Nutrition best practices are all the rage! It seems that we’re supposed to eat more protein, fewer carbs, more fiber, less gluten, and add fresh produce and fermented foods for a healthier gut. And if we want to lose weight, apparently, we shouldn’t eat dinner after 6 p.m.

But what happens when these food rules don’t stand up to a closer look?

The problem is that much of this advice starts with legitimate science, then gets exaggerated, oversimplified, or turned into a broad generalization that may not apply to everyone.

So, this week, we’re taking a closer look at six popular dietary “rules” to see what the research really says.

Myth #1: You can lose weight by not eating after 6 p.m.

The claim: If you stop eating early in the evening, you’ll lose weight because your body doesn’t burn calories as efficiently at night.

The reality: Your metabolism doesn’t shut down at 6 p.m. And calories don’t suddenly become more fattening when the sun goes down.

There is some legitimate science behind the idea of eating earlier. Our metabolism follows a circadian rhythm, and our bodies generally handle glucose more efficiently earlier in the day. Late-night eating can also interfere with sleep and may encourage mindless snacking.

But eating earlier isn’t necessarily a weight-loss strategy in itself. And eating later is not a recipe for weight gain.

In a 2022 study published in the New England Journal of Medicine, researchers followed 139 adults with obesity who were assigned to either eat only between 8 a.m. and 4 p.m. or reduce their daily calories without restricting their eating hours. After one year, both groups lost weight, but the difference between them wasn’t statistically significant.

A smaller, carefully controlled 2024 study went a step further. Researchers provided participants with meals containing the same calories and nutrients but different eating schedules. After 12 weeks, the people who ate during a restricted window lost no more weight than those who ate throughout the day.

The takeaway? Eating earlier and establishing a cutoff can help eliminate unnecessary evening snacks. But any weight-loss advantage comes from fewer snacks, not the time of day they are eaten. So, if you want to eat dinner with other adults later in the evening, you won’t be ruining your weight loss efforts.

Myth #2: Brown rice is much healthier than white rice

The claim: Choosing brown rice over white rice is the healthy choice and reduces your risk of developing type 2 diabetes.

The reality: Brown rice has some nutritional advantages, but the difference isn’t as meaningful as brown rice proponents suggest.

Brown and white rice begin as the same grain. Brown rice retains its bran and germ, which contain fiber, vitamins, minerals, and beneficial plant compounds. White rice has those layers removed, making it softer, quicker to cook, and easier to digest.

Rice is rich in starch, which digestion turns into glucose, or blood sugar. If the body struggles to regulate it, type 2 diabetes can eventually develop. Brown rice generally provides more fiber and magnesium and produces a somewhat smaller blood sugar response. The fiber in the bran slows the breakdown of starch, so glucose enters the bloodstream more slowly.

A huge longitudinal study that followed almost 200,000 Americans for 14-22 years showed that the brown rice eaters had a 16% lower risk of developing diabetes. But the study didn’t account for the fact that brown rice eaters had generally healthier lifestyles. When researchers controlled the experiment and instructed participants to eat either brown or white rice, the difference in risk evaporated.

Here’s another wrinkle: Brown rice tends to contain more inorganic arsenic, a naturally occurring contaminant that rice absorbs from soil and water. Arsenic concentrates in the outer layers of the grain, which are removed when rice is processed into white rice.

That doesn’t mean brown rice is dangerous or that white rice is healthier. It means neither deserves its reputation as a nutritional hero or villain.

And there is a hack that can mitigate the glucose spikes that can be attributed to white rice. Cool it!

When rice is cooked and then cooled (typically in the refrigerator for 12 to 24 hours), the digestible starch molecules crystallize into a form called resistant starch. Resistant starch acts more like dietary fiber in your digestive system. It breaks down and absorbs more slowly, which helps blunt blood sugar and insulin spikes rather than releasing glucose into the bloodstream all at once. Cooled white rice behaves much like brown rice.

If you enjoy brown rice, great. If you prefer white rice, you can absolutely include it in a healthy diet. Variety, reasonable portions, temperature, and the overall quality of your meals matter much more than the color of your rice.

