Scientists created a new way to measure diet quality that looks at three important things: eating lots of different plants, having the right amount of animal products, and avoiding ultra-processed foods. They tested this measurement tool called SUSDIET on 5,000 Australian adults and found it successfully predicted who had healthier weights and better heart health. This tool could help doctors, researchers, and people everywhere understand whether their diet is both good for their body and good for the planet.

The Quick Take

  • What they studied: Can scientists create a single score that measures whether a diet is healthy for people AND sustainable for the environment?
  • Who participated: 5,000 Australian adults aged 19 and older who participated in a national nutrition survey
  • Key finding: The new SUSDIET score successfully identified people eating healthier diets and showed those with higher scores had lower rates of obesity and belly fat
  • What it means for you: This tool may help you understand if your diet is balanced in the right ways—with plenty of plants, appropriate animal products, and fewer processed foods. However, this is one study in one country, so more research is needed before making major changes based on this score alone.

The Research Details

Researchers worked with nutrition experts from the United Nations to decide what makes a diet both healthy and sustainable. They created a scoring system that gives points for eating different types of plant foods (like vegetables, fruits, grains, nuts, and beans), having appropriate amounts of animal products (like meat, fish, dairy, and eggs), and avoiding ultra-processed foods (like sugary drinks, packaged snacks, and fast food).

They then tested this scoring system on real people using data from an Australian national survey that tracked what 5,000 adults actually ate. They calculated SUSDIET scores for each person and looked at whether people with higher scores had better health markers like healthier weights and normal blood pressure. They used statistical methods to see if the score actually predicted these health outcomes.

Previous diet quality tools only looked at health benefits or only at environmental impact—not both together. This study matters because it creates one unified tool that captures what nutrition experts believe makes a truly sustainable healthy diet. This approach is important because it recognizes that our food choices affect both our personal health and the planet’s health.

This study used real-world data from a large, nationally representative survey, which is a strength. The researchers used appropriate statistical methods to test their tool. However, this is one study in one country (Australia), so results may not apply equally to all populations. The study shows the tool works, but more research in different countries and populations would strengthen confidence in the findings.

What the Results Show

The SUSDIET score ranges from 0 to 15, with higher scores indicating a healthier and more sustainable diet. Among the 5,000 Australian adults studied, the average score was 5.83, meaning most people scored in the lower-to-middle range. This suggests that most Australian adults could improve their diet quality by eating more plant variety and fewer ultra-processed foods.

People with higher SUSDIET scores had better nutrient profiles, meaning their diets contained more of the vitamins, minerals, and other nutrients their bodies need. Most importantly, people with higher scores had significantly lower odds of being obese or having excess belly fat, which are important risk factors for heart disease and diabetes.

The study found that SUSDIET scores varied based on age, education level, and income—suggesting that diet quality is influenced by life circumstances. The tool successfully captured the three key dimensions experts identified: plant food variety, appropriate animal product intake, and avoidance of ultra-processed foods. This suggests the scoring system is measuring what it’s supposed to measure.

This research builds on existing diet quality tools like the Mediterranean Diet Score and Healthy Eating Index, but goes further by explicitly including environmental sustainability alongside health benefits. Previous tools focused mainly on health outcomes. This new tool recognizes that truly sustainable diets must be good for both people and the planet, which aligns with recommendations from major international health organizations.

The study only included Australian adults, so results may not apply equally to people in other countries with different food systems and cultures. The study used survey data where people reported what they ate, which can be less accurate than directly measuring food intake. The study shows associations between diet quality and health, but cannot prove that improving your SUSDIET score will definitely improve your health—only that they appear related. More research is needed to test whether the tool works equally well in different populations.

The Bottom Line

If you want to improve your diet quality according to SUSDIET principles, focus on: eating a wider variety of plant-based foods (vegetables, fruits, whole grains, nuts, seeds, legumes), including appropriate amounts of animal products rather than excessive amounts, and reducing ultra-processed foods. These changes appear to support both personal health and environmental sustainability. Confidence level: Moderate—this is one study, but it aligns with major health organization recommendations.

This tool is most relevant for adults interested in understanding their overall diet quality. It’s particularly useful for researchers, public health professionals, and policymakers tracking population nutrition. People with specific medical conditions should consult their doctor before making major dietary changes. This tool is less relevant for children, as their nutritional needs differ from adults.

Changes in weight and health markers typically take 4-12 weeks to become noticeable, though some people may see improvements in energy and digestion sooner. Long-term benefits for heart health and disease prevention develop over months and years of consistent healthy eating.

Want to Apply This Research?

  • Track daily plant food variety by counting how many different plant-based food groups you eat each day (aim for at least 5-6 different types). Log portion sizes of animal products to ensure they’re appropriate rather than excessive.
  • Use the app to set a weekly goal: try one new plant-based food each week and identify one ultra-processed food to replace with a whole food alternative. Create a shopping list based on the 12 plant food groups to ensure variety.
  • Calculate your weekly SUSDIET score by logging foods into the app, which automatically categorizes them. Track your score weekly and set a goal to increase it by 1-2 points per month. Monitor how you feel (energy levels, digestion) and take body measurements monthly to see if improvements align with score increases.

This research presents one tool for measuring diet quality and is not a substitute for personalized medical advice. Before making significant dietary changes, especially if you have existing health conditions, take medications, or have food allergies, consult with your doctor or registered dietitian. This study was conducted in Australia and may not apply equally to all populations. The SUSDIET score shows associations with health outcomes but does not prove that improving your score will guarantee health improvements. Individual results vary based on overall lifestyle, genetics, and other factors.