Does Protein Really Curb Your Appetite?

“Satisfies hunger longer,” promise Special K Protein Shakes, which are mostly blends of water, nonfat milk, whey protein concentrate, soy protein isolate, and sugar. “With every tasty shake, you’ll get the nutritional benefits of 10g protein and 5g fiber that can help satisfy your hunger so you can lose weight.”


What the research shows 

Some studies—many of them funded by the food industry—report that higher-protein foods make people feel more full than lower-protein foods.1 But the best studies find no difference.2

Barbara Rolls is director of the Laboratory for the Study of Human Ingestive Behavior at Penn State University, where she studies what affects appetite and how much people eat.

“Our study gave people real foods, like chicken casserole or shrimp stir-fry, but with 10, 15, 20, 25, or 30 percent of their calories from protein,” she says. “The entrées looked and tasted the same and had the same fat and calories.”

The protein level in the food didn’t matter. “Protein had no impact on hunger or how many calories people ate at other meals.”

Liquid vs solid food

What’s more, a drink—with or without protein—may be less satiating than a solid food.

For example, researchers fed 120 lean and 60 obese adults a solid or liquid version of a high-carb food, a high-fat food, or a high-protein food. All the foods had the same number of calories. In each case, the participants ate more calories on the days they got the liquids.3 Other studies find the same.4

Effect on weight

And longer-term studies find little difference—a pound or two—or no difference in weight loss when dieters eat higher-protein versus normal-protein diets.5,6

“To count on a little more protein to satisfy hunger and then translate that to weight loss, that’s really a leap,” notes Rolls. “Even if people say they’re less hungry, that doesn’t mean they’re going to eat less.”

Still, if you’re cutting calories, it makes sense to cut carbs or fat rather than protein because protein will help prevent muscle loss when dieting.

But why bother with a Special K Protein Shake that costs about $1.50? A 10 oz. bottle has 10 grams of protein and 180 calories (thanks, in part, to its added sugar). You can get that much protein in 10 oz. of fat-free milk for only 110 calories and less money.

And the fiber in Special K’s shake comes largely from maltodextrin and polydextrose, processed fibers that may have little or no effect on appetite or regularity.

Want a better meal of protein and fiber? Try a bowl of fat-free greek yogurt, fruit, and nuts.


1 Am. J. Clin. Nutr. 87(suppl):1558S, 2008.
2 J. Am. Diet. Assoc. 111: 290, 2011.
3 Int. J. Obesity 31: 1688, 2007.
4 Brit. J. Nutr. 106: 37, 2011.
5 J. Nutr. 143: 591, 2013.
6 Nutr. Metab. Cardiovasc. Dis. 24: 224, 2014.

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One Reply to “Does Protein Really Curb Your Appetite?”

  1. From my own experience (vis-a-vis any scientifically obtained research data) … eating a high protein diet DOES produce and maintain a greater sensation of satiety than does a more “typical” or average diet. I must stress, though, that my high protein diet probably has a much higher protein content than what is described in the article as “real” foods …, ie., certainly no chicken (or any other type of) casserole.
    For almost 2 years, I have focused my nutritional intake on high quality, high protein foods (chicken, fish, eggs – not fried – some beef, minimal pork) that is typically broiled/baked/stir-fried … but certainly not prepared in the form of a casserole, nor breaded, or smothered with cheese (as is too often the case in some parts of the country). I also consume 30 – 60 grams of a powered protein drink daily. I would add, here, that I also eat probably more than the FDA recommended amounts of fruits and vegetables on a daily basis, as well as minimal amounts of “white” carbs (anything made from wheat flour – bread, etc., + white potatoes, white rice, pasta … though that is not pertinent to the point I am trying to make.) My total caloric intact is probably no more than what it was prior to the time I started following this diet … maybe even less. Nevertheless, I find that consuming this kind of diet produces -especially in the middle of the day, after I have had a high protein content breakfast and fruit – a sensation of satiety that I almost never experienced prior to the time that I started following this way of eating. Prior to 2 years ago, I was eating what may be considered a more typical or average American diet, which included a “typical” amount of white carbs that produced the typical sensation of fullness followed by hunger again within approximately 2 hours, which would then stimulate me to eat more of the same, followed by short-term satiety, then hunger, eating, satiety, hunger, eating, satiety, etc., etc. That cycle has been broken, and I have to attribute it to the high protein content content of my meals … particularly my morning meal. Perhaps the researchers in the article did not find any appreciable impact on hunger in the subjects tested, but I would venture to guess that they simply did not sufficiently increase the the protein level of the food consumed by the test subjects for it to make a significant impact.

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