Since eating more fat and protein (while cutting down on the carbs), I seem to get fuller faster. Sometimes I won’t even finish my plate, which basically never happened before! I’m guessing it has something to do with eating more primal foods, and it makes sense from an anthropological standpoint (getting full on less food is advantageous in a survival sense)… but are there any science or lab studies that have actually examined this phenomenon?
Does a diet rich in fat and protein actually sate hunger more effectively? Funny you should ask, Paul. Your experience is more common than you might think.
In addition to receiving numerous reader comments just like yours that corroborate the fat-protein-satiety idea, I also have my own personal experience. As some of you may know, I used to be a professional long-distance (marathon-long) runner . I was “fit,” but I was fueling my activities with massive amounts of carbohydrates. To put it into perspective, a typical evening snack was a half gallon of ice cream. How typical? Every night. Despite the amount of food I was taking in, I was always hungry… even when I wasn’t training. Eventually, the joint pain, respiratory infections, and general unhappiness with the toll my lifestyle was taking on my body prompted me to shed the carbs and rethink my entire food/fitness/life philosophy. The path was long and winding, but I eventually began upping my fat and protein until I arrived at the Primal Blueprint . The first thing I noticed upon dropping carbs and upping fats/protein was the immediate change in appetite. Simply put, I didn’t have much of one anymore.
Now, I look around at what other people my age and size are eating, and I feel like I eat like a bird. Sure, there are times where I eat a massive meal, like after a workout-fast session  or a grueling day, but most of the time I’m just not that hungry. Comments like yours, my own experiences, and a recent study all support the notion that the fat and protein content of the Primal Blueprint diet is the driving satiating force.
We already knew how protein worked to satisfy the appetite . Proteins are digested much more slowly than carbohydrates; theirs is a steady breakdown into absorbable nutrients, whereas the ingested carbohydrate causes an immediate and potent spike in blood sugar that leaves you wanting more. You’re not going to binge on steaks and lamb chops like you would with potato chips.
As for fat, Dr. Reza Norouzy, from King’s College of London, provides an explanation . He knew that low GI diets are “known to cause reduced appetite,” but the mechanisms as to how had (heretofore) never been established. His team gave either a high GI diet or a low GI diet to twelve healthy volunteers and examined two markers in each participant: insulin and GLP-1, a gut hormone known to increase “fullness and suppression of appetite.”
Those who ate a lower GI meal had 20% higher levels of GLP-1 and 38% lower levels of insulin, suggesting an actual physiological mechanism behind the idea that fat and protein increase satiety. Though the specifics of the diet weren’t available, we can surmise that a lower GI means relatively fewer carbohydrates and more fat and protein.
You’ve probably gathered that calories are definitely not king around here ; that we tend to focus more on the source of calories, rather than the quantity. Still, some people do worry about calorie counts. For that crowd, take heart: eating more fat and protein while avoiding carbs with a high GI increases appetite-curbing GLP-1. The more GLP-1 you have coursing through your veins, the less you are likely to eat.
Sounds easy enough to me.