As a weight management specialist, I often discuss the impacts of dietary choices on metabolic health with my patients. I get patients who Google everything or believe myths over facts. I have had people who often question whether consuming high protein has any effect on insulin function and fat storage.
We know that insulin is secreted when we consume food, and its production is increased when we have high carbohydrate intake. In the same way, when we consume protein, our pancreas releases insulin to help amino acids enter our cells. Insulin is a hormone that helps regulate blood sugar levels by facilitating the uptake of glucose into cells. However, insulin also plays a role in fat storage, and the insulin response to protein differs significantly from that of carbohydrates in several key ways.
First, protein stimulates both insulin and glucagon release simultaneously. This hormonal balance is critical because glucagon opposes many of insulin’s effects, particularly its fat-storage promotion. The amino acids’ composition matters because Branched-chain amino acids like leucine are insulin secretagogues, that is, they promote the secretion of insulin.
Consuming protein beyond the body’s needs can have some metabolic consequences. Research shows that overfeeding with diets containing varying protein levels like 5%, 15% and as high as 25% of energy from protein over 8 weeks led to increased total body fat mass, visceral adipose tissue and deep subcutaneous fat across all groups.
So, what happens during protein overfeeding?
When we consume protein in excess, our body’s immediate needs for tissue synthesis and other metabolic pathways get activated.
The thermic effect of protein is roughly 20-30% during digestion and processing, while carbohydrates are 5-10%. While protein can undergo gluconeogenesis, that is, protein getting converted to glucose, the body doesn’t convert excess dietary protein to glucose unless physiologically necessary.
The protein oversupply stimulates muscle protein synthesis when combined with resistance exercise. This anabolic pathway changes amino acids from potential fat storage pathways and increases overall energy expenditure through expanded lean mass.
When protein is consumed in mixed meals, it reduces the glycaemic and insulin response to co-ingested carbohydrates through delayed gastric emptying and enhanced incretin hormone release. This improves post-meal metabolic parameters.
To summarise, while adequate protein intake is essential for health, overconsumption can lead to increased fat storage and potential alterations in insulin function. Balancing protein intake within recommended guidelines, alongside a well-rounded diet, is key to maintaining optimal metabolic health.
