A recent study tested whether high-protein diets improve appetite control, satiety, and food cravings as well as reduce carbohydrate and fat intake.
The popularity of high-protein diets as a tool for weight loss is on the rise. Consumption of high-protein diets has been associated with improving satiety and decreasing fat mass. Satiety, defined as the state of feeling completely full, is influenced by various factors such as the endocrine system, the gastrointestinal system, and the cognitive system. Interestingly, a diet rich in proteins seems to influence some of these systems. Protein is, therefore, the most satiating macronutrient, followed by carbohydrates and fats.
Researchers have shown a strong association between satiety and high-protein diets, but there are not many studies that compared high-protein diets with normal-protein diets. This comparison could be of significance since different types of proteins induce distinct effects on satiety. Furthermore, there are only a few studies that have determined whether increased protein consumption counteracts elevated hunger and improves satiety during the period of energy restriction.
A new study recently published in the Journal of Nutrition examined whether the consumption of high-protein diets reduces carbohydrate and fat intake by improving satiety, appetite control, and food cravings. The researchers further compared the effects of high-protein diets and normal-protein diets on daily satiety in overweight women.
The study, conducted from January 2014 to May 2015, recruited 17 overweight and sedentary but healthy women from Columbia, Missouri. The women aged 18-52 years consumed three isocaloric energy-restriction diets each for six days. The three diets included a high-protein diet (124 gm protein/day), or normal-protein diet (48 gm protein/day) both with 60% of protein from beef and 40% from plant sources (HP-BEEF and NP-BEEF respectively), or an unmatched protein diet with 100% of protein from plant sources (NP-PLANT). The participants were assessed on day six for appetite, satiety, and food cravings. On day seven participants were provided with carbohydrate and fat-rich foods as they desired in a free-living environment.
Effects of a High-Protein Diet
The researchers observed a reduction of 16% in hunger, 15% in the desire to eat, and 15% in food cravings caused by HP-BEEF. Daily fullness increased by 25% in HP-BEEF compared with NP-BEEF and NP-PLANT. However, researchers did not observe any voluntary reduction in the consumption of carbohydrate or fat-rich foods due to high-protein diet consumption.
Comparison Between Protein Types
Different protein types affect satiety and food intake in different ways. When plant and beef proteins were compared within the NP diets in this study, there was no significant difference observed for appetite, satiety, and subsequent food intake between protein types. Regarding energy intake, NP-BEEF diet had a lower percentage of energy from carbohydrates but a greater percentage of energy from fat compared with the NP-PLANT diet.
Strengths and Limitations
The main strength of this study is a comparison of plant and beef protein types as controls. The study duration of six days is a major limitation of the study. In addition, the study did not include comparisons of plant-based high-protein diet and effects of ad libitum snacking. The researchers also did not include the physiologic biomarkers of ingestive behavior and behavioral modifications in this study.
This study showed that consumption of high-protein diets containing approximately 30 g of protein at each meal reduces food cravings and prospective food consumption while it increases satiety throughout the day compared with normal-protein diets having the same or different protein types. The high-protein diet, however, did not reduce ad libitum energy, carbohydrate or fat intake in overweight, healthy women. While these findings highlight the positive effects of high-protein diets on satiety, they also put forward a need for adherence to dietary strategies for weight loss and weight maintenance. Further research is needed to understand whether behavioral modifications will influence ad libitum food intake in people consuming high-protein diets.
Written by Preeti Paul, MS Biochemistry
Reference: Jess A Gwin et al., Increased Protein Consumption during the Day from an Energy-Restricted Diet Augments Satiety but Does Not Reduce Daily Fat or Carbohydrate Intake on a free-living Test Day in Overweight Women. Journal of Nutrition, October 2017