When it comes to living a sustainable life, diet plays a big role. According to the Harvard T.H. Chan School of Public Health, agriculture is the No. 1 cause of the planet’s environmental changes, which includes climate change, destruction of forests and deserts, and damage to oceans and coastal reefs.

But not many consumers are aware of these issues. A December 2018 Nielsen survey found that while 46 percent of people surveyed believed it was important to buy local foods, only 16 percent knew about the effect livestock has on climate change. One study found the use of animals for food, as well as livestock feed, accounts for 57 percent of total food production emissions. There’s one group that seems committed to having a positive impact on the environment: young people. A 2021 survey by Simon-Kucher and Partners found 42 percent of Millennials and 39 percent of Gen Z are willing to buy the more sustainable option, even if it costs more.

Is your diet negatively impacting the environment without you realizing it? Here, take a look at how 11 of today’s most popular diets stack up when it comes to sustainability, in order from most sustainable to least.

1. Vegan Diet

A vegan diet replaces all animal products with fruits, vegetables, nuts, legumes, seeds, and grains.

Pros According to a 2022 report by the United Nations Intergovernmental Panel on Climate Change, plant-based diets produce substantial environmental and health benefits. One study found the vegan diet is best when it comes to lowering greenhouse gas emissions, followed by vegetarian, pescatarian, and flexitarian diets. Another study found the vegan diet accounts for the lowest amount of greenhouse gas emissions out of all diets the study researchers looked at. “This study shows that the vegan diet is the most eco-friendly diet,” says Hana Kahleova, MD, PhD, director of clinical research for Physicians Committee for Responsible Medicine in Washington, DC. She adds that a vegan diet that avoids fish can help reverse the declining numbers of fish in the world and encourage diversity of life in the oceans. Switching to a plant-based diet could also cut your grocery costs by up to one-third, according to one study.

Cons Dr. Kahleova says one of the cons to the vegan diet is that not many people follow it. People tend to adopt the same food preferences as their peers, which in the United States means eating meat regularly, though Kahleova believes the cultural norms are changing and more people seem to be adopting a plant-based diet. Another hurdle that people looking to eat a vegan diet may face is poor access to food permitted in this approach. While plant-based eating can be less expensive, it isn’t so for everyone. Healthy food options as a whole can be scarce or more expensive than unhealthy ones in certain parts of the country. A study looked at food prices in four Kentucky counties. The researchers found nutritious food items, including vegetarian staples like fresh fruits, veggies, almonds, and brown rice, cost the most per serving — more than packaged and processed foods, including meat — in the rural food desert.

2. Vegetarian Diet

A vegetarian diet eliminates meat, poultry, and fish in favor of plant-based foods (hence why some vegetarians refer to themselves as “plant-based”).

Pros A study found cutting meat out of one’s diet can reduce greenhouse gas emissions by 34 percent. A plant-based diet, such as a vegetarian or vegan diet, is also the most sustainable in terms of land and water use than diets that include meat, Kahleova says. In fact, another study found a meat-free diet can reduce a person’s water footprint by about 55 percent.

Cons If you’re eating the same meals year-round, your vegetarian diet may not be as virtuous as you think. Transporting foods to your area affects the environment, so it’s important to plan your meals around foods that are local and in season, says Wesley McWhorter, DrPH, RDN, director of Lifestyle Medicine at Suvida Healthcare in Houston, Texas. “Don’t be cooking cauliflower when it’s not cauliflower season,” he says. Instead, visit your local farmers market for ingredients, or better yet, plant a garden in your backyard.

3. Flexitarian Diet

A flexitarian diet includes nuts, legumes, fruits, and vegetables, as well as moderate amounts of non-processed meat, fish, and dairy.

Pros Terri Brownlee, MPH, RDN, director of nutrition and wellness for Bon Appétit Management Company, a restaurant company based in Redwood City, California, known for its low-carbon diet, likes flexitarianism because it’s easy for many people to follow. Following this diet doesn’t mean people have to swear off meat forever — they likely will just need to reduce their intake and rely more heavily on plant-based sources, which will have a positive effect on the environment. “A diet’s environmental impact is only as big as the number of people who can be persuaded to adopt it,” she says. “The flexitarian diet strikes an ‘I can see myself doing this’ chord for many.” It’s also closely aligned with the diet that the 37 scientists behind the EAT-Lancet Commission (PDF) said will be the most beneficial for people’s health and the planet.

Cons Animal products are still on the table with flexitarianism, so it’s not as environmentally friendly as stricter diets, such as vegetarianism or veganism.

4. DASH Diet

According to Mayo Clinic, the DASH diet aims to lower cholesterol levels by encouraging foods that are low in sodium and rich in potassium, magnesium, and calcium, such as low-fat dairy items, vegetables, fruit, fish, lean poultry, nuts, whole grains, and limited amounts of red meat and sugar.

Pros The emphasis on consuming plant-based foods, which carry a lower environmental impact than foods that come from animals, is a good thing, Brownlee says.

Cons The diet eliminates red meat, but still allows dairy products and poultry. These items don’t contribute nearly the amount of greenhouse gas emissions as red meat, but they are worse for the environment than plant-based items such as lentils and nuts, according to the World Resources Institute protein source scorecard.

5. Mediterranean Diet

The Mediterranean diet is a mainly plant-based eating plan that prioritizes heart-healthy foods, such as olive oil and nuts, and calls for eating fish more frequently than red meat. Try to limit your red meat eating to a few times per month or less, Brownlee says.

