Researchers studied over 2,000 young adults to understand what makes people feel happier and more satisfied with life. They looked at three main habits: how well people sleep, how much they exercise, and what they eat. The big discovery? Getting good sleep was the most important factor for feeling good, followed by eating fruits and vegetables. Interestingly, eating healthy foods might even help protect your mood on days when you didn’t sleep well. This research suggests that these three simple habits work together to boost mental health and happiness in young adults.

The Quick Take

  • What they studied: How sleep quality, physical activity, and eating habits affect how happy and satisfied young adults feel with their lives
  • Who participated: Over 2,000 young adults between ages 17-25 from New Zealand, the United Kingdom, and the United States. Researchers used three different studies, including one where people wore fitness trackers to measure activity automatically
  • Key finding: Sleep quality was the strongest predictor of well-being across all studies. Eating more fruits and vegetables came in second. Physical activity also helped, especially when looking at day-to-day changes. Interestingly, eating well might help protect your mood even on days when you didn’t sleep enough
  • What it means for you: If you want to feel better mentally and emotionally, focus first on improving your sleep, then add more fruits and vegetables to your diet, and include regular physical activity. These three habits appear to work together to boost your overall happiness and life satisfaction

The Research Details

This research used three different approaches to study young adults. The first study surveyed 1,032 people one time to see how their sleep, exercise, and eating habits connected to their happiness. The second and third studies asked people to keep daily diaries for several weeks, recording how they slept, what they ate, and how they felt each day. This daily diary approach is powerful because it shows how these habits affect mood from day to day, not just overall patterns. In the third study, participants also wore fitness trackers that automatically measured their physical activity, which is more accurate than just asking people to remember how much they exercised.

By studying the same people over time and looking at day-to-day changes, researchers can better understand cause and effect. The use of fitness trackers alongside self-reported activity strengthens the findings because it removes the possibility that people are just remembering their exercise incorrectly. Looking at multiple datasets from different countries helps confirm that these patterns aren’t just true in one place but appear to be universal among young adults.

This study is reliable because it used large groups of participants (over 2,000 total), multiple independent studies that confirmed the same patterns, and objective measurement tools like fitness trackers. The researchers also controlled for other factors that might affect happiness, like age, gender, income level, and depression symptoms. However, because this is a cross-sectional study (taking a snapshot in time rather than following people over years), we can’t say for certain that these habits cause better mental health—only that they’re connected

What the Results Show

Sleep quality emerged as the strongest factor linked to well-being in all three studies. Young adults who reported better sleep also reported feeling happier and more satisfied with life. This pattern held true whether researchers looked at overall differences between people or day-to-day changes within the same person. The second most important factor was eating fruits and vegetables. People who ate more produce reported better mental well-being. Physical activity also showed a consistent relationship with well-being, particularly when looking at day-to-day patterns—meaning that on days when people were more active, they tended to feel better emotionally. Importantly, these three habits appeared to work together in an additive way, meaning that doing all three was better than doing just one or two.

One particularly interesting finding was a ‘buffering effect’ at the daily level: eating more fruits and vegetables appeared to protect people’s mood on days when they hadn’t slept well. This suggests that good nutrition might help offset some of the negative emotional effects of poor sleep. The use of objective fitness tracker data confirmed the patterns seen with self-reported exercise, which increases confidence in the findings. The research also showed that these relationships held true across different countries and cultures, suggesting these patterns are fairly universal among young adults.

This research builds on existing knowledge that sleep, exercise, and diet are important for physical health. What’s new here is the strong evidence that these same three habits are equally important for mental health and happiness in young adults specifically. Previous research has looked at these factors separately, but this study shows how they work together. The finding that sleep is the most powerful factor aligns with growing research showing sleep’s critical role in mental health, but the discovery that nutrition might buffer against poor sleep’s emotional effects is a newer insight.

Because this study took snapshots of people’s lives rather than following them over many years, we can’t prove that improving sleep, exercise, or diet will definitely make someone happier—only that they’re connected. People reported their own sleep quality and eating habits, which might not be perfectly accurate. The study focused on young adults in English-speaking countries, so results might not apply to other age groups or cultures. Additionally, the researchers couldn’t account for all possible factors that affect happiness, such as relationships, work stress, or mental health conditions

The Bottom Line

Young adults should prioritize getting consistent, good-quality sleep as the first step to improving mental well-being (high confidence). Adding more fruits and vegetables to daily meals is the second priority (high confidence). Including regular physical activity, even moderate amounts, appears beneficial for daily mood (moderate to high confidence). These three habits work best together, so combining all three offers the greatest benefit. Starting with sleep improvement and then adding dietary changes may be a practical approach.

This research is most relevant to young adults ages 17-25 who want to improve their mental health and overall happiness. It’s particularly useful for people who feel their mood varies day-to-day and want practical ways to feel better. Parents, educators, and healthcare providers working with young adults should also pay attention to these findings. However, this research doesn’t replace professional mental health treatment for people with depression, anxiety, or other mental health conditions—it’s a complement to, not a substitute for, professional care.

Sleep quality improvements might affect mood within days to weeks. Dietary changes may take 2-4 weeks to show noticeable effects on well-being. Physical activity benefits can appear within days for daily mood but may take several weeks for larger overall changes. Most people should expect gradual improvements rather than dramatic overnight changes. Consistency matters more than perfection—maintaining these habits regularly is more important than occasional efforts

Want to Apply This Research?

  • Track sleep quality (using a 1-10 scale each morning), daily fruit and vegetable servings (count actual servings), and minutes of physical activity. Record daily well-being or mood on a simple 1-10 scale. After 2-3 weeks, review the data to see which habit has the strongest connection to your mood on any given day
  • Start by setting one specific sleep goal (like a consistent bedtime), add one fruit or vegetable to each meal, and commit to 20-30 minutes of activity most days. Use the app to log these daily and see real-time connections between your habits and how you feel. Celebrate small wins to build momentum
  • Weekly reviews of the three habits and mood scores help identify patterns. Monthly summaries show progress over time. If mood improves, continue the habits. If not, adjust one variable at a time to see what works best for you personally. Share data with a healthcare provider if mood concerns persist despite lifestyle improvements

This research shows associations between lifestyle habits and well-being but does not prove these habits cause better mental health. This information is educational and should not replace professional mental health treatment. If you experience persistent sadness, anxiety, or other mental health concerns, please consult with a healthcare provider or mental health professional. Always talk to a doctor before making significant changes to your exercise routine, especially if you have existing health conditions.