Fatigue is surprisingly common. In one 2024 survey, 88% of U.S. adults said they regularly experience symptoms of fatigue, a finding that may not surprise anyone who works with clients day after day. You hear it when they arrive for an early session already drained, cancel because they “just don’t have it today” or move through a workout as if someone turned down the volume on their energy.

For health and exercise professionals, those moments can be tricky. You want to help, but you also know fatigue is complicated. Clinical estimates vary widely depending on how fatigue is defined, and persistent fatigue should never be brushed off as laziness or lack of discipline. It can be related to sleep, stress, work hours, recovery, training load, mental health, food intake, medication use or an underlying medical condition.

A recently published study in Nutrients adds another possible piece to the conversation: nutrition. Specifically, the researchers looked at homocysteine, a blood marker that can be influenced by vitamin B12 and folate status, and how it may relate to fatigue and motivation in healthy adults.

The findings are interesting, but they require a careful read. They do not mean you should recommend B-vitamin supplements for fatigue. However, they do suggest that a food-first conversation about balanced eating may be relevant when clients complain of persistent low energy or low motivation.

That distinction is exactly where your professional judgment matters.

What the Researchers Studied

Led by Professor Hiroaki Kanouchi and colleagues at Osaka Metropolitan University, the study examined data from 602 healthy adults in Japan, including 204 men and 398 women. Participants lived in the Kobe and Osaka areas and had taken part in a preventive health research program between April 2018 and March 2020.

The researchers measured blood levels of homocysteine, folate, vitamin B12 and the active form of vitamin B6. They also asked participants to report on fatigue and motivation using established questionnaires and rating scales. Importantly, people who reported taking supplements or vitamin B-complex products were not included in the final analysis. That helped the researchers focus more closely on usual nutrition status rather than the possible effects of supplement use.

Homocysteine is an amino acid the body produces during normal metabolism. The body typically keeps it in check with help from several B vitamins, especially folate, vitamin B12 and vitamin B6. When folate or B12 status is lower, homocysteine levels may rise.

That does not make homocysteine a simple “B-vitamin meter.” Levels can also be affected by kidney function, genetics and other factors. A more useful way to think about it is this: Homocysteine may offer a window into a broader metabolic picture, and that picture may have some relationship to how tired or motivated a person feels.

What the Researchers Found

The first finding was clear: Participants with higher homocysteine levels generally had lower folate and vitamin B12 levels. That was true for both men and women.

The fatigue and motivation findings were more nuanced. Among men, those with the highest homocysteine levels reported more physical fatigue than those with the lowest levels. Among women, those with the highest homocysteine levels reported lower motivation than those with the lowest levels. In other words, higher homocysteine levels were associated with greater physical fatigue in men and decreased motivation in women, even after the researchers accounted for factors such as age, sleep duration, workload and dietary habits.

It’s important to remember that this was not a clinical trial. The researchers did not give participants B vitamins and then measure whether fatigue improved. They took a snapshot in time and looked for patterns. In another part of the analysis, when homocysteine was examined differently, the links with physical fatigue in men and motivation in women were no longer statistically significant. The study authors describe the findings as exploratory, meaning they point to an idea that deserves more research rather than a conclusion that should immediately change practice.

Why This May Matter to Your Clients

Even with these limitations, the study is useful because it gives you a more complete way to think about fatigue. Many clients assume low energy means they need more caffeine, more willpower or a new pre-workout product. Others blame themselves for being lazy or unmotivated. This study supports a more compassionate and more professional message: Fatigue and motivation are complex, and nutrition may be one part of the larger picture.

The study also highlights an important distinction between fatigue and motivation. Fatigue is the feeling of being physically or mentally worn down. Motivation is the drive to start or continue doing something. They often overlap, but they are not exactly the same. That is a helpful point when working with clients who say, “I’m not tired exactly; I just can’t get myself going.”

The findings also reinforce something you already know from practice: Lifestyle habits rarely operate in isolation. Sleep, training load, food intake, recovery, stress and work demands all interact. In this study, the researchers accounted for several of those factors, including sleep, work hours, exercise habits, body weight, kidney function and dietary variety.