Myth #3: Fermented foods are the secret to a healthy gut

The claim: Eating yogurt, kimchi, sauerkraut, kefir, and other fermented foods will replenish your good bacteria and transform your gut microbiome.

The reality: Fermented foods can be good for you, but their benefits are more complicated than the marketing suggests.

Fermentation occurs when microorganisms such as bacteria or yeast break down sugars in food. The process can create distinctive flavors, improve preservation, and sometimes make certain nutrients easier to digest.

Some fermented foods contain live microorganisms that may interact with our existing gut bacteria. But not all fermented foods contain live microbes by the time we eat them. Heat processing, for example, can kill the organisms involved in fermentation. And even when live microbes are present, they don’t necessarily take up permanent residence in our intestines.

There is encouraging research. In a small 2021 Stanford University study, 36 healthy adults were assigned either a diet rich in fermented foods or one high in fiber. After 10 weeks, the fermented-food group showed increased diversity of gut microorganisms and reductions in several markers of inflammation. That’s promising, but we still don’t know which foods, quantities, and microbial strains are most beneficial for different people. And we don’t know whether any of these changes affect a person’s overall gut health.

More importantly, many fermented foods we can buy at the grocery store have been heat-treated, killing off the live bacteria. You need to check labels for “live and active cultures.” Those aren’t always easy to find. Also, some fermented foods can be high in sodium or added sugar. Kombucha, for example, isn’t automatically a health drink simply because bacteria helped make it. Most store-bought kombucha brands have lots of added sugar.

The best-established approach to supporting a healthy gut remains eating a varied, fiber-rich diet that includes vegetables, fruits, beans, nuts, and whole grains. These foods provide nourishment for the beneficial microorganisms already living in your digestive tract.

If you enjoy yogurt, kefir, or kimchi, keep eating them. Just don’t feel obligated to start fermenting cabbage in your kitchen to achieve optimal health.

Myth #4: We’d all be healthier if we gave up gluten

The claim: Gluten causes inflammation, digestive problems, and weight gain, so we should reduce or eliminate it.

The reality: For most people, gluten is a perfectly ordinary, even healthy, dietary protein.

Gluten is found naturally in wheat, barley, and rye. It gives bread its elasticity and helps baked goods hold their shape. It’s also become one of the most unfairly maligned ingredients in the grocery store.

For people with celiac disease, gluten is genuinely dangerous. It triggers an autoimmune response that damages the lining of the small intestine and interferes with nutrient absorption. People with celiac disease must avoid gluten completely.

Other people may have a wheat allergy or non-celiac gluten sensitivity, which can produce symptoms such as bloating, abdominal pain, or diarrhea.

But for the vast majority of people, there’s no convincing evidence that eliminating gluten improves health, reduces inflammation, or promotes weight loss.

In fact, unnecessarily eliminating gluten can make a diet less nutritious. Whole grains containing gluten provide fiber, B vitamins, iron, and other important nutrients. Many packaged gluten-free alternatives contain less fiber and more sugar or fat than the foods they’re replacing.

There’s also evidence that some people who believe they’re sensitive to gluten may actually be reacting to other components of wheat, particularly certain fermentable carbohydrates called “fructans.”

If you consistently experience symptoms after eating wheat products, it’s worth investigating. But talk with a healthcare professional before eliminating gluten, especially if celiac disease is a possibility. Removing gluten before testing for celiac can make the results unreliable.

For everyone else, there’s no reason to give up whole-wheat bread just because someone on social media insists that gluten causes inflammation.

Myth #5: Cutting out carbs is the fastest and best way to lose weight

The claim: Carbohydrates cause insulin spikes, insulin causes fat storage, and eliminating carbs is the key to rapid weight loss.

The reality: Low-carbohydrate diets can be effective for weight loss, but they aren’t inherently superior or sustainable.

When you sharply reduce carbohydrates, your body begins using up glycogen, the stored form of glucose found primarily in your muscles and liver. Glycogen is stored along with water, so as glycogen levels fall, your body releases that water.

