Researchers studied 62 people who do high-intensity functional training (like CrossFit) to understand what they eat and how their bodies are built. They found that these athletes eat lots of lean meat and home-cooked meals, but most don’t eat enough dairy, fruits, vegetables, and whole grains. Interestingly, about 77% of these athletes take dietary supplements—averaging six different ones—with protein powder, creatine, caffeine, and electrolyte drinks being the most popular. The study suggests that some athletes might be using supplements to fill nutrition gaps instead of getting nutrients from real food.

The Quick Take

  • What they studied: What do people who do intense functional training eat, what supplements do they take, and what do their bodies look like?
  • Who participated: 62 athletes (36 men and 26 women) with an average age of 36 years who regularly participate in high-intensity functional training workouts
  • Key finding: Most of these athletes eat lean meats and cook at home, but only about 20% eat the recommended amounts of dairy, fruits, vegetables, and whole grains. About 77% use supplements, with the average athlete taking around six different ones.
  • What it means for you: If you do intense functional training, you might want to check if you’re eating enough whole foods like fruits, vegetables, and dairy instead of relying only on supplements. This is especially important because supplements work best when combined with a healthy diet.

The Research Details

Researchers recruited 62 people who regularly do high-intensity functional training and asked them to fill out an online survey about their eating habits and supplement use. They also measured body fat percentage using a scientific method called the Siri 3-compartment model, which uses body measurements to estimate how much of a person’s weight is fat versus muscle and bone.

The study combined two types of information: numbers (like how many people take supplements) and written responses (like why people choose to take or stop taking supplements). For the written responses, researchers read through all the answers and grouped similar reasons together to find common themes.

This approach is useful because it captures both the ‘what’ (facts and numbers) and the ‘why’ (people’s reasons and experiences) of how these athletes eat and supplement.

Most previous research only looked at elite professional athletes or only collected numbers without asking people about their reasons. This study looked at regular gym-goers and asked them to explain their choices, which gives a more complete picture of what typical functional training athletes actually do.

This study describes what it found without making strong claims about cause and effect. The researchers were honest about only describing patterns rather than proving that one thing causes another. The study included both men and women and a range of ages, which makes the findings more representative. However, because people volunteered to participate, there may be some bias toward people who are more interested in nutrition.

What the Results Show

The athletes’ body composition varied quite a bit. Men ranged from 6.5% to 27.6% body fat, while women ranged from 10.6% to 37.6% body fat, showing that there’s no single ’typical’ body type among functional training athletes.

When it came to food, most athletes reported eating lean meats regularly and cooking meals at home, which are positive habits. However, only about 20% of the athletes ate the recommended daily servings of dairy products, fruits, vegetables, and whole grains. This suggests that even though these athletes are very active, many may not be getting all the nutrients their bodies need from whole foods.

Supplement use was extremely common: 77.4% of the athletes reported taking dietary supplements. On average, each athlete used about six different supplements. The most popular supplements were protein powder (from dairy), creatine (which helps muscles), caffeine (for energy), and electrolyte drinks (which replace minerals lost through sweat).

When asked why they used supplements, athletes most commonly said they wanted to improve their health, help their bodies recover from workouts, and fill gaps in their nutrition. When athletes stopped taking supplements, the most common reason was that they didn’t notice any difference in how they felt or performed.

The study found that some athletes appeared to be using supplements as a replacement for eating whole foods rather than as an addition to a healthy diet. This is important because supplements work best when they complement—not replace—a diet rich in real foods. The variety in body composition among these athletes suggests that there’s no single diet or supplement routine that works for everyone.

Earlier research mostly focused on professional or elite athletes and only looked at numbers without asking people about their experiences. This study fills a gap by looking at regular people who do functional training and asking them to explain their choices. The finding that most athletes don’t eat enough fruits, vegetables, and dairy aligns with general nutrition research showing that many active people have similar gaps in their diets.

This study only describes what these athletes do—it doesn’t prove that their eating habits cause their body composition or performance. Because people volunteered to participate, the group might not represent all functional training athletes (for example, people more interested in nutrition might have been more likely to join). The study was done at one point in time, so we don’t know if these habits change over time. Additionally, athletes self-reported their eating habits, which means some may not have remembered accurately or may have reported what they thought was ‘correct’ rather than what they actually do.

The Bottom Line

If you do high-intensity functional training, focus on eating whole foods first—especially lean meats, dairy, fruits, vegetables, and whole grains—before relying on supplements. Supplements appear to work best when they fill specific gaps in your diet, not when they replace real food. Consider talking to a nutrition professional to identify which supplements (if any) would actually help you based on your individual diet and goals. (Moderate confidence: based on descriptive research rather than controlled trials)

This research is most relevant to people who do high-intensity functional training and are thinking about their nutrition and supplement use. It’s also useful for coaches and trainers who work with these athletes. People with specific health conditions should talk to their doctor before making changes based on this research.

Changes in eating habits typically take 2-4 weeks to become routine. If you add or change supplements, give them at least 4-8 weeks to see if they make a noticeable difference in how you feel or perform. If you don’t notice benefits after that time, it may not be worth continuing.

Want to Apply This Research?

  • Track daily servings of the five food groups (lean proteins, dairy, fruits, vegetables, whole grains) for two weeks to see where your diet might have gaps. Use a simple checklist: Did I eat dairy today? Did I eat fruit? Did I eat vegetables? Did I eat whole grains? This helps identify whether supplements are truly needed or if whole foods could fill the gap.
  • Choose one whole food to add to your diet this week instead of adding a new supplement. For example, if you’re not eating enough vegetables, commit to adding one vegetable to dinner each night. Track this in your app and see how you feel after two weeks before considering whether a supplement would help.
  • Every two weeks, review your food tracking to see which food groups you’re consistently missing. If you’re missing dairy, fruits, vegetables, or whole grains, try adding those foods first. Only consider supplements for nutrients you genuinely can’t get from food. Rate your energy and recovery on a scale of 1-10 weekly to see if changes in your diet or supplements actually make a difference for you personally.

This research describes eating habits and supplement use among functional training athletes but does not prove that specific diets or supplements cause particular results. Individual nutrition needs vary based on age, sex, training intensity, health conditions, and personal goals. Before making significant changes to your diet or starting new supplements, especially if you have any health conditions or take medications, consult with a healthcare provider or registered dietitian. This article is for educational purposes and should not replace professional medical or nutritional advice.