How to choose a 2020 diet based on science

Diets for longevity, weight loss, and brain health explained.

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Everybody, everywhere, is keen to give other people diet advice. In this swirl of you should cut carbs, eat clean, or choose ‘superfoods’, it’s easy to lose sight of which diets are backed by research, and which are just hype.

The good news is that this year Inverse did the work for you — combing through the latest and most robust scientific studies to figure out the best diet for you, depending on your goals.

Whether your aim is to safely lose weight, live longer, or simply be healthier, there’s a diet that can likely help. But it’s important to note that this article is designed to provide helpful information and break down complicated science behind diets — not give medical advice. Any dietary intervention should be considered with the guidance of a health professional. Think of this as a jumping-off point for your decision: Eating well is key to good health, but not all diets are right for everyone.

To eat for longevity, pick the Mediterranean diet

The Greeks seemingly have it pretty good: a rich history, beautiful coastlines, and a healthy approach to eating. At the end of 2019, U.S. News ranked 35 diets from best to worst and the Mediterranean Diet came in at number one.

Research indicates the “MedDiet” helps prevent heart disease, improves cognitive function, and promotes longevity. In 2014, a study led by Harvard University, scientists found that women who adhered to a Mediterranean diet actually had longer telomeres than women who did not. Telomeres are pieces of your DNA that are considered a biomarker for age. Shorter telomeres are associated with higher risks of dying early and developing chronic diseases.

Meanwhile, a study published in 2018 in the British Journal of Nutrition found that elderly Italians who closely adhered to the Mediterranean diet were more likely to live longer than their peers who did not.

Eating the Mediterranean diet means filling your plate with lots of fresh fruits and vegetables, as well as omega-3 dense fish, olive oil, nuts. The diet keeps saturated fat, red meat, and sugar levels low but still allows moderate amounts of foods that can feel indulgent, like wine and cheese. The diet is flexible which enables its long term success, keeping people fit and healthy over a lifetime.

To eat green and live well, pick the plant-based or flexitarian diet

Monique Tello, a professor at Harvard Medical School and physician at Massachusetts General Hospital, gave Inverse some simple, but scientifically sound advice: If you want to live a long life and stay out of the hospital, eat lots of plants.

“We have so much evidence — overwhelming mountains of evidence on millions and millions and millions of people’s data — that a plant-based diet is the healthiest diet,” Tello told Inverse in July. “Most people do not have to be completely vegan, but they do have to be, for the most part, eating plants.”

As a general rule of thumb, nutritionists recommend getting the bulk of your energy from plant sources: greens, veggies, fruits, as well as whole grains, nuts, and seeds. Eating nutrient-rich plant foods packed with antioxidants helps reduce inflammation — and could serve as a performance hack for athletes.

Going plant-based doesn’t have to mean giving up dairy or eggs entirely, and the rare consumption of meat is fine. The flexitarian diet is similar to the MedDiet — it involves eating vegetarian most of the time while enjoying the occasional steak when the craving strikes. In turn, emerging evidence suggests that the flexitarian diet could be beneficial for body weight, improved metabolic health, blood pressure, and a reduced risk of type 2 diabetes.

Going completely vegetarian or vegan is a decision linked to health pros and cons. These diets have been shown to have lower cholesterol levels, better weight maintenance, but some studies also suggest, if not undertaken carefully, excluding animal products could lead to missing micronutrients like B12, critical for optimizing physiological function.

To quickly lose weight, pick the keto diet

If you’re like 50 percent of American adults, you’ve tried to slim down in the past year. Many people search for a shortcut to dropping pounds, and although some studies show dieting doesn’t lead to long term weight loss, certain diets do seem to enable weight loss safely and quickly. One diet that’s done the trick for thousands of people is the ketogenic diet.

Eating keto involves replacing carbohydrates with lots of fat and moderate levels of protein. However — this isn’t a free pass to load your plate with salami or cheese. Instead, a healthy keto diet includes lots of greens, olive oil, nuts, and some fish. The dietary approach kickstarts a biological process called ketogenesis, where the body burns fat for fuel, not its usual favorite energy source, glucose.

