It’s a modern paradox. Scroll through social media and you’ll see no shortage of wellness influencers talking about the importance of protein, often holding up ultra-processed, high-protein bars, shakes and snack foods to the camera. But a few posts later, another group warns about the dangers of ultra-processed foods. So, which is it?
To complicate things further, a recent study published in the journal Radiology raised concerns. Researchers found that, compared to those who consumed more whole foods, individuals whose diets were high in ultra-processed foods had more fat infiltrating their thigh muscles. One headline summed it up starkly: ‘Your junk food is turning your thighs into well-marbled steaks.’
To work out whether high-protein ultra-processed foods deserve a place in your diet, I looked at the research and spoke to an expert.
First, About That Study…
As it turns out, the Radiology study did not distinguish between ultra-processed, high-protein foods and other types of ultra-processed food. That means participants may have been eating protein bars, but their diets could just as easily have been high in fat and refined carbohydrate-rich snacks. Plus, the average age of participants was around 60 – not exactly representative 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 protein sources with increased muscle fat.
‘The takeaway from studies like this is that poor overall diet quality is linked with poorer muscle quality, not that all ultra-processed foods harm your muscles,’ says Phillips.
Even so, the study raises a valid question: if a large portion of your daily protein intake comes from processed foods, will it affect your results?
Are You Still Making Gains if Most of Your Protein Is Ultra-Processed?
According to Phillips, muscle-building largely comes down to total protein intake and amino acid profile.
‘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 the same.’
(Phillips is referring to the NOVA classification system, which groups foods based on their level of processing. Protein powders, shakes and bars fall into the ultra-processed category.)
Essential amino acids – particularly leucine – play a key role in muscle protein synthesis, and the body doesn’t distinguish whether that leucine comes from a whey supplement or, say, a steak. If you’re choosing a protein supplement or fortified food, aim for options that contain leucine. If that information isn’t available, prioritise high-quality whole-food protein sources such as meat, dairy, soy foods, lentils and salmon.
Total daily protein intake matters, too. Despite the conflicting advice, Phillips’ research suggests there is a ceiling, beyond which additional protein offers little benefit. For most healthy individuals, that sits at around 1.6 grams of protein per kilogram of body weight per day.
There are exceptions. Younger people doing resistance training may benefit from hitting that 1.6g per kilogram target, while adults over 65 may do well with between 1.2 and 1.6g per kilogram. Individual goals, health and life stage all matter.
‘The 1.6g per kg figure isn’t a hard ceiling,’ Phillips adds. ‘It’s the point where the extra muscle return from adding more protein starts to level off. Older lifters and those training hard can reasonably push towards 2.0g per kg without harm, but the additional benefit becomes difficult to detect.’
The Bottom Line
As a dietitian, I recommend getting the majority of your protein from whole foods. That said, life isn’t always ideal. In those situations, protein supplements such as bars and powders can be a practical fallback.
There’s no need to micromanage your diet. Consistency in the quality and variety of the food you eat – including protein – is what matters most
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Abby Langer, RD is the owner of Abby Langer Nutrition, a Toronto-based nutrition consulting and communications company