Welcome back! For Day 4 of the challenge, let’s do a short and fun activity based around a concept called cognitive reserve.

Decades of research show that people who have more years of education, more cognitively demanding jobs or more mentally stimulating hobbies all tend to have a reduced risk of cognitive impairment as they get older.

Experts think this is partly thanks to cognitive reserve: Basically, the more brain power you’ve built up over the years, the more you can stand to lose before you experience impairment. Researchers still don’t agree on how to measure cognitive reserve, but one theory is that better connections between different brain regions corresponds with more cognitive reserve.

To build up these connections, you need to stimulate your brain, said Dr. Joel Salinas, a neurologist at NYU Langone Health and the founder and chief medical officer of the telehealth platform Isaac Health. To do that, try an activity that is “challenging enough that it requires some effort but not so challenging that you don’t want to do it anymore,” he said.

Speaking a second language has been shown to be good for cognition, as has playing a musical instrument, visiting a museum and doing handicrafts like knitting or quilting. Reading is considered a mentally stimulating hobby, and experts say you’ll get an even bigger benefit if you join a book club to make it social. Listen to a podcast to learn something new, or, better yet, attend a lecture in person at a local college or community center, said Dr. Zaldy Tan, the director of the Memory and Healthy Aging Program at Cedars-Sinai. That adds a social component, plus the extra challenge of having to navigate your way there, he said.

A few studies have found that playing board games like chess can be good for your brain; the same goes for doing crossword puzzles. It’s possible that other types of puzzles, like those you find in brain teaser books or from New York Times Games, can also offer a cognitive benefit.

But there’s a catch: To get the best brain workout, the activity should not only be challenging but also new. If you do “Wordle every day, it’s like well, then you’re very, very good at Wordle, and the Wordle part of your brain has grown to be fantastic,” said Dr. Linda Selwa, a clinical professor of neurology at the University of Michigan Medical School. “But the rest of your mind might still need work.”

So play a game you’re not used to playing, Dr. Selwa said. “The novelty seems to be what’s driving brain remodeling and growth.”

Today, we want you to push yourself out of your cognitive comfort zone. Check out an online lecture or visit a museum with your challenge partner. Or try your hand at a new game, below. Share what novel thing you did today in the comments, and I’ll see you tomorrow for Day 5.

Time-restricted eating has gained popularity in recent years, but a recent study suggests that intermittent fasting — while effective for weight loss — might not live up to the hype in terms of wider benefits.

The small German study found that participants who were placed on two different time-restricted eating schedules lost weight, but experienced no improvement in blood glucose, blood pressure, cholesterol or other key cardiometabolic markers.

The participants included 31 overweight or obese women. One group ate between 8 a.m. and 4 p.m. and the other group ate between 1 p.m. and 9 p.m. for a two-week period, while maintaining their typical caloric intake, according to a press release.

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The findings, which were published in the journal Science Translational Medicine, suggest that the widely touted cardiometabolic benefits of intermittent fasting may be a result of eating fewer calories rather than meal timing, the researchers say.

The participants also showed a shift in their circadian rhythms (sleep/wake cycles) when they were placed on the time-restricted eating schedules, but the associated health impacts are not known.

The study did have some limitations. Some researchers have cast doubt on the significance of the study due to its small size.

“It is severely underpowered to detect any difference, considering how gentle the intervention is,” Dr. Dr. Jason Fung, a Canadian physician, author and researcher, told Fox News Digital. He also noted that the participants were fasting for 16 hours a day instead of the normal 12 to 14 hours.

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Lauren Harris-Pincus, a registered dietitian nutritionist in New Jersey, agreed that the findings could be due to the fact that there was no intentional caloric restriction, and reiterated that the sample size is “quite small.” 

“As a registered dietitian, I only recommend time-restricted eating when it is carefully planned and shifted earlier within the day,” Harris-Pincus, who was not involved in the study, told Fox News Digital.

“Only one in 10 Americans consumes the recommended number of fruits and veggies, and 93% miss the mark on fiber goals. Restricting an eating window necessitates more careful meal planning to ensure adequate intake of macro- and micronutrients.”

