Researchers May Have Found the Best Type of Protein for Weight Loss, New Study Shows

Their study compared four types of diets.

Whether you're just beginning your fitness journey or have years under your belt, you've probably heard the back and forth on the positives and negatives of high-protein diets. While some claim it's the key to weight loss, others say diets with too much protein can negatively affect your overall health, especially your kidneys. 

According to a new study from the American Society for Microbiology, not only can a diet rich in protein alter your gut microbiome for the better like gut health supplements can, but one type of protein, in particular, may be particularly effective for promoting weight loss. 

Over a month-long period, a research team at the University of Illinois Chicago conducted a series of experiments on 16 mice to determine the effects of amino acids in protein-rich diets on gut bacteria, weight loss, and body fat percentage. 

For the first two weeks, the mice were fed a diet of standard chow made up mostly of carbohydrates. At the third-week mark, the mice were broken up into four different groups where the diets were enriched with varying levels of either branched-chain or aromatic amino acids. The first group kept a standard protein diet, while the second had a diet with a 10 percent increase in aromatic amino acids, the third had a 10 percent bump in branched-chain amino acids, and the fourth had a 5 percent increase in aromatic amino acids and a 5 percent jump in branched-chain amino acids.

At the end of the four weeks, they found that the mice consuming aromatic amino-acid-rich proteins (phenylalanine, tyrosine, tryptophan, and histidine) experienced the greatest weight and fat mass loss compared to those on standard protein and branched-chain-amino-acid-rich protein diets. They also found that higher protein diets, regardless of the kind, significantly improved the overall gut health as compared to the diet higher in carbohydrates. 

Related: How Much Protein You Need to Eat Every Day

While the fact that protein was a key factor in the mice's weight and fat loss is no surprise, the question still remains: What is the correlation between a healthier gut and positive changes in one's body composition? 

"We know that diets high in aromatic amino acids may affect the host's immune response. This could potentially alter gut permeability and trigger inflammatory responses, which in turn could influence the composition of the gut microbiome and favor certain microbes over others," says graduate student Samson Adejumo, the study's lead researcher.

“These results imply that beyond the type of diet, the type of gut microbiome that metabolizes the diet is much more important," Adejumo told Medical News Today. "The gut microbiome metabolism of the diet has the biggest impact on the host body composition.”

While more research is needed to conclusively state that high-protein diets are the sole cause of positive changes in the gut microbiome, the findings in this study are in line with past research that outlines the beneficial impacts of protein-rich diets on body recomposition. A study published in 2020, for example, found that a high-protein diet not only appears to increase muscle growth and fat loss but may also have beneficial effects on bone when combined with exercise.

"These findings provide a crucial foundation for understanding how protein diets influence the gut microbiome and open doors for further investigations into the role of diet in promoting a healthy gut and overall health," Adejumo said. 

If you want to add more aromatic amino acids to your diet, fish, nuts, eggs, and meat are excellent sources.