Real-world examples of vegan vs. omnivore diets: health impact examples for science projects

Before you design your project, it helps to see concrete examples of vegan vs. omnivore diets: health impact examples from real studies and everyday life. Researchers don’t just ask, “Who’s healthier?” They measure specific markers: LDL cholesterol, blood pressure, body mass index (BMI), blood sugar, inflammation, and more.

In recent years, large observational studies and clinical trials have compared people who follow vegan, vegetarian, and omnivorous diets. For example, a 2019 analysis of plant-based diets and heart disease risk published through Harvard’s nutrition resources found that people who ate more plant-based foods and fewer animal products had lower rates of coronary heart disease and type 2 diabetes, especially when the plant foods were minimally processed.

When you turn these findings into a science fair project, you’re not trying to copy the entire study. Instead, you use examples of how scientists compare groups, control for variables, and interpret results. Let’s walk through some specific health impact examples you can borrow and adapt.

Examples of vegan vs. omnivore diets: health impact examples you can measure

Here are several real-world examples of vegan vs. omnivore diets: health impact examples that translate well into student projects. Think of these as starting points—you can scale them up or down depending on your grade level and access to equipment.

Example 1: Vegan vs. omnivore cholesterol and heart health markers

One of the clearest differences between vegan and omnivore diets shows up in blood lipids (fats in the blood).

Research trend:
Studies summarized by the National Institutes of Health (NIH) and Harvard T.H. Chan School of Public Health show that people following vegan or mostly plant-based diets tend to have:

• Lower LDL (“bad”) cholesterol
• Slightly higher or similar HDL (“good”) cholesterol
• Lower total cholesterol overall

For instance, a 2023 review of randomized trials reported that plant-based diets can reduce LDL cholesterol by around 10–15% compared to omnivorous control diets, especially when saturated fat from meat and dairy is replaced with unsaturated fat from nuts, seeds, and vegetable oils.

Science fair angle:
You probably can’t draw blood at school, but you can model this difference by:

• Surveying vegan, vegetarian, and omnivore students or family members about their typical intake of saturated fat (butter, cheese, fatty meats) vs. unsaturated fat (olive oil, nuts, avocado).
• Using online nutrition databases (like the USDA FoodData Central) to estimate daily saturated fat intake.
• Comparing average estimated saturated fat intake by diet type and discussing how that might affect LDL levels, using data from sources like the CDC and NIH on cholesterol and heart disease risk.

This gives you a real example of how diet patterns can shift a measurable health marker.

Example 2: Blood pressure and sodium in vegan vs. omnivore diets

Blood pressure is another area where diet matters. Vegan diets often include more potassium-rich foods (fruits, vegetables, beans) and less sodium from processed meats.

Research trend:
The DASH diet (Dietary Approaches to Stop Hypertension), supported by the NIH and National Heart, Lung, and Blood Institute, is not strictly vegan, but it pushes eating patterns in a more plant-heavy direction. Studies show it can lower blood pressure, especially when sodium is reduced.

Real-world pattern:
People who eat vegan often:

• Eat more whole foods like beans, lentils, vegetables, and whole grains.
• Eat fewer processed meats like bacon, sausage, and deli turkey, which are typically high in sodium.

Science fair angle:
You can create a one-day or three-day food diary project:

• Ask volunteers who identify as vegan and omnivore to record everything they eat for 24–72 hours.
• Use an online nutrient calculator to estimate sodium and potassium intake.
• Compare group averages and discuss how these differences might affect blood pressure, using background from CDC hypertension pages.

This becomes one of your best examples of how dietary patterns connect to a specific health outcome.

Example 3: Body weight and BMI trends in vegan vs. omnivore populations

Another common question: do vegans tend to weigh less than omnivores?

Research trend:
Large cohort studies (for example, the Adventist Health Studies in the U.S.) have repeatedly found that, on average, vegans have lower BMI than omnivores, with vegetarians and pescatarians falling in between. This doesn’t prove that going vegan automatically causes weight loss, but it’s a strong association.

