Does Protein Really Curb Your Appetite?

It's hard not to get misled by misinformation, or hype, when you're searching for reliable information on weight management. The daily rush to publish makes even seemingly reliable sources vulnerable to "getting it wrong"—because it takes time to do enough research to make sure you've got it right.

Nutrition Action didn't 'get it right' with their recent post on protein and appetite: Does Protein Really Curb Your Appetite?

After more than two decades specializing in weight management I have 52 papers tagged under "appetite regulation" in my research database. Appetite regulation is a fascinating and important topic within weight management. I covered it in my 6-hour Advanced Training in Weight Management CE workshop back in 2003 and 2004, and since then have only seen one other seminar on macronutrients and appetite regulation cross my desk. I know the key papers off the top of my head, and I know that the fact that protein has a higher satiety value is not even a question among researchers who are experts in that area.

That said, there are several important caveats:

• Liquid proteins are NOT more satiating than other macronutrients (carbohydrates and fat). Liquid calories in general have little to no effect on satiety.
• Highly processed proteins are less satiating. (And certainly there's nothing more processed than protein powders. The fat-free cheese used in a study the Nutrition Action piece discussed is also highly processed source of protein.)

So Nutrition Action got this much right: protein shakes and Special K won’t be items that keep hunger at bay.

A third caveat:

• The leaner the protein is the more satiating it will be. The leanest protein sources are shellfish and white-fleshed fish (like cod) which are almost pure protein.

Why are the leanest proteins more satiating? It's because fat is nearly the least satiating macronutrient; therefor the more fat a protein has the less satiating it is.

A little known fact is that the satiety value of the macronutrients actually aligns with their TEF (thermic effect of food). The hierarchical order of both satiety value and thermic effect is: protein>carbohydrate>fat>alcohol. 

In fact the conclusion of several of the best long-term clinical trials (12-months) pitting high-protein diets against a balanced or low-fat diet concluded that the difference in weight loss is related to lower (free living) energy-intake which they attribute to the higher satiety to value of protein.

Barbara Rolls (who Nutrition Action interviewed for their article) has long been an advocate for the passé notion that reduced energy density (low-fat) is the key to reducing energy intake and weight loss. This despite data that shows that when you switch to a low-fat regime within a few days subjects just start eating more to compensate (for the reduced energy value). That data was clear 15 years ago, about the time the awareness of the affect of protein on satiety was just coming into the mainstream.

Nutrition Action suggests that the idea that protein staves off hunger stems from food industry research. I'd be the last person to disagree that food industry will co-opt any thread of research it can use to its advantage.

However, the early research (and by far the bulk of the research) in the area of macronutrients and appetite regulation comes from untainted basic science sources well before academia arguably became an arm of industry.

The bottom line: high-quality lean proteins will stave off hunger longer than carbohydrate or fat (unlike protein shakes, Special K, or any highly processed source of protein).

Actionable advice: Whenever you try to cut your energy intake, choosing to also actively manage hunger—by using your knowledge of appetite regulation–is just common sense and will definitely support your efforts.The latest advice (for several objectives including healthy-weight-loss and maintaining lean body mass in aging) is to shoot for 25 to 30-grams of protein at each meal.

For additional information see the links below!

All the best!
-Dorene 

References:

• Macronutrient effects on appetite. Int'l J Obesity 1995;19(Suppl 5): S11-S19.
• Energy Density of Foods: Effect on Energy Intake. Critical Reviews in Food Science and Nutrition 2000;40(6):481-515.
• Clarifying Concepts about Macronutrients' Effects on Satiation and Satiety. J Am Diet Assoc. 2004;104:1151-1153.
• A randomized trial of a low-carbohydrate diet for obesity. N Engl J Med 2003;348(21):2082-90.

You may also be interested in: 

• Protein and the Thermic Effect of Food
• Protein Mythology... get the Facts!
• Which Protein Foods are Best at Keeping Hunger Away?
• 5 Things you need to know about Protein for healthy weight loss