The American Egg Board-funded study found that eating high quality protein (eggs) for breakfast leads to greater satiety and a lower calorie intake at lunchtime than a lower quality protein (cereal) breakfast.
It was presented at the 19th European Congress on Obesity in Lyon, France, last week.
A previous study by the same researchers at Pennington Biomedical Research Center demonstrated that an egg breakfast, compared to a bagel breakfast of similar calories, increased feelings of fullness and reduced food intake at lunch.
However, it did not examine whether it was the amount or type of protein that may have contributed to the findings.
“In the previous study we did not match the macronutrient content of the two breakfasts like for like, so we did not know whether it was the protein content that was responsible for the findings,” lead researcher Dr Nikhil Dhurandhar told Nutraingredients.
In the latest study the quality of protein distinguished two breakfast meals that were nearly identical in the amount of calories and protein provided.
“We matched the two breakfasts in terms of weight, calories, and the percentage of carbohydrate, protein and fat, so that the main difference was the source of protein,” said Dr Dhurandhar.
He explained that with a biological value (BV) of 100, eggs are considered the golden standard for protein, because they provide all ten essential amino acids. Therefore, the egg breakfast supplied high quality protein while the cereal breakfast provided lower quality protein (wheat protein has a BV of 42).
20 obese men and women aged between 18 and 60 took part in the randomised, crossover trial. Each subject had to eat one of the breakfast meals for a week, followed by a ‘wash-out’ week, before eating the other breakfast meal for a week. During each breakfast week, on days one and seven the participants were also offered lunch three hours after breakfast. On these days the researchers collected data via blood samples and questionnaires and covertly measured how much participants were eating during lunch.
Participants reported feeling fuller following the egg breakfast and tests of their hunger hormone levels supported their self-reported observations. When tested after eating the egg breakfast, levels of the hunger signalling hormone ghrelin were significantly lower and levels of the hormone that signals fullness, PYY, were significantly higher. In addition, the actual food intake of participants was considerably lower during the egg breakfast week than during the wheat breakfast week.
“I was surprised by the results, because these breakfasts were so close to each other they were almost identical,” admitted Dr Dhurandhar. “The results indicate that protein quality, not just quantity, may affect satiety.”
The findings are currently under review by an unnamed peer-reviewed journal.