Real example:
In these studies, average BMI tends to be in the normal range for vegans, while omnivores are more likely to fall into the overweight range. Researchers think this is partly due to higher fiber intake and lower energy density in plant-based diets.

Science fair angle:
Without collecting sensitive weight data from classmates, you can:

• Use anonymized, self-reported height and weight from volunteers who agree to participate.
• Calculate BMI for each participant and group them as vegan, vegetarian, or omnivore.
• Compare group averages and discuss confounding variables (exercise, genetics, sleep, etc.).

This gives you a clear example of vegan vs. omnivore diets: health impact examples that involves simple math and statistics.

Example 4: Gut health and fiber intake

Gut health has exploded as a research trend around 2024–2025. The gut microbiome (the community of bacteria in your intestines) responds strongly to what you eat.

Research trend:
Plant-based diets are typically higher in dietary fiber, which feeds beneficial gut bacteria. Omnivore diets can be high in fiber too, but many Western-style omnivore diets rely heavily on refined grains and low-fiber processed foods.

Real examples include:

• Vegans and vegetarians often consume 25–40 grams of fiber per day from beans, lentils, vegetables, and whole grains.
• Many omnivores in the U.S. average closer to 15 grams per day, below the recommended intake, according to CDC and USDA data.

Science fair angle:
You can’t easily measure gut bacteria at school, but you can:

• Collect 3-day food logs from volunteers and estimate fiber intake using an online database.
• Compare average fiber intake among vegan, vegetarian, and omnivore participants.
• Discuss how fiber links to bowel regularity, colon health, and long-term disease risk, referencing sources like Mayo Clinic or NIH.

This is another strong example of how diet type can shift a specific, measurable nutrient.

Example 5: Micronutrient differences and supplementation

Not all differences favor vegan diets. Some nutrients are easier to get from animal foods.

Research trend:
Common nutrients of concern for vegans include:

• Vitamin B12
• Iron (especially in menstruating teens and adults)
• Omega-3 fatty acids (EPA and DHA)
• Calcium and vitamin D, depending on food choices and sun exposure

Real example:
Many vegans rely on fortified plant milks, nutritional yeast, or supplements for B12. Omnivores typically get B12 from meat, fish, eggs, and dairy. Studies show that people on long-term vegan diets who do not use B12 supplements are at higher risk of deficiency.

Science fair angle:
You can design a survey-based project:

• Ask vegan and omnivore participants about their use of supplements and fortified foods.
• Compare how many in each group report taking B12, vitamin D, or multivitamins.
• Use information from NIH Office of Dietary Supplements to explain recommended intakes and potential health effects of deficiency.

This gives a balanced example of vegan vs. omnivore diets: health impact examples, showing that every diet pattern has trade-offs.

Example 6: Real examples of performance and energy levels

Athletic performance and daily energy are popular topics, especially with the rise of plant-based athletes.

Research trend:
Recent sports nutrition studies suggest that well-planned vegan diets can support endurance performance as well as omnivorous diets, as long as athletes pay attention to protein, iron, and total calories.

Real examples include:

• Professional athletes like plant-based ultramarathoners and NBA players who follow mostly vegan diets and report good performance and recovery.
• Recreational athletes who switch from omnivore to vegan and notice changes in energy, digestion, or recovery times.

Science fair angle:
You can’t run a professional trial, but you can:

• Survey athletes at your school about diet type (vegan, vegetarian, omnivore).
• Ask about self-reported energy levels, recovery time after workouts, and frequency of sports injuries.
• Analyze patterns and compare them to published data from sports nutrition research.

This gives you another example of how diet might influence functional outcomes, not just lab numbers.

Example 7: Environmental and ethical health impacts

Most science fairs focus on physical health, but there’s growing interest in mental well-being and environmental health.