The result can be a surprisingly rapid drop on the scale during the first week or two. Unfortunately, much of that initial loss is water rather than body fat.

Over time, low-carbohydrate diets, like Atkins, Keto, and Paleo, can produce meaningful fat loss, simply because they help people reduce their overall calorie intake. But other approaches can work just as well.

In the landmark DIETFITS trial, published in JAMA in 2018, researchers randomly assigned 609 adults to either a healthy low-fat or healthy low-carbohydrate diet. After one year, the two groups showed virtually the same weight loss.

Other studies and reviews have found a modest short-term weight-loss advantage for lower-carbohydrate diets. But that advantage diminishes with time as fluids stabilize.

And carbohydrates aren’t all alike. Sugary drinks, candy, and highly refined snack foods have very different nutritional profiles from beans, oats, vegetables, fruit, and whole grains.

The latter provide fiber, vitamins, minerals, and important fuel for our brains and muscles. Eliminating them can make it harder to meet nutritional needs, and restrictive diets can be difficult to maintain.

If reducing carbs helps you manage your appetite and weight, that’s a reasonable approach. But you don’t have to give up fruit, beans, or your morning oatmeal to be healthy or lose weight. In fact, eating the complex carbs that you like can make it much easier for you to maintain a healthy diet long-term.

Myth #6: Fresh fruits and vegetables are healthier than frozen

The claim: Fresh produce is more nutritious than frozen produce because freezing destroys important vitamins and nutrients.

The reality: Frozen fruits and vegetables are often just as nutritious as fresh, and sometimes even more so.

Here’s why. Most frozen produce is picked at peak ripeness and frozen relatively quickly, preserving much of its nutritional value. Fresh produce, on the other hand, may spend days traveling from farm to supermarket, followed by several more days in your refrigerator. During that time, some vitamins, particularly vitamin C, can gradually break down. And, as we were reminded this summer, fresh produce has been known to come with organisms that make us sick.

Freezing itself preserves most nutrients quite well. However, vegetables are often briefly blanched in hot water or steam before freezing to prevent deterioration. That process can reduce certain heat-sensitive vitamins, including vitamin C and some B vitamins. Other nutrients, including fiber and minerals, remain largely unaffected.

Researchers at the University of California, Davis compared the nutritional content of fresh, frozen, and refrigerated produce, including broccoli, carrots, spinach, strawberries, and blueberries. They found that frozen produce generally retained nutrients as well as fresh produce, and in some cases contained higher levels of certain vitamins than fresh produce that had been stored for several days.

There are practical advantages, too. Frozen produce is often less expensive, lasts much longer, requires little preparation, and can dramatically reduce food waste. And having a bag of frozen broccoli or berries on hand makes it a lot easier to include fruits and vegetables in your meals, even when you haven’t been to the grocery store.

One caution: Frozen vegetables packaged with sauces, butter, or seasonings can contain substantial amounts of sodium or saturated fat. And frozen fruit with added sugar isn’t quite the same as plain frozen fruit.

The bottom line? Fresh, frozen, or a combination of both, the healthiest fruits and vegetables are the ones you’ll actually eat. And if a bag of frozen spinach saves you from discovering another slimy science experiment in your refrigerator’s produce drawer, that’s a bonus.

The bottom line: Stop looking for magic rules

The common thread running through these myths is that nutrition rarely comes down to one food, one ingredient, or one rule.

What time you eat matters less for weight loss than how much you eat overall. Brown rice is superior more in theory than in fact. Fermented foods may help your gut, but the right fermentation formula is unclear and often hard to find. Gluten is a problem for some people, not most people. And carbohydrates aren’t the enemy.

A healthy eating pattern doesn’t require you to eliminate whole categories of foods. Just be sensible. We all know fruit is healthier than candy.

Focus on variety, reasonable portions, plenty of fiber, adequate protein, and foods you actually enjoy. And remember that consistency matters more than perfection.

After all, if eating well requires you to give up bread, rice, pasta, and dinner after 6 p.m., there’s a pretty good chance “the diet” won’t last very long.