How to Eat for Your Health — And the Planet’s Health, Too

For people with diabetes, eating a healthy diet doesn’t have to conflict with environmental sustainability. In fact, the two may be complementary — even as concerns about planetary health are growing. 

How will we feed a healthy and sustainable diet to an estimated 10 billion people in 2050? That issue has been driving the EAT-Lancet Commission on Food, Planet, Health since 2019. The group, led by Walter Willett, DrPH, professor of epidemiology and nutrition at Harvard’s T.H. Chan School of Public Health, believes it now has the framework for what they call a “planetary health diet.”

We spoke with Dr. Willett to learn more about the planetary health diet and how it overlaps — or perhaps doesn’t — with a healthy diabetes diet. 

The research has led Willett to believe that there’s no way humans can continue the current approach to food systems, with diets so fixated on processed foods and red meat. Our modern eating pattern is both bad for our health and terrible for the environment.

“The huge, fundamental threat to human civilization is the rate of climate change that we’re experiencing now,” he said. “In the long term, we can’t be healthy without a healthy planet. The way we’re producing our foods and what we eat is driving climate change.”

What Exactly Is the Planetary Health Diet?

The first thing to know is that there is no precise formula for the diet. Instead, the planetary health diet is what Willett called a dietary pattern targeted for a healthy population emphasizing modest amounts of animal protein, with the balance being whole grains, fruits, vegetables, and legumes. 

The commission does offer, however, a sense of the proportionality of what a plate of food within this framework would look like:

“A planetary health plate should consist by volume of approximately half a plate of vegetables and fruits; the other half, displayed by contribution to calories, should consist of primarily whole grains, plant protein sources, unsaturated plant oils, and (optionally) modest amounts of animal sources of protein.”  

The planetary health plate.

Willett explained that the diet “minimizes risks of noncommunicable diseases, including cardiovascular disease, diabetes, cancer, and other conditions, and also stays within planetary boundaries.”

He noted the researchers went through all of the major food groups one by one, asking what would be the optimal intake of grains — specifically whole grains — as well as fruits, vegetables, red meat and plant protein sources, added fats, added sugar, and salt. Using existing scientific evidence, the commission developed global scientific targets for both healthy diets and sustainable food production. That’s the basis for a planetary health diet. 

“Interestingly, after looking at all the world’s literature when we put it all together, it was very consistent with a traditional Mediterranean diet,” he said, although he also refers to it as a flexitarian diet.

Willett did praise the American Diabetes Association (ADA)’s approach. “The ADA already has what would qualify as a planetary health diet. It leans more toward the plant-based part of the picture.”

The researchers sought to develop an intersection between what they call a “safe operating space for food systems” where healthy and sustainable diets meet around the globe. The bottom line is a largely plant-based diet that could also include modest amounts of fish, meat, and dairy. 

Not only is this a diet that could prevent 11 million deaths a year, but the associated food production parameters also could potentially decrease the risk of “irreversible and potentially catastrophic shifts in the Earth system,” according to the EAT-Lancet Commission report.  

How Does the Planetary Health Diet Work for People With Diabetes?

If you look at expert resources like the ADA, there is no one diet recommended for people managing diabetes, whether type 1 or 2. But it does have some common guidelines:

Eat plenty of nonstarchy vegetables.
Eat less sugar and fewer refined grains.
Choose whole foods over highly processed foods.

And, of course, there’s the admonition to eat fewer carbs to improve blood sugar. In fact, the ADA has noted that we don’t truly need carbs.

Willett doesn’t go that far, but he did tell Healio, “You don’t really have to have any grains in a diet.” In our discussion, he explained that humans can make enough glucose from protein for the central nervous system’s use of glucose but said that a no-grains approach was extreme. Whole grains offer a lot of positive benefits, such as fiber and micronutrients.

