Scientists reviewed 13 studies to understand how different diets affect a special protein in your brain called BDNF. This protein is important for memory, learning, and protecting your brain. The research found that fasting (eating less often) and ketogenic diets (low-carb, high-fat eating) seemed to increase BDNF levels in adults. However, other types of diets showed mixed or unclear results. While these findings are interesting, scientists say we need more research to fully understand how diet changes can help our brains work better and stay healthy.

The Quick Take

  • What they studied: How different eating patterns and diets affect a brain protein called BDNF that helps with memory, learning, and brain protection
  • Who participated: The review looked at 13 different research studies involving adults. The studies tested various diets including fasting, ketogenic (low-carb) diets, and other eating patterns
  • Key finding: Fasting and ketogenic diets appeared to increase BDNF levels in the brain, while most other diets showed little to no effect. However, results varied between studies
  • What it means for you: If you’re interested in supporting your brain health through diet, fasting or ketogenic approaches may be worth exploring—but talk to your doctor first. These aren’t magic solutions, and more research is needed to understand how much these diet changes actually help in real life

The Research Details

This was a systematic review, which means scientists searched through thousands of published studies to find the best evidence on a specific topic. The researchers looked through three major scientific databases (PubMed, Web of Science, and Scopus) and found 7,633 articles related to diet and BDNF. They carefully reviewed each one and selected 13 high-quality studies that tested how different diets affected BDNF levels in adults.

The researchers followed strict guidelines called PRISMA 2020 to make sure they did their work fairly and completely. They extracted detailed information from each study, including how the study was designed, who participated, and what results were found. They also rated the quality of each study using a standard method called the Cochrane approach to make sure they were only looking at reliable research.

A systematic review is like a super-thorough book report where scientists combine the best evidence from many studies. This approach is important because it helps us see the big picture instead of relying on just one study. By looking at multiple studies together, researchers can spot patterns and understand whether findings are consistent or if results vary. This type of review is considered one of the strongest types of scientific evidence because it brings together the most reliable information available

This review followed strict international guidelines for how to conduct and report systematic reviews, which is a good sign. The researchers looked at the quality of each individual study they included. However, because the 13 studies they found had different methods and tested different types of diets, it’s harder to draw firm conclusions. The fact that results were mixed across studies suggests we need more consistent research before making strong claims

What the Results Show

The main finding was that fasting-based diets and ketogenic diets (very low in carbohydrates, high in fat) appeared to increase BDNF levels in adults. BDNF is a protein that acts like fertilizer for your brain cells, helping them grow, connect, and stay healthy. When BDNF levels go up, it may support better memory, learning, and protection against brain aging.

However, the picture wasn’t completely clear. Other types of diets—like Mediterranean diets, low-fat diets, or standard calorie-restricted diets—showed inconsistent results. Some studies found small increases in BDNF, while others found no change at all. This variation suggests that not all diets affect BDNF the same way, and the effect might depend on individual differences or how long people follow the diet.

The review also noted that calorie restriction (eating fewer calories overall) seemed to have some positive effect on BDNF, though the results weren’t as consistent as with fasting. The researchers found that the timing and duration of dietary interventions mattered—some diets needed to be followed for several weeks before BDNF changes were noticeable. Additionally, the studies measured BDNF in different ways (blood tests versus other methods), which made it harder to compare results directly across studies

This review adds to growing evidence that what we eat influences brain chemistry. Previous research suggested that exercise and certain nutrients boost BDNF, and this review confirms that eating patterns also play a role. However, this is one of the first comprehensive reviews to specifically look at how different diets affect BDNF. The findings align with some earlier research suggesting that fasting and ketogenic diets have brain-protective effects, but the mixed results for other diets suggest the science is still evolving

Several important limitations should be considered. First, only 13 studies met the criteria for inclusion, which is a relatively small number. Second, these studies used different methods and tested different populations, making direct comparisons difficult. Third, most studies were short-term, so we don’t know if BDNF increases last long-term or if they translate to real improvements in memory or brain function. Fourth, the studies measured BDNF in blood rather than directly in the brain, which may not perfectly reflect what’s happening in brain tissue. Finally, we don’t know if higher BDNF levels actually lead to better thinking, memory, or brain health in everyday life

The Bottom Line

Based on this review, fasting or ketogenic diets may help increase BDNF levels (moderate confidence). However, these diets aren’t for everyone and should only be tried under medical supervision, especially if you have health conditions. For most people, a balanced diet combined with regular exercise is a safer, evidence-based approach to brain health. If you’re interested in trying fasting or ketogenic eating, consult your doctor first to make sure it’s appropriate for you

This research is most relevant to people interested in brain health, cognitive function, and aging well. It may be particularly interesting to people concerned about memory loss or cognitive decline. However, people with diabetes, eating disorders, or certain medical conditions should not try fasting or ketogenic diets without medical supervision. Pregnant women and children should also avoid these diets. If you’re on medications, talk to your doctor before making major dietary changes

Based on the studies reviewed, changes in BDNF levels typically appeared within 2-8 weeks of starting a fasting or ketogenic diet. However, it’s unclear how long these changes last or when (or if) they translate to noticeable improvements in memory or thinking. Most people would need to follow the diet consistently to maintain any BDNF increases

Want to Apply This Research?

  • Track your diet type (fasting windows, ketogenic macros, or other patterns) alongside weekly cognitive assessments like memory tests or focus duration to see if dietary changes correlate with mental clarity and brain performance
  • Users could experiment with a 4-week intermittent fasting trial (such as 16:8 fasting) while logging energy levels, mental clarity, and mood daily to observe personal responses before committing to longer-term dietary changes
  • Establish a baseline of cognitive function and mood, then track weekly changes in mental clarity, memory, focus, and energy while following a specific diet. Use consistent metrics (like timed memory games or focus duration) to measure changes objectively over 8-12 weeks

This review summarizes scientific research but is not medical advice. BDNF is a complex brain protein, and while increasing it may be beneficial, higher BDNF levels don’t guarantee better brain function or health outcomes. Fasting and ketogenic diets are not appropriate for everyone and may be harmful for people with certain medical conditions, eating disorders, diabetes, or those taking specific medications. Before making significant dietary changes, especially fasting or ketogenic diets, consult with your healthcare provider or registered dietitian. This research is preliminary, and more studies are needed to understand how dietary changes affect real-world brain health and function. Individual results vary significantly.