Effect of High-Protein Breakfast Meals on Within-Day Appetite and Food Intake in Healthy Men and Women

Breakfast is always an area of interest as it is literally the only meal you cannot miss. After all, if you never break the fast, then you will die of starvation. But regardless of whether breakfast comes at 8am or noon, its composition can have a strong influence on dietary adherence for the remainder of the day. For instance, protein is known to be the most satiating nutrient, and some research suggests that its effects on hunger are most pronounced at breakfast relative to subsequent eating occasions.

Unfortunately, most short-term feeding studies use liquid meals that are able to hide the dietary manipulations from the participants. While results may apply to some smoothie drinkers, it doesn’t represent a realistic scenario for most. As such, researchers from the University of Aberdeen publishing in the journal Food and Nutrition Sciences set out to explore the effects on appetite that various high-protein meals had in men and women.

Twenty non-smoking, healthy, normal weight men (n=5) and women (n=15) who worked sedentary jobs were recruited to eat four different breakfasts of similar macronutrient composition (30% protein; 40% carbohydrate; 30% fat) on four different occasions.

  • Maintenance meal (MTD; 640 kcal), containing cereal with milk, toast with jam, ham, and scrambled eggs
  • Weight-loss bacon breakfast (WL-B; 510 kcal), containing cereal with milk, a warm bacon and cheese toasted sandwich, and grilled tomatoes
  • WL-C chicken salad (510 kcal)
  • WL-S as a fruit dairy smoothie (510 kcal)

Every subject had their energy expenditure estimated with a ventilated hood and activity factor. The MTD meal was 30% of total energy expenditure while the WL meals were 30% of resting metabolic rate.

“The fact that all breakfasts were high in protein and fed to WL or maintenance requirements was hidden from the volunteers. Participants were made aware that two hours after breakfast, they could snack from a buffet. This was a selection of sweet and savory, high-calorie and low-calorie 26 ready-to-eat foods including crisps, yoghurt, cheese, biscuits, sandwiches, fruit, ready meals, soup and vegetables.”

The buffet was offered again at lunch, five hours after breakfast, and hunger and fullness were assessed every 30 minutes from breakfast to after lunch. As it turns out, energy intake was not significantly different among any of the conditions; during the MTD condition the extra energy intake at breakfast was compensated for by reduced snacking. However, the WL-S and WL-C left subjects significantly hungrier and less full than the WL-B and the MTD, which were both rated equally despite the caloric difference.

Bottom line

If there is anything we have learned from nutritional psychology, it is that everything influences how we eat and our perceptions of each bite we take. Previous research has clearly shown portion size to influence bite size and eating rate, the color of a coffee mug to influence the taste of the coffee, and the servings listed on a nutritional label to affect how much we consume.

If perception truly does play a role in appetite regulation, then perhaps the subjects of the current study perceived a warm-cooked breakfast to be more satisfying than a smoothie or cold salad. Moreover, perhaps they also perceived the bacon to be higher calorie than what it actually was, putting it on par with the maintenance meal. Whatever the reason, it does thus appear prudent to eat at least one home-cooked meal per day.

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