We Actually Know What We Should Eat – The Wall Street Journal

Consider breakfast, long touted as the most important meal of the day. Last year, a meta-analysis of existing research on breakfast in the British Medical Journal challenged the value of the meal, finding that it may contribute to weight gain. Indeed, in recent years, intermittent fasting has become a popular weight-loss preoccupation and a new justification for waiting until lunchtime for the day’s first meal. But now, of course, a new study in the Journal of Clinical Endocrinology and Metabolism has arrived to suggest that having a big breakfast actually helps to control weight—evidence directly at odds with the fashionable 16-hour fast.

So what to do in the morning? That question is unlikely to be resolved, but luckily, it doesn’t have to be. Eating a big or small breakfast, or none at all, can be part of a healthy overall dietary pattern—or not. Nutritional health is about the kinds of foods we eat, not just their calorie count or when we eat them. Weight is about energy balance: how the daily intake of fuel that we metabolize aligns with our body’s needs.

“Diet” is a word that has been twisted to mean something that someone invents for the fastest possible weight loss. There’s always a new one to “go on” for short-term results. But what diet really means is how you get the nutrition you need throughout your life.

Before the 20th century, humans knew what to eat: Little or no junk (not much existed); animal products in moderation (far less was available); and relatively unprocessed plant foods in abundance. That’s what almost all traditional diets comprised, though there were variations on this theme that we might now call low-fat, low-carb, vegan, pescatarian and so on.

In eras before that, it was even simpler: Humans ate everything we could find that wasn’t poisonous, and as long as we found enough of it in sufficient variety, we generally did fine. Just as wild cats eat meat, pandas eat bamboo and fish eat algae, humans ate what was good for them. Before there was science, we knew how to do this, just as we knew how to breathe air before analyzing its composition.

But beginning in the 19th century and accelerating through the 20th, mass production and marketing of new foods began to dominate. Science and industry combined to find ways to create shelf-stable, nutrient-poor, high-calorie ultra-processed foods, from cheeseburgers to sodas, as well as almost anything you see in a vending machine or next to the checkout counter. These have generated a public health crisis that requires us to relearn what every human once knew from instinct and experience.

The now-constant barrage of headlines about nutrition science can make us feel like we’re doing everything wrong. Some people respond by tuning out and continuing to eat what’s familiar. Others jump on the bandwagon of each thrilling new diet that promises everything. Most of these deliver temporary results from severe restrictions that no one can maintain. Rapid weight loss is followed by rapid regain, creating a desperation that makes people eager for the next promise of magic.

The truth is that all good diets feature one or another balanced assemblage of wholesome, real foods—mostly plants. Even now, with our instincts suppressed, we know what a good diet is. We picture chickpeas, not Doritos; pinto beans, not jelly beans; broccoli, not Bratwurst.

Yet the way we eat is the leading cause of premature death in the U.S. today. Highly processed foods, especially meats, and added sugar and salt are all significant contributors to heart disease and other chronic killers. Even our comparatively high health care costs are partly due to the damaging effects of unhealthy eating and the pharmaceuticals to treat them.

So how to assess the daily barrage of diet news? First, we need some perspective on nutritional research. New findings don’t usually reverse what we knew before; they add context, bit by bit. Second, we should stop obsessing about particular nutrients—such as whether fat is “good” or not. The short answer is that unsaturated fats from nuts, seeds, fruits and fish tend to be beneficial, while saturated fats, commonly found in meat and dairy and far too commonly consumed, tend to be detrimental. Fiber and added sugars are simpler to sum up—in our modern habits we badly need more of the former and less of the latter.

But the best approach is to focus on actual foods rather than to fixate on their components. From a food-by-food vantage point, some principles emerge that will outlast all diet fads.

Beans: A few years ago, a theory that natural proteins called lectins in beans and legumes might be bad for us gave rise to a bestselling book trying to talk people out of eating them. But we already knew, based on massive evidence, that people eating beans and legumes routinely had better health, not worse.

A 2010 study found the single largest reduction in heart disease risk among women who replaced beef with beans. Another published in 2016, which followed more than 100,000 people for more than 30 years, showed markedly lower mortality when more calories came from plant protein—notably beans—than from animal protein. Beans are one of the most common foods in the world’s “blue zones,” where people routinely live to 100.

Meat: In an influential report published last year, the EAT-Lancet Commission on food, planet and health concluded that per-capita meat consumption in developed countries needs to go down by nearly 90% to keep food production within sustainable boundaries. Fortunately, we don’t have to choose between what is best for our health and for sustaining the planet: They match. Both would benefit greatly if we shift our diets toward more plant-based nutrition.

To be fair, whether meat-eating is good for us is a question complicated by the sort of meat we’re considering. Nearly 35% of the calories in the flesh of modern, grain-fed beef cattle comes from fat, much of it saturated. Grass-fed beef, chicken and lean turkey each provide incremental improvement. But the meat our ancestors ate had a far more beneficial nutritional profile—which is still the case for wild game today because of its varied diet and unimpeded exercise.

Dairy: Are milk products good or bad? Yes—depending on what dairy, what farm, your metabolism, your genes and what it replaces in your diet. Milk (either whole or skim) is a good thing if it is replacing Coke or Pepsi. Good cheese is an upgrade from cheese puffs. Greek yogurt is a far better snack than pork rinds.

But you are subject to nutritional liabilities, not benefits, if the milk replaces water, because it increases your intake of saturated fats. Opting for cheese over raw almonds or choosing yogurt over bean salad are dietary downgrades. Those swaps get you less of the nutritional necessities that today’s diets tend to lack, such as fiber and antioxidants.

Dairy can confer health benefits, but an optimal diet doesn’t require dairy. Similarly, eggs make a better breakfast than doughnuts, but partly due to their cholesterol they lose out to steel-cut oats with mixed berries and nuts.

Fish: A 2010 study from Harvard showed that cardiovascular disease in women was reduced when protein from beans replaced protein from meat and poultry—and even fish. Salmon and other fish rich in omega-3 fatty acids are good if they displace red and processed meat. But what about if they substitute for beans and lentils? Recent studies suggest not, but we need more long-term research to be sure.

There is no one best diet. Good diets can be low or high in fat or carbohydrates, as long as they are made up of wholesome foods, and mostly plants. The quintessentially healthy Mediterranean diet is high in fat, most of it unsaturated, much of it from olive oil, nuts, seeds and avocado. But the famous diet of long-lived residents of Okinawa is low in fat because it is centered around diverse vegetables, grains and soybeans, with very limited meat, poultry and fish.

If you adopt an eating pattern that has stood the test of generations, you are almost certain to be better off than with a diet introduced as breaking news. We are overdue in America for a grown-up conversation about diet for health. If you agree, pull up a chair.

—Mr. Bittman is the author of many food books, including “How to Cook Everything.” Dr. Katz, a specialist in preventive medicine and public health, is the founding director of the Yale-Griffin Prevention Research Center. This essay is adapted from their new book, “How to Eat: All Your Food and Diet Questions Answered,” published by Houghton Mifflin Harcourt.