All calories are not the same when you consider their effect on appetite and satiety. As a number of studies show, diets higher in protein are more satiating, and it’s the most filling of the three macronutrients. In addition, research shows diets higher in protein are more effective for weight loss, partially due to the greater satiety they offer. Eating protein also slightly increases energy expenditure since it takes more energy to digest, break down and absorb protein. That means more calories burned.
Why is protein so satiating? Some experts believe protein is filling and satisfying because it reduces the glycemic response to a meal. If you eat a sugary snack, your blood sugar rapidly rises and drops, giving you those old, familiar cravings an hour or two after you’ve eaten. When you eat a protein snack, you don’t get those feelings of extreme hunger and fatigue soon after a meal. According to a study published in the Journal of Clinical Endocrinology and Metabolism, it isn’t necessarily the lower glycemic response that suppresses appetite, but the fact the protein heightens the release of a hormone called CCK that puts the brake on appetite.
No doubt protein is your ally if you’re trying to reduce your calorie consumption or lose weight, but recently the focus has shifted to plant-based sources of protein due to concerns about health and the environment. Does plant protein offer the same satiety benefits as protein that comes from animals?
Which Types of Protein Are Most Satiating?
A study published in the Nutrition Journal compared 20 grams of different types of proteins, including whey, egg albumin, maltodextrin, and pea protein, in terms of their effects on satiety. The winners in the group were casein and pea protein. Although casein is an animal-derived protein and the main protein found in milk, pea protein is plant-based in origin. This study suggests that at least one form of plant protein, pea protein, is as effective at suppressing appetite as whey protein – but what about whole foods?
It would be interesting to see a study that compares whole food sources of plant-based and animal-based protein to each other to see whether one is more satiating than the other. Unfortunately, head-to-head comparisons of plant and animal proteins in whole food form haven’t been forthcoming. On the other hand, plant-based proteins have another filling dietary component that animal protein doesn’t – fiber. Take legumes, for example. Beans and lentils, a good source of plant-based protein, contain fiber and resistant starch. These days you hear more and more about resistant starch, a form of carbohydrates that you can’t break down or absorb, but still, contribute to satiety. Your digestive tract can’t break down resistant starch, but bacteria in your small intestinal tract can, and when they do they produce short-chain fatty acids that help keep the lining of your colon healthy. You won’t get that from eating a piece of meat. Resistant starch causes little or no effect on blood sugar and because they aren’t absorbed, they aren’t a source of calories. In fact, resistant starch may improve insulin sensitivity, thereby enhancing metabolic health.
Plant sources of protein, such as soy, beans, lentils, whole grains, and nuts also contain a variety of phytochemicals, not found in meat, which offer a variety of other health benefits. A number of studies link diets rich in plant-based foods with a lower risk of heart disease and stroke.
Seventh-day Adventists who eat a plant-based diet exclusively live, on average, 4 to 7 years longer than other Californians, although they also lead an otherwise healthy lifestyle as well, so it may not all be attributable to diet.
Are There Downsides to Consuming Plant Protein over Animal Protein?
If you’re trying to build lean body mass, you may have to consume a greater amount and diversity of plant proteins to maximize muscle protein synthesis. For one, plant-based proteins are an incomplete protein source, meaning they lack one or more of the essential amino acids your body needs for protein synthesis but can’t make on its own. You can get the essential amino acids your body needs by eating legumes and whole grains since each provides essential amino acids the other lacks. Plus, soy is a complete source of essential amino acids.
Leucine is an important amino acid that “turns on” muscle protein synthesis. It along with other branched-chain amino acids, like valine and isoleucine, activate the mTOR pathway, a pathway that ramps up new muscle protein synthesis. Protein from plant sources contains about 7% leucine while animal proteins average around 9%, slightly more. So, if you consume equal quantities of animal protein and plant protein, the animal protein may be better at switching on muscle protein synthesis. Of course, you can make up for this by eating more plant protein to supply your body with more leucine.
The Bottom Line
A diet higher in protein is more satiating and may give you an edge when you’re trying to lose weight or control hunger. Because of the fiber in plant protein, it, too, is satiating. When you consider that protein and fiber are two dietary components strongly linked with satiety, eating foods with both, like beans and lentils, should curb your desire to eat. One meta-analysis showed people who ate a little more than half a cup of beans or peas daily felt 30% fuller.
If you’re currently getting most of your protein from meat and dairy, branch out a little and try some plant-based protein foods like unprocessed soy, nuts, lentils, beans and higher protein whole grains such as quinoa. If you use protein powder after a workout, give pea protein, hemp, or rice protein a try. Plant sources of protein have beneficial dietary components, including phytochemicals, you won’t get from eating animal foods. You don’t have to go vegetarian or vegan to enjoy protein from plants. Branch out a little and try something different. There’s more than one way to get your protein.
References:
Nutrition Journal 2011, 10:139 doi:10.1186/1475-2891-10-139.
Nutr Metab Cardiovasc Dis. 2011 Sep;21 Suppl 2:B16-31. doi: 10.1016/j.numecd.2010.12.008. Epub 2011 May 11.
J Clin Endocrinol Metab. 2006 Apr; 91(4):1477-83.
Adv Nutr November 2010 Adv Nutr vol. 1: 17-30, 2010.
Today’s Dietitian. Vol. 15 No. 9 P. 70. September 2013.
Live Science. “Want to Live Longer? Eat a Plant-Based Diet” June 3, 2013.
Science Daily. “Eating more dietary pulses can increase fullness, may help manage weight” August, 2014.
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I went on a vegan diet for 6 months and gained 20 pounds. I had never experienced such hunger in my life and was ravenous. Brown rice, pasta, beans. All the healthy stuff, but calorie dense. It didn’t help. I’m convinced animal protein is much more filling than vegetable protein. I’m off the diet and now I have to lose this weight. A big fail for me.