Pros Limiting red meat is good for the environment because beef is a major contributor to environmental problems, according to the World Resources Institute. A study found if Spaniards chose a Mediterranean diet over a Western one, greenhouse gas emissions would be reduced by 72 percent, land use by 58 percent, and energy consumption by 52 percent.

Cons Eating fish is healthy, per the NHS, but Brownlee says it’s not always good for the environment.The United Nations Food and Agriculture Organization reports nearly 90 percent of marine fish stocks are either overexploited or depleted. Unsure about how to choose a sustainable option? Visit the Monterey Bay Aquarium's Seafood Watch’s website (or download their app) to learn if the fish you’re planning to order or buy is an ocean-friendly choice, based on the type of fish and where it came from. Generally, you’ll want to buy local when possible because you’ll be more likely to know the fish’s origins and because buying fresh fish that travels by plane to get to your plate isn’t a sustainable approach.

6. Eco-Friendly Versions of the Keto and Atkins Diets

Following the ketogenic diet (or “keto” for short) or Atkins diet in a more environmentally sustainable way involves choosing plant-based foods over animal-based ones wherever possible, McWhorter says. Some may choose to follow the diets while avoiding meat altogether.

Pros Putting less of an emphasis on consuming animal products has a positive effect on the environment. “Over the past few years, the research is catching up to prove that it takes less water, land, and energy resources to produce plant-based foods than it does animal foods,” Brownlee says.

Cons Although the eco versions of keto and Atkins are more sustainable than the regular approaches, they still may include animal products, such as eggs, yogurt, and cheese, so they’re not as sustainable as they could be. On the World Resources Institute protein source scorecard, dairy ranks as medium in terms of the impact on greenhouse gas emissions, which contribute to climate change. Only beef, lamb, and goat received a worse score.

7. Whole30

The 30-day diet encourages followers to eat whole foods, such as vegetables, seafood, and unprocessed meat, and eliminate processed foods, including sugar, dairy, and bread.

Pros Whole30 followers eliminate highly processed foods from their diet, which “leads to choosing food that generate less package waste, which is beneficial, and eliminating dairy does have a positive environmental impact,” Brownlee says.

Cons The diet encourages followers to consume moderate amounts of animal products, such as meat, seafood, poultry, and eggs, “which have documented environmental problems,” Brownlee says. At the same time, it calls for eliminating grains and legumes, which are better for the environment than animal products.

8. Commercial Weight Loss Programs

Popular commercial weight loss programs, such as WW (Weight Watchers), promote weight loss by teaching followers how to make healthy food choices and eat in moderation.

Pros One plus to these types of programs is they teach proper portion size, which can help reduce the amount of food that ends up in the trash.

Cons Many of these diets have a whole line of grocery store products that fit within the diet guidelines. It’s meant to be convenient, but it also places a large focus on packaged foods, which means more processing and packaging when compared with people who follow a non-commercial diet. Single-serve grocery store items, such as frozen meals, in particular can be detrimental to the environment, McWhorter says.

9. The Keto Diet and the Atkins Diet

Both of these diets are ultra low in carbohydrates, but there’s a key distinction between the two: The keto diet encourages followers to eat a high-fat diet, while Atkins is higher in protein, McWhorter says.

Pros It’s possible for keto followers to source many high-fat items from plants, such as nuts and avocado, which is a plus for the environment, McWhorter says.

Cons Both of these diets are generally heavy on animal fats and protein, which can have negative environmental effects. According to an article, meat products are the biggest source of methane, which has global warming potential. Atkins is typically heavier on animal products than keto, given its high-protein nature, McWhorter says. But don’t assume just because a food comes from a plant that it’s good for the environment. McWhorter points out that palm oil, a high-fat ingredient allowed on keto and Atkins, has contributed to the deforestation of rainforests around the world.

10. Paleo Diet

The paleo diet attempts to recreate a “caveman diet” by emphasizing fruit, veggies, wild-caught seafood, and grass-fed meat instead of foods with grains, dairy, and sugar.

Pros Choosing local, grass-fed meat is better than buying what’s typically available at mass-market grocery stores, and paleo dieters who subscribe to the snout-to-tail approach, which means eating as many parts of the animal as possible, reduces the amount of meat that goes to waste.

Cons Paleo is still very meat heavy, which is bad for the environment no matter where that meat comes from. Plus, many paleo dieters load up on processed meat, like bacon, McWhorter says. Processed meats are worse for the environment because they require a lot more energy to create, McWhorter says.

11. Carnivore Diet

The carnivore diet involves eating meat, fish, and eggs, with some other animal products, including butter, yogurt, and cheese.

Pros Because the diet centers on animal products, there are not any environmental benefits to note.

Cons The high-meat diet is extreme and comes with negative environmental risks. The July 2014 Climatic Change study found the average high meat eater contributed greenhouse gas emissions of 7.19 kilograms (kg) of carbon dioxide equivalents per day, compared with 2.89 kg a day per average vegan. “That means that dietary greenhouse gas emissions in meat-eaters are approximately twice as high as those in vegans,” Kahleova says. Given what research tells us about how meat impacts greenhouse gas emissions, water pollution, and the deforestation involved in feeding grain to animals, “the carnivore diet is now an unmitigated environmental disaster,” Brownlee says.

Additional reporting by Kate Daniel.