Protein is well-known for its satiating properties, but studies thathave tried to determine the difference in satiating properties between animal- and plant-based proteins have so far proved inconclusive, according to researchers from the University of Minnesota, led by Angela Bonnema.
The scientists therefore decided to determine whether a meal containing beef, a high source of protein, had more satiety-inducing potential that a bean-based meal with a moderate protein content and high fibre content.
Subjects were given beef meatloaf, which provided 26 g protein and 3 g fibre and on a separate occasion, a bean meatloaf which provided 17 g protein and 12 g fibre. The researchers found that there was no significant difference in the amount of food or snacks eaten later in the day.
“The findings of this study suggest that a high protein beef meal compared to a lower protein bean meal with high fibre content are similar in terms of appetite effects.”
Great expectations
But Bonnema et al. found that the order in which they gave the subjects the meatloaf had an impact on expected satiety. Those who knew they would receive the bean meal on the second visit anticipated feeling less full. "That is, subjects who anticipated the bean meal were less satiated than those who did not know whether they would receive the beef or bean meal."
Before beginning the experiment, subjects were told that they would be eating beef and bean-based meatloaves over the course of the two-week experiment. “In disclosing this information [the order of the meals], it is possible that some individuals who had received the beef meat loaf meal for the first visit then anticipated the consumption of a less familiar, bean-based meat loaf meal and therefore rated their hunger as less or unsure of how to rate. This phenomenon could be explained by the term food neophobia.”
The authors suggested this may be due to the relative unfamiliarity of a bean-based meatloaf, which meant they were unsure of how to rate their hunger or expected satiety. They called for further research to determine the impact of this neophobia.
Could it also be that plant-based sources of protein suffer from a satiety image problem in consumers' eyes?
A 2014 report by marketing company Acosta highlighted consumer uncertainty about "whether you can achieve sufficient protein levels from a meat-free diet and what kinds of meat alternative offerings are available.”
The report added: “Many consumers indicate interest in meat alternatives, but need guidance in making smart choices.”
The study
A total of 28 male and female subjects aged 16 to 65 years took part in the study and were given a test meal four hours after eating breakfast on two different occasions. The two meals were identical in calorie content, fat and weight, and were served with 400 ml water.
Participants were instructed to record their food intake for the rest of the day, and then rated their hunger, fullness, prospective food intake, palatability and gastrointestinal tolerance.
Fibre also played a part in boosting immediate satiety after fifteen minutes after eating – but this then levelled off to be on a par with beef. “This could be due to the bulking effects of the fibre in the bean meal leading to greater gastric distension which can impact early satiety signalling,” wrote Bonnema et al.
Both meatloaves had similar ratings for palatability but beef performed better for pleasantness.
Source: Journal of Food Science
Article first published online: 13 August 2015 doi: 10.1111/1750-3841.12991
“The Effects of a Beef-Based Meal Compared to a Calorie Matched Bean-Based Meal on Appetite and Food Intake”
Authors: A.L. Bonnema, D. Altschwager, W. Thomas and J. L. Slavin.