That does not mean a more varied diet will automatically fix fatigue. It does mean that asking about eating patterns belongs in the same conversation as asking about sleep, recovery, stress and training load.

What the Study Does Not Prove

The most important scope-safe takeaway is what this study does not show.

It does not prove that low vitamin B12 or folate causes fatigue in healthy adults, nor does it prove that lowering homocysteine improves motivation or that B-vitamin supplements can treat fatigue. In fact, when the researchers looked at folate and vitamin B12 directly, neither one was clearly linked with physical fatigue in men or motivation in women.

That is why the supplement conversation requires caution. The study suggests a possible relationship among B-vitamin status, homocysteine, fatigue and motivation, but it does not support telling clients that B vitamins will solve persistent fatigue.

The limitations are also important. The study looked at one point in time, so it cannot show cause and effect. Fatigue and motivation were self-reported. The researchers did not measure inflammation, which may also play a role in fatigue. Other factors, such as stress and hormones, may have influenced the results. Participants were also recruited through a preventive health program, so they may have been more health-conscious than the general population.

For your work with clients, that means no overpromising. You can’t tell a client that “you’re tired because you need B12,” or that they should “take folate and your motivation will come back.” You should also steer clear of lab interpretation and recommending supplement protocols unless your training, credential and local regulations specifically allow you to provide that level of guidance.

The Food-First Message

The safest and most useful way to apply this study is to bring the conversation back to daily eating patterns. Folate and vitamin B12 help the body manage homocysteine levels, so encouraging clients to eat a variety of nutrient-rich foods is a practical, scope-safe way to support overall energy, recovery and health.

That is a message most health and exercise professionals can share: A varied, balanced eating pattern supports normal metabolism and may help support energy, recovery and overall health. This is nutrition education, not medical nutrition therapy.

For example, you might say to a client, “Researchers are beginning to look at how nutrition may be connected to fatigue and motivation. I can’t diagnose a deficiency or recommend supplements to treat fatigue, but we can look at whether your meals regularly include foods that provide key B vitamins. Since your fatigue has been ongoing, it would also be smart to discuss it with your healthcare provider.”

That kind of language keeps the focus where it belongs: education, behavior support and referral.

Practical Application: Staying in Scope

For health and exercise professionals, this study can become a better client conversation, not a supplement recommendation.

Start by listening for patterns. Is the client tired after a sudden increase in training volume? Are they sleeping five hours a night? Are they skipping breakfast, underfueling workouts or relying on coffee until midafternoon? Have they recently changed medications, started a vegetarian or vegan diet, experienced heavy menstrual bleeding, lost weight unintentionally or described symptoms such as dizziness, shortness of breath, numbness, tingling or persistent low mood?

Those details matter. Some point toward coaching opportunities. Others call for referral.

Next, stay in your lane with nutrition. You can educate clients about food sources of B vitamins. You can help them build more consistent meals. You can encourage dietary variety, including vegetables, beans, fruits, dairy foods, eggs, fish, poultry, meat or fortified foods, depending on their preferences and needs. You can help them notice whether low-energy days are associated with skipped meals, inadequate carbohydrate intake, low protein intake or poor recovery habits.

In practice, this means focusing on what falls within your role: education, behavior support and referral. A qualified healthcare provider can evaluate possible B-vitamin deficiencies, order and interpret labs, and determine whether supplementation is appropriate. If a client’s fatigue is persistent, unexplained, worsening or interfering with daily life, helping that client connect with the right provider is part of responsible, client-centered care.

The referral piece is not a failure of coaching; it is good care. A registered dietitian nutritionist can provide individualized nutrition assessment and meal planning. A physician, nurse practitioner or other qualified healthcare provider can evaluate medical causes of fatigue, order appropriate labs and determine whether supplementation or treatment is warranted.

Your value is in connecting the dots without pretending to be the whole healthcare team. You can help clients understand that fatigue is not always about toughness, discipline or motivation. Sometimes it is a signal to examine a client’s recovery routines or their diet, or it could be an indication that medical care is needed. Often, it is more than one thing at once.

This study gives you one more evidence-informed reason to have that conversation carefully.