Is Fat Killing Your Gains? Surprising Pork Burger Study Stuns Scientists

Lean pork enhanced muscle growth after training better than high-fat pork, despite equal protein amounts.

A recent study examined how adults respond to weight training when followed by a meal containing the same amount of protein but with different fat content. Participants consumed either a high-fat or a lean ground pork burger, and researchers measured the resulting muscle-building activity.

The outcome surprised the scientists, reinforcing the idea that the process of muscle-protein synthesis after exercise depends not only on the amount of protein consumed but also on the type of food providing it.

The findings were published in the American Journal of Clinical Nutrition.

Whole foods versus processed proteins

“What we’re finding is that not all high-quality animal protein foods are created equal,” said Nicholas Burd, a professor of health and kinesiology at the University of Illinois Urbana-Champaign, who led the research with graduate student Žan Zupančič.

Earlier research from Burd’s group demonstrated that eating whole eggs after weight training stimulated muscle-protein synthesis more effectively than eating only egg whites, despite equal protein content. Another experiment from the same lab showed that salmon supported greater post-exercise muscle growth than a processed mixture engineered to contain the same nutrients in identical ratios.

Together, these findings suggest that whole foods generally provide stronger stimulation of protein synthesis than processed alternatives, and in some cases, the fat content of whole foods may even enhance muscle-building, Burd noted.

Designing the pork patties for study

For this latest trial, researchers applied advanced tracing methods to measure muscle-protein synthesis in 16 young, physically active adults. To create the test meals, they collaborated with the University of Illinois Meat Science Laboratory, which carefully prepared the pork patties for the study.

“That took us a year because it was so hard to get those fat ratios correct,” Burd said. All the meat used in the study came from a single pig, and the researchers sent the patties off to another laboratory for analysis. Once the lean-to-fat ratios and other macros were confirmed, the pork burgers were frozen until needed in the feeding part of the study.

Prior to the exercise and feeding portion of the study, each participant was given an infusion of isotope-labeled amino acids. This technique enabled the researchers to follow how rapidly these labeled amino acids were incorporated into muscle tissue. Blood samples were also collected at multiple points to monitor amino acid concentrations in circulation.

To establish a baseline for muscle-protein synthesis, the team performed muscle biopsies on participants both before the infusion began and again after the first two hours.

“And then we took them to the gym,” Burd said. “And they were wheeling that infusion pump and everything else with them.”

Testing exercise and feeding interventions

At the gym, the study subjects engaged in an acute bout of leg presses and leg extensions and then returned to the lab for a meal of either a high-fat pork burger, a lean pork burger or a carbohydrate drink. Five hours after the meal, another muscle biopsy was taken to measure protein synthesis in response to the weight-training and feeding intervention.

After a break of a few days, 14 of the 16 participants “crossed over, switching to a different feeding intervention to minimize the impact of individual differences in muscle-building responses,” Burd said.

The analysis revealed, as expected, that the amino acid content of the blood was significantly higher in those who ate pork than in those who consumed a carbohydrate drink. But the lean-pork group saw the greatest gains in amino acid levels in the blood. This was true for total and essential amino acids, the team found.

“When you see an increased concentration of amino acids in the blood after you eat, you get a pretty good idea that that is coming from the food that you just ate,” Burd said.

Lean pork supports more protein synthesis

Those who consumed the lean pork burger after a bout of weight training also had a greater rate of muscle-protein synthesis than those who ate the high-fat pork burger. This was a surprise to Burd, as “the previous studies using fattier foods, such as whole eggs or salmon, generally showed enhanced post-exercise muscle-protein synthesis compared with lower fat food such as egg whites or nutritional supplements,” he said.

Although weight training boosted muscle-protein synthesis in the groups eating pork, the protein in the high-fat burger seemed to have no added benefit in the hours after participants consumed it, while the protein in the lean pork gave muscle-protein synthesis a boost.

“For some reason, the high-fat pork truly blunted the response,” Burd said. “In fact, the people who ate the high-fat pork only had slightly better muscle-building potential than those who drank a carbohydrate sports beverage after exercise.”

Exercise remains the primary driver

Interpreting the results of this study for people who want to optimize muscle gains from weight-training is tricky, Burd said. It could be that processing the ground pork patties, which involved grinding the meat and adding the fattier meat to the lean, affected the kinetics of digestion.

“There was a little larger rise in the amino acids available from eating lean pork, so it could have been a bigger trigger for muscle-protein synthesis,” Burd said. “But that seems to be specific to the ground pork. If you’re eating other foods, like eggs or salmon, the whole foods appear to be better despite not eliciting a large rise in blood amino acids.”

Burd stresses that exercise is the strongest stimulus for muscle-protein synthesis.

“Most of the muscle response is to weight-training, and we use nutrition to try to squeeze out the remaining potential,” he said. “When it comes to eating after weight-training, what we’re finding is that some foods, particularly whole, unprocessed foods seem to be a better stimulus.”

Reference: “Ingestion of a lipid-rich meat matrix blunts the postexercise increase of myofibrillar protein synthesis rates in healthy adults: a randomized controlled trial” by Žan Zupančič, Andrew T Askow, Takeshi M Barnes, Max T Deutz, Alexander V Ulanov, Ryan N Dilger, Anna C Dilger, Jared W Willard, Richard WA Mackenzie, Jocelyn E Harseim, Diego Hernández-Saavedra and Nicholas A Burd, 7 September 2025, The American Journal of Clinical Nutrition.
DOI: 10.1016/j.ajcnut.2025.09.001

The National Pork Board’s Pork Checkoff program supported this research.

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