“But for someone with diabetes who would like to really go with a low-carbohydrate diet, you could do that by thinking of, for example, plant sources of protein,” Willett said. “Soy has a modest amount of carbohydrate and has quite a bit of protein. You can eat healthy fats by eating nuts, which have very little carbohydrate.”

Willett said that while the planetary health diet approach is geared to a “generally healthy population,” it would be beneficial to people with diabetes, especially type 2 diabetes.

“It involves a moderate intake of carbohydrates and fat, but there’s a lot of attention to the quality of carbohydrates,” he explained, “really minimizing refined grains and emphasizing whole grains and small amounts of potatoes, which have a high glycemic index.”

For people with type 1 diabetes, Willett acknowledged, “We don’t really have enough data that’s specifically derived for people with type 1 diabetes to say that we have evidence that the planetary health type plan will be good for someone with type 1 diabetes.”

“But still,” he continued, “I think it’s very likely that a diet more plant-forward, emphasizing plant protein sources, is likely to be good for a person with type 1 diabetes, because it does mean that carbohydrate intake will be modest, and includes healthier fats and healthier sources of protein for anyone who’s at higher risk of cardiovascular disease. This makes it very likely that this would be good for someone who has type 1 diabetes as well.”

Designing a Diabetes-Friendly Planetary Health Diet

Of course, we need to recognize that all plants aren’t equal when it comes to the glycemic index. Some, like potatoes, bananas, sweet potatoes, and watermelon, rank pretty high. For a person without diabetes, that may not be an issue, but people with diabetes still should be focused on vegetables and fruits with a lower glycemic index and limit portions of those that are higher. So, for people with diabetes, a planetary health diet doesn’t confer free-for-all consumption of plant-based foods.

Beyond that, given that the planetary health diet is essentially flexitarian, people with diabetes already weighing choices like the Mediterranean diet or keto diet can make those work within the planetary health diet framework.

“It really comes down to about two servings of animal source protein a day that could be part of a planetary health diet, with one serving of dairy, another serving of poultry or fish or eggs, with red meat kept at no more than one serving a week because that has a really big planetary health impact. But there’s a huge amount of flexibility there.”

Yes, he said, a keto diet is on the table — but with a twist.

“The biggest threat for most people with diabetes is excessive increases in cardiovascular disease,” Willett said, “and high consumption of saturated fat was related to increases in cardiovascular disease among people who already had diabetes. But you could have the metabolic benefits of a keto diet, but emphasizing plant sources of protein, including nuts. Replacing red meat with nuts is something I think pretty much everybody should think of as a priority.”

For those on medications like Ozempic, which has the effect of reducing appetite, that could be a benefit to planetary health if it reduced food production and led to healthier people.

“If everybody ate just a little bit less, that would be good for the planet,” Willett acknowledged, “especially those who are overweight or obese. Of course, it’s still very important what we eat. The general point is that these drugs will benefit some people, but current prices are a big issue. More fundamentally, when we look at diet and health overall, excessive weight is clearly a problem. But if everyone did lose weight and still ate the current American diet, they would still not be healthy. It’s the quality of the diet as well as exercise.”

Are the EAT-Lancet Commission researchers on a path toward developing examples of planetary health diets for healthcare professionals and consumers? Well, it’s complicated. It is a global initiative, and the ideal diet in Central Africa will be different from those in South America and Northern Europe, not to mention the many regions of the United States. And then there’s the issue of drilling down to diets for people with health conditions that require dietary restrictions. 

“We haven’t specifically had an agenda to look at people with clinically specific issues like diabetes, and that would be a good thing to do,” said Willett. 

About EAT-Lancet 2.0.

EAT-Lancet Commission Summary Report.

Diet of Plant-Based Foods, With Daily Protein and Dairy Servings, May Be Ideal for Planet. Healio. November 2, 2023.

What Is the Glycemic Food Index? Cleveland Clinic. October 21, 2021.

Red Meat Consumption Associated With Increased Type 2 Diabetes Risk. Harvard T.H. Chan School of Public Health. October 19, 2023.


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