Today, high-protein diets and protein supplements for weight loss are all over social media, and protein-enriched cereals, chips, waters and coffee drinks line grocery store shelves.
There is something to the idea that prioritizing protein can help you control your appetite and lose some weight, said Stuart Phillips, a professor of kinesiology at McMaster University in Canada. But, he added, the extent of those benefits has been "oversold" by influencers. Here's what the research shows.
How Protein Affects Appetite
Most of the studies looking into how protein affects appetite are limited by their size and scope, meaning they have measured how small groups of participants responded to single, high-protein meals or snacks, said Tanya Halliday, an associate professor of health and kinesiology at the University of Utah.
But when you look at the studies' results together, they suggest a consistent pattern. In a 2020 review of 49 such studies, for instance, researchers found that participants tended to feel more satisfied and less hungry after eating protein-rich meals and snacks than they did after eating lower-protein versions.
Many of the same studies have also looked at what hormones are released from the gut after eating. High-protein meals typically prompted lower blood levels of ghrelin (a hormone that makes you feel hungry) and higher blood levels of hormones like GLP-1 (which help you feel full).
High-protein meals can also cause food to move slowly through your stomach and intestines, keeping you feeling fuller for longer, said Heather Leidy, an associate professor of nutritional sciences at the University of Texas at Austin.
But research suggests that these feelings last for only about three to four hours after eating, Dr. Leidy said. And they don't consistently translate to eating less at the next meal, or over weeks or months of following a high-protein diet, said Richard Mattes, a professor of nutrition science at Purdue University in Indiana.
Protein is just one of many factors that may affect how much you eat, Dr. Mattes said. Your mood, genetics, relationship with food and food environment (the food at grocery stores, in restaurants and at work, for example) play roles, too.
That said, if prioritizing protein makes you feel more satisfied, with fewer food cravings and steadier energy levels throughout the day, that's a real benefit, said Julia Lloyd, a dietitian who specializes in weight management at Massachusetts General Hospital.
How Protein Affects Weight
As to whether a high-protein diet can help you lose weight or keep it off, the evidence is mixed but suggests that there is a small benefit.
In a 2021 review of 37 clinical trials, researchers found that when people who were overweight or obese followed higher-protein diets for an average of eight months, they lost about 3.5 more pounds than when they followed lower-protein diets. And in a 2019 review of studies on overweight or obese adults who had recently lost weight, researchers found that following higher-protein diets for between three and 12 months resulted in slightly less weight regain compared with lower-protein diets.
That may be, at least in part, because digesting protein burns slightly more calories than digesting carbohydrates or fats, Dr. Halliday said.
Following a higher protein diet during weight loss may also help you lose weight in a healthier way — shedding a little more fat and less lean mass, which includes muscle, Dr. Phillips said.
Prioritizing protein may nudge you toward a healthier weight, but you still need to pay attention to calories, Dr. Phillips said, adding that the best way to conserve your muscle during weight loss is to do resistance training, like lifting weights.
He recommended consuming 1.2 to 1.6 grams of protein per kilogram of body weight — the target in the new dietary guidelines — to feel sated, support weight loss and help build muscle. Most Americans, he added, are already eating close to this amount.
It's best to get your protein from whole foods, Dr. Leidy said. Protein shakes, bars and other foods infused with the nutrient are less likely to be as satiating because they tend to be digested more quickly; and they generally offer a less healthful balance of nutrients like fiber, vitamins and minerals, she said.
To feel full throughout the day (and be healthy in general), it's important to focus on fiber in addition to protein, Ms. Lloyd said.
Most people in the United States eat enough protein, Ms. Lloyd said, but just 6 percent get enough fiber. Consuming adequate fiber will not only help you feel fuller for longer, it can also reduce your risk of developing various health issues like cardiovascular disease, colorectal cancer and Type 2 diabetes.