Some studies suggest that the keto diet is more effective at helping obese individuals lose weight than a low-fat diet. However, long term data on the mental and physiological impacts of going keto are missing. Physicians have cautioned against drastically cutting carbs and eating so much fat — especially saturated fat — noting that the diet could lead to nutritional deficiencies or threaten heart health.

Furthermore, people may lose weight in the short term but whether they keep it off in the long term isn’t clear. Due to its nutritional drawbacks and unsustainability, the keto diet landed second to last on U.S. News’ diet ranking of the best diets overall. But it was ranked number three when it came to “best fast weight-loss diets.”

Despite the risks and restrictions, the diet is soaring in popularity.

“Part of the reason why it’s become so popular is that there’s this almost evangelical quality to the people that get on it,” Ethan Weiss, a cardiologist at the University of California, San Francisco, and founder of Keyto, a company manufacturing breathalyzers to monitor ketone levels, told Inverse in July.

“It’s almost like people have felt they have discovered the fountain of youth, and they want to share it with everybody. That’s very unusual in weight loss.”

To eat for brain health, pick intermittent fasting

Intermittent fasting (IF) also gripped the public’s attention in 2019. The eating pattern is simple: eating normally interspersed with long breaks (around 16 hours, typically) between food. IF can also mean skipping breakfast or fasting for an entire day.

"The bottom line is that, in the brain, intermittent fasting will increase the resistance of nerve cells to various types of stress."

Mark Mattson, a neuroscientist at the Johns Hopkins University School of Medicine, has studied intermittent fasting and its impacts on aging and the brain since the nineties. He told Inverse that IF can have tremendous, positive effects on the brain linked to longevity.

“The bottom line is that, in the brain, intermittent fasting will increase the resistance of nerve cells to various types of stress,” Mattson explained.

That’s because IF can enhance the formation of new synapses, Mattson says. Recent research also suggests IF increases the number of mitochondria in individual nerve cells.

In a 2006 literature review, Mattson and co-authors determined that IF, along with calorie restriction, can support the production of neurotrophic factors (peptides and proteins that support the growth and survival of neurons), antioxidant enzymes, and help repair the pathways that make the brain stronger, healthier, and more efficient.

However, these brain-boosting effects aren’t exclusive to intermittent fasting — similar effects have been seen with the Mediterranean diet and plant-based approaches. And the drawbacks — stress from going hungry, exacerbation of unhealthy eating patterns, or potentially missing out on key nutrients — might make intermittent fasting a no-go for some people.

To diet sustainably, pick intuitive eating

Most diets require giving up certain foods or limiting intake. But a restrictive approach to eating can create psychological turmoil, pose long term risks to mental health, and even exacerbate eating disorders. Sometimes, the best diet is no diet at all.

Intuitive eating, an approach to food that focuses on paying attention to your body’s bodily cues, trusting your gut, and eating what you crave, offers a path to rejecting diet culture while staying healthy.

“When you are not at war with your body, and you can listen to these powerful messages, you actually have the ability to get your needs met both psychologically and biologically,” Evelyn Tribole, one of the pioneers of intuitive eating, told Inverse in July.

Studies suggest that intuitive eating can boost self-esteem, help people avoid the yo-yo effect of dieting, focus less on what they eat, and maintain long-term health.

The choice is yours

Ultimately, research shows most diets fail. A 2007 literature review revealed one third to two thirds of dieters regain more weight than they lost on their diets.

That’s not an excuse to toss healthy eating out the window. Instead of trying to revamp your entire approach, try making small, incremental changes that last. Maybe add a serving of veggies or skip sugar in your coffee for two months and see how you feel. Scientists say it takes an average of 66 days to transform a daily choice into a habit. And it’s these lasting behavioral shifts that will add up to longer, healthier years, not short term dietary restriction or giving up a food group.

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