You might not know this, but all of those pills, powders and drinks that either help you lose weight or bulk up don't have to be approved by the U.S. Food and Drug Administration — even though they look a lot like food and/or drugs.
In fact, they don't have to go through much red tape before hitting store shelves.
"It's very concerning to me, and it should be concerning to consumers," said nutrition and physiology professor Pam Hinton.
That's Dr. Pam Hinton, a nutrition and exercise physiology professor at the University of Missouri.
"It's only when something goes wrong that the FDA gets involved. That's really the opposite of how we regulate foods and drugs. ... It's a billion-dollar business, and the goal of the companies is to make money," Hinton said.
Sure, the products claim to enhance your workouts or melt that fat right off you, but can you really be sure they're doing what they say? The short answer is no.
"Often times, they'll use ingredients that cause a tingling sensation. ... So you feel like you're doing something before you actually start working out. Do they actually cause or promote a better workout? That's probably debatable," said Jeff Smith, director of fitness at Wilson's Fitness in Columbia, Missouri.
See, the products aren't usually scrutinized by the FDA unless there's evidence they harm people or contain ingredients not listed on the label.
But that doesn't generally happen until after they've hit the market. And we're talking potentially years after.
Lyndsay Meyer of the FDA told Newsy: "These products are sometimes being made in people's basements. ... We might not ever be able to track down someone who's making a product.
"[For example], you're making a supplement; we start to investigate that product because we found it contains a hidden drug ingredient. You realize maybe we're onto you, so the next day, you just print up a new label, call it something else and then the agency is back to square one."
SEE MORE: Dietary Supplements Lead To Over 20,000 ER Visits Yearly
Essentially, any of the claims the products make are backed up solely by the companies trying to sell them.
So while a company might claim its protein powder contains a certain amount of protein, studies have shown that's not always the case.
"Every year, there are reports of products that have ingredients in them that aren't listed on the label. There are products that have contaminants in them. Then, there are always some reports of some products that have negative health consequences," Hinton said.
We reached out to GNC, a manufacturer and distributor of these products. But after about a month trying to arrange an interview, we couldn't get anything set up.
SEE MORE: Asking For A Friend: How Do I Fix 'Skinny Fat'?
The truth is, most of the supplements you're buying are actually just substitutes for food. Want to skip the protein powders? You could potentially increase your daily intake of foods like steak, chicken or fish to get that same level.
But there are a few caveats.
"Even going to the grocery store, what is on the back of the label. Can you completely and 100 percent guarantee that's exactly what is in that product? They have leeway, too," Smith said.
If you do reach for the pills or powders to help accomplish your fitness goals, there are some ways to see if you're buying a reliable product.
In short, do your research. It's best to go with established companies that have a good track record. Also, you're more than likely going to get what you pay for. Cheap out on the product, and you might be short-changing your workouts.
This video includes clips from Warner Bros. / "Space Jam" and GNC.