If you live on planet Earth, you have probably taken a moment to evaluate your diet in the new year. And, if you’re like most of us, you’ve probably broken whatever overly ambitious promises you made to yourself by this time. But what you eat has effects beyond the desired improvement to your waistline.

The World Resources Institute, a not-for-profit environmental research group, said on Monday that humanity is not on track to meet Mission 2020, the parameters laid out to prevent catastrophic global warming and irreversible environmental damage.

With the global population projected to reach 10 billion by 2050, what humanity eats has growing implications for topsoil, pollution, greenhouse gases and deforestation.

Palm oil, found in everything from bread to ice cream, is destroying Sumatran rainforests. Sugar cane fertilizers are devastating the Great Barrier Reef. And meat consumption results in 60% of agriculture’s greenhouse gas emissions.

Photograph: Tim Hussin and Erin Brethauer/The Guardian

So, as we reconsider our New Year’s resolutions, how can we transform (or even tweak) our diets to be better to ourselves and the planet?

We asked four leading experts – chefs, scientists and nutritionists – what to eat for a healthy environment.

Samin Nosrat is the author of the bestselling cookbook Salt, Fat, Acid, Heat: Mastering the Elements of Good Cooking. A documentary series based on the book is now streaming on Netflix. Occasionally, she also shares her recipes with the Guardian.

“The answer is really simple. Eat as many vegetables as possible. That is my guide. Not that I’m always able to stick to it, but I try to make plates that are at least two-thirds vegetables, and then maybe a little bit of grain.

“I don’t actually cook that much meat at home, I think that’s another big one. Wrapped into that is so much about global warming, and water, and animal welfare, and cost. A lot of stuff gets answered when you eat more vegetables.

“In general, I am an extreme person, and often that ends up leading myself to points of insanity. I have tried to be the person who only ate eggs from the chickens whose name I knew.

“I do think having constraints and any kind of limitations forces you to be creative. I think that’s true for anything – as a cook, a writer. When you say: ‘Oh, yeah, I am only going to eat vegetables or vegetable-derived foods,’ it forces you to look at what you can have – or what you can’t have – and how to develop flavors. A lot of my favorite tastes are weird vegan hippie foods. I love nutritional yeast, I love soy sauce and tamari.

“I’ve never tried to go vegan. I don’t think using a little parm is going to be the end of the world. That is not the greatest and most immediate source of global danger. Meat really is.”

Photograph: Neilson Barnard/Getty Images for New York Times

Marion Nestle is an emerita professor of nutrition at New York University, the author of six books on food and a former government adviser on socioeconomic influences of food.

“Fortunately, the diet that is best for the health of people and planetary sustainability is the same, and so simple that the journalist Michael Pollan can do it in seven words: ‘Eat food. Not too much. Mostly plants.’ My translation: eat a largely plant-based diet, balance calorie intake with expenditure and don’t eat too much junk food.

“Vegan diets are fine (but make sure to eat a variety of plant foods and get an adequate source of vitamin B12). Vegetarian diets with some animal products require no special advice. Both are healthy for people and the planet.”

Photograph: Ali Smith/The Guardian

Dan Barber is the award-winning author and chef of Blue Hill and Blue Hill at Stone Barns restaurants. He also served on former president Barack Obama’s council on physical fitness, sports and nutrition.

“My advice is not to have a prescription of what to eat, but to think about where you are in the world. The idea as we move forward with more consciousness about where our food is coming from and where it’s grown, is to think about creating a diet that mimics what a local regional landscape really wants to be growing.

“The first place to look is organic agriculture, because organic sets a level playing field. It dictates that you’re farming in way that keeps the fertility locked and loaded for the next crop. You don’t have to do that in a chemical system because you can put in enough fertilizer. The idea is having a diet that is radically diverse, but it also needs to be reflective of what the particular landscape is telling you it wants.

“For a lot of places in the world, those negotiations have been worked out over thousands of years. Our difficulty, in the US, is that we don’t have that kind of history or negotiations.

“For people in this country, the challenge is to learn more about their regional environment and about farming just in their region, and what does well. [In the north-east that means] winter root vegetables, grass-fed meats … and brassica are really part of the diet for this time of year. But it’s not the same as southern California.

“It’s getting to know your environment. In most places in the world, you can get a look at the cuisine that has been passed through many, many, many generations.

“If your paradigm is you want to eat locally, in this sort of landscape [New York] – this landscape is about grass, and about animals; it’s not about vegetables.

“I’m not advocating for more meat, I’m advocating for meat that has proper portions. I love steak, but I don’t have it every day.

“We’re talking about regenerative agriculture, where the land is left better off. Maybe paying a little bit more for it and eating a little bit less of it.”

Nicoletta Pellegrini researchers human diet and nutrition at the University of Parma in Italy. She recently examined the environmental impacts of vegan, vegetarian and omnivorous diets.

“As animal products have a high environmental impact, the exclusion of these products reduces the environmental impact of diet. However, as our study demonstrated, the vegan approach was not associated with significantly lower environmental footprints when compared to ovo-lacto-vegetarian one.

“A likely explanation might be that the real plant-based diets are generally characterized by industrially, highly processed plant-based meat and dairy substitutes. These products have a higher environmental impact than the unprocessed plant-based foodstuffs. Moreover, the lower energy density of plant-based foodstuffs results in a higher food intake for vegans with respect to ovo-lacto-vegetarians (around 12.5% in terms of food weight), possibly explaining the lack of environmental benefits of a vegan diet in comparison with an ovo-lacto-vegetarian choice.

“High meat consumption and high-fat vegetarian diets were hypothesized to require more land resources than other food choices. When impact data were adjusted by energy intake, the analysis brought to light an extremely high environmental impact of some subjects, in particular fruitarians.

“To reach an environmentally sustainable solution, animal-based foodstuffs should be partially replaced with fruits, vegetables, legumes and cereals, according to nutritional guidelines.

“Educating people to make little changes in their dietary behaviours could be a key action towards a reduction of environmental impact of the diet without ignoring the effect of diet on their health.”

These interviews have been lightly edited and condensed