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Unhealthiest Proteins for Weight Loss, According to Experts

Not all forms of this essential macronutrient get the green light from nutritionists.
FACT CHECKED BY Olivia Tarantino

The word "protein" on food packages attracts people like live bait rings the dinner bell to largemouth bass. We hunt down protein because we know it builds muscle at the same time it helps us lose weight. Protein is a key macronutrient for all sorts of important processes in our bodies. For example, protein… preserves our muscle mass as we age, keeps us from losing muscle at the same time we're losing weight, satisfies hunger longer than the other macronutrients, is more difficult for the body to turn into fat, requires the body to use more energy to process through digestion (known as the "thermic effect of food"), and can help reduce calorie intake by staving off hunger pangs.

But your body doesn't react to all proteins the same way. Some proteins are more useful for muscle building than others. And some proteins are unhealthy to eat regularly. Here is what some experts had to say about the unhealthiest proteins for weight loss.

And for more on protein, read Ways Eating Protein Can Help You Lose Weight, Say Dietitians.


Processed meats and cheeses

deli meats on wood plate

Processed meats that have been preserved by smoking or salting, curing, or adding chemical preservatives like bacon, sausage, lunch meat, and hot dogs, are among the worst proteins for good health. "Unfortunately, when these meats are preserved, nitrates are added, which generates compounds that can lead to cancer," says Gretchen San Miguel, MD, chief medical officer at Medi-Weightloss. Processed meats have been classified as a Group 1 Carcinogen by the World Health Organization.

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Processed cheese

american cheese

Although cheese may not come to mind when you think of protein, the dairy product is actually a good source of the macronutrient. That being said, it may not be the best source of protein for weight loss.

"Many people wanted to follow a ketogenic diet and turn to cheeses as a low-carb alternative not realize that cheese (like processed meats) is very high in calories, unhealthy saturated fats, processed oils and may also have hormonal additives," says Dr. San Miguel. "Consuming too much can lead to high cholesterol, excess calories and impact overall health."

Cow's milk and cheese, while good sources of protein, can also be highly inflammatory for most people. "If you are trying to lose weight (especially in your middle section) and you constantly have GI problems, I would omit dairy," says Heather Hanks, MS, a nutritionist with InstaPot Life. "Inflammation can make it hard to lose weight."


High-fat, grain-fed red meat

Raw ground beef

"Research has shown that people who consume a large amount of grain-fed red meats have a high risk of heart attack and stroke due to their high content in saturated fat," says Dr. San Miguel.

Grain-fed beef is typically feed-lot beef, where cattle are fed corn and other grains. Grain-fed beef lacks heart-healthy omega 3 fatty acids and contains more saturated fats. Dr. San Miguel recommends opting for grass-fed beef or lean meats such as pork loin, fish, and chicken breast. Grass-fed beef tends to be lower in fat, and contain more omega-3s, the healthy fats also found in oily fish, plus more vitamin E. Beef that feeds on grass also is a rich source of CLA (conjugated linolenic acid), which studies in the Journal of the American Heart Association have shown is associated with a lower risk of heart failure.


Deep fried proteins

fried chicken

Fat is a healthy, essential macronutrient, but the type of fat matters," says David Sautter, NASM-Certified Fitness Nutrition Specialist at Top Fitness Magazine. "When you deep fry a food (like chicken or fish), you can increase the amount of trans-fat you're eating; trans-fat has been linked to heart disease, canceling out the benefits you'd ordinally get from eating the protein baked, steamed, or sauteed."


Certain protein powders

protein powder scoop

Protein powders for homemade meal replacements are wildly popular for controlling calories. "Unfortunately, many protein powders have added ingredients that may actually stall weight loss," says Trista Best, RD, a registered dietitian nutritionist at Balance One Supplements. She notes that milk-based (whey and casein) protein powders may not be beneficial for people with dairy allergies or intolerances. She recommends trying pea protein is better because it doesn't contain common allergens and is not inflammatory like whey protein can be. Select a vegan powder made with all 20 amino acids, she says.

Read moreWhat Happens To Your Body When You Eat Whey Protein Powder


Beef jerky

beef jerky

"Beef jerky where sugar is the second ingredient is on my list of the worst proteins," says Jay Cowin, NNCP, RNT, RNC, a registered nutritionist and director of formulations at ASYSTEM, who explains that just because it is an easy grab-and-go food doesn't mean you should rely on it as a protein source. Cowin points out that we often quickly grab packaged foods that boast "high protein" without looking at ingredients and comparing sugar and sodium levels. Some beef jerky brands can have as much sugar as dessert and more sodium than a couple bags of pretzels, so it's important to "look for grass-fed jerky that promises zero sugar, no corn syrup, and no artificial preservatives," he suggests. See: The Best and Worst Beef Jerky—Ranked!

Jeff Csatari
Jeff Csatari, a contributing writer for Eat This, Not That!, is responsible for editing Galvanized Media books and magazines and for advising journalism students through the Zinczenko New Media Center at Moravian University in Bethlehem, PA. Read more about Jeff