What makes us feel well—not just physically, but mentally? For young adults navigating one of the most stressful stages of life, this question is more important than ever. A new study has found that three everyday behaviors—sleep quality, fruit and vegetable intake, and physical activity—are deeply connected to psychological well-being. And the surprising twist? Eating more fruits and vegetables might actually soften the mental toll of a poor night’s sleep.
The research, led by Dr. Jack Cooper, formerly of the University of Otago in New Zealand, and colleagues, was published in the open-access journal PLOS One. By analyzing the daily habits of young adults in three different countries, the team discovered a consistent message: what you eat, how you move, and how you sleep can shift your mood—sometimes within just one day.
Why Young Adults?
The focus on people aged 17 to 25 was no accident. This age group is standing on the threshold of independence, often juggling pressures from education, careers, finances, and relationships—all while forming lifelong habits. Rates of stress, anxiety, and burnout are particularly high in this demographic. Yet much of the scientific research on mental health has traditionally focused on illness—like depression or anxiety disorders—rather than the broader and equally important concept of positive psychological well-being.
That gap is what Cooper and his colleagues wanted to fill. Instead of looking only at what harms young adults, they turned their attention to what helps them feel good, function well, and thrive.
Three Studies, One Message
To uncover the links, the researchers drew on data from three separate studies:
- A survey of over 1,000 young adults in New Zealand, the U.K., and the U.S.
- A 13-day diary study of 818 New Zealand participants who logged their habits daily.
- An eight-day diary study of 236 New Zealand participants who also wore Fitbits to track activity levels.
Across these different designs, locations, and measures, the results pointed in the same direction. Better sleep quality emerged as the strongest and most reliable predictor of improved well-being. Next came fruit and vegetable consumption, and then physical activity.
Importantly, the effects were not only seen between different individuals but also within the same person on different days. For example, if someone ate more fruits and vegetables than usual on Tuesday, their psychological well-being tended to be higher on Tuesday compared to Monday. This suggests that the benefits are real, immediate, and personal.
The Surprising Role of Fruits and Vegetables
While the link between sleep and mood may feel intuitive, the finding that fruits and vegetables can buffer the effects of poor sleep is particularly intriguing. On days when participants reported less-than-ideal sleep, those who ate above-average amounts of fruits and vegetables still experienced a well-being boost.
Why might this be? Fruits and vegetables are packed with vitamins, minerals, and antioxidants that support brain health and regulate mood-related neurotransmitters. They also help manage inflammation and oxidative stress, both of which can worsen mental fatigue. In essence, nutrition may provide the brain with some of the resilience it needs to weather a rough night.
Movement Matters Too—But Differently
Physical activity also played a role, but its effects were a little more nuanced. Exercise seemed to have a stronger impact when comparing an individual’s daily ups and downs rather than comparing across the group as a whole. In other words, what mattered most was not whether someone was more active than their peers, but whether they were more active than their own personal average.
This reinforces an encouraging message: you don’t need to hit an external benchmark or train like an athlete to benefit. Simply moving a bit more than usual—walking an extra 10 minutes, taking the stairs, or going for a bike ride—can give you a same-day lift in mood.
Why These Findings Matter
For many young adults, well-being can feel like something out of their control, determined by grades, bills, relationships, or luck. But this research suggests that even modest changes in daily habits can make a tangible difference. Dr. Cooper emphasizes:
“Young adults don’t have to reach some objective benchmark of healthiness to see well-being improvement. Sleeping a little better, eating a little healthier, or exercising even for 10 minutes longer than you normally do was associated with improvements to how you feel that day.”
This makes well-being feel less like a distant goal and more like something accessible—an everyday practice of small, manageable choices.
The Strongest Predictor: Sleep Quality
Among the three behaviors studied, sleep stood out as the most consistent and powerful predictor. Good sleep quality was linked to next-day improvements in mood and well-being across all three studies. Senior author Professor Tamlin Conner of the University of Otago’s Psychology Department explained:
“Of these healthy habits, sleep quality stood out as the strongest and most consistent predictor of next-day well-being, but eating fruit and vegetables and being active also helped boost well-being.”
This reinforces what sleep researchers have been saying for decades: sleep is not a luxury, it is a foundation. For young adults facing late-night study sessions, endless scrolling, or the temptation of nightlife, prioritizing rest may be one of the most powerful mental health strategies available.
A Holistic Picture of Well-Being
One of the study’s most hopeful insights is that these behaviors are independent and additive. This means that you don’t have to choose between focusing on diet, sleep, or exercise—each contributes its own unique benefit. The more of them you combine, the better the outcome.
In practice, this creates a holistic and flexible roadmap:
- Struggling with sleep? Boost your fruit and vegetable intake.
- Feeling too busy to exercise intensely? Even light movement still helps.
- Can’t eat perfectly every day? A solid night’s rest can buffer the effects.
Rather than aiming for perfection in one area, small improvements across all three can add up to meaningful gains in well-being.
Looking Forward
The authors note that while this research is promising, it does have limitations. The studies were relatively short in duration, involved primarily young adults from three countries, and cannot prove causation—only association. Future research will need to include more diverse populations and longer-term data.
Still, the consistency of the findings across different countries and methods suggests that the link between daily habits and mental well-being is both strong and universal.
Thriving, Not Just Surviving
The transition to adulthood is rarely easy. It’s a time of independence, but also uncertainty. Financial pressures mount, social networks shift, and educational or career demands can feel overwhelming. Against this backdrop, simple daily habits can make a profound difference.
As Professor Conner reminds us, “This age group faces unique pressures… Understanding what lifestyle factors support well-being can help young adults not just ‘get by’ but thrive during this critical life stage.”
The message is both scientifically grounded and deeply human: better days are built from better nights of sleep, colorful plates of food, and moments of movement. You don’t need to change everything at once. Each small step counts. Each choice nudges you closer to resilience, balance, and joy.
More information: Cooper JR, From surviving to thriving: How sleep, physical activity, and diet shape well-being in young adults, PLOS One (2025). DOI: 10.1371/journal.pone.0329689
