IT’S A MODERN paradox. Jump on social media and you’ll hear any number of wellness influencers talking about the importance of protein, often waving ultra-processed, high-protein bars, shakes, and snack foods before the camera. But then a few scrolls down and a different subset warns about the dangers of ultra-processed foods. So, which is it?
To make all this even more complicated, there’s a horrifying study that was recently published in the journal Radiology. The researchers found that, compared to individuals who consumed more whole foods, those whose diets were high in ultra-processed foods had more fat infiltrating their thigh muscles. “Your Junk Food Is Turning Your Thighs Into Well-Marbled Steaks,” read one headline.
To determine whether or not you should incorporate or avoid high-protein ultra-processed foods in your diet, I dug into the research and asked an actual expert.
First, About That Study…
AS IT TURNS out, the Radiology study did not distinguish between ultra-processed, high-protein foods versus other types of food. Which means the study participants may have been eating protein bars, but they may have also had diets that were high in fat and carb-rich snack foods. Plus, the average age of the study’s participants was around 60, which is not exactly a good cross-section of the general population.
Stuart Phillips, PhD, a protein researcher and professor of kinesiology at McMaster University, doesn’t see a reason to link all ultra-processed proteins with muscle fat.
“The takeaway from studies like this is that poor overall diet quality tracks with poorer muscle quality, not that all UPFs harm your muscles,” Phillips says.
Still, even though this study had some pretty major flaws, it raises the question: If a good portion of your daily protein intake comes from processed foods, will it hurt your overall goals? Let’s take a look.
Are You Still Making Gains if Most of Your Protein is Ultra-Processed?
ACCORDING TO PHILLIPS, the physiology of muscle building comes down to adequate protein dose and which amino acids a person consumes.
"If the protein dose, amino acid profile, and daily total are adequate, processing level is largely irrelevant to muscle protein synthesis and muscle-building outcomes,” he says. “A whey isolate is not a Twinkie, even if NOVA treats them as the same."
(Phillips is referencing the NOVA classification system, which sorts foods into categories based on their level of processing. Protein powders, shakes, and bars fall into NOVA’s ultra-processed food category.)
Essential amino acids, especially leucine, are a key factor in muscle protein synthesis, and our bodies don’t care if that leucine comes from a whey supplement or from, say, a steak. If you’re choosing a protein supplement or packaged fortified food, try to ensure that it contains leucine. If that information is not available, prioritize high-quality, whole proteins that are good sources of leucine—meat, soy foods, dairy, lentils, and salmon are a few.
Total daily protein intake matters, too. There’s so much conflicting advice around how much protein we need each day, but Phillips’ researchhas found that there’s actually a ceiling to protein intake beyond which there are no further gains. That ceiling, for most healthy individuals, is 1.6 grams of protein per kilogram of actual body weight daily.
While Phillips does recommend aiming for the 1.6 number, there are exceptions to the rule. Younger people who are doing resistance training may find a benefit at 1.6g per kilogram per day, but people who are over 65 years of age may be fine with anything between 1.2 and 1.6g per kilogram per day. It’s important to be flexible, while considering your personal goals, health history, and life stage.
"The 1.6 g/kg figure isn't a hard ceiling,” says Phillips. “It's the point where the extra muscle return from adding more protein really flattens out. Older lifters and hard-training individuals can reasonably push toward 2.0 g/kg without harm, but the benefit of doing so becomes hard to find."
As a dietitian, I recommend getting the majority of your protein from whole foods. I also understand that life can make this difficult sometimes. In those cases, I absolutely tell my clients to fall back on protein supplements like bars and powders.
There’s no need to micromanage your protein, or your diet. Just ensuring that you’re consistent with the variety and quality of the food you eat—including protein—is good enough.
Abby Langer, RD is the owner of Abby Langer Nutrition, a Toronto-based nutrition consulting and communications company
