March 24, 2016  

Losing weight with a high-protein diet can help adults sleep better

Wayne Campbell

Wayne Campbell  
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WEST LAFAYETTE, Ind. — Overweight and obese adults who are losing weight with a high-protein diet are more likely to sleep better, according to new research from Purdue University

"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," said Wayne Campbell, a professor of nutrition science. "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."

These findings are published in the American Journal of Clinical Nutrition, which is affiliated with the American Society for Nutrition. The research was funded by Beef Checkoff, National Pork Board, National Dairy Council, Purdue Ingestive Behavior Research Center and National Institutes of Health.

A pilot study found that in 14 participants, consuming more dietary protein resulted in better sleep after four weeks of weight loss. Then, in the main study, 44 overweight or obese participants were included to consume either a normal-protein or a higher-protein weight loss diet. After three weeks of adapting to the diet, the groups consumed either 0.8 or 1.5 grams of protein for each kg of body weight daily for 16 weeks. The participants completed a survey to rate the quality of their sleep every month throughout the study. Those who consumed more protein while losing weight reported an improvement in sleep quality after three and four months of dietary intervention.

A dietitian designed a diet that met each study participant's daily energy need and 750 calories in fats and carbohydrates were trimmed per day while maintaining the protein amount based on whether they were in the higher- or normal-protein group. The sources of protein used in the two studies varied from beef, pork, soy, legumes and milk protein.

"Short sleep duration and compromised sleep quality frequently lead to metabolic and cardiovascular diseases and premature death," said Jing Zhou, a doctoral student in nutrition science and the study's first author. "Given the high prevalence of sleep problems it's important to know how changes to diet and lifestyle can help improve sleep."

Campbell's lab also has studied how dietary protein quantity, sources and patterns affect appetite, body weight and body composition.

"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 said. "Sleep is recognized as a very important modifier of a person's health, and our research is the first to address the question of how a sustained dietary pattern influences sleep. We've showed an improvement in subjective sleep quality after higher dietary protein intake during weight loss, which is intriguing and also emphasizes the need for more research with objective measurements of sleep to confirm our results."

The other co-authors are Jung Eun Kim, a postdoctoral research associate in nutrition science; Cheryl Armstrong, a research associate in nutrition science; and Ningning Chen, a graduate student in statistics.

Campbell, whose expertise and research focuses on understanding how protein nutrition and exercise influence adults' health as they age, served as a member of the 2015 Dietary Guidelines Advisory Committee, which helped provide the scientific foundation for the nation’s 2015-2020 Dietary Guidelines for Americans

Writer: Amy Patterson Neubert, 765-494-9723,

Source: Wayne Campbell,   

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Note to Journalists: Journalists interested in a copy of the American Journal of Clinical Nutrition article "Higher-Protein Diets Improve Indexes of Sleep in Energy-Restricted Overweight and Obese Adults: Results from 2 Randomized Controlled Trials" can contact Amy Patterson Neubert, Purdue News Service, at 765-494-9723,


Higher-Protein Diets Improve Indexes of Sleep in Energy-Restricted Overweight and Obese Adults: Results from 2 Randomized Controlled Trials

Jing Zhou, Jung Eun Kim, Cheryl LH Armstrong, Ningning Chen, and Wayne W. Campbell

Background: Limited and inconsistent research findings exist about the effect of dietary protein intake on indexes of sleep.

Objective: We assessed the effect of protein intake during dietary energy restriction on indexes of sleep in overweight and obese adults in 2 randomized, controlled feeding studies.

Design: For study 1, 14 participants [3 men and 11 women; mean ± SE age: 56 ± 3 y; body mass index (BMI; in kg/m2): 30.9 ± 0.6] consumed energy-restricted diets (a 750-kcal/d deficit) with either beef and pork (BP; n = 5) or soy and legume (SL; n = 9) as the main protein sources for 3 consecutive 4-wk periods with 10% (control), 20%, or 30% of total energy from protein (random order). At baseline and the end of each period, the global sleep score (GSS) was assessed with the use of the Pittsburgh Quality Index (PSQI) questionnaire. For study 2, 44 participants (12 men and 32 women; age 52 ± 1 y; BMI: 31.4 ± 0.5) consumed a 3-wk baseline energy-balance diet with 0.8 g protein/kg baseline body mass per day. Then, study 2 subjects consumed either a normal-protein [NP (control); n = 23] or a high protein (HP; n = 21) (0.8 compared with 1.5g/kg per day, respectively) energy-restricted diet (a 750-kcal/d deficit) for 16 wk. The PSQI was administered during baseline week 3 and intervention weeks 4, 8, 12, and 16. GSSs ranged from 0 to 21 arbitrary units (au), with a higher value representing a worse GSS during the preceding month.

Results: In study 1, we showed that a higher protein quantity improved GSSs independent of the protein source. The GSS was higher (P < 0.05) when 10% (6.0 ± 0.4 au) compared with 20% (5.0 ± 0.4 au) of protein was consumed with 30% protein (5.4 ± 0.6 au) intermediate. In study 2, at baseline, the GSS was not different between NP (5.2 ± 0.5 au) and HP (5.4 ± 0.5 au) groups. Over time, the GSS was unchanged for the NP group and improved for the HP group (P-group-by-time interaction < 0.05). After intervention (week 16), GSSs for NP and HP groups were 5.9 ± 0.5 and 4.0 ± 0.6 au, respectively (P < 0.01).

Conclusion: The consumption of a greater proportion of energy from protein while dieting may improve sleep in overweight and obese adults. 

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