Whey Protein Drink Ingestion before Breakfast Suppressed Energy Intake at Breakfast and Lunch, but Not during Dinner, and Was Less Suppressed in Healthy Older than Younger Men

Abstract

Ageing is associated with changes in feeding behavior. We have reported that there is suppression of energy intake three hours after whey protein drink ingestion in young, but not older, men. This study aimed to determine these effects over a time period of 9 h. Fifteen younger (27 ± 1 years, 25.8 ± 0.7 kg/m²) and 15 older (75 ± 2 years, 26.6 ± 0.8 kg/m²) healthy men were studied on three occasions on which they received, in a randomized order, a 30 g/120 kcal, 70 g/280 kcal whey-protein, or control (~2 kcal) drink. Ad-libitum energy intake (sum of breakfast, lunch, and dinner) was suppressed in a protein load responsive fashion (P = 0.001). Suppression was minimal at breakfast, substantial at lunch (~-16%, P = 0.001), no longer present by dinner, and was less in older than younger men (-3 ± 4% vs. -8 ± 4%, P = 0.027). Cumulative protein intake was increased in the younger and older men (+20% and +42%, P < 0.001). Visual analogue scale ratings of fullness were higher and desire to eat and prospective food consumption were lower after protein vs. control, and these effects were smaller in older vs. younger men (interaction effect P < 0.05). These findings support the use of whey-protein drink supplements in older people who aim to increase their protein intake without decreasing their overall energy intake.

Keywords: appetite; energy intake; gastric emptying; whey protein.

Figure 1

Energy intake at breakfast, lunch, and dinner following whey protein ingestion in healthy young and older men. Mean (± SEM) ad libitum energy intake (kcal; left) at breakfast (light grey bars), lunch (dark grey bars), and dinner (black bars) following drink ingestion containing flavored water (control, ~2 kcal) or whey protein (30 g/120 kcal or 70 g/280 kcal) and cumulative energy intake (kcal; right; sum total energy intake at breakfast, lunch, and dinner combined (dark grey bars) and protein drink (white bars)) in young (left; n = 15) and older (right; n = 15) men. Age and protein load main effects and interaction effects were determined by repeated measures ANOVA. * The 70 g protein drink suppressed energy intake (sum of breakfast, lunch, and dinner) compared with the control (protein load effect P = 0.012, post-hoc P = 0.023).

Figure 2

Suppression of energy intake by whey protein at breakfast, lunch, and dinner and total suppression of energy intake in healthy young and older men. Mean (± SEM) suppression of energy intake (kcal) at breakfast, lunch, and dinner following whey protein (30 g/120 kcal or 70 g/280 kcal) ingestion compared to control (~2 kcal) in young (black shading; n = 15) and older (grey shading; n = 15) men. Age and protein load main effects and interaction effects were determined by using repeated-measures ANOVA. Energy intake was suppressed by protein (protein load main effect P = 0.012). Suppression of energy intake by 70 g protein (P = 0.007) was evident, particularly at lunch (P = 0.001). Suppression of energy intake (sum of breakfast, lunch, and dinner) by protein was less in healthy older than younger men (main effect of age P = 0.027).

Figure 3

Mean (± SEM) protein intake (g) at breakfast (light grey bars), lunch (dark grey bars), and dinner (black bars) following drink ingestion containing flavored water (control, ~2kcal) or whey protein (30 g/120 kcal or 70 g/280 kcal; white bars) in young (left; n = 15) and older (right; n = 15) men. Age and protein load main effects and interaction effects were determined by using repeated-measures ANOVA. * Cumulative protein intake (sum of protein drink plus protein intake at meals) was increased in a protein load responsive fashion comparably in the healthy young and older men (main effect of age P = 0.71, protein load main effect P < 0.001, interaction effect P = 0.54).

Figure 4

Mean (± SEM) Gastric Retention (%) of drinks containing flavored water (control, ~2 kcal) or whey protein (30 g/120 kcal or 70 g/280 kcal; open bars) in young (left; n = 15) and older (right; n = 15) men. Age and protein load main effects and interaction effects were determined by using repeated-measures ANOVA. * Gastric Retention, calculated based on the antral areas, were larger after both protein drinks compared to control (main effect of age P = 0.27, protein main effect P < 0.001, interaction effect P = 0.091).

Figure 5

Mean (± SEM) visual analogue scores (VAS; 0–545 min) of hunger (A,B), fullness (C,D), desire to eat (E,F), and prospective food consumption (G,H) following overnight fasting (t = −5) and after drink ingestion (t = 0, 5, 20, 35, 65, 80, 95, 275, 305, 320, 335, 515, 545, 560, 575 min) containing flavored water (control, ~2 kcal) or whey protein (30 g/120 kcal or 70 g/280 kcal; open bars) and immediately before and after breakfast (B), lunch (L), and dinner (D) in young (left; n = 15) and older (right; n = 15) men. Age and protein load main effects and interaction effects were determined using repeated-measures ANOVA. Protein affected ^# fullness (protein load main effect P < 0.001), ^ desire to eat (P < 0.001), and * prospective food consumption (P = 0.002) in a protein load related fashion. Older compared to younger men had lower desire to eat (main effect of age P = 0.028) and fullness (P = 0.003, interaction effect P < 0.001).