I used to think my morning bowl of oatmeal was a small rebellion. One spoonful of honey, half a banana, and I felt like I was cheating on my own diet. Then I read about a four-week diet trial from the University of Sydney and had to put the spoon down.
Here’s the thing that stuck with me: the trial didn’t ask 104 adults aged 65 to 75 to eat less. It asked them to eat differently. Four weeks. That was all it took for the diets that changed something to lower a calculated biological-age score. And the direction of the change depends on one thing: what’s on the plate.
So let me walk you through what the trial actually found, what the score means, and the small swaps I’m making on my own plate this month. No perfection required. 80/20 is enough.
What the Trial Actually Did
The research team supplied every meal. The 104 participants, all aged 65 to 75, were randomly assigned to one of four diets, and for four weeks the researchers provided their food. That’s the kind of control you don’t get on a Tuesday night in your own kitchen, which is part of why the results are worth taking seriously.
Every diet got 14% of its energy from protein. Two were omnivorous, with half the protein coming from animal foods. The other two were semi-vegetarian, with 70% of the protein from plants. Each came in a higher-fat and a higher-carb version. That design let the researchers change one thing at a time: where the protein came from, and how much fat replaced carbohydrates.
What the score measures
“Biological age” here is a score calculated from routine blood and body measurements: cholesterol, insulin, C-reactive protein (a blood marker of inflammation), and blood pressure. The result is an estimate of how old the body appears on those measures, not how many birthdays you’ve had. That distinction matters, because it keeps the claim honest.
What changed
The omnivorous high-fat diet most closely resembled what participants normally ate. That group showed no meaningful change. The other three groups all showed reductions, with the omnivorous high-carb group giving the clearest result.
What the researchers won’t claim
The study’s lead author, Dr Caitlin Andrews, was careful. “It’s too soon to say definitively that specific changes to diet will extend your life,” she said. A lower calculated score doesn’t necessarily mean aging itself has been permanently reversed, and the researchers don’t yet know whether the changes last. The participants were also non-smokers without serious illnesses such as type 2 diabetes.
So treat the result as a signal. The body looked younger on that set of measures, and that’s worth having on its own.
Keep the Carbs, Change the Kind
If you’ve been told to cut carbs as you get older, this trial complicates that. Its clearest result came from a higher-carb diet.
There’s a catch, and it’s the one that makes this feel doable instead of scary. As BBC Science Focus reported, those carbohydrates were minimally processed. Supermarket white bread and chips wouldn’t be expected to give the same result. That’s the difference between a bowl of barley and a white bread roll.
Refining wheat strips away more than half of its B vitamins, 90% of its vitamin E, and nearly all of its fiber, according to Harvard’s Nutrition Source. And eating whole grains in place of refined ones substantially lowers total and LDL cholesterol, triglycerides, and insulin. Cholesterol and insulin are both among the markers behind the biological-age score in this trial. The connection is quiet, but it’s real.
The swaps are simple:
- White rice for brown rice, barley, or bulgur
- Sugary cereal for plain oats
- White bread for bread with a whole grain listed first or second in the ingredients, which is the label check Harvard recommends
Keep the portion. Change the grain.
Move More of Your Protein to Plants
The semi-vegetarian diets took 70% of their protein from plants. Every diet held protein at the same share of energy, so what shifted was where it came from. That’s the part I find least intimidating. Nobody’s cutting protein. We’re just moving some of it.
Beans, lentils, and chickpeas do most of the work here. They’re an inexpensive source of protein, complex carbohydrates, and fiber, and their texture lets them stand in for meat in a lot of dishes. I grew up in upstate New York, and a pot of lentil soup has always been the kind of food that makes a kitchen smell like someone cares.
The evidence goes beyond this one trial. A meta-analysis of 11 clinical trials found that eating pulses, the edible seeds of legume plants, lowered total cholesterol by about 7% and LDL cholesterol by about 6%.
Start with a meal you already cook:
- Swap half the ground meat in a pasta sauce or chili for lentils
- Add chickpeas to a salad in place of some of the chicken
- Build one weekly soup around beans or split peas
If beans leave you bloated, soaking dried beans for at least three hours before cooking may help. One caution for this age group: the trial kept protein steady rather than cutting it. If your appetite has shrunk, or you’ve been told to follow a special diet for kidney disease or another condition, ask your doctor or a dietitian how much protein you need before making any changes.
Trim the Fat You Don’t Notice
The one diet that showed no change was the omnivorous high-fat diet. And a lot of added fat never registers as a choice. It gets poured into the pan or spread on toast without a second thought.
Three habits cut it without a single new recipe:
- Measure cooking oil with a spoon instead of pouring from the bottle
- Go lighter on butter and cheese, both on Harvard’s list of foods to limit
- Keep red meat to smaller portions, which Harvard’s Healthy Eating Plate also advises
When you do use fat, the type matters. Harvard’s guidance is to use healthy oils such as olive and canola for cooking and at the table, and to limit butter. One caveat, and I like that the researchers say it out loud: the semi-vegetarian high-fat diet also lowered the score, so the trial can’t pin the effect on fat alone. Their own summary is that cutting either fat or animal protein was linked to a lower score. That’s why this swap works best alongside the one above.
Change Enough to Count
This is the least comfortable finding. The diet that looked most like people’s usual eating did nothing measurable. A single token swap may not be enough. Aim to change most meals, not one.
A gentle place to start is the side of the plate. Harvard’s Healthy Eating Plate puts it plainly: the more vegetables, and the greater the variety, the better. Potatoes and fries don’t count. Add fruit of any color where you’d normally reach for a sweet snack. If you’re adding beans, whole grains, and extra vegetables at once, go slowly. Tufts nutrition scientist Jennifer Lee advises increasing fiber gradually, and warns that too much fiber without enough water can leave you constipated. I learned that the hard way once, and I’m not doing it again.
Track the Numbers You Can Check
You can’t calculate this biological-age score at home. But several of the measurements behind it are routine. Two of them, blood pressure and cholesterol, can be checked at a normal doctor’s appointment. If you want to know whether a change is working for you, get a baseline before you start, then recheck after a few weeks of eating differently.
If you take medication for blood pressure, cholesterol, or blood sugar, or follow a diet your doctor prescribed, talk to your doctor before changing what you eat. Eating differently can shift those readings, and your doctor may need to know.
And a note before you start: I’m a registered dietitian, but this isn’t professional medical advice. Your situation is yours, and your doctor knows your history. Use this as a starting point for a conversation, not a prescription.
FAQ
Not necessarily. The trial’s clearest result came from a higher-carb diet, as long as the carbs are minimally processed: whole grains, not white bread and chips. Keep the portion, change the kind of grain.
The semi-vegetarian arms of the trial took 70% of protein from plants, and every arm kept protein at 14% of energy. Start with one or two meals a week where plants carry the protein, and adjust from there.
No. Blood pressure and cholesterol are the two markers from the score you can check at a routine appointment. Get a baseline before you start, then recheck after a few weeks of eating differently.
Whether a month of lentils and brown rice adds years to your life is a question this trial can’t quite answer, and its authors say so plainly. But it does show that a score built from markers doctors already watch can move quickly in adults 65 to 75, and that the direction of movement depends on what’s on the plate. Give it four weeks and check the numbers that matter to you. The overall score may be out of reach for now, but your blood pressure and cholesterol aren’t.
a note from Hazel: I used to think healthy eating was about subtracting: less sugar, less butter, less of everything. This trial reminded me that it’s about swapping the kind of food, not the amount of it. That’s a lot less exhausting. And honestly, a plate that makes you feel calm instead of deprived is already worth something.