10 diet myths overturned in the past decade, from 'fat makes you fat' to 'supplements are harmless'

keto diet keto diet
Fat went from demonized to glorified.
  • Nutrition advice is constantly changing, with competing, and even contradictory, recommendations appearing from reputable sources.
  • The past 10 years have led to major shifts in what we know about healthy eating, and how we think about nutrition, diets, and food. 
  • Here are some of the biggest nutrition and diet myths that were dispelled in the last decade. 

Myth: Eating fat makes you fat.

Butter and other high-fat foods are calorie-dense, but don't automatically lead to weight gain.
lutavia/Getty Images

The low-fat diet craze may have had it's heyday in the late 1990s, but the myth that fat is bad for you or leads to weight gain persisted well into the 2000s and beyond.

But the past few years have shown that "lite" versions of popular products are actually worse for your health, increasing the risk of heart disease and other ailments previously linked to high-fat foods.  


Plenty of high-fat foods are perfectly healthy. However, fat is still more calorie-dense than either carbs or protein, so it can have mixed effects on weight loss.

In addition, the type of fat matters, since saturated fats are linked to more risks of heart disease and other illnesses than unsaturated fat. The long-term effects of high-fat, low-carb diets aren't yet well understood. 

Experts still recommend a balance of fat, protein, and carbs for an optimal diet


Myth: Diets or detoxes are the best way to lose weight.

juice cleanse
You don't need to detox, since your body has a natural system of doing that for you, thanks to your liver and kidneys.
Iudina Ekaterina/Shutterstock

From juice cleanses and fad diets to dubious "flat belly tea" and other too-good-to-be-true products, detoxes for weight loss and wellness were a major trend appearing to finally wind down at the end of this decade.

Research has consistently found that extreme, quick-fix diet plans don't work and aren't good for your health long-term. Instead, the best strategies are healthy, sustainable changes made gradually over time, as part of a lifestyle you can stick to in the long run. 

Particularly for young people, strict or overzealous diets can also cause disordered eating and other mental health issues. 

And the pseudoscience claims of various cleansing techniques aren't proven to work, and may hurt.

"We each have a liver and kidneys to do that job without needing a detox diet that is, in most cases, inadequately balanced and lacking in so many important nutrients," registered dietitian Bonnie Taub Dix previously told Insider.


Myth: Grazing, or eating small meals frequently, is the healthiest eating pattern.

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Snacking, even on healthy foods like veggies and nuts, has fallen out of favor.

The old advice: Eat small, frequent meals to fuel your metabolism, lose weight, and sustain energy. 

The new rage: Try intermittent fasting, or limiting all of your daily meals to a strict time period. Depending on the style of fasting, this may mean eating just 10 hours to 16 hours a day, or it could mean eating normally five days of the week but abstaining from food entirely the other two days. 


At the same time, growing concern about processed foods have made people wary of most convenient snack foods, like chips and candy bars. Even granola bars and yogurt can pack a lot of sugar with few nutritional benefits.  

"I would encourage everyone to revisit this snacking thing, like is there a way we can eat differently?" cancer researcher Dr. Miriam Merad said in August when her own study on fasting was released. "Maybe eating two times a day would be entirely sufficient and very beneficial, in fact, in terms of health."


Myth: Breakfast is the most important meal of the day.

Eating a big meal may not be the best way to start your morning.

While there good evidence showing that front-loading your calories is more beneficial for weight loss than eating that same amount in the evening, it may not be the best strategy for everyone. 

If, for instance, you're following the trendy intermittent fasting plan which promotes fasting for 16 hours a day and eating during the remaining 8, your first meal not come until lunchtime or later. 

And some people simply may not be hungry in the morning, said Maya Nahra, a registered dietitian at Nuuaria Habit and Behavior Change Program.

"The truth is, eat when you're hungry and stop when you're full," she previously told Insider. "We are bombarded by external food cues. Learning when your individual body is hungry and full is hugely important to your health."

There's also evidence that if you're looking to lose weight, putting off breakfast until after a morning run or other exercise could be best for burning fat. 

Myth: A calorie is a calorie.

calorie counting
Calories count, but the micronutrients and other components of foods are a major factor in how they affect our health.
Evan Lorne/Shutterstock

Nutrition used to be thought of as a simple balancing act of calories — eat fewer to lose weight, eat too many and you'll gain weight. 

But a growing number of studies have shown it's more complicated than that, since vitamins, minerals, fiber, and other factors all play a crucial role in our health.

Certain foods like leafy greens and other fresh produce can have a beneficial effect on the good bacteria in our gut, which can lead to a lower risk of diseasesweight loss, and other health benefits, even if you don't eat fewer total calories. 

On the other end of the grocery aisle, newer research suggests that processed foods may be worse for us than just having too many calories. 

In May, nutrition experts at the National Institutes of Health uncovered some of the first evidence that the way our bodies take in processed, ready-to-eat, and ready-to-heat foods can drive us to eat as many as 500 additional calories a day, increasing risk of obesity and related illness. 

Myth: BMI is a an accurate marker of health.

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Health and nutrition is more complicated than body weight.
PhotoStock-Israel / Getty


Over the past decade, though, exercise scientists, doctors, and other experts have come to realize that's a problem. BMI doesn't specifically measure excess body fat, nor does it account for factors like age and muscle mass, which are crucial to health. This means that people like elite athletes can be defined as obese based on high BMI, even if they're at peak health.

"It's just a measure of weight to height, not a measure of health," Kelly Coffey, a certified personal trainer, previously told Insider.

Now the field is looking toward other ways of determining baseline markers of health. One such alternative is waist circumference, since many of the negative health affects of obesity are linked to high levels of abdominal fat. Several studies have documented a link between high amounts of abdominal fat and an increased risk of heart disease and diabetes, for example.

Others argue that health shouldn't be based on weight, body fat, or body shape at all, and really on health behaviors like physical activity, mental health care, and sleep. 


Myth: Vegetarian food is always healthier.

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Meat substitutes have made it possible to create vegetarian and even vegan versions of fast food, but that doesn't make them healthy.
Melia Robinson

Although there's a growing trend of people cutting back on meat or eliminating animal products entirely for their health, vegetarian doesn't necessarily mean healthier.

More and more research suggests that the most nutritious way to eat is less about specific dietary restrictions and more about getting plenty of whole, unprocessed foods. 

Recent research on Blue Zones, areas of the world where people live the longest, has found that what seems to be most important is a diet high in healthy fats from things like nuts, olive oil, and seafood, and fiber from veggies and legumes. 

Plenty of junk foods are already free of animal products, but are high in calories, processed fats, and refined sugars with few nutrients. 

For instance, this year KFC joins the growing list of fast food companies offering meatless options, but their fried "chicken" isn't, nutritionally speaking, any better for you than the traditional version. 

"Processed foods, whether they're meat-based or plant-based, aren't a nutritional need in our diet, especially when they involve low-quality oils," Whitney Stuart, a board-certified and registered dietitian, previously told Insider.


Myth: Everyone should take vitamin supplements.

Extra vitamins probably won't hurt you, but if you're already eating a balanced diet, they may be a waste of money.
Sarah Schmalbruch/INSIDER

Although not all supplements are the same, research has increasingly shown that for most people, taking vitamins D, vitamin E, calcium, iron, and multivitamins is unnecessary.

A recent meta-analysis, for instance, found that people who were taking vitamin D supplements didn't have a decreased risk of heart disease, stroke, or heart attack, nor were they any less likely to die of any cause.

Other supplements, including vitamins C and E, haven't been proven to be beneficial, despite anecdotes that they can boost your immune system or otherwise improve your well-being. 

It's clear there's no substitute for eating whole foods, which contain a wealth of other micronutrients like polyphenols that supplements don't. These compounds are linked to health benefits like lower blood pressure, reduced risk of disease, and a longer life expectancy.  

"[Whole foods] are accompanied by many nonessential but beneficial nutrients, such as hundreds of carotenoids, flavonoids, minerals, and antioxidants that aren't in most supplements," Clifford Lo, an associate professor of nutrition at the Harvard School of Public Health, said in a recent blog post.

Myth: Artificial sweeteners are better for you than regular sugar.

Despite the popularity of diet sodas, sugar substitutes like aspartame aren't any healthier than the real thing.
successo images/Shutterstock

It's clear why we're drawn to the idea of diet soda, candy, and other items that are sweet without sugar: They're calorie free. 


A study of more than 450,000 people across 10 European countries in the journal Jama Internal Medicine suggests that drinking two or more sweet-tasting beverages a day — whether they're filled with real sugar or imitation low- and no-calorie versions of sweetness — is linked with more early deaths, and more deadly heart issues. The finding held true even in people who maintained a healthy weight.  

Still, there's inconsistent evidence that artificial sweeteners are downright dangerous. Despite fears that aspartame and others are linked to cancer, extensive research (including more than 100 studies) has suggested they are safe.

Studies hinting otherwise have been mainly on mice and insects, meaning there's little evidence to support those claims in humans.

Myth: More protein is always better.

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Relying too heavily on protein shakes and supplements could be doing you more harm than good.
Getty/Peter Berglund

Protein has become an increasingly favored macronutrient, touted for its muscle-building, fat-burning potential. As a result, people are adding it into everything from cookies to coffee. 

But protein, by itself, is just a nutrient. In order to build muscle or burn fat, you have to also be going to the gym or otherwise using your body to encourage tissue repair and growth. And protein still contains calories, so too much of it, without exercise, can cause you to gain weight instead of adding lean muscle mass. 

Most people, especially Americans, get plenty of protein from their diets without a supplement. It only takes about 0.5 to 0.7 grams per pound of body weight for sedentary people to meet their daily recommended intakes. That's around 62 to 88 grams of daily protein for a 125-pound person; a roasted chicken breast already gets you more than halfway there.

Athletes may need a little more, but anything beyond about 1 gram per pound of body weight a day can actually have negative effects on your health, causing dehydration and kidney stress. 

Some protein bars, shakes, and products can also be high in sugar and other unwanted additives, so pay close attention to labeling if you still decide to use protein supplements. 

Read more:

9 fitness trends that were all the rage in the 2010s, from CrossFit to exergaming

Intermittent fasting was the hottest diet trend of 2019, according to Google. Here's what else topped the list.

Nutrition myths that we stopped believing in 2019, including the carnivore diet and 'superfoods'

I lost 5 pounds in 30 days trying the trendy Whole30 diet. Here's why I still wouldn't recommend it.

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