Researchers studied over 1,000 Iranian teenagers to see if eating a diet that’s good for both people and the planet could help them maintain a healthy weight and feel better overall. They found that teens who followed the EAT-Lancet planetary health diet—which focuses on plant-based foods and sustainable eating—had lower rates of obesity and reported better quality of life compared to those who didn’t follow it as closely. This research suggests that choosing foods that help the environment might also be one of the best things teenagers can do for their own health.

The Quick Take

  • What they studied: Whether eating a sustainable, planet-friendly diet helps teenagers avoid obesity and feel happier and healthier in their daily lives.
  • Who participated: 1,038 Iranian students with an average age of 15 years old, studied during the 2024-2025 school year. The group included students from different backgrounds and family income levels.
  • Key finding: Teenagers who most closely followed the planetary health diet were about 56% less likely to have belly fat, 56% less likely to be overweight overall, and 59% less likely to report feeling unhappy or unhealthy compared to those who followed it least.
  • What it means for you: Eating more plant-based foods and fewer processed items—the kind of diet that helps save the planet—may help you maintain a healthy weight and feel better mentally and physically. However, this study shows a connection, not proof that the diet causes these benefits.

The Research Details

This was a cross-sectional study, which means researchers took a snapshot of teenagers’ eating habits and health at one point in time, rather than following them over months or years. The researchers asked 1,038 students detailed questions about what they ate using a 147-item food frequency questionnaire—basically a very thorough food survey. They also measured the students’ height and weight to calculate obesity, and asked them to complete a quality-of-life survey that measures how they feel physically, emotionally, and socially.

The researchers then used statistical analysis to look for connections between how well students followed the planetary health diet and their weight and quality of life. They were careful to account for other factors that might affect the results, like age, sex, family income, how much sleep students got, and how much time they spent on screens.

This approach is important because it allows researchers to study real-world eating patterns in a large group of teenagers without having to control every aspect of their lives. By measuring actual food intake and health outcomes together, the study can show whether sustainable eating and better health go hand-in-hand. The researchers also controlled for other lifestyle factors, which helps make sure the diet itself—not just other healthy habits—is connected to the benefits.

This study has several strengths: it included over 1,000 participants, used validated tools to measure diet and quality of life, and carefully controlled for other factors that might affect the results. However, because it’s a cross-sectional study (a snapshot in time), it can only show that these factors are connected, not that eating this way actually causes weight loss or better quality of life. The study was conducted in Iran, so results may not apply equally to teenagers in other countries with different food availability and cultures.

What the Results Show

The average planetary health diet score among the teenagers was 50.79 out of a possible scale, with scores ranging from 19.66 to 94.46. This suggests there was wide variation in how well different students followed the diet.

Teenagers in the highest group for following the planetary health diet had significantly lower rates of obesity. Specifically, they were 56% less likely to have general obesity (the study showed an odds ratio of 0.44, meaning about half the risk) and 44% less likely to have belly fat specifically (odds ratio of 0.56). These differences remained even after accounting for other factors like age, sex, family income, sleep, and screen time.

Beyond weight, teenagers who followed the diet most closely also reported better quality of life. They were 59% less likely to report problems with their physical health, emotions, or social life (odds ratio of 0.41). This suggests the benefits go beyond just the number on a scale—these teens felt better overall.

The study found that the planetary health diet’s benefits appeared consistent across different measures of obesity and health. The fact that improvements showed up in both general weight measures and belly fat specifically suggests the diet may help with different types of weight problems. The quality-of-life improvements are particularly noteworthy because they indicate that teenagers following this diet not only weighed less but also reported feeling better emotionally and socially, which is important for overall wellbeing during the teenage years.

This research builds on growing evidence that plant-based and sustainable diets are linked to better health outcomes. Previous studies have shown connections between plant-based eating and lower obesity rates in adults, and this study extends those findings to teenagers. The addition of quality-of-life measures is relatively newer—most previous research focused only on weight, so this study provides a more complete picture of how diet affects teenagers’ overall wellbeing.

The biggest limitation is that this study only shows a connection between diet and health at one point in time; it doesn’t prove that changing your diet will cause weight loss or better quality of life. The study was conducted only in Iran, so the results may not apply the same way to teenagers in other countries where different foods are available and cultural eating patterns are different. Additionally, the study relied on teenagers’ memory of what they ate, which can be inaccurate. The researchers couldn’t control for all possible factors that might affect weight and quality of life, such as genetics or physical activity levels.

The Bottom Line

Based on this research, teenagers should consider eating more plant-based foods, whole grains, legumes, nuts, and vegetables while reducing processed foods and animal products—not just for the planet, but potentially for their own health too. This is a moderate-confidence recommendation because the study shows a strong connection but doesn’t prove cause-and-effect. Parents and schools might encourage sustainable eating as part of broader health promotion. However, this should be done thoughtfully to ensure teenagers still get all the nutrients they need.

This research is most relevant to teenagers, parents, school nutrition programs, and public health officials interested in adolescent health. It’s particularly important for teenagers struggling with weight or quality-of-life issues. However, teenagers with certain medical conditions, food allergies, or nutritional needs should consult with a doctor or nutritionist before making major dietary changes. The findings may be less directly applicable to teenagers in countries with very different food systems or cultural eating patterns than Iran.

Based on this type of research, you wouldn’t expect overnight changes. Typically, improvements in weight and how you feel take several weeks to months of consistent eating changes. Quality-of-life improvements might appear sooner than weight changes—some people report feeling better emotionally and having more energy within 2-4 weeks of dietary changes. However, this study doesn’t tell us exactly how long it takes, so individual results will vary.

Want to Apply This Research?

  • Track daily servings of plant-based foods (vegetables, fruits, whole grains, legumes, nuts) versus animal products and processed foods. Set a goal like ’eat 5+ servings of plants daily’ and log what you eat. Also track a simple quality-of-life score (1-10 rating of how you felt that day physically and emotionally) weekly to see if improvements appear over time.
  • Start by adding one plant-based meal per week, then gradually increase to two or three. Use the app to find recipes for sustainable meals, set reminders to eat more vegetables and whole grains, and get notifications when you hit daily plant-based food goals. You could also use the app to learn which foods are most sustainable for the planet while being nutritious.
  • Use the app to track your planetary health diet score monthly, monitor your weight or how your clothes fit weekly, and rate your overall quality of life (energy, mood, social connections) every two weeks. Create a dashboard that shows your progress over 3-6 months to see if following the diet more closely correlates with feeling better and maintaining a healthier weight.

This research shows a connection between following a sustainable diet and better health outcomes in teenagers, but it does not prove that changing your diet will definitely cause these benefits for you. This study was conducted in Iran and may not apply equally to all teenagers worldwide. Before making significant dietary changes, especially if you have existing health conditions, food allergies, or nutritional concerns, please consult with your doctor, school nurse, or a registered dietitian. This information is for educational purposes and should not replace professional medical advice. If you’re struggling with weight or quality-of-life issues, seek guidance from a healthcare professional who can provide personalized recommendations based on your individual needs.