF PHOTO BY MICHAEL JOHNSON
The meals, and dozens of accompanying medical tests, are part of a new 5-year, $189 million study backed by the National Institutes of Health that aims to cut through the confusion on a basic, but complicated question: What is the best diet?
Researchers across the U.S. will track the diets of around 10,000 people as they measure how their body responds in order to generate a massive data set that can be mined by artificial intelligence, allowing health care providers to one day provide customized diet advice. About 1,200 people from around Louisiana will be tracked by researchers at Pennington, one of just six clinical centers involved in the program. Some of them, like McKinnon, will live at the facility in two-week increments as researchers collect everything from their gut bacteria to their nail clippings.
In the future, researchers imagine a tailored diet that could be prescribed like personalized medicine, taking into account your medical history, genes, goals, stress level and even what food is available regionally. It’s called Nutrition for Precision Health, a subset of the federal government’s All of Us research program, and it’s based on the idea that a diet that makes one person feel great might not be ideal for another.
“We know that for shoes, one size does not fit all,” said Eric Ravussin, associate executive director for clinical science at Pennington. “But it’s true for anything in life. And especially when it comes to nutrition.”
Choosing diets
Research Specialist Callie Nipple adds a premade entray to a tray as she prepares a meal for a participant in a nutrition study at Pennington on Friday, April 12, 2024 in Baton Rouge, Louisiana.
STAFF PHOTO BY MICHAEL JOHNSON
Inside Pennington’s metabolic kitchen, research specialist Callie Nipple put mini Oreos onto a scale, one by one. Next to her, 36 Ziploc bags of Frosted Flakes in various amounts awaited sorting for participants. Each patient gets a specialized calorie count. The measurements are precise. When participants are done, researchers log the remaining food.
“Everything is weighed out to a 10th of a gram,” said Gina Castelluccio, another research specialist.
Participants especially like a zucchini “zoodle” meatball dish, an alternative to wheat-based noodles, said Nipple.
The zoodles are part of the third diet participants cycle through, called the orange diet, which is high-fat, low-carb. The first is the purple diet, a highly processed, salty diet that includes convenience food like chicken nuggets. Second is blue, which is similar to a Mediterranean or DASH diet that emphasizes plant foods.
Items for orange meals line trays as researchers carefully prepare each meal according to what each participants is assigned at a nutrition study at Pennington on Friday, April 12, 2024 in Baton Rouge, Louisiana.
STAFF PHOTO BY MICHAEL JOHNSON
Most participants don’t live at the center, so the kitchen prepares food for people to pick up every few days. A courier also drops off food in New Orleans. But living at the center, what researchers call module three, does have its perks: a $6,200 payment for six weeks total, separated into three two-week stays. And while McKinnon sometimes gets lonely for her normal life, the staff keeps her company.
“These girls are so good to me,” said McKinnon, gesturing to the half dozen nurses and employees who watch her eat, measure her water intake, take her blood and go on walks around the campus with her. “They’ve all become like best friends.”
Research Specialist Gina Castelluccio carries a sealed bag for a participant to pickup for a nutrition study at Pennington on Friday, April 12, 2024 in Baton Rouge, Louisiana.
STAFF PHOTO BY MICHAEL JOHNSON
Those not living at the center — known as module 2 — get about $2,000, in addition to three daily meals with snacks for the duration of the study. Generally, people are happy with the meals.
“They love that they don’t have to buy their own food,” said Leann Redman, associate executive director for scientific education. “I think one good sign is that we’ve had requests for recipes.”
Redman and other researchers deliberated over the best diets to include in the massive study, even holding a taste testing party at Pennington. The diets needed to be different enough from each other to elicit a noticeable response in measurable health metrics.
Participants also record the food they normally eat over a two week period, known as module one. That pays about $300, and doesn’t require people to necessarily continue with the meal portion of the study. Since a large chunk of the overall results will be from people in Louisiana, the Cajun diet — things like jambalaya, poboys, gumbo and crawfish — will play a significant role in understanding food’s effect on the body.
“We know we have foods here that are enjoyed only in Louisiana and people come here to eat those,” said Redman. “That’s why having a location for this project in the South is so important to understanding nutrition for Americans.”
For decades, diet trends have cycled in and out of fashion. In the ‘80s and ‘90s, low-fat and calorie-counting regimens took hold. By the 2000s, the Atkins Diet demonized carbs and called for embracing fat, promising weight loss by eating butter, eggs and steak. A decade later, plant-based diets surged, along with intermittent fasting and the pursuit of ketosis, a more streamlined version of Atkins.
At the same time, a bevy of research points to increasing health problems linked to diet, and obesity continues to rise. Louisiana has more obese adults than almost any other state, according to the Centers for Disease Control and Prevention. Over 40% of Louisiana adults have a body mass index over 30. A decade ago, the obesity rate was 31% in Louisiana. In the 1990s, it was around 15%.
But the relationship between genetics, food and the environment is complicated. And people who hang on to extra weight face a stigma, said Dr. Taniya De Silva, an endocrinologist and associate dean of student affairs at LSU Health New Orleans. Typical diet advice might not work for them.
“People say, ‘Oh, they must just be sitting in front of the TV and eating,’” said De Silva. “And yet when we look at it, we know that some people are more inclined to have a higher BMI.”
For some people, a strict diet may cause their metabolism to slow in order to maintain a certain weight. For those, this study could be illuminating.
It’s also unique in that researchers are truly controlling what participants eat, said De Silva, who is not involved in the study. Often, studies rely on diet recall. In this study, participants who live at the center have their luggage checked for snacks or seasonings at the door.
Understanding results
A few days on the purple diet, the one consisting of processed foods, and McKinnon’s blood pressure started to rise. She felt bloated.
“I never felt sick,” said McKinnon. “I just felt a little off.”
Although each diet only lasts for two weeks, that’s enough time to see an impact. While participants won’t see much weight loss or gain, as the diets are formulated to maintain weight, they could see inflammation markers go up or down, said De Silva. Insulin production may vary, which is the body’s response to sugar, said Ravussin.
Items for purple meals line trays as researchers carefully prepare each meal according to what each participants is assigned at a nutrition study at Pennington on Friday, April 12, 2024 in Baton Rouge, Louisiana.
STAFF PHOTO BY MICHAEL JOHNSON
But researchers aren’t going into the study with hypotheses. Rather, they hope to take the vast amount of data collected to feed into an algorithm that will help illuminate how some people respond to a low amount of carbs or particular foods.
“It’s called exploratory science,” said Ravussin. “We’re going to discover the new pathways being associated with such-and-such food in your diet.”
For example, researchers will map the exact bacteria in each participants’ gut, down to the species. Certain types of microbacteria are associated with high and low body weights. Gut bacteria has been linked to diseases like Alzheimer’s.
“It’s important to make people realize that with small differences they can make in their diet, in their physical activity, or in their sleep, they can make big differences in their health,” said Ravussin.
Most participants are motivated, in part, by a fascination with nutrition and how their body responds. They ask questions. McKinnon has a copy of her bone density scan she plans to take to her doctor. Much of the data researchers collect will be available to participants. And already, she’s thinking more about how food makes her feel.
“I think it’s helped me to rethink the way I eat,” said McKinnon. “I will adjust my diet when I go home, which is a good part of the whole program.”
