How Protein Aids in Satiety and Weight Loss

Protein has long been considered the go-to supplement by weightlifters and bodybuilders to increase muscle mass. But the more we learn about this macronutrient, the clearer it becomes that protein’s benefits extend far beyond sports nutrition. In fact, a growing body of research indicates that it can promote satiety (helping you feel full for longer periods of time) and, as a result, aid in weight loss.

Here is one of the major ways it is thought to work. A major blood vessel, called the portal vein, is responsible for draining blood from your gastrointestinal tract. Your portal vein is lined with mu-opioid receptors (MORs). These MORs are a main communication channel between your gut and your brain. When MORs are stimulated, they send the message to your brain that you’re still hungry and that you should eat more. When MORs are inhibited, the brain receives the opposite signal to limit food consumption. Researchers have found that certain byproducts of protein digestion called peptides send signals to the brain and gut that lead to the suppression of MORs, resulting in the curbing of appetite.

Additionally, protein stimulates the production of cholecystokinin (CCK), a hormone that signals satiety, and inhibits the release of a hormone called ghrelin, which sends out the “I’m hungry” message.

Animal and human studies that have tested the effectiveness of protein in this regard have revealed that, compared to fats and carbohydrates, protein produces stronger and longer feelings of fullness.

One study examined blood levels of ghrelin in 10 volunteers who received, on separate occasions, a high-carbohydrate, high-fat, and high-protein meal. While ghrelin levels fell after all three meals, after 180 minutes, only the high-protein meal maintained those low levels. This means the “I’m full” message lasted the longest following the protein-rich meals. Given these results, the researchers suggested that, “partial substitution of dietary protein for carbohydrate or fat may promote longer-term postprandial ghrelin suppression and satiety.”

In another study, scientists compared high-protein vs. normal-protein breakfasts on appetite, satiety, and snacking in overweight or obese girls.

For six days, 20 participants ate either cereal (13 g protein) or an egg/beef-rich breakfast (35 g protein), or skipped breakfast altogether. While eating any kind of meal was better than going hungry when it came to long-term daily fullness, the high-protein breakfasts produced greater satiety than the normal-protein meals. The high-protein meals (but not the normal-protein meals) also lowered ghrelin and elevated peptide concentrations—both of which, as mentioned earlier, keep appetite suppressed for longer periods of time.

Another study in obese men demonstrated that increasing protein to 25 percent of calories reduced the desire for late-night snacking by 50 percent and reduced obsessive thoughts about food by 60 percent.

A Weight Loss Boon

Not surprisingly, boosting your protein intake can also help with weight loss.

A study of 65 overweight or obese participants assigned either high-carbohydrate, high-protein, or control diets resulted in weight loss after six months of 5.1 kg (11 lbs) in the high-carb group and 8.9 kg (20 lbs) in the high-protein group. The high-protein group also lost more fat and decreased their triglycerides and free fatty acids compared to the other groups.

In another trial, 46 overweight or obese women who followed similar-calorie high-protein or normal-protein diets for 12 weeks all lost body fat and weight, but the high-protein dieters lost less lean body mass, and they had higher perception of satiety and pleasure, despite being on reduced-calorie diets.

Picking a Protein

Proteins are made up of 20 amino acids—nine of which are essential (they come from food alone), the remainder of which are nonessential (the body can produce them on its own).

Proteins from animal sources often offer all, or most, of the essential amino acids in highly absorbable forms.

Eggs are, by far, one of the best food sources of complete protein. They contain all 20 amino acids, and one medium egg has about 6 grams of protein.

Of course, chicken, pork, and red meat are also significant protein sources, as are certain nuts (such as pistachios) and milk and other dairy products. In fact, milk-based proteins, namely whey and casein, contain glycomacropeptide, a peptide that fuels CCK production.⁷

And let’s not forget about fish such as salmon, trout, and shrimp, which are great sources of both proteins and omega-3 fats…an optimal nutrient combination!

If you’re not a meat or dairy connoisseur, grains such as quinoa, buckwheat, and amaranth are top vegetarian protein choices. (In fact, quinoa and amaranth are complete proteins, containing all nine of the essential amino acids.)

Strive to include protein with every meal you eat. And to ensure you’re getting sufficient amounts, also consider supplementing with whey protein powder. It’s not just for bodybuilders! Anyone can (and should) use it. Whether you mix it with water, add it to a smoothie or shake, or sprinkle it on top of yogurt, chicken, a salad or some other food, adding whey is an effortless way to make sure you’re consuming plenty of protein intake and enhancing satiety. You can find many quality whey products at health food stores and vitamin/supplement retailers.