These longevity meal swaps may lower your biological age — while saving time and money

• A new study tracked the "biological age" of people who swapped some of their meat for more veggies.
• Eating more vegetables and complex carbohydrates seemed to improve basic health metrics.
• Importantly, people didn't lose strength when they cut back on animal protein, from 50% to 30%.

Pump up the veggies, beans, and nuts, and pare down the meat, just a little bit.

That appears to be the takeaway from a new study tracking how changes to the typical "Western" diet, subbing in more vegetables and lowering saturated fat content, might contribute to healthy aging.

The study, conducted in Australia, fed roughly 100 healthy adults aged 65 to 75 a rotating menu of freshly prepared, unprocessed meals for one month, only changing up how much fat, meat, and carbohydrates different people ate on different diets.

The study was short, but on both functional measurements like grip strength, as well as clinical tests and measures of an emerging health metric called "biological age," people appeared to derive a slight health benefit from replacing some of their daily meat with plant proteins, and replacing saturated fat with more complex carbohydrates.

"What we wanted to do was a study that actually provided some real information about the causal relationship between macronutrients and health in old age," senior study author Alistair Senior, a nutrition scientist at the Charles Perkins Centre at the University of Sydney, told Business Insider.

The results lend more evidence to the idea that cutting back on, but not necessarily eliminating, meat can be good for a person's long-term health.

"Even our vegetarian diets weren't 100% vegetarian," Senior said. "They aim for about 70% of the protein coming from plant sources, and 30% from animal sources."

Three diet tweaks made a typical 'Western' diet healthier

For the study, researchers split participants into four different groups. They were instructed to only eat the food given to them during weekly meal deliveries for a full month. No alcohol, no extra sweets, no ultra-processed snacks.

"It's not perfect, people cheat, people might not be reporting everything they eat, but I think we did as good as is feasible," Senior said.

There were two "omnivore" diets:

• Diet 1: 14% protein, ~40% fat, ~40% carbohydrates

A meal on this plan was the closest to a standard, "Western" diet, with half of the protein intake coming from animal products.

For example: chicken tikka masala with white rice and green beans.

• Diet 2: 14% protein, ~30% fat, ~50% carbohydrates.

Similar to the first diet, with half of the protein from animal sources. This diet includes more carbohydrates from whole grains and vegetables, and has a lower fat content, with ingredients like brown rice and quinoa included more often.

And there were two "pro-veg" diets:

• Diet 3: 14% protein (less meat), ~40% fat, ~40% carbohydrates

For example: yellow coconut curry with rice, veggies and tofu.

• Diet 4: 14% protein (less meat), ~30% fat, ~50% carbohydrates.

A meal on this plan includes more carbohydrates like potatoes.

For example, a veggie-heavy cottage pie, with peas and carrots on the side, was on the menu.

People on diets 2, 3, and 4 all ended the month with measurable improvements to their "biological age," as measured with the Klemera-Doubal Method, which includes data from regular blood tests a doctor might order at an annual exam, like blood pressure, cholesterol, and creatinine levels. People who ate diet No. 1, the high-fat pro-meat "Western" diet, saw no change on their "biological age" tests. All four diet groups lost about the same amount of weight, an average of roughly four pounds, three of those being fat (this may just be a result of the nature of the trial, as a no-junk-food, no alcohol plan).

The study, while still preliminary, suggests older adults don't have to load up on meat to maintain their muscles and strength as they age.

Why meat may be bad for longevity

When people reduce their meat and saturated fat intake, they change the forces that are acting on their cells.

Senior says the amino acids in animal proteins turn on pro-growth pathways that tell our cells to grow and reproduce. Too much cell growth in old age can be a bad thing, propelling disease processes like cancer. Longevity scientists are also studying how the opposite of cellular growth and proliferation, what's called autophagy, the process by which starving cells eat and recycle themselves, may be a longevity-booster.

Meat consumption also amps up oxidative stress on cells, and can increase chronic inflammation, which is linked to many age-related chronic diseases, like high blood pressure, Type 2 diabetes, and heart disease. In particular, animal proteins that are not "lean" and have a higher saturated fat content, like those in red and — most especially — processed meat, are known to be pro-inflammatory, whereas protein-rich foods like fish, beans, and eggs tend to be more anti-inflammatory.

Sneak fiber into your meals

Longevity researcher Dan Belsky, who studies biological aging, and who was not involved in the study, said it is a "reassuring" finding for nutrition science.

"On balance it seems like maybe a little less meat, a little more veg in your diet is a good thing," Belsky, an associate professor of epidemiology at Columbia University, said. This idea goes along with decades of other research, in studies that have tracked what people eat over months and years, and looked at their health outcomes. Even among identical twins, people who eat more plants and less meat seem to do better on standard health measurements.

"We know we can manage our risk for heart disease, diabetes, reduce our risk for many cancers," Belsky said.

Nutrition is personal. How individuals respond to different foods can vary a lot, based on our genetics, our gut microbiome, and lifestyle.

Still, decades of research suggest a diet high in red meat is not great for your health and longevity.

Senior says you can easily mix your meat with other protein sources, like beans.

If you're making a bolognese sauce, why not substitute half of the meat for lentils? Beans are famously rich in dietary fiber, which can improve blood sugar, lower cholesterol, and tamp down inflammation.

"We're not even saying you need to go for a fully vegetarian diet, but trying to substitute some of that [meat] out might do the trick," he said.