Research trend:
Reports from organizations like the EAT-Lancet Commission and various public health agencies suggest that shifting toward more plant-based diets can reduce greenhouse gas emissions and land use. That doesn’t directly change your blood pressure tomorrow, but it affects long-term planetary health, which circles back to human health.

Real examples include:

• Comparing the estimated carbon footprint of a typical vegan meal (beans, rice, vegetables) vs. an omnivore meal (beef burger, fries, soda).
• Looking at water use data for beef vs. legumes from environmental research.

Science fair angle:
You can design a project that:

• Chooses three common vegan meals and three common omnivore meals.
• Uses published life-cycle assessment data to estimate greenhouse gas emissions and water use for each meal.
• Discusses how dietary choices might influence long-term public health through climate change, air quality, and resource availability.

This is a different type of example of vegan vs. omnivore diets: health impact examples, expanding “health” beyond the individual.

Turning these examples into a strong science fair project

You’ve seen several examples of vegan vs. omnivore diets: health impact examples. The next step is choosing one question and tightening it into something you can actually study in a few weeks.

You might focus on questions like:

• Do vegan students at my school consume more fiber than omnivore students?
• Is average estimated saturated fat intake lower in vegan vs. omnivore diets in my sample?
• Are vegans more likely than omnivores to use dietary supplements such as B12 or vitamin D?
• How do self-reported energy levels compare between vegan and omnivore athletes at my school?

Keep the design simple and honest about limitations. You’re not trying to settle the global debate about diet—you’re showing that you understand how to form a hypothesis, collect data, and interpret it using real-world examples of current nutrition science.

FAQ: common questions and examples for your project

What are some easy examples of vegan vs. omnivore diets I can compare?

Simple examples include:

• Breakfast: oatmeal with soy milk, fruit, and nuts (vegan) vs. scrambled eggs, bacon, and white toast (omnivore).
• Lunch: lentil soup and whole-grain bread (vegan) vs. cheeseburger and fries (omnivore).
• Dinner: tofu stir-fry with brown rice (vegan) vs. chicken Alfredo with white pasta (omnivore).

You can plug these into a nutrition calculator to compare calories, fiber, saturated fat, and protein.

What is one example of a good science fair question about vegan vs. omnivore diets?

An accessible example of a science fair question is: “Do vegan students at my school consume more dietary fiber on average than omnivore students?” It’s specific, measurable, and grounded in existing research.

Are vegan diets always healthier than omnivore diets?

No. A vegan diet built mostly on sugary drinks, fries, and ultra-processed snacks can be less healthy than an omnivore diet rich in fish, vegetables, fruits, and whole grains. Many studies suggest that whole-food, plant-forward patterns are linked with better health outcomes, but the quality of the food matters more than the label.

Can teenagers safely follow a vegan diet?

Most major nutrition organizations say that well-planned vegan diets can support healthy growth in teenagers, but planning is important. Teens need enough calories, protein, iron, calcium, vitamin D, and vitamin B12. Reliable sources like Mayo Clinic and NIH emphasize that supplements or fortified foods are usually necessary for B12.

How can I avoid bias when using examples of vegan vs. omnivore diets in my project?

State your hypothesis clearly, but stay open to whatever your data shows. Use neutral language in your survey questions, report your sample size, and mention limitations like small sample size or self-reported data. Judges appreciate honesty more than trying to “prove” one diet is automatically better.

Final thoughts: choosing the best examples for your project

When you pick among these examples of vegan vs. omnivore diets: health impact examples, think about three things:

• What you can actually measure (nutrients, survey responses, BMI, meal footprints).
• How much time and access you have (classmates, family, online tools).
• Which question you personally find interesting (heart health, gut health, performance, environment).

Use authoritative sources like the CDC, NIH, Harvard T.H. Chan School of Public Health, Mayo Clinic, or WebMD to back up your background research and discussion. That way, your science fair project doesn’t just compare opinions—it stands on real, current data and clear, well-explained examples of vegan vs. omnivore diets: health impact examples.