"Most research looks at the effects of sleep on diet and weight control, and our research flipped that question to ask what are the effects of weight loss and diet—specifically the amount of protein—on sleep," study author Wayne Campbell said in a press release. "We found that while consuming a lower calorie diet with a higher amount of protein, sleep quality improves for middle-age adults. This sleep quality is better compared to those who lost the same amount of weight while consuming a normal amount of protein."
The study—published in the American Journal of Clinical Nutrition—was broken into two parts, a pilot and a larger trial. It was also funded by Beef Checkoff, National Pork Board, National Dairy Council, Purdue Ingestive Behavior Research Center, and National Institutes of Health.
In the pilot study, researchers found all 14 of their participants consuming a protein-heavy diet experienced better sleep after four weeks of weight loss. In the main study, 44 overweight or obese participants ate either a normal-protein or a high-protein (amount of protein in grams not indicated) weight-loss diet. A dietitian designed a personalized diet for every study participant's daily energy need; plus, 750 calories in fats and carbohydrates were trimmed each day (protein amount stayed the same). The protein sources varied, including beef, pork, soy, legumes, and milk protein in both studies. After three weeks, the groups consumed either 0.8 (normal-protein group) or 1.5 (high-protein group) kilograms of protein for each kg of their body weight every day for 16 weeks. The participants completed a survey to rate the quality of their sleep every month throughout the study.
Ultimately, those who consumed more protein while losing weight reported an improvement in sleep quality after three and four months.
This knowledge—how lifestyle and diet impacts sleep—could be huge for preventing metabolic irregularities, cardiovascular disease, and premature death, the researchers say, given how many people suffer from compromised sleep quality and duration.
"This research adds sleep quality to the growing list of positive outcomes of higher-protein intake while losing weight, and those other outcomes include promoting body fat loss, retention of lean body mass and improvements in blood pressure," Campbell says.
Luckily, MensFitness.com has tons of great recipes and tips for helping you get more protein in your diet—whether you're trying to lose weight or just maintain it. After all, protein is key to building muscle, too.