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The expert also cautioned that skipping breakfast to enable a later eating window may result in lower intake of the “nutrients of concern” in the American diet, including calcium, potassium, fiber and vitamin D. 

Looking ahead, the researchers said more studies are needed to explore the effects of time-restricted eating over longer time periods. It also remains to be seen how the combination of caloric restriction and time-restricted eating may affect outcomes. Future research could also explore how different populations may respond.

“I only recommend time-restricted eating when it is carefully planned and shifted earlier within the day.”

Dr. Daryl Gioffre, a gut health specialist and celebrity nutritionist in New York, noted that the study didn’t account for critical factors like chronic stress, sleep quality, medications, hormone status and baseline metabolic health.

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“All of these can significantly blunt fat loss and cardiometabolic improvements,” Gioffre, who also was not involved in the research, told Fox News Digital.

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“Cortisol, the body’s primary stress hormone, is naturally highest in the morning, which overlaps with one of the fasting windows studied,” he went on. “If stress is elevated, cortisol alone can block fat burning, disrupt blood sugar regulation, and mask cardiovascular improvements, regardless of calorie intake or eating window.”

Gioffre did agree, however, that growing research shows intermittent fasting — when done correctly and sustained over time — can improve insulin regulation, reduce inflammation, support fat loss and contribute to better cardiovascular health.

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“These are outcomes that simply cannot be captured in a short, stress-blind study like this,” he added.

Fox News Digital reached out to the researchers for comment.

Today, you’re going to do perhaps the single best thing for your brain.

When I asked neurologists about their top behaviors for brain health, they all stressed the importance of physical activity.

“Exercise is top, No. 1, when we’re thinking about the biggest bang for your buck,” said Dr. Gregg Day, a neurologist at the Mayo Clinic.

Numerous studies have shown that people who exercise regularly tend to perform better on attention, memory and executive functioning tests. There can be a small cognitive boost immediately after a workout, and the effects are sustained if people exercise consistently. And while staying active can’t guarantee you won’t develop dementia, over the long term, it is associated with a lower risk of it.

Researchers think that moving your muscles benefits your brain in part because of special signaling molecules called exerkines. During and after a workout, your muscles, fat and other organs release these molecules into the bloodstream, some of which make their way up to the brain. There, those exerkines go to work, helping to facilitate the growth of new connections between neurons, the repair of brain cells and, possibly, the birth of new neurons.

Exercise also appears to improve blood flow in the brain. That ramps up the delivery of good things to brain cells, like oxygen, glucose and those amazing exerkines. And it helps remove more bad things, namely toxic proteins, like amyloid, that can build up and damage brain cells, increasing the risk for Alzheimer’s.

All of the changes brought on by exercise are “essentially allowing your brain to age more slowly than if you’re physically inactive,” said Kirk Erickson, the chair of neuroscience at the AdventHealth Research Institute.

The benefits are particularly pronounced in the hippocampus, a region critical for learning and memory. In older adults, the hippocampus shrinks 1 to 2 percent a year, and it is one of the main areas affected by Alzheimer’s. Researchers think physical activity helps to offset some of that loss.

The best exercise you can do for your brain is the one you’ll do consistently, so find something that you enjoy and that fits easily into your life.

Walking is one option; two neurologists I spoke to said they got their exercise in by walking at least part of the way to their offices. Recent research suggests that just a few thousand steps a day can reduce the risk of dementia. It’s important to get your heart rate up, though, so “walk as though you’re trying to get somewhere on time,” said Dr. Linda Selwa, a clinical professor of neurology at the University of Michigan Medical School.

Or you could try swimming, cycling, Pilates, weight lifting, yoga, pickleball, dancing, gardening — any type of physical exertion can be beneficial.

If the thought of working out feels like a drag, try pairing it with something else you enjoy doing, like listening to an audiobook. This is a trick that Katherine Milkman, a professor who studies habits at The Wharton School of the University of Pennsylvania, calls “temptation bundling.”

For Day 3, we’re asking you to spend at least 20 minutes exercising for your brain. Go for a walk with your accountability partner if they’re nearby. (If not, call them and do a walk-and-talk.) Or let us find you a new workout to try, using the tool below. As usual, we can all meet in the comments to catch up and check in.