The first lesson in diet and nutrition 101 is to forget everything you think you know about diet and nutrition.
Because chances are as soon as you've got it down, more advice or another diet pops up.
Take cholesterol and fats, for example: until 2015, the USDA recommended no more than 300 milligrams of cholesterol daily.
For some perspective, a single egg has 186 milligrams.
But the government removed the limit in 2015.
Officials couldn't prove the link between dietary cholesterol and cholesterol in the blood.
You may remember the food pyramid from your grade school days.
It suggested a diet of six to 11 servings of breads, cereal, rice and pasta, three to five servings of vegetables and even fewer servings of meat, dairy, fruit and fats.
The USDA scrapped that dietary guide over a decade ago and replaced it with "My Plate" showing a new way of how to section and balance your meals.
Your food choices add up, and they all matter. So where do you start?
The USDA recommends fruits and vegetables should now make up half of your plate with less protein, dairy and grains.
But this year over half of Americans said they'd never seen "My Plate" before, or knew little about it.
Then there's calorie confusion: how many calories should we put on our plates?
"Calories are important outside of weight loss for overall health, especially for longevity. So we want to take care of our body with really good quality calories,"said Grey.
Some food-tracking apps like "My Fitness Pal" are based on a minimum 1,200 calorie daily diet for the quickest weight loss results.
Historians trace this number back to one of the first modern diet books ever released in 1918.
At the time the author Lulu Hunt Peters suggested 1,200 calories a day would keep someone's weight controlled. It was also unpatriotic to "be fat" while thousands were starving during the WWI era.
Study: It's What We're NOT Eating That's Killing Us
Certified Nutritionist Liana Warner Grey is among a chorus of food experts who say eating 1,200 calories a day is not only unhealthy, it's the amount a toddler should eat.
"The 1,200 calories a day is definitely a myth. We need need more fuel, more clean calories to get us through the day," said Grey.
Current USDA guidelines say adult women need between 1,600 to 2,400 calories a day, depending on their height, weight and activity level.
Adult men need 2,000 to 3,000 calories a day.
And one approach doesn't fit all.
A 2019 study found even identical twins don't react to food the same way, suggesting no single diet exists that works for everyone.
Doctors say there are many other lesser-known factors like stress.
"The more stress people that people were experiencing, the more weight they were gaining," said Dr. Arthur Evans, the CEO of the American Psychological Association.
Out-of-whack hormones like cortisol or leptin also contribute to weight gain.
Even what type of sugar we eat.
"The brain responds differently to different sugars. So corn syrup hits very differently in the body than what monk fruit or honey will do because those sugars actually provide nutritional value," said Grey.
Researchers say celebrity influence also plays a major role in what we eat.
A study in The Journal of the American Medical Association this year looked at some of the most followed celebrity accounts on Instagram.
They found an overwhelming number of posts about food and drinks that were unhealthy by U.S. nutritional standards.
One of the studies authors says celebrities and social media have the kind of influence that can help sustain eating trends and set norms.
"This can really contribute to followers' perception of what is common what is valued in society right now," said Bradley Turnwald, a behavioral scientist at The University of Chicago.
On TikTok, videos tagged "nutrition" have amassed nearly eight billion views, and posts about diet hit over 20 billion views.
Many contradict one another .
Dr. Idrees Mughal told the New York Times viewers tag him in 100 to 200 videos every day for help.
The British doctor, who has a Master's in nutrition, dedicates his entire TikTok to scientifically debunking hundreds of claims.
For example someone said on TikTok, "eggs are one of the worst foods you can eat, full of fat and cholesterol."
Mughal says "eggs are one of the most nutrient rich foods we could eat, as well as being a well high quality protein and digestible amino acids. Eggs are top of the list."
TikTok says it has measures to address harmful diet and nutrition advice.
The company says it removes creators who violate their disordered eating policies and flags potentially harmful searches.
But even research that experts cite isn’t always cut and dried. And variables or research blindspots can get lost in a catchy headline.
Nutritionists say the perfect diet study is unachievable.
They emphasize a "healthy" diet isn't one size fits everybody.
And that drowning out the noise and listening your own body is best.
