What protein at breakfast does to appetite
Researchers who compared high-protein and low-protein breakfasts found the protein version left people less hungry within hours, though it did not change how much they ate at lunch.
A study by researchers at Newcastle University, published in the European Journal of Nutrition, compared three breakfasts in 18 healthy adults. Two were high in protein: a 30g plant-based drink and a 30g animal-based meal of eggs, salmon and toast. The third was a 10.3g low-protein breakfast of toast with chocolate spread.
Both high-protein breakfasts significantly increased two hormones linked to fullness, GLP-1 and PYY, compared with the low-protein breakfast (p less than 0.004, according to the study).
Hunger, rated on a scale by participants, was lower after the plant-based high-protein drink than after the low-protein breakfast (p = 0.001).
There was no difference in how full or hungry participants felt between the plant-based drink and the equivalent animal-based breakfast, the study found.
Despite the hormone and hunger-rating differences, the study found no significant difference in how much food participants ate at an ad libitum lunch afterwards, across any of the three breakfasts.
The study’s authors noted limitations. Of the 18 participants, only six were older adults, aged 65 and over. That small older group reduced the statistical power of the age comparison. The design also did not include a plant-based solid food or an animal-based liquid option, which would have shown whether form, rather than protein source, affected the results.
A separate systematic review and meta-analysis of ten randomised controlled trials in children and adolescents, published in the journal Nutrients, found that a protein-rich breakfast was linked to lower energy intake at the next meal (mean difference, minus 111.2 kcal), higher fullness ratings and lower hunger ratings than a normal or low-protein breakfast.
That review’s authors concluded a protein-rich breakfast “could be an excellent strategy for weight management”, but added that most of the studies they included were of low quality and “the results ought to be interpreted cautiously.”
The NHS Eatwell Guide lists protein foods, including eggs, fish, dairy, pulses, nuts and lean meat, as one of the main food groups that should feature in a balanced breakfast, alongside wholegrain and lower-sugar options.
Neither study looked at long-term weight change, and the Newcastle University trial measured effects only on the day of the meal itself. Anyone with concerns about their diet or weight should speak to a doctor or a